1 <!doctype birddoc system>
6 This documentation can have 4 forms: sgml (this is master copy), html, ASCII
7 text and dvi/postscript (generated from sgml using sgmltools). You should always
10 This is a slightly modified linuxdoc dtd. Anything in <descrip> tags is
11 considered definition of configuration primitives, <cf> is fragment of
12 configuration within normal text, <m> is "meta" information within fragment of
13 configuration - something in config which is not keyword.
17 Copyright 1999 - 2022 CZ.NIC, z.s.p.o , distribute under GPL version 2 or later.
23 <title>BIRD 2.0 User's Guide
25 Ondrej Filip <it/<feela@network.cz>/,
26 Martin Mares <it/<mj@ucw.cz>/,
27 Maria Matejka <it/<mq@jmq.cz>/,
28 Ondrej Zajicek <it/<santiago@crfreenet.org>/
32 This document contains user documentation for the BIRD Internet Routing Daemon project.
35 <!-- Table of contents -->
38 <!-- Begin the document -->
45 <label id="what-is-bird">
47 <p>The name `BIRD' is actually an acronym standing for `BIRD Internet Routing
48 Daemon'. Let's take a closer look at the meaning of the name:
50 <p><em/BIRD/: Well, we think we have already explained that. It's an acronym
51 standing for `BIRD Internet Routing Daemon', you remember, don't you? :-)
53 <p><em/Internet Routing/: It's a program (well, a daemon, as you are going to
54 discover in a moment) which works as a dynamic router in an Internet type
55 network (that is, in a network running either the IPv4 or the IPv6 protocol).
56 Routers are devices which forward packets between interconnected networks in
57 order to allow hosts not connected directly to the same local area network to
58 communicate with each other. They also communicate with the other routers in the
59 Internet to discover the topology of the network which allows them to find
60 optimal (in terms of some metric) rules for forwarding of packets (which are
61 called routing tables) and to adapt themselves to the changing conditions such
62 as outages of network links, building of new connections and so on. Most of
63 these routers are costly dedicated devices running obscure firmware which is
64 hard to configure and not open to any changes (on the other hand, their special
65 hardware design allows them to keep up with lots of high-speed network
66 interfaces, better than general-purpose computer does). Fortunately, most
67 operating systems of the UNIX family allow an ordinary computer to act as a
68 router and forward packets belonging to the other hosts, but only according to a
69 statically configured table.
71 <p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program
72 running on background which does the dynamic part of Internet routing, that is
73 it communicates with the other routers, calculates routing tables and sends them
74 to the OS kernel which does the actual packet forwarding. There already exist
75 other such routing daemons: routed (RIP only), GateD (non-free),
76 <HTMLURL URL="http://www.zebra.org" name="Zebra"> and
77 <HTMLURL URL="http://sourceforge.net/projects/mrt" name="MRTD">,
78 but their capabilities are limited and they are relatively hard to configure
81 <p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
82 to support all the routing technology used in the today's Internet or planned to
83 be used in near future and to have a clean extensible architecture allowing new
84 routing protocols to be incorporated easily. Among other features, BIRD
88 <item>both IPv4 and IPv6 protocols
89 <item>multiple routing tables
90 <item>the Border Gateway Protocol (BGPv4)
91 <item>the Routing Information Protocol (RIPv2, RIPng)
92 <item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
93 <item>the Babel Routing Protocol
94 <item>the Router Advertisements for IPv6 hosts
95 <item>a virtual protocol for exchange of routes between different
96 routing tables on a single host
97 <item>a command-line interface allowing on-line control and inspection
98 of status of the daemon
99 <item>soft reconfiguration (no need to use complex online commands to
100 change the configuration, just edit the configuration file and
101 notify BIRD to re-read it and it will smoothly switch itself to
102 the new configuration, not disturbing routing protocols unless
103 they are affected by the configuration changes)
104 <item>a powerful language for route filtering
107 <p>BIRD has been developed at the Faculty of Math and Physics, Charles
108 University, Prague, Czech Republic as a student project. It can be freely
109 distributed under the terms of the GNU General Public License.
111 <p>BIRD has been designed to work on all UNIX-like systems. It has been
112 developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD
113 and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively
114 easy due to its highly modular architecture.
116 <p>BIRD 1.x supported either IPv4 or IPv6 protocol, but had to be compiled separately
117 for each one. BIRD~2 supports both of them with a possibility of further extension.
118 BIRD~2 supports Linux at least 3.16, FreeBSD 10, NetBSD 7.0, and OpenBSD 5.8.
119 Anyway, it will probably work well also on older systems.
121 <sect>Installing BIRD
124 <p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make)
125 and Perl, installing BIRD should be as easy as:
131 vi /usr/local/etc/bird.conf
135 <p>You can use <tt>./configure --help</tt> to get a list of configure
136 options. The most important ones are: <tt/--with-protocols=/ to produce a slightly smaller
137 BIRD executable by configuring out routing protocols you don't use, and
138 <tt/--prefix=/ to install BIRD to a place different from <file>/usr/local</file>.
144 <p>You can pass several command-line options to bird:
147 <tag><label id="argv-config">-c <m/config name/</tag>
148 use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>.
150 <tag><label id="argv-debug">-d</tag>
151 enable debug messages to stderr, and run bird in foreground.
153 <tag><label id="argv-debug-file">-D <m/filename of debug log/</tag>
154 enable debug messages to given file.
156 <tag><label id="argv-foreground">-f</tag>
157 run bird in foreground.
159 <tag><label id="argv-group">-g <m/group/</tag>
160 use that group ID, see the next section for details.
162 <tag><label id="argv-help">-h, --help</tag>
163 display command-line options to bird.
165 <tag><label id="argv-local">-l</tag>
166 look for a configuration file and a communication socket in the current
167 working directory instead of in default system locations. However, paths
168 specified by options <cf/-c/, <cf/-s/ have higher priority.
170 <tag><label id="argv-parse">-p</tag>
171 just parse the config file and exit. Return value is zero if the config
172 file is valid, nonzero if there are some errors.
174 <tag><label id="argv-pid">-P <m/name of PID file/</tag>
175 create a PID file with given filename.
177 <tag><label id="argv-recovery">-R</tag>
178 apply graceful restart recovery after start.
180 <tag><label id="argv-socket">-s <m/name of communication socket/</tag>
181 use given filename for a socket for communications with the client,
182 default is <it/prefix/<file>/var/run/bird.ctl</file>.
184 <tag><label id="argv-user">-u <m/user/</tag>
185 drop privileges and use that user ID, see the next section for details.
187 <tag><label id="argv-version">--version</tag>
188 display bird version.
191 <p>BIRD writes messages about its work to log files or syslog (according to config).
195 <label id="privileges">
197 <p>BIRD, as a routing daemon, uses several privileged operations (like setting
198 routing table and using raw sockets). Traditionally, BIRD is executed and runs
199 with root privileges, which may be prone to security problems. The recommended
200 way is to use a privilege restriction (options <cf/-u/, <cf/-g/). In that case
201 BIRD is executed with root privileges, but it changes its user and group ID to
202 an unprivileged ones, while using Linux capabilities to retain just required
203 privileges (capabilities CAP_NET_*). Note that the control socket is created
204 before the privileges are dropped, but the config file is read after that. The
205 privilege restriction is not implemented in BSD port of BIRD.
207 <p>An unprivileged user (as an argument to <cf/-u/ options) may be the user
208 <cf/nobody/, but it is suggested to use a new dedicated user account (like
209 <cf/bird/). The similar considerations apply for the group option, but there is
210 one more condition -- the users in the same group can use <file/birdc/ to
213 <p>Finally, there is a possibility to use external tools to run BIRD in an
214 environment with restricted privileges. This may need some configuration, but it
215 is generally easy -- BIRD needs just the standard library, privileges to read
216 the config file and create the control socket and the CAP_NET_* capabilities.
220 <label id="architecture">
223 <label id="routing-tables">
225 <p>The heart of BIRD is a routing table. BIRD has several independent routing tables;
226 each of them contains routes of exactly one <m/nettype/ (see below). There are two
227 default tables -- <cf/master4/ for IPv4 routes and <cf/master6/ for IPv6 routes.
228 Other tables must be explicitly configured.
231 These routing tables are not kernel forwarding tables. No forwarding is done by
232 BIRD. If you want to forward packets using the routes in BIRD tables, you may
233 use the Kernel protocol (see below) to synchronize them with kernel FIBs.
236 Every nettype defines a (kind of) primary key on routes. Every route source can
237 supply one route for every possible primary key; new route announcement replaces
238 the old route from the same source, keeping other routes intact. BIRD always
239 chooses the best route for each primary key among the known routes and keeps the
240 others as suboptimal. When the best route is retracted, BIRD re-runs the best
241 route selection algorithm to find the current best route.
244 The global best route selection algorithm is (roughly) as follows:
247 <item>Preferences of the routes are compared.
248 <item>Source protocol instance preferences are compared.
249 <item>If source protocols are the same (e.g. BGP vs. BGP), the protocol's route selection algorithm is invoked.
250 <item>If source protocols are different (e.g. BGP vs. OSPF), result of the algorithm is undefined.
253 <p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected
254 route from a list of entries for one network. Optionally, these lists of entries
255 are kept completely sorted (according to preference or some protocol-dependent
256 metric). See <ref id="rtable-sorted" name="sorted"> table option for details.
258 <sect>Routes and network types
261 <p>BIRD works with several types of routes. Some of them are typical IP routes,
262 others are better described as forwarding rules. We call them all routes,
263 regardless of this difference.
265 <p>Every route consists of several attributes (read more about them in the
266 <ref id="route-attributes" name="Route attributes"> section); the common for all
270 <item>IP address of router which told us about this route
271 <item>Source protocol instance
272 <item>Route preference
273 <item>Optional attributes defined by protocols
276 <p>Other attributes depend on nettypes. Some of them are part of the primary key, these are marked (PK).
278 <sect1>IPv4 and IPv6 routes
279 <label id="ip-routes">
281 <p>The traditional routes. Configuration keywords are <cf/ipv4/ and <cf/ipv6/.
284 <item>(PK) Route destination (IP prefix together with its length)
285 <item>Route next hops (see below)
288 <sect1>IPv6 source-specific routes
289 <label id="ip-sadr-routes">
291 <p>The IPv6 routes containing both destination and source prefix. They are used
292 for source-specific routing (SSR), also called source-address dependent routing
293 (SADR), see <rfc id="8043">. Currently limited mostly to the Babel protocol.
294 Configuration keyword is <cf/ipv6 sadr/.
297 <item>(PK) Route destination (IP prefix together with its length)
298 <item>(PK) Route source (IP prefix together with its length)
299 <item>Route next hops (see below)
302 <sect1>VPN IPv4 and IPv6 routes
303 <label id="vpn-routes">
305 <p>Routes for IPv4 and IPv6 with VPN Route Distinguisher (<rfc id="4364">).
306 Configuration keywords are <cf/vpn4/ and <cf/vpn6/.
309 <item>(PK) Route destination (IP prefix together with its length)
310 <item>(PK) Route distinguisher (according to <rfc id="4364">)
311 <item>Route next hops
314 <sect1>Route Origin Authorization for IPv4 and IPv6
315 <label id="roa-routes">
317 <p>These entries can be used to validate route origination of BGP routes.
318 A ROA entry specifies prefixes which could be originated by an AS number.
319 Their keywords are <cf/roa4/ and <cf/roa6/.
322 <item>(PK) IP prefix together with its length
323 <item>(PK) Matching prefix maximal length
327 <sect1>Flowspec for IPv4 and IPv6
328 <label id="flow-routes">
330 <p>Flowspec rules are a form of firewall and traffic flow control rules
331 distributed mostly via BGP. These rules may help the operators stop various
332 network attacks in the beginning before eating up the whole bandwidth.
333 Configuration keywords are <cf/flow4/ and <cf/flow6/.
336 <item>(PK) IP prefix together with its length
337 <item>(PK) Flow definition data
338 <item>Flow action (encoded internally as BGP communities according to <rfc id="5575">)
341 <sect1>MPLS switching rules
342 <label id="mpls-routes">
344 <p>MPLS routes control MPLS forwarding in the same way as IP routes control IP
345 forwarding. MPLS-aware routing protocols produce both labeled IP routes and
346 corresponding MPLS routes. Configuration keyword is <cf/mpls/.
349 <item>(PK) MPLS label
350 <item>Route next hops
353 <sect1>Route next hops
354 <label id="route-next-hop">
356 <p>This is not a nettype. The route next hop is a complex attribute common for many
357 nettypes as you can see before. Every next hop has its assigned device
358 (either assumed from its IP address or set explicitly). It may have also
359 an IP address and an MPLS stack (one or both independently).
360 Maximal MPLS stack depth is set (in compile time) to 8 labels.
362 <p>Every route (when eligible to have a next hop) can have more than one next hop.
363 In that case, every next hop has also its weight.
365 <sect>Protocols and channels
366 <label id="protocols-concept">
368 <p>BIRD protocol is an abstract class of producers and consumers of the routes.
369 Each protocol may run in multiple instances and bind on one side to route
370 tables via channels, on the other side to specified listen sockets (BGP),
371 interfaces (Babel, OSPF, RIP), APIs (Kernel, Direct), or nothing (Static, Pipe).
373 <p>There are also two protocols that do not have any channels -- BFD and Device.
374 Both of them are kind of service for other protocols.
376 <p>Each protocol is connected to a routing table through a channel. Some protocols
377 support only one channel (OSPF, RIP), some protocols support more channels (BGP, Direct).
378 Each channel has two filters which can accept, reject and modify the routes.
379 An <it/export/ filter is applied to routes passed from the routing table to the protocol,
380 an <it/import/ filter is applied to routes in the opposite direction.
382 <sect>Graceful restart
383 <label id="graceful-restart">
385 <p>When BIRD is started after restart or crash, it repopulates routing tables in
386 an uncoordinated manner, like after clean start. This may be impractical in some
387 cases, because if the forwarding plane (i.e. kernel routing tables) remains
388 intact, then its synchronization with BIRD would temporarily disrupt packet
389 forwarding until protocols converge. Graceful restart is a mechanism that could
390 help with this issue. Generally, it works by starting protocols and letting them
391 repopulate routing tables while deferring route propagation until protocols
392 acknowledge their convergence. Note that graceful restart behavior have to be
393 configured for all relevant protocols and requires protocol-specific support
394 (currently implemented for Kernel and BGP protocols), it is activated for
395 particular boot by option <cf/-R/.
397 <p>Some protocols (e.g. BGP) could be restarted gracefully after both
398 intentional outage and crash, while others (e.g. OSPF) after intentional outage
399 only. For planned graceful restart, BIRD must be shut down by
400 <ref id="cli-graceful-restart" name="graceful restart"> command instead of
401 regular <ref id="cli-down" name="down"> command. In this way routing neighbors
402 are notified about planned graceful restart and routes are kept in kernel table
408 <p>Multiprotocol Label Switching (MPLS) is a networking technology which works
409 below IP routing but above the link (e.g. ethernet) layer. It is described in
412 In regular IP forwarding, the destination address of a packet is independently
413 examined in each hop, a route with longest prefix match is selected from the
414 routing table, and packet is processed accordingly. In general, there is no
415 difference between border routers and internal routers w.r.t. IP forwarding.
417 In MPLS forwarding, when a packet enters the network, it is classified (based on
418 destination address, ingress interface and other factors) into one of forwarding
419 equivalence classes (FECs), then a header with a MPLS label identifying the FEC
420 is attached to it, and the packet is forwarded. In internal routers, only the
421 MPLS label is examined, the matching MPLS route is selected from the MPLS
422 routing table, and the packet is processed accordingly. The specific value of
423 MPLS label has local meaning only and may change between hops (that is why it is
424 called label switching). When the packet leaves the network, the MPLS header is
427 The advantage of the MPLS approach is that other factors than the destination
428 address can be considered and used consistently in the whole network, for
429 example IP traffic with multiple overlapping private address ranges could be
430 mixed together, or particular paths for specific flows could be defined. Another
431 advantage is that MPLS forwarding by internal routers can be much simpler than
432 IP forwarding, as instead of the longest prefix match algorithm it uses simpler
433 exact match for MPLS route selection. The disadvantage is additional complexity
434 in signaling. For further details, see <rfc id="3031">.
436 MPLS-aware routing protocols not only distribute IP routing information, but
437 they also distribute labels. Therefore, they produce labeled routes - routes
438 representing label switched paths (LSPs) through the MPLS domain. Such routes
439 have IP prefix and next hop address like regular (non-labeled) routes, but they
440 also have local MPLS label (in route attribute <ref id="rta-mpls-label"
441 name="mpls_label">) and outgoing MPLS label (as a part of the next hop). They
442 are stored in regular IP routing tables.
444 Labeled routes are used for exchange of routing information between routing
445 protocols and for ingress (IP -> MPLS) forwarding, but they are not directly
446 used for MPLS forwarding. For that purpose <ref id="mpls-routes" name="MPLS
447 routes"> are used. These are routes that have local MPLS label as a primary key
448 and they are stored in the MPLS routing table.
450 In BIRD, the whole process generally works this way: A MPLS-aware routing
451 protocol (say BGP) receives routing information including remote label. It
452 produces a route with attribute <ref id="rta-mpls-policy" name="mpls_policy">
453 specifying desired <ref id="mpls-channel-label-policy" name="MPLS label policy">.
454 Such route then passes the import filter (which could modify the MPLS label
455 policy or perhaps assign a static label) and when it is accepted, a local MPLS
456 label is selected (according to the label policy) and attached to the route,
457 producing labeled route. When a new MPLS label is allocated, the MPLS-aware
458 protocol automatically produces corresponding MPLS route. When all labeled
459 routes that use specific local MPLS label are retracted, the corresponding MPLS
460 route is retracted too.
462 There are three important concepts for MPLS in BIRD: MPLS domains, MPLS tables
463 and MPLS channels. MPLS domain represents an independent label space, all
464 MPLS-aware protocols are associated with some MPLS domain. It is responsible for
465 label management, handling label allocation requests from MPLS-aware protocols.
466 MPLS table is just a routing table for MPLS routes. Routers usually have one
467 MPLS domain and one MPLS table, with Kernel protocol to export MPLS routes into
470 MPLS channels make protocols MPLS-aware, they are responsible for keeping track
471 of active FECs (and corresponding allocated labels), selecting FECs / local
472 labels for labeled routes, and maintaining correspondence between labeled routes
475 Note that local labels are allocated to individual MPLS-aware protocols and
476 therefore it is not possible to share local labels between different protocols.
483 <label id="config-intro">
485 <p>BIRD is configured using a text configuration file. Upon startup, BIRD reads
486 <it/prefix/<file>/etc/bird.conf</file> (unless the <tt/-c/ command line option
487 is given). Configuration may be changed at user's request: if you modify the
488 config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
489 config. Then there's the client which allows you to talk with BIRD in an
492 <p>In the config, everything on a line after <cf/#/ or inside <cf>/* */</cf> is
493 a comment, whitespace characters are treated as a single space. If there's a
494 variable number of options, they are grouped using the <cf/{ }/ brackets. Each
495 option is terminated by a <cf/;/. Configuration is case sensitive. There are two
496 ways how to name symbols (like protocol names, filter names, constants etc.).
497 You can either use a simple string starting with a letter (or underscore)
498 followed by any combination of letters, numbers and underscores (e.g. <cf/R123/,
499 <cf/my_filter/, <cf/bgp5/) or you can enclose the name into apostrophes (<cf/'/)
500 and than you can use any combination of numbers, letters, underscores, hyphens,
501 dots and colons (e.g. <cf/'1:strange-name'/, <cf/'-NAME-'/, <cf/'cool::name'/).
503 <p>Here is an example of a simple config file. It enables synchronization of
504 routing tables with OS kernel, learns network interfaces and runs RIP on all
505 network interfaces found.
510 export all; # Default is export none
512 persist; # Don't remove routes on BIRD shutdown
529 <label id="global-opts">
532 <tag><label id="opt-include">include "<m/filename/";</tag>
533 This statement causes inclusion of a new file. The <m/filename/ could
534 also be a wildcard, in that case matching files are included in
535 alphabetic order. The maximal depth is 8. Note that this statement can
536 be used anywhere in the config file, even inside other options, but
537 always on the beginning of line. In the following example, the first
538 semicolon belongs to the <cf/include/, the second to <cf/ipv6 table/.
539 If the <file/tablename.conf/ contains exactly one token (the name of the
540 table), this construction is correct:
543 include "tablename.conf";;
546 <tag><label id="opt-log">log "<m/filename/" [<m/limit/ "<m/backup/"] | syslog [name <m/name/] | stderr | udp <m/address/ [port <m/port/] all|{ <m/list of classes/ }</tag>
547 Set logging of messages having the given class (either <cf/all/ or <cf>{
548 error|trace [, <m/.../] }</cf> etc.) into selected destination - a file
549 specified as a filename string (with optional log rotation information),
550 syslog (with optional name argument), the stderr output, or as a UDP
551 message (in <rfc id="3164"> syslog format).
554 <cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
555 <cf/debug/ for debugging messages,
556 <cf/trace/ when you want to know what happens in the network,
557 <cf/remote/ for messages about misbehavior of remote machines,
558 <cf/auth/ about authentication failures,
559 <cf/bug/ for internal BIRD bugs.
561 Logging directly to file supports basic log rotation -- there is an
562 optional log file limit and a backup filename, when log file reaches the
563 limit, the current log file is renamed to the backup filename and a new
566 You may specify more than one <cf/log/ line to establish logging to
567 multiple destinations. Default: log everything to the system log, or
568 to the debug output if debugging is enabled by <cf/-d//<cf/-D/
571 <tag><label id="opt-debug-protocols">debug protocols all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
572 Set global defaults of protocol debugging options.
573 See <ref id="proto-debug" name="debug"> in the following section.
576 <tag><label id="opt-debug-channels">debug channels all|off|{ states|routes|filters|events [, <m/.../] }</tag>
577 Set global defaults of channel debugging options.
578 See <ref id="channel-debug" name="debug"> in the channel section.
581 <tag><label id="opt-debug-tables">debug tables all|off|{ states|routes|filters|events [, <m/.../] }</tag>
582 Set global defaults of table debugging options.
583 See <ref id="table-debug" name="debug"> in the table section.
586 <tag><label id="opt-debug-commands">debug commands <m/number/</tag>
587 Control logging of client connections (0 for no logging, 1 for logging
588 of connects and disconnects, 2 and higher for logging of all client
589 commands). Default: 0.
591 <tag><label id="opt-debug-latency">debug latency <m/switch/</tag>
592 Activate tracking of elapsed time for internal events. Recent events
593 could be examined using <cf/dump events/ command. Default: off.
595 <tag><label id="opt-debug-latency-limit">debug latency limit <m/time/</tag>
596 If <cf/debug latency/ is enabled, this option allows to specify a limit
597 for elapsed time. Events exceeding the limit are logged. Default: 1 s.
599 <tag><label id="opt-watchdog-warn">watchdog warning <m/time/</tag>
600 Set time limit for I/O loop cycle. If one iteration took more time to
601 complete, a warning is logged. Default: 5 s.
603 <tag><label id="opt-watchdog-timeout">watchdog timeout <m/time/</tag>
604 Set time limit for I/O loop cycle. If the limit is breached, BIRD is
605 killed by abort signal. The timeout has effective granularity of
606 seconds, zero means disabled. Default: disabled (0).
608 <tag><label id="opt-mrtdump">mrtdump "<m/filename/"</tag>
609 Set MRTdump file name. This option must be specified to allow MRTdump
610 feature. Default: no dump file.
612 <tag><label id="opt-mrtdump-protocols">mrtdump protocols all|off|{ states|messages [, <m/.../] }</tag>
613 Set global defaults of MRTdump options. See <cf/mrtdump/ in the
614 following section. Default: off.
616 <tag><label id="opt-filter">filter <m/name local variables/{ <m/commands/ }</tag>
617 Define a filter. You can learn more about filters in the following
620 <tag><label id="opt-function">function <m/name/ (<m/parameters/) [ -> <m/return type/ ] <m/local variables/ { <m/commands/ }</tag>
621 Define a function. You can learn more about functions in the following chapter.
623 <tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
624 Define a protocol instance called <cf><m/name/</cf> (or with a name like
625 "rip5" generated automatically if you don't specify any
626 <cf><m/name/</cf>). You can learn more about configuring protocols in
627 their own chapters. When <cf>from <m/name2/</cf> expression is used,
628 initial protocol options are taken from protocol or template
629 <cf><m/name2/</cf> You can run more than one instance of most protocols
630 (like RIP or BGP). By default, no instances are configured.
632 <tag><label id="opt-template">template rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
633 Define a protocol template instance called <m/name/ (or with a name like
634 "bgp1" generated automatically if you don't specify any <m/name/).
635 Protocol templates can be used to group common options when many
636 similarly configured protocol instances are to be defined. Protocol
637 instances (and other templates) can use templates by using <cf/from/
638 expression and the name of the template. At the moment templates (and
639 <cf/from/ expression) are not implemented for OSPF protocol.
641 <tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
642 Define a constant. You can use it later in every place you could use a
643 value of the same type. Besides, there are some predefined numeric
644 constants based on /etc/iproute2/rt_* files. A list of defined constants
645 can be seen (together with other symbols) using 'show symbols' command.
647 <tag><label id="opt-attribute">attribute <m/type/ <m/name/</tag>
648 Declare a custom route attribute. You can set and get it in filters like
649 any other route attribute. This feature is intended for marking routes
650 in import filters for export filtering purposes instead of locally
651 assigned BGP communities which have to be deleted in export filters.
653 <tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
654 Set BIRD's router ID. It's a world-wide unique identification of your
655 router, usually one of router's IPv4 addresses. Default: the lowest
656 IPv4 address of a non-loopback interface.
658 <tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
659 Set BIRD's router ID based on an IPv4 address of an interface specified by
660 an interface pattern.
661 See <ref id="proto-iface" name="interface"> section for detailed
662 description of interface patterns with extended clauses.
664 <tag><label id="opt-hostname">hostname "<m/name/"</tag>
665 Set hostname. Default: node name as returned by `uname -n'.
667 <tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
668 During graceful restart recovery, BIRD waits for convergence of routing
669 protocols. This option allows to specify a timeout for the recovery to
670 prevent waiting indefinitely if some protocols cannot converge. Default:
673 <tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
674 This option allows to specify a format of date/time used by BIRD. The
675 first argument specifies for which purpose such format is used.
676 <cf/route/ is a format used in 'show route' command output,
677 <cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
678 used for other commands and <cf/log/ is used in a log file.
680 "<m/format1/" is a format string using <it/strftime(3)/ notation (see
681 <it/man strftime/ for details). It is extended to support sub-second
682 time part with variable precision (up to microseconds) using "%f"
683 conversion code (e.g., "%T.%3f" is hh:mm:ss.sss time). <m/limit/ and
684 "<m/format2/" allow to specify the second format string for times in
685 past deeper than <m/limit/ seconds.
687 There are several shorthands: <cf/iso long/ is a ISO 8601 date/time
688 format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F
689 %T"/. Similarly, <cf/iso long ms/ and <cf/iso long us/ are ISO 8601
690 date/time formats with millisecond or microsecond precision.
691 <cf/iso short/ is a variant of ISO 8601 that uses just the time format
692 (hh:mm:ss) for near times (up to 20 hours in the past) and the date
693 format (YYYY-MM-DD) for far times. This is a shorthand for <cf/"%T"
694 72000 "%F"/. And there are also <cf/iso short ms/ and <cf/iso short us/
695 high-precision variants of that.
697 By default, BIRD uses the <cf/iso short ms/ format for <cf/route/ and
698 <cf/protocol/ times, and the <cf/iso long ms/ format for <cf/base/ and
701 <tag><label id="opt-table"><m/nettype/ table <m/name/ [ { <m/option/; [<m/.../] } ]</tag>
702 Define a new routing table. The default routing tables <cf/master4/ and
703 <cf/master6/ are defined implicitly, other routing tables have to be
704 defined by this option. See the <ref id="rtable-opts"
705 name="routing table configuration section"> for routing table options.
707 <tag><label id="opt-mpls-domain">mpls domain <m/name/ [ { <m/option/; [<m/.../] } ]</tag>
708 Define a new MPLS domain. MPLS domains represent independent label
709 spaces and are responsible for MPLS label management. All MPLS-aware
710 protocols are associated with some MPLS domain. See the <ref id="mpls-opts"
711 name="MPLS configuration section"> for MPLS domain options.
713 <tag><label id="opt-eval">eval <m/expr/</tag>
714 Evaluates given filter expression. It is used by the developers for testing of filters.
718 <sect>Routing table options
719 <label id="rtable-opts">
721 <p>Most routing tables do not need any options and are defined without an option
722 block, but there are still some options to tweak routing table behavior. Note
723 that implicit tables (<cf/master4/ and <cf/master6/) can be redefined in order
727 <tag><label id="table-debug">debug all|off|{ states|routes|filters [, <m/.../] }</tag>
728 Set table debugging options. Like in <ref id="proto-debug"
729 name="protocol debugging">, tables are capable of writing trace
730 messages about its work to the log (with category <cf/trace/).
731 For now, this does nothing, but in version 3, it is used. Default: off.
733 <tag><label id="rtable-sorted">sorted <m/switch/</tag>
734 Usually, a routing table just chooses the selected (best) route from a
735 list of routes for each network, while keeping remaining routes unsorted.
736 If enabled, these lists of routes are kept completely sorted (according
737 to preference or some protocol-dependent metric).
739 This is needed for some protocol features (e.g. <cf/secondary/ option of
740 BGP protocol, which allows to accept not just a selected route, but the
741 first route (in the sorted list) that is accepted by filters), but it is
742 incompatible with some other features (e.g. <cf/deterministic med/
743 option of BGP protocol, which activates a way of choosing selected route
744 that cannot be described using comparison and ordering). Minor advantage
745 is that routes are shown sorted in <cf/show route/, minor disadvantage
746 is that it is slightly more computationally expensive. Default: off.
748 <tag><label id="rtable-trie">trie <m/switch/</tag>
749 BIRD routing tables are implemented with hash tables, which is efficient
750 for exact-match lookups, but inconvenient for longest-match lookups or
751 interval lookups (finding superprefix or subprefixes). This option
752 activates additional trie structure that is used to accelerate these
753 lookups, while using the hash table for exact-match lookups.
755 This has advantage for <ref id="rpki" name="RPKI"> (on ROA tables),
756 for <ref id="bgp-gateway" name="recursive next-hops"> (on IGP tables),
757 and is required for <ref id="bgp-validate" name="flowspec validation">
758 (on base IP tables). Another advantage is that interval results (like
759 from <cf/show route in .../ command) are lexicographically sorted. The
760 disadvantage is that trie-enabled routing tables require more memory,
761 which may be an issue especially in multi-table setups. Default: off.
763 <tag><label id="rtable-min-settle-time">min settle time <m/time/</tag>
764 Specify a minimum value of the settle time. When a ROA table changes,
765 automatic <ref id="proto-rpki-reload" name="RPKI reload"> may be
766 triggered, after a short settle time. Minimum settle time is a delay
767 from the last ROA table change to wait for more updates. Default: 1 s.
770 <tag><label id="rtable-max-settle-time">max settle time <m/time/</tag>
771 Specify a maximum value of the settle time. When a ROA table changes,
772 automatic <ref id="proto-rpki-reload" name="RPKI reload"> may be
773 triggered, after a short settle time. Maximum settle time is an upper
774 limit to the settle time from the initial ROA table change even if
775 there are consecutive updates gradually renewing the settle time.
778 <tag><label id="rtable-gc-threshold">gc threshold <m/number/</tag>
779 Specify a minimum amount of removed networks that triggers a garbage
780 collection (GC) cycle. Default: 1000.
782 <tag><label id="rtable-gc-period">gc period <m/time/</tag>
783 Specify a period of time between consecutive GC cycles. When there is a
784 significant amount of route withdraws, GC cycles are executed repeatedly
785 with given period time (with some random factor). When there is just
786 small amount of changes, GC cycles are not executed. In extensive route
787 server setups, running GC on hundreds of full BGP routing tables can
788 take significant amount of time, therefore they should use higher GC
789 periods. Default: adaptive, based on number of routing tables in the
790 configuration. From 10 s (with <= 25 routing tables) up to 600 s (with
791 >= 1500 routing tables).
795 <sect>Protocol options
796 <label id="protocol-opts">
798 <p>For each protocol instance, you can configure a bunch of options. Some of
799 them (those described in this section) are generic, some are specific to the
800 protocol (see sections talking about the protocols).
802 <p>Several options use a <m/switch/ argument. It can be either <cf/on/,
803 <cf/yes/ or a numeric expression with a non-zero value for the option to be
804 enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
805 disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
809 <tag><label id="proto-disabled">disabled <m/switch/</tag>
810 Disables the protocol. You can change the disable/enable status from the
811 command line interface without needing to touch the configuration.
812 Disabled protocols are not activated. Default: protocol is enabled.
814 <tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
815 Set protocol debugging options. If asked, each protocol is capable of
816 writing trace messages about its work to the log (with category
817 <cf/trace/). You can either request printing of <cf/all/ trace messages
818 or only of the selected types: <cf/states/ for protocol state changes
819 (protocol going up, down, starting, stopping etc.), <cf/routes/ for
820 routes exchanged with the routing table, <cf/filters/ for details on
821 route filtering, <cf/interfaces/ for interface change events sent to
822 the protocol, <cf/events/ for events internal to the protocol and
823 <cf/packets/ for packets sent and received by the protocol. Classes
824 <cf/routes/ and <cf/filters/ can be also set per-channel using
825 <ref id="channel-debug" name="channel debugging option">) Default: off.
827 <tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
828 Set protocol MRTdump flags. MRTdump is a standard binary format for
829 logging information from routing protocols and daemons. These flags
830 control what kind of information is logged from the protocol to the
831 MRTdump file (which must be specified by global <cf/mrtdump/ option, see
832 the previous section). Although these flags are similar to flags of
833 <cf/debug/ option, their meaning is different and protocol-specific. For
834 BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
835 received BGP messages. Other protocols does not support MRTdump yet.
837 <tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
838 This option can be used to override global router id for a given
839 protocol. Default: uses global router id.
841 <tag><label id="proto-description">description "<m/text/"</tag>
842 This is an optional description of the protocol. It is displayed as a
843 part of the output of 'show protocols all' command.
845 <tag><label id="proto-vrf">vrf "<m/text/"|default</tag>
846 Associate the protocol with specific VRF. The protocol will be
847 restricted to interfaces assigned to the VRF and will use sockets bound
848 to the VRF. A corresponding VRF interface must exist on OS level. For
849 kernel protocol, an appropriate table still must be explicitly selected
850 by <cf/table/ option.
852 By selecting <cf/default/, the protocol is associated with the default
853 VRF; i.e., it will be restricted to interfaces not assigned to any
854 regular VRF. That is different from not specifying <cf/vrf/ at all, in
855 which case the protocol may use any interface regardless of its VRF
858 Note that for proper VRF support it is necessary to use Linux kernel
859 version at least 4.14, older versions have limited VRF implementation.
860 Before Linux kernel 5.0, a socket bound to a port in default VRF collide
861 with others in regular VRFs. In BGP, this can be avoided by using
862 <ref id="bgp-strict-bind" name="strict bind"> option.
864 <tag><label id="proto-channel"><m/channel name/ [{<m/channel config/}]</tag>
865 Every channel must be explicitly stated. See the protocol-specific
866 configuration for the list of supported channel names. See the
867 <ref id="channel-opts" name="channel configuration section"> for channel
871 <p>There are several options that give sense only with certain protocols:
874 <tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
875 Specifies a set of interfaces on which the protocol is activated with
876 given interface-specific options. A set of interfaces specified by one
877 interface option is described using an interface pattern. The interface
878 pattern consists of a sequence of clauses (separated by commas), each
879 clause is a mask specified as a shell-like pattern. Interfaces are
880 matched by their name.
882 An interface matches the pattern if it matches any of its clauses. If
883 the clause begins with <cf/-/, matching interfaces are excluded. Patterns
884 are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
885 means eth0 and all non-ethernets.
887 Some protocols (namely OSPFv2 and Direct) support extended clauses that
888 may contain a mask, a prefix, or both of them. An interface matches such
889 clause if its name matches the mask (if specified) and its address
890 matches the prefix (if specified). Extended clauses are used when the
891 protocol handles multiple addresses on an interface independently.
893 An interface option can be used more times with different interface-specific
894 options, in that case for given interface the first matching interface
897 This option is allowed in Babel, BFD, Device, Direct, OSPF, RAdv and RIP
898 protocols. In OSPF protocol it is used in the <cf/area/ subsection.
904 <cf>interface "*" { type broadcast; };</cf> - start the protocol on all
905 interfaces with <cf>type broadcast</cf> option.
907 <cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
908 protocol on enumerated interfaces with <cf>type ptp</cf> option.
910 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
911 on all interfaces that have address from 192.168.0.0/16, but not from
914 <cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
915 ethernet interfaces that have address from 192.168.1.0/24.
917 <tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
918 This option specifies the value of ToS/DS/Class field in IP headers of
919 the outgoing protocol packets. This may affect how the protocol packets
920 are processed by the network relative to the other network traffic. With
921 <cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
922 octet (but two bits reserved for ECN are ignored). With <cf/dscp/
923 keyword, the value (0-63) is used just for the DS field in the octet.
924 Default value is 0xc0 (DSCP 0x30 - CS6).
926 <tag><label id="proto-tx-priority">tx priority <m/num/</tag>
927 This option specifies the local packet priority. This may affect how the
928 protocol packets are processed in the local TX queues. This option is
929 Linux specific. Default value is 7 (highest priority, privileged traffic).
931 <tag><label id="proto-pass">password "<m/password/" | <m/bytestring/ [ { <m>password options</m> } ] </tag>
932 Specifies a password that can be used by the protocol as a shared secret
933 key. Password option can be used more times to specify more passwords.
934 If more passwords are specified, it is a protocol-dependent decision
935 which one is really used. Specifying passwords does not mean that
936 authentication is enabled, authentication can be enabled by separate,
937 protocol-dependent <cf/authentication/ option.
939 A password can be specified as a string or as a sequence of hexadecimal
940 digit pairs (<ref id="type-bytestring" name="bytestring">).
942 This option is allowed in BFD, OSPF, RIP, and Babel protocols. BGP has
943 also <cf/password/ option, but it is slightly different and described
944 separately. Default: none.
947 <p>Password option can contain section with some (not necessary all) password sub-options:
950 <tag><label id="proto-pass-id">id <M>num</M></tag>
951 ID of the password, (0-255). If it is not specified, BIRD will choose ID
952 based on an order of the password item in the interface, starting from
953 1. For example, second password item in one interface will have default
954 ID 2. ID 0 is allowed by BIRD, but some other implementations may not
955 allow it. ID is used by some routing protocols to identify which
956 password was used to authenticate protocol packets.
958 <tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
959 The start time of the usage of the password for packet signing.
960 The format of <cf><m/time/</cf> is <tt>YYYY-MM-DD [hh:mm:ss[.sss]]</tt>.
962 <tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
963 The last time of the usage of the password for packet signing.
965 <tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
966 The start time of the usage of the password for packet verification.
968 <tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
969 The last time of the usage of the password for packet verification.
971 <tag><label id="proto-pass-from">from "<m/time/"</tag>
972 Shorthand for setting both <cf/generate from/ and <cf/accept from/.
974 <tag><label id="proto-pass-to">to "<m/time/"</tag>
975 Shorthand for setting both <cf/generate to/ and <cf/accept to/.
977 <tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 | blake2s128 | blake2s256 | blake2b256 | blake2b512 )</tag>
978 The message authentication algorithm for the password when cryptographic
979 authentication is enabled. The default value depends on the protocol.
980 For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3 and
981 Babel it is HMAC-SHA-256.
986 <sect>Channel options
987 <label id="channel-opts">
989 <p>Every channel belongs to a protocol and is configured inside its block. The
990 minimal channel config is empty, then it uses default values. The name of the
991 channel implies its nettype. Channel definitions can be inherited from protocol
992 templates. Multiple definitions of the same channel are forbidden, but channels
993 inherited from templates can be updated by new definitions.
996 <tag><label id="channel-debug">debug all|off|{ states|routes|filters [, <m/.../] }</tag>
997 Set channel debugging options. Like in <ref id="proto-debug"
998 name="protocol debugging">, channels are capable of writing trace
999 messages about its work to the log (with category <cf/trace/). You can
1000 either request printing of <cf/all/ trace messages or only of the
1001 selected types: <cf/states/ for channel state changes (channel going up,
1002 down, feeding, reloading etc.), <cf/routes/ for routes propagated
1003 through the channel, <cf/filters/ for details on route filtering,
1004 remaining debug flags are not used in channel debug. Default: off.
1006 <tag><label id="proto-table">table <m/name/</tag>
1007 Specify a table to which the channel is connected. Default: the first
1008 table of given nettype.
1010 <tag><label id="proto-preference">preference <m/expr/</tag>
1011 Sets the preference of routes generated by the protocol and imported
1012 through this channel. Default: protocol dependent.
1014 <tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/boolean filter expression/</tag>
1015 Specify a filter to be used for filtering routes coming from the
1016 protocol to the routing table. <cf/all/ is for keeping all routes,
1017 <cf/none/ is for dropping all routes. Default: <cf/all/ (except for
1020 <tag><label id="proto-export">export <m/filter/</tag>
1021 This is similar to the <cf>import</cf> keyword, except that it works in
1022 the direction from the routing table to the protocol. Default: <cf/none/
1023 (except for EBGP and L3VPN).
1025 <tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
1026 Usually, if an import filter rejects a route, the route is forgotten.
1027 When this option is active, these routes are kept in the routing table,
1028 but they are hidden and not propagated to other protocols. But it is
1029 possible to show them using <cf/show route filtered/. Note that this
1030 option does not work for the pipe protocol. Default: off.
1032 <tag><label id="proto-rpki-reload">rpki reload <m/switch/</tag>
1033 Import or export filters may depend on route RPKI status (using
1034 <cf/roa_check()/ operator). In contrast to to other filter operators,
1035 this status for the same route may change as the content of ROA tables
1036 changes. When this option is active, BIRD activates automatic reload of
1037 affected channels whenever ROA tables are updated (after a short settle
1038 time). When disabled, route reloads have to be requested manually. The
1039 option is ignored if <cf/roa_check()/ is not used in channel filters.
1040 Note that for BGP channels, automatic reload requires
1041 <ref id="bgp-import-table" name="import table"> or
1042 <ref id="bgp-export-table" name="export table"> (for respective
1043 direction). Default: on.
1045 <tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
1046 Specify an import route limit (a maximum number of routes imported from
1047 the protocol) and optionally the action to be taken when the limit is
1048 hit. Warn action just prints warning log message. Block action discards
1049 new routes coming from the protocol. Restart and disable actions shut
1050 the protocol down like appropriate commands. Disable is the default
1051 action if an action is not explicitly specified. Note that limits are
1052 reset during protocol reconfigure, reload or restart. Default: <cf/off/.
1054 <tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
1055 Specify an receive route limit (a maximum number of routes received from
1056 the protocol and remembered). It works almost identically to <cf>import
1057 limit</cf> option, the only difference is that if <cf/import keep
1058 filtered/ option is active, filtered routes are counted towards the
1059 limit and blocked routes are forgotten, as the main purpose of the
1060 receive limit is to protect routing tables from overflow. Import limit,
1061 on the contrary, counts accepted routes only and routes blocked by the
1062 limit are handled like filtered routes. Default: <cf/off/.
1064 <tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
1065 Specify an export route limit, works similarly to the <cf>import
1066 limit</cf> option, but for the routes exported to the protocol. This
1067 option is experimental, there are some problems in details of its
1068 behavior -- the number of exported routes can temporarily exceed the
1069 limit without triggering it during protocol reload, exported routes
1070 counter ignores route blocking and block action also blocks route
1071 updates of already accepted routes -- and these details will probably
1072 change in the future. Default: <cf/off/.
1075 <p>This is a trivial example of RIP configured for IPv6 on all interfaces:
1083 <p>This is a non-trivial example.
1088 import filter { ... };
1089 export filter { ... };
1096 <p>And this is even more complicated example using templates.
1099 local 198.51.100.14 as 65000;
1103 import filter { ... };
1108 import filter { ... };
1114 neighbor 198.51.100.130 as 64496;
1116 # IPv4 channel is inherited as-is, while IPv6
1117 # channel is adjusted by export filter option
1119 export filter { ... };
1126 <label id="mpls-opts">
1128 <p>The MPLS domain definition is mandatory for a MPLS router. All MPLS channels
1129 and MPLS-aware protocols are associated with some MPLS domain (although usually
1130 implicitly with the sole one). In the MPLS domain definition you can configure
1131 details of MPLS label allocation. Currently, there is just one option,
1134 <p>Note that the MPLS subsystem is experimental, it is likely that there will be
1135 some backward-incompatible changes in the future.
1138 <tag><label id="mpls-domain-label-range">label range <m/name/ { start <m/number/; length <m/number/; [<m/.../] }</tag>
1139 Define a new label range, or redefine implicit label ranges <cf/static/
1140 and <cf/dynamic/. MPLS channels use configured label ranges for dynamic
1141 label allocation, while <cf/static/ label range is used for static label
1142 allocation. The label range definition must specify the extent of the
1143 range. By default, the range <cf/static/ is 16-1000, while the range
1144 <cf/dynamic/ is 1000-10000.
1147 <p>MPLS channel should be defined in each MPLS-aware protocol in addition to its
1148 regular channels. It is responsible for label allocation and for announcing MPLS
1149 routes to the MPLS routing table. Besides common <ref id="channel-opts"
1150 name="channel options">, MPLS channels have some specific options:
1153 <tag><label id="mpls-channel-domain">domain <m/name/</tag>
1154 Specify a MPLS domain to which this channel and protocol belongs.
1155 Default: The first defined MPLS domain.
1157 <tag><label id="mpls-channel-label-range">label range <m/name/</tag>
1158 Use specific label range for dynamic label allocation. Note that static
1159 labels always use the range <cf/static/. Default: the range <cf/dynamic/.
1161 <tag><label id="mpls-channel-label-policy">label policy static|prefix|aggregate|vrf</tag>
1162 Label policy specifies how routes are grouped to forwarding equivalence
1163 classes (FECs) and how labels are assigned to them.
1165 The policy <cf/static/ means no dynamic label allocation is done, and
1166 static labels must be set in import filters using the route attribute
1167 <ref id="rta-mpls-label" name="mpls_label">.
1169 The policy <cf/prefix/ means each prefix uses separate label associated
1170 with that prefix. When a labeled route is updated, it keeps the label.
1171 This policy is appropriate for IGPs.
1173 The policy <cf/aggregate/ means routes are grouped to FECs according to
1174 their next hops (including next hop labels), and one label is used for
1175 all routes in the same FEC. When a labeled route is updated, it may
1176 change next hop, change FEC and therefore change label. This policy is
1177 appropriate for BGP.
1179 The policy <cf/vrf/ is only valid in L3VPN protocols. It uses one label
1180 for all routes from a VRF, while replacing the original next hop with
1183 Default: <cf/prefix/.
1186 <p>This is a trivial example of MPLS setup:
1189 label range bgprange { start 2000; length 1000; };
1198 route 2001:db8:1:1/64 mpls 100 via 2001:db8:1:2::1/64 mpls 200;
1210 label range bgprange;
1211 label policy aggregate;
1219 <chapt>Remote control
1220 <label id="remote-control">
1222 <p>You can use the command-line client <file>birdc</file> to talk with a running
1223 BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
1224 changed with the <tt/-s/ option given to both the server and the client). The
1225 commands can perform simple actions such as enabling/disabling of protocols,
1226 telling BIRD to show various information, telling it to show routing table
1227 filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
1228 get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
1229 client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
1230 be passed to the client, to make it dump numeric return codes along with the
1231 messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
1232 own applications could do that, too -- the format of communication between BIRD
1233 and <file/birdc/ is stable (see the programmer's documentation).
1235 <p>There is also lightweight variant of BIRD client called <file/birdcl/, which
1236 does not support command line editing and history and has minimal dependencies.
1237 This is useful for running BIRD in resource constrained environments, where
1238 Readline library (required for regular BIRD client) is not available.
1240 <p>Many commands have the <m/name/ of the protocol instance as an argument.
1241 This argument can be omitted if there exists only a single instance.
1243 <p>Here is a brief list of supported functions:
1246 <tag><label id="cli-show-status">show status</tag>
1247 Show router status, that is BIRD version, uptime and time from last
1250 <tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
1251 Show the list of interfaces. For each interface, print its type, state,
1252 MTU and addresses assigned.
1254 <tag><label id="cli-show-protocols">show protocols [all]</tag>
1255 Show list of protocol instances along with tables they are connected to
1256 and protocol status, possibly giving verbose information, if <cf/all/ is
1259 <!-- TODO: Move these protocol-specific remote control commands to the protocol sections -->
1260 <tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
1261 Show detailed information about OSPF interfaces.
1263 <tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
1264 Show a list of OSPF neighbors and a state of adjacency to them.
1266 <tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
1267 Show detailed information about OSPF areas based on a content of the
1268 link-state database. It shows network topology, stub networks,
1269 aggregated networks and routers from other areas and external routes.
1270 The command shows information about reachable network nodes, use option
1271 <cf/all/ to show information about all network nodes in the link-state
1274 <tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
1275 Show a topology of OSPF areas based on a content of the link-state
1276 database. It is just a stripped-down version of 'show ospf state'.
1278 <tag><label id="cli-show-ospf-lsadb">show ospf lsadb [global | area <m/id/ | link] [type <m/num/] [lsid <m/id/] [self | router <m/id/] [<m/name/] </tag>
1279 Show contents of an OSPF LSA database. Options could be used to filter
1282 <tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
1283 Show detailed information about RIP interfaces.
1285 <tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
1286 Show a list of RIP neighbors and associated state.
1288 <tag><label id="cli-show-static">show static [<m/name/]</tag>
1289 Show detailed information about static routes.
1291 <tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/] [address (<m/IP/|<m/prefix/)] [(interface|dev) "<m/name/"] [ipv4|ipv6] [direct|multihop] [all]</tag>
1292 Show information about BFD sessions. Options could be used to filter
1293 entries, or in the case of the option <cf/all/ to give verbose output.
1295 <tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
1296 Show the list of symbols defined in the configuration (names of
1297 protocols, routing tables etc.).
1299 <tag><label id="cli-show-route">show route [[(for|in)] <m/prefix/|for <m/IP/] [table (<m/t/|all)] [(import|export) table <m/p/.<m/c/] [filter <m/f/|where <m/cond/] [(export|preexport|noexport) <m/p/] [protocol <m/p/] [(stats|count)] [<m/options/]</tag>
1300 Show contents of specified routing tables, that is routes, their metrics
1301 and (in case the <cf/all/ switch is given) all their attributes.
1303 <p>You can specify a <m/prefix/ if you want to print routes for a
1304 specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
1305 the entry which will be used for forwarding of packets to the given
1306 destination. Finally, if you use <cf>in <m/prefix/</cf>, you get all
1307 prefixes covered by the given prefix.
1308 By default, all routes for each network are printed with
1309 the selected one at the top, unless <cf/primary/ is given in which case
1310 only the selected route is shown.
1312 <p>The <cf/show route/ command can process one or multiple routing
1313 tables. The set of selected tables is determined on three levels: First,
1314 tables can be explicitly selected by <cf/table/ switch, which could be
1315 used multiple times, all tables are specified by <cf/table all/. Second,
1316 tables can be implicitly selected by channels or protocols that are
1317 arguments of several other switches (e.g., <cf/export/, <cf/protocol/).
1318 Last, the set of default tables is used: <cf/master4/, <cf/master6/ and
1319 each first table of any other network type.
1321 <p>There are internal tables when <cf/(import|export) table/ options
1322 are used for some channels. They can be selected explicitly with
1323 <cf/(import|export) table/ switch, specifying protocol <m/p/ and
1326 <p>You can also ask for printing only routes processed and accepted by
1327 a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
1328 </cf> or matching a given condition (<cf>where <m/condition/</cf>).
1330 The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
1331 printing of routes that are exported to the specified protocol or
1332 channel. With <cf/preexport/, the export filter of the channel is
1333 skipped. With <cf/noexport/, routes rejected by the export filter are
1334 printed instead. Note that routes not exported for other reasons
1335 (e.g. secondary routes or routes imported from that protocol) are not
1336 printed even with <cf/noexport/. These switches also imply that
1337 associated routing tables are selected instead of default ones.
1339 <p>You can also select just routes added by a specific protocol.
1340 <cf>protocol <m/p/</cf>. This switch also implies that associated
1341 routing tables are selected instead of default ones.
1343 <p>If BIRD is configured to keep filtered routes (see <cf/import keep
1344 filtered/ option), you can show them instead of routes by using
1345 <cf/filtered/ switch.
1347 <p>The <cf/stats/ switch requests showing of route statistics (the
1348 number of networks, number of routes before and after filtering). If
1349 you use <cf/count/ instead, only the statistics will be printed.
1351 <tag><label id="cli-mrt-dump">mrt dump table <m/name/|"<m/pattern/" to "<m/filename/" [filter <m/f/|where <m/c/]</tag>
1352 Dump content of a routing table to a specified file in MRT table dump
1353 format. See <ref id="mrt" name="MRT protocol"> for details.
1355 <tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
1356 Reload configuration from a given file. BIRD will smoothly switch itself
1357 to the new configuration, protocols are reconfigured if possible,
1358 restarted otherwise. Changes in filters usually lead to restart of
1361 The previous configuration is saved and the user can switch back to it
1362 with <ref id="cli-configure-undo" name="configure undo"> command. The
1363 old saved configuration is released (even if the reconfiguration attempt
1364 fails due to e.g. a syntax error).
1366 If <cf/soft/ option is used, changes in filters does not cause BIRD to
1367 restart affected protocols, therefore already accepted routes (according
1368 to old filters) would be still propagated, but new routes would be
1369 processed according to the new filters.
1371 If <cf/timeout/ option is used, config timer is activated. The new
1372 configuration could be either confirmed using <cf/configure confirm/
1373 command, or it will be reverted to the old one when the config timer
1374 expires. This is useful for cases when reconfiguration breaks current
1375 routing and a router becomes inaccessible for an administrator. The
1376 config timeout expiration is equivalent to <cf/configure undo/
1377 command. The timeout duration could be specified, default is 300 s.
1379 <tag><label id="cli-configure-confirm">configure confirm</tag>
1380 Deactivate the config undo timer and therefore confirm the current
1383 <tag><label id="cli-configure-undo">configure undo</tag>
1384 Undo the last configuration change and smoothly switch back to the
1385 previous (stored) configuration. If the last configuration change was
1386 soft, the undo change is also soft. There is only one level of undo, but
1387 in some specific cases when several reconfiguration requests are given
1388 immediately in a row and the intermediate ones are skipped then the undo
1389 also skips them back.
1391 <tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
1392 Read and parse given config file, but do not use it. useful for checking
1393 syntactic and some semantic validity of an config file.
1395 <tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
1396 Enable, disable or restart a given protocol instance, instances matching
1397 the <cf><m/pattern/</cf> or <cf/all/ instances.
1399 <tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
1400 Reload a given protocol instance, that means re-import routes from the
1401 protocol instance and re-export preferred routes to the instance. If
1402 <cf/in/ or <cf/out/ options are used, the command is restricted to one
1403 direction (re-import or re-export).
1405 This command is useful if appropriate filters have changed but the
1406 protocol instance was not restarted (or reloaded), therefore it still
1407 propagates the old set of routes. For example when <cf/configure soft/
1408 command was used to change filters.
1410 Re-export always succeeds, but re-import is protocol-dependent and might
1411 fail (for example, if BGP neighbor does not support route-refresh
1412 extension). In that case, re-export is also skipped. Note that for the
1413 pipe protocol, both directions are always reloaded together (<cf/in/ or
1414 <cf/out/ options are ignored in that case).
1416 <tag><label id="cli-down">down</tag>
1419 <tag><label id="cli-graceful-restart">graceful restart</tag>
1420 Shut BIRD down for graceful restart. See <ref id="graceful-restart"
1421 name="graceful restart"> section for details.
1423 <tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
1424 Control protocol debugging.
1426 <tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
1427 Dump contents of internal data structures to the debugging output.
1429 <tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
1430 Control echoing of log messages to the command-line output.
1431 See <ref id="opt-log" name="log option"> for a list of log classes.
1433 <tag><label id="cli-eval">eval <m/expr/</tag>
1434 Evaluate given expression.
1439 <label id="filters">
1442 <label id="filters-intro">
1444 <p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
1445 There are two objects in this language: filters and functions. Filters are
1446 interpreted by BIRD core when a route is being passed between protocols and
1447 routing tables. The filter language contains control structures such as if's and
1448 switches, but it allows no loops. An example of a filter using many features can
1449 be found in <file>filter/test.conf</file>.
1451 <p>Filter gets the route, looks at its attributes and modifies some of them if
1452 it wishes. At the end, it decides whether to pass the changed route through
1453 (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
1460 if defined( rip_metric ) then
1466 if rip_metric > 10 then
1467 reject "RIP metric is too big";
1473 <p>As you can see, a filter has a header, a list of local variables, and a body.
1474 The header consists of the <cf/filter/ keyword followed by a (unique) name of
1475 filter. The list of local variables consists of <cf><M>type name</M>;</cf>
1476 pairs where each pair declares one local variable. The body consists of <cf>
1477 { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
1478 can group several statements to a single compound statement by using braces
1479 (<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
1480 block of code conditional.
1482 <p>BIRD supports functions, so that you don not have to repeat the same blocks
1483 of code over and over. Functions can have zero or more parameters and they can
1484 have local variables. If the function returns value, then you should always
1485 specify its return type. Direct recursion is possible. Function definitions look
1489 function name() -> int
1492 int another_variable = 5;
1496 function with_parameters(int parameter) -> pair
1503 <p>Like in C programming language, variables are declared inside function body,
1504 either at the beginning, or mixed with other statements. Declarations may
1505 contain initialization. You can also declare variables in nested blocks, such
1506 variables have scope restricted to such block. There is a deprecated syntax to
1507 declare variables after the <cf/function/ line, but before the first <cf/{/.
1508 Functions are called like in C: <cf>name(); with_parameters(5);</cf>. Function
1509 may return values using the <cf>return <m/[expr]/</cf> command. Returning a
1510 value exits from current function (this is similar to C).
1512 <p>Filters are defined in a way similar to functions except they cannot have
1513 explicit parameters and cannot return. They get a route table entry as an implicit parameter, it
1514 is also passed automatically to any functions called. The filter must terminate
1515 with either <cf/accept/ or <cf/reject/ statement. If there is a runtime error in
1516 filter, the route is rejected.
1518 <p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1519 from the command line client. An example session might look like:
1522 pavel@bug:~/bird$ ./birdc -s bird.ctl
1525 10.0.0.0/8 dev eth0 [direct1 23:21] (240)
1526 195.113.30.2/32 dev tunl1 [direct1 23:21] (240)
1527 127.0.0.0/8 dev lo [direct1 23:21] (240)
1529 show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1530 bird> show route filter { if 127.0.0.5 ˜ net then accept; }
1531 127.0.0.0/8 dev lo [direct1 23:21] (240)
1537 <label id="data-types">
1539 <p>Each variable and each value has certain type. Booleans, integers and enums
1540 are incompatible with each other (that is to prevent you from shooting oneself
1544 <tag><label id="type-bool">bool</tag>
1545 This is a boolean type, it can have only two values, <cf/true/ and
1546 <cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1548 <tag><label id="type-int">int</tag>
1549 This is a general integer type. It is an unsigned 32bit type; i.e., you
1550 can expect it to store values from 0 to 4294967295. Overflows are not
1551 checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1553 <tag><label id="type-pair">pair</tag>
1554 This is a pair of two short integers. Each component can have values
1555 from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1556 The same syntax can also be used to construct a pair from two arbitrary
1557 integer expressions (for example <cf/(1+2,a)/).
1559 Operators <cf/.asn/ and <cf/.data/ can be used to extract corresponding
1560 components of a pair: <cf>(<m/asn/, <m/data/)</cf>.
1562 <tag><label id="type-quad">quad</tag>
1563 This is a dotted quad of numbers used to represent router IDs (and
1564 others). Each component can have a value from 0 to 255. Literals of
1565 this type are written like IPv4 addresses.
1567 <tag><label id="type-string">string</tag>
1568 This is a string of characters. There are no ways to modify strings in
1569 filters. You can pass them between functions, assign them to variables
1570 of type <cf/string/, print such variables, use standard string
1571 comparison operations (e.g. <cf/=, !=, <, >, <=, >=/), but
1572 you can't concatenate two strings. String literals are written as
1573 <cf/"This is a string constant"/. Additionally matching (<cf/˜,
1574 !˜/) operators could be used to match a string value against
1575 a shell pattern (represented also as a string).
1577 <tag><label id="type-bytestring">bytestring</tag>
1578 This is a sequences of arbitrary bytes. There are no ways to modify
1579 bytestrings in filters. You can pass them between function, assign
1580 them to variables of type <cf/bytestring/, print such values,
1581 compare bytestings (<cf/=, !=/).
1583 Bytestring literals are written as a sequence of hexadecimal digit
1584 pairs, optionally colon-separated. A bytestring specified this way
1585 must be either at least 16 bytes (32 digits) long, or prefixed by the
1586 <cf/hex:/ prefix: <cf/01:23:45:67:89:ab:cd:ef:01:23:45:67:89:ab:cd:ef/,
1587 <cf/0123456789abcdef0123456789abcdef/, <cf/hex:/, <cf/hex:12:34:56/,
1590 A bytestring can be made from a hex string using <cf/from_hex()/
1591 function. Source strings can use any number of dots, colons, hyphens
1592 and spaces as byte separators: <cf/from_hex(" 12.34 56:78 ab-cd-ef ")/.
1594 <tag><label id="type-ip">ip</tag>
1595 This type can hold a single IP address. The IPv4 addresses are stored as
1596 IPv4-Mapped IPv6 addresses so one data type for both of them is used.
1597 Whether the address is IPv4 or not may be checked by <cf>.is_v4</cf>
1598 which returns a <cf/bool/. IP addresses are written in the standard
1599 notation (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special
1600 operator <cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out
1601 all but first <cf><M>num</M></cf> bits from the IP address. So
1602 <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1604 <tag><label id="type-prefix">prefix</tag>
1605 This type can hold a network prefix consisting of IP address, prefix
1606 length and several other values. This is the key in route tables.
1608 Prefixes may be of several types, which can be determined by the special
1609 operator <cf/.type/. The type may be:
1611 <cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
1612 are written as <cf><m/ipaddress//<m/pxlen/</cf>. There are two special
1613 operators on these: <cf/.ip/ which extracts the IP address from the
1614 pair, and <cf/.len/, which separates prefix length from the pair.
1615 So <cf>1.2.0.0/16.len = 16</cf> is true.
1617 <cf/NET_IP6_SADR/ nettype holds both destination and source IPv6
1618 prefix. The literals are written as <cf><m/ipaddress//<m/pxlen/ from
1619 <m/ipaddress//<m/pxlen/</cf>, where the first part is the destination
1620 prefix and the second art is the source prefix. They support the same
1621 operators as IP prefixes, but just for the destination part. They also
1622 support <cf/.src/ and <cf/.dst/ operators to get respective parts of the
1623 address as separate <cf/NET_IP6/ values.
1625 <cf/NET_VPN4/ and <cf/NET_VPN6/ prefixes hold an IP prefix with VPN
1626 Route Distinguisher (<rfc id="4364">). They support the same special
1627 operators as IP prefixes, and also <cf/.rd/ which extracts the Route
1628 Distinguisher. Their literals are written
1629 as <cf><m/vpnrd/ <m/ipprefix/</cf>
1631 <cf/NET_ROA4/ and <cf/NET_ROA6/ prefixes hold an IP prefix range
1632 together with an ASN. They support the same special operators as IP
1633 prefixes, and also <cf/.maxlen/ which extracts maximal prefix length,
1634 and <cf/.asn/ which extracts the ASN.
1636 <cf/NET_FLOW4/ and <cf/NET_FLOW6/ hold an IP prefix together with a
1637 flowspec rule. Filters currently do not support much flowspec parsing,
1638 only <cf/.src/ and <cf/.dst/ operators to get source and destination
1639 parts of the flowspec as separate <cf/NET_IP4/ / <cf/NET_IP6/ values.
1641 <cf/NET_MPLS/ holds a single MPLS label and its handling is currently
1644 <tag><label id="type-vpnrd">vpnrd</tag>
1645 This is a route distinguisher according to <rfc id="4364">. There are
1646 three kinds of RD's: <cf><m/asn/:<m/32bit int/</cf>, <cf><m/asn4/:<m/16bit int/</cf>
1647 and <cf><m/IPv4 address/:<m/32bit int/</cf>
1649 <tag><label id="type-ec">ec</tag>
1650 This is a specialized type used to represent BGP extended community
1651 values. It is essentially a 64bit value, literals of this type are
1652 usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1653 <cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1654 route target / route origin communities), the format and possible values
1655 of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1656 used kind. Similarly to pairs, ECs can be constructed using expressions
1657 for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1658 <cf/myas/ is an integer variable).
1660 <tag><label id="type-lc">lc</tag>
1661 This is a specialized type used to represent BGP large community
1662 values. It is essentially a triplet of 32bit values, where the first
1663 value is reserved for the AS number of the issuer, while meaning of
1664 remaining parts is defined by the issuer. Literals of this type are
1665 written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1666 pairs, LCs can be constructed using expressions for its parts, (e.g.
1667 <cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1669 Operators <cf/.asn/, <cf/.data1/, and <cf/.data2/ can be used
1670 to extract corresponding components of LCs:
1671 <cf>(<m/asn/, <m/data1/, <m/data2/)</cf>.
1673 <tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1674 Filters recognize four types of sets. Sets are similar to strings: you
1675 can pass them around but you can't modify them. Literals of type <cf>int
1676 set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1677 values and ranges are permitted in sets.
1679 For pair sets, expressions like <cf/(123,*)/ can be used to denote
1680 ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1681 <cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1682 <cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1683 such expressions are translated to a set of intervals, which may be
1684 memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1685 (1,4..20), (2,4..20), ... (65535, 4..20)/.
1687 EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1688 10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1689 (like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1692 Also LC sets use similar expressions like pair sets. You can use ranges
1693 and wildcards, but if one field uses that, more specific (later) fields
1694 must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1695 is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1698 You can also use expressions for int, pair, EC and LC set values.
1699 However, it must be possible to evaluate these expressions before daemon
1700 boots. So you can use only constants inside them. E.g.
1709 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1710 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1711 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1714 Sets of prefixes are special: their literals does not allow ranges, but
1715 allows prefix patterns that are written
1716 as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1717 Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1718 pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1719 first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1720 identical and <cf>l <= len1 <= h</cf>. A valid prefix pattern
1721 has to satisfy <cf>low <= high</cf>, but <cf/pxlen/ is not
1722 constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1723 prefix set literal if it matches any prefix pattern in the prefix set
1726 There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1727 is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1728 (where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1729 network prefix <cf><m/address//<m/len/</cf> and all its subnets.
1730 <cf><m/address//<m/len/-</cf> is a shorthand for
1731 <cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1732 <cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1735 For example, <cf>[ 1.0.0.0/8, 2.0.0.0/8+, 3.0.0.0/8-, 4.0.0.0/8{16,24}
1736 ]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1737 <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1738 <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1739 matches all prefixes (regardless of IP address) whose prefix length is
1740 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1741 address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{15,17} ]</cf>
1742 is true, but <cf>1.0.0.0/16 ˜ [ 1.0.0.0/8- ]</cf> is false.
1744 Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1745 in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1746 <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1747 <cf>192.168.0.0/16{24,32}</cf>.
1749 It is not possible to mix IPv4 and IPv6 prefixes in a prefix set. It is
1750 currently possible to mix IPv4 and IPv6 addresses in an ip set, but that
1751 behavior may change between versions without any warning; don't do it
1752 unless you are more than sure what you are doing. (Really, don't do it.)
1754 <tag><label id="type-enum">enum</tag>
1755 Enumeration types are fixed sets of possibilities. You can't define your
1756 own variables of such type, but some route attributes are of enumeration
1757 type. Enumeration types are incompatible with each other.
1759 <tag><label id="type-bgppath">bgppath</tag>
1760 BGP path is a list of autonomous system numbers. You can't write
1761 literals of this type. There are several special operators on bgppaths:
1763 <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1765 <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1767 <cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1769 Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1770 ASN, for example if the path contains an AS set element as the first (or
1771 the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1772 may be used to get last ASN before any AS set.
1774 <cf><m/P/.len</cf> returns the length of path <m/P/.
1776 <cf><m/P/.empty</cf> makes the path <m/P/ empty. Can't be used as a value, always modifies the object.
1778 <cf><m/P/.prepend(<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1781 <cf><m/P/.delete(<m/A/)</cf> deletes all instances of ASN <m/A/ from
1782 from path <m/P/ and returns the result. <m/A/ may also be an integer
1783 set, in that case the operator deletes all ASNs from path <m/P/ that are
1784 also members of set <m/A/.
1786 <cf><m/P/.filter(<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1787 not members of integer set <m/A/, and returns the result.
1788 I.e., <cf/filter/ do the same as <cf/delete/ with inverted set <m/A/.
1790 Methods <cf>prepend</cf>, <cf>delete</cf> and <cf>filter</cf> keep the
1791 original object intact as long as you use the result in any way. You can
1792 also write e.g. <cf><m/P/.prepend(<m/A/);</cf> as a standalone statement.
1793 This variant does modify the original object with the result of the operation.
1795 <tag><label id="type-bgpmask">bgpmask</tag>
1796 BGP masks are patterns used for BGP path matching (using <cf>path
1797 ˜ [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1798 as used by UNIX shells. Autonomous system numbers match themselves,
1799 <cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1800 <cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1801 is 4 3 2 1, then: <tt>bgp_path ˜ [= * 4 3 * =]</tt> is true,
1802 but <tt>bgp_path ˜ [= * 4 5 * =]</tt> is false. There is also
1803 <cf/+/ operator which matches one or multiple instances of previous
1804 expression, e.g. <tt>[= 1 2+ 3 =]</tt> matches both path 1 2 3 and path
1805 1 2 2 2 3, but not 1 3 nor 1 2 4 3. Note that while <cf/*/ and <cf/?/
1806 are wildcard-style operators, <cf/+/ is regex-style operator.
1808 BGP mask expressions can also contain integer expressions enclosed in
1809 parenthesis and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>.
1810 You can also use ranges (e.g. <tt>[= * 3..5 2 100..200 * =]</tt>)
1811 and sets (e.g. <tt>[= 1 2 [3, 5, 7] * =]</tt>).
1813 <tag><label id="type-clist">clist</tag>
1814 Clist is similar to a set, except that unlike other sets, it can be
1815 modified. The type is used for community list (a set of pairs) and for
1816 cluster list (a set of quads). There exist no literals of this type.
1817 There are special operators on clists:
1819 <cf><m/C/.len</cf> returns the length of clist <m/C/.
1821 <cf><m/C/.empty</cf> makes the list <m/C/ empty. Can't be used as a value, always modifies the object.
1823 <cf><m/C/.add(<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1824 returns the result. If item <m/P/ is already in clist <m/C/, it does
1825 nothing. <m/P/ may also be a clist, in that case all its members are
1826 added; i.e., it works as clist union.
1828 <cf><m/C/.delete(<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1829 <m/C/ and returns the result. If clist <m/C/ does not contain item
1830 <m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1831 case the operator deletes all items from clist <m/C/ that are also
1832 members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1833 analogously; i.e., it works as clist difference.
1835 <cf><m/C/.filter(<m/P/)</cf> deletes all items from clist <m/C/ that are
1836 not members of pair (or quad) set <m/P/, and returns the result. I.e., <cf/filter/ do the same
1837 as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1838 works analogously; i.e., it works as clist intersection.
1840 Methods <cf>add</cf>, <cf>delete</cf> and <cf>filter</cf> keep the
1841 original object intact as long as you use the result in any way. You can
1842 also write e.g. <cf><m/P/.add(<m/A/);</cf> as a standalone statement.
1843 This variant does modify the original object with the result of the operation.
1845 <cf><m/C/.min</cf> returns the minimum element of clist <m/C/.
1847 <cf><m/C/.max</cf> returns the maximum element of clist <m/C/.
1849 Operators <cf/.min/, <cf/.max/ can be used together with <cf/filter/
1850 to extract the community from the specific subset of communities
1851 (e.g. localpref or prepend) without the need to check every possible
1852 value (e.g. <cf/filter(bgp_community, [(23456, 1000..1099)]).min/).
1854 <tag><label id="type-eclist">eclist</tag>
1855 Eclist is a data type used for BGP extended community lists. Eclists
1856 are very similar to clists, but they are sets of ECs instead of pairs.
1857 The same operations (like <cf/add/, <cf/delete/ or <cf/˜/ and
1858 <cf/!˜/ membership operators) can be used to modify or test
1859 eclists, with ECs instead of pairs as arguments.
1861 <tag><label id="type-lclist">lclist</tag>
1862 Lclist is a data type used for BGP large community lists. Like eclists,
1863 lclists are very similar to clists, but they are sets of LCs instead of
1864 pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/˜/
1865 and <cf/!˜/ membership operators) can be used to modify or test
1866 lclists, with LCs instead of pairs as arguments.
1871 <label id="operators">
1873 <p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1874 parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a<b, a>=b)/.
1875 Logical operations include unary not (<cf/!/), and (<cf/&&/), and or
1876 (<cf/||/). Special operators include (<cf/˜/,
1877 <cf/!˜/) for "is (not) element of a set" operation - it can be used on
1878 element and set of elements of the same type (returning true if element is
1879 contained in the given set), or on two strings (returning true if first string
1880 matches a shell-like pattern stored in second string) or on IP and prefix
1881 (returning true if IP is within the range defined by that prefix), or on prefix
1882 and prefix (returning true if first prefix is more specific than second one) or
1883 on bgppath and bgpmask (returning true if the path matches the mask) or on
1884 number and bgppath (returning true if the number is in the path) or on bgppath
1885 and int (number) set (returning true if any ASN from the path is in the set) or
1886 on pair/quad and clist (returning true if the pair/quad is element of the
1887 clist) or on clist and pair/quad set (returning true if there is an element of
1888 the clist that is also a member of the pair/quad set).
1890 <p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1891 examines a ROA table and does <rfc id="6483"> route origin validation for a
1892 given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1893 checks the current route (which should be from BGP to have AS_PATH argument) in
1894 the specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1895 ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1896 ROAs but none of them match. There is also an extended variant
1897 <cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1898 prefix and an ASN as arguments.
1901 <sect>Control structures
1902 <label id="control-structures">
1904 <p>Filters support several control structures: conditions, for loops and case
1907 <p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/commandT/;
1908 else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/;
1909 <M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1910 omitted. If the <cf><m>boolean expression</m></cf> is true, <m/commandT/ is
1911 executed, otherwise <m/commandF/ is executed.
1913 <p>For loops allow to iterate over elements in compound data like BGP paths or
1914 community lists. The syntax is: <cf>for [ <m/type/ ] <m/variable/ in <m/expr/
1915 do <m/command/;</cf> and you can also use compound command like in conditions.
1916 The expression is evaluated to a compound data, then for each element from such
1917 data the command is executed with the item assigned to the variable. A variable
1918 may be an existing one (when just name is used) or a locally defined (when type
1919 and name is used). In both cases, it must have the same type as elements.
1921 <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1922 <m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1923 ... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1924 on the left side of the ˜ operator and anything that could be a member of
1925 a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1926 grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1927 between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1928 neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1930 <p>Here is example that uses <cf/if/ and <cf/case/ structures:
1933 if 1234 = i then printn "."; else {
1935 print "You need {} around multiple commands";
1938 for int asn in bgp_path do {
1939 printn "ASN: ", asn;
1940 if asn < 65536 then print " (2B)"; else print " (4B)";
1944 2: print "two"; print "I can do more commands without {}";
1945 3 .. 5: print "three to five";
1946 else: print "something else";
1951 <sect>Route attributes
1952 <label id="route-attributes">
1954 <p>A filter is implicitly passed a route, and it can access its attributes just
1955 like it accesses variables. There are common route attributes, protocol-specific
1956 route attributes and custom route attributes. Most common attributes are
1957 mandatory (always defined), while remaining are optional. Attempts to access
1958 undefined attribute result in a runtime error; you can check if an attribute is
1959 defined by using the <cf>defined( <m>attribute</m> )</cf> operator. One notable
1960 exception to this rule are attributes of bgppath and *clist types, where
1961 undefined value is regarded as empty bgppath/*clist for most purposes.
1963 Attributes can be defined by just setting them in filters. Custom attributes
1964 have to be first declared by <ref id="opt-attribute" name="attribute"> global
1965 option. You can also undefine optional attribute back to non-existence by using
1966 the <cf>unset( <m/attribute/ )</cf> operator.
1968 Common route attributes are:
1971 <tag><label id="rta-net"><m/prefix/ net</tag>
1972 The network prefix or anything else the route is talking about. The
1973 primary key of the routing table. Read-only. (See the <ref id="routes"
1974 name="chapter about routes">.)
1976 <tag><label id="rta-scope"><m/enum/ scope</tag>
1977 The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1978 local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1979 link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1980 <cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1981 interpreted by BIRD and can be used to mark routes in filters. The
1982 default value for new routes is <cf/SCOPE_UNIVERSE/.
1984 <tag><label id="rta-preference"><m/int/ preference</tag>
1985 Preference of the route. Valid values are 0-65535. (See the chapter
1986 about routing tables.)
1988 <tag><label id="rta-from"><m/ip/ from</tag>
1989 The router which the route has originated from.
1991 <tag><label id="rta-gw"><m/ip/ gw</tag>
1992 Next hop packets routed using this route should be forwarded to.
1994 <tag><label id="rta-proto"><m/string/ proto</tag>
1995 The name of the protocol which the route has been imported from.
1998 <tag><label id="rta-source"><m/enum/ source</tag>
1999 what protocol has told me about this route. Possible values:
2000 <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
2001 <cf/RTS_RIP/, <cf/RTS_OSPF/, <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/,
2002 <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/, <cf/RTS_PIPE/, <cf/RTS_BABEL/.
2004 <tag><label id="rta-dest"><m/enum/ dest</tag>
2005 Type of destination the packets should be sent to
2006 (<cf/RTD_ROUTER/ for forwarding to a neighboring router,
2007 <cf/RTD_DEVICE/ for routing to a directly-connected network,
2008 <cf/RTD_MULTIPATH/ for multipath destinations,
2009 <cf/RTD_BLACKHOLE/ for packets to be silently discarded,
2010 <cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
2011 returned with ICMP host unreachable / ICMP administratively prohibited
2012 messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
2013 <cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
2015 <tag><label id="rta-ifname"><m/string/ ifname</tag>
2016 Name of the outgoing interface. Sink routes (like blackhole, unreachable
2017 or prohibit) and multipath routes have no interface associated with
2018 them, so <cf/ifname/ returns an empty string for such routes. Setting it
2019 would also change route to a direct one (remove gateway).
2021 <tag><label id="rta-ifindex"><m/int/ ifindex</tag>
2022 Index of the outgoing interface. System wide index of the interface. May
2023 be used for interface matching, however indexes might change on interface
2024 creation/removal. Zero is returned for routes with undefined outgoing
2025 interfaces. Read-only.
2027 <tag><label id="rta-onlink"><m/bool/ onlink</tag>
2028 Onlink flag means that the specified nexthop is accessible on the
2029 interface regardless of IP prefixes configured on the interface.
2030 The attribute can be used to configure such next hops by first setting
2031 <cf/onlink = true/ and <cf/ifname/, and then setting <cf/gw/. Possible
2032 use case for setting this flag is to automatically build overlay IP-IP
2035 <tag><label id="rta-weight"><m/int/ weight</tag>
2036 Multipath weight of route next hops. Valid values are 1-256. Reading
2037 returns the weight of the first next hop, setting it sets weights of all
2038 next hops to the specified value. Therefore, this attribute is not much
2039 useful for manipulating individual next hops of an ECMP route, but can
2040 be used in BGP multipath setup to set weights of individual routes that
2041 are merged to one ECMP route during export to the Kernel protocol
2042 (with active <ref id="krt-merge-paths" name="marge paths"> option).
2044 <tag><label id="rta-gw-mpls"><m/int/ gw_mpls</tag>
2045 Outgoing MPLS label attached to route (i.e., incoming MPLS label on the
2046 next hop router for this label-switched path). Reading returns the label
2047 value and setting it sets it to the start of the label stack. Setting
2048 implicit-NULL label (3) disables the MPLS label stack. Only the first
2049 next hop and only one label in the label stack supported right now. This
2050 is experimental option, will be likely changed in the future to handle
2051 full MPLS label stack.
2053 <tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
2054 The optional attribute that can be used to specify a distance to the
2055 network for routes that do not have a native protocol metric attribute
2056 (like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
2057 compare internal distances to boundary routers (see below).
2059 <tag><label id="rta-mpls-label"><m/int/ mpls_label</tag>
2060 Local MPLS label attached to the route. This attribute is produced by
2061 MPLS-aware protocols for labeled routes. It can also be set in import
2062 filters to assign static labels, but that also requires static MPLS
2065 <tag><label id="rta-mpls-policy"><m/enum/ mpls_policy</tag>
2066 For MPLS-aware protocols, this attribute defines which
2067 <ref id="mpls-channel-label-policy" name="MPLS label policy"> will be
2068 used for the route. It can be set in import filters to change it on
2069 per-route basis. Valid values are <cf/MPLS_POLICY_NONE/ (no label),
2070 <cf/MPLS_POLICY_STATIC/ (static label), <cf/MPLS_POLICY_PREFIX/
2071 (per-prefix label), <cf/MPLS_POLICY_AGGREGATE/ (aggregated label),
2072 and <cf/MPLS_POLICY_VRF/ (per-VRF label). See <ref
2073 id="mpls-channel-label-policy" name="MPLS label policy"> for details.
2075 <tag><label id="rta-mpls-class"><m/int/ mpls_class</tag>
2076 When <ref id="mpls-channel-label-policy" name="MPLS label policy"> is
2077 set to <cf/aggregate/, it may be useful to apply more fine-grained
2078 aggregation than just one based on next hops. When routes have different
2079 value of this attribute, they will not be aggregated under one local
2080 label even if they have the same next hops.
2083 <p>Protocol-specific route attributes are described in the corresponding
2087 <sect>Other statements
2088 <label id="other-statements">
2090 <p>The following statements are available:
2093 <tag><label id="assignment"><m/variable/ = <m/expr/</tag>
2094 Set variable (or route attribute) to a given value.
2096 <tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
2097 Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
2099 <tag><label id="return">return <m/expr/</tag>
2100 Return <cf><m>expr</m></cf> from the current function, the function ends
2103 <tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
2104 Prints given expressions; useful mainly while debugging filters. The
2105 <cf/printn/ variant does not terminate the line.
2110 <label id="protocols">
2113 <label id="aggregator">
2116 <label id="aggregator-intro">
2117 <p>The Aggregator protocol explicitly merges routes by the given rules. There
2118 are four phases of aggregation. First routes are filtered, then sorted into buckets,
2119 then buckets are merged and finally the results are filtered once again.
2120 Aggregating an already aggregated route is forbidden.
2122 <p>This is an experimental protocol, use with caution.
2124 <sect1>Configuration
2125 <label id="aggregator-config">
2127 <tag><label id="aggregator-table">table <m/table/</tag>
2128 The table from which routes are exported to get aggregated.
2130 <tag><label id="aggregator-export">export <m/.../</tag>
2131 A standard channel's <cf/export/ clause, defining which routes are accepted into aggregation.
2133 <tag><label id="aggregator-rule">aggregate on <m/expr/ | <m/attribute/ [<m/, .../]</tag>
2134 All the given filter expressions and route attributes are evaluated for each route. Then routes
2135 are sorted into buckets where <em/all/ values are the same. Note: due to performance reasons,
2136 all filter expressions must return a compact type, e.g. integer, a BGP
2137 (standard, extended, large) community or an IP address. If you need to compare e.g. modified
2138 AS Paths in the aggregation rule, you can define a custom route attribute and set this attribute
2139 in the export filter. For now, it's mandatory to say <cf/net/ here, we can't merge prefixes yet.
2141 <tag><label id="aggregation-merge">merge by { <m/filter code/ }</tag>
2142 The given filter code has an extra symbol defined: <cf/routes/. By iterating over <cf/routes/,
2143 you get all the routes in the bucket and you can construct your new route. All attributes
2144 selected in <cf/aggregate on/ are already set to the common values. For now, it's not possible
2145 to use a named filter here. You have to finalize the route by calling <cf/accept/.
2147 <tag><label id="aggregator-import">import <m/.../</tag>
2148 Filter applied to the route after <cf/merge by/. Here you can use a named filter.
2150 <tag><label id="aggregator-peer-table">peer table <m/table/</tag>
2151 The table to which aggregated routes are imported. It may be the same table
2156 <label id="aggregator-example">
2159 protocol aggregator {
2161 export where defined(bgp_path);
2162 /* Merge all routes with the same AS Path length */
2163 aggregate on net, bgp_path.len;
2165 for route r in routes do {
2166 if ! defined(bgp_path) then { bgp_path = r.bgp_path }
2167 bgp_community = bgp_community.add(r.bgp_community);
2172 peer table agr_result;
2180 <label id="babel-intro">
2182 <p>The Babel protocol
2183 (<rfc id="8966">) is a loop-avoiding distance-vector routing protocol that is
2184 robust and efficient both in ordinary wired networks and in wireless mesh
2185 networks. Babel is conceptually very simple in its operation and "just works"
2186 in its default configuration, though some configuration is possible and in some
2189 <p>The Babel protocol is dual stack; i.e., it can carry both IPv4 and IPv6
2190 routes over the same IPv6 transport. For sending and receiving Babel packets,
2191 only a link-local IPv6 address is needed.
2193 <p>BIRD implements an extension for IPv6 source-specific routing (SSR or SADR),
2194 but must be configured accordingly to use it. SADR-enabled Babel router can
2195 interoperate with non-SADR Babel router, but the later would ignore routes
2196 with specific (non-zero) source prefix.
2198 <sect1>Configuration
2199 <label id="babel-config">
2201 <p>The Babel protocol support both IPv4 and IPv6 channels; both can be
2202 configured simultaneously. It can also be configured with <ref
2203 id="ip-sadr-routes" name="IPv6 SADR"> channel instead of regular IPv6
2204 channel, in such case SADR support is enabled. Babel supports no global
2205 configuration options apart from those common to all other protocols, but
2206 supports the following per-interface configuration options:
2209 protocol babel [<name>] {
2210 ipv4 { <channel config> };
2211 ipv6 [sadr] { <channel config> };
2212 randomize router id <switch>;
2213 interface <interface pattern> {
2214 type <wired|wireless|tunnel>;
2217 hello interval <time>;
2218 update interval <time>;
2220 tx class|dscp <number>;
2221 tx priority <number>;
2224 check link <switch>;
2225 next hop ipv4 <address>;
2226 next hop ipv6 <address>;
2227 extended next hop <switch>;
2232 send timestamps <switch>;
2233 authentication none|mac [permissive];
2234 password "<text>";
2235 password "<text>" {
2237 generate from "<date>";
2238 generate to "<date>";
2239 accept from "<date>";
2240 accept to "<date>";
2241 from "<date>";
2243 algorithm ( hmac sha1 | hmac sha256 | hmac sha384 |
2244 hmac sha512 | blake2s128 | blake2s256 | blake2b256 | blake2b512 );
2251 <tag><label id="babel-channel">ipv4 | ipv6 [sadr] <m/channel config/</tag>
2252 The supported channels are IPv4, IPv6, and IPv6 SADR.
2254 <tag><label id="babel-random-router-id">randomize router id <m/switch/</tag>
2255 If enabled, Bird will randomize the top 32 bits of its router ID whenever
2256 the protocol instance starts up. If a Babel node restarts, it loses its
2257 sequence number, which can cause its routes to be rejected by peers until
2258 the state is cleared out by other nodes in the network (which can take on
2259 the order of minutes). Enabling this option causes Bird to pick a random
2260 router ID every time it starts up, which avoids this problem at the cost
2261 of not having stable router IDs in the network. Default: no.
2263 <tag><label id="babel-type">type wired|wireless|tunnel </tag>
2264 This option specifies the interface type: Wired, wireless or tunnel. On
2265 wired interfaces a neighbor is considered unreachable after a small number
2266 of Hello packets are lost, as described by <cf/limit/ option. On wireless
2267 interfaces the ETX link quality estimation technique is used to compute
2268 the metrics of routes discovered over this interface. This technique will
2269 gradually degrade the metric of routes when packets are lost rather than
2270 the more binary up/down mechanism of wired type links. A tunnel is like a
2271 wired interface, but turns on RTT-based metrics with a default cost of 96.
2272 Default: <cf/wired/.
2274 <tag><label id="babel-rxcost">rxcost <m/num/</tag>
2275 This option specifies the nominal RX cost of the interface. The effective
2276 neighbor costs for route metrics will be computed from this value with a
2277 mechanism determined by the interface <cf/type/. Note that in contrast to
2278 other routing protocols like RIP or OSPF, the <cf/rxcost/ specifies the
2279 cost of RX instead of TX, so it affects primarily neighbors' route
2280 selection and not local route selection. Default: 96 for wired interfaces,
2283 <tag><label id="babel-limit">limit <m/num/</tag>
2284 BIRD keeps track of received Hello messages from each neighbor to
2285 establish neighbor reachability. For wired type interfaces, this option
2286 specifies how many of last 16 hellos have to be correctly received in
2287 order to neighbor is assumed to be up. The option is ignored on wireless
2288 type interfaces, where gradual cost degradation is used instead of sharp
2291 <tag><label id="babel-hello">hello interval <m/time/ s|ms</tag>
2292 Interval at which periodic Hello messages are sent on this interface,
2293 with time units. Default: 4 seconds.
2295 <tag><label id="babel-update">update interval <m/time/ s|ms</tag>
2296 Interval at which periodic (full) updates are sent, with time
2297 units. Default: 4 times the hello interval.
2299 <tag><label id="babel-port">port <m/number/</tag>
2300 This option selects an UDP port to operate on. The default is to operate
2301 on port 6696 as specified in the Babel RFC.
2303 <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
2304 These options specify the ToS/DiffServ/Traffic class/Priority of the
2305 outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
2306 option for detailed description.
2308 <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
2309 This option specifies the size of buffers used for packet processing.
2310 The buffer size should be bigger than maximal size of received packets.
2311 The default value is the interface MTU, and the value will be clamped to a
2312 minimum of 512 bytes + IP packet overhead.
2314 <tag><label id="babel-tx-length">tx length <m/number/</tag>
2315 This option specifies the maximum length of generated Babel packets. To
2316 avoid IP fragmentation, it should not exceed the interface MTU value.
2317 The default value is the interface MTU value, and the value will be
2318 clamped to a minimum of 512 bytes + IP packet overhead.
2320 <tag><label id="babel-check-link">check link <m/switch/</tag>
2321 If set, the hardware link state (as reported by OS) is taken into
2322 consideration. When the link disappears (e.g. an ethernet cable is
2323 unplugged), neighbors are immediately considered unreachable and all
2324 routes received from them are withdrawn. It is possible that some
2325 hardware drivers or platforms do not implement this feature. Default:
2328 <tag><label id="babel-next-hop-ipv4">next hop ipv4 <m/address/</tag>
2329 Set the next hop address advertised for IPv4 routes advertised on this
2330 interface. Default: the preferred IPv4 address of the interface.
2332 <tag><label id="babel-next-hop-ipv6">next hop ipv6 <m/address/</tag>
2333 Set the next hop address advertised for IPv6 routes advertised on this
2334 interface. If not set, the same link-local address that is used as the
2335 source for Babel packets will be used. In normal operation, it should not
2336 be necessary to set this option.
2338 <tag><label id="babel-extended-next-hop">extended next hop <m/switch/</tag>
2339 If enabled, BIRD will accept and emit IPv4 routes with an IPv6 next
2340 hop when IPv4 addresses are absent from the interface as described in
2341 <rfc id="9229">. Default: yes.
2343 <tag><label id="babel-rtt-cost">rtt cost <m/number/</tag>
2344 The RTT-based cost that will be applied to all routes from each neighbour
2345 based on the measured RTT to that neighbour. If this value is set,
2346 timestamps will be included in generated Babel Hello and IHU messages, and
2347 (if the neighbours also have timestamps enabled), the RTT to each
2348 neighbour will be computed. An additional cost is added to a neighbour if
2349 its RTT is above the <ref id="babel-rtt-min" name="rtt min"> value
2350 configured on the interface. The added cost scales linearly from 0 up to
2351 the RTT cost configured in this option; the full cost is applied if the
2352 neighbour RTT reaches the RTT configured in the <ref id="babel-rtt-max"
2353 name="rtt max"> option (and for all RTTs above this value). Default: 0
2354 (disabled), except for tunnel interfaces, where it is 96.
2356 <tag><label id="babel-rtt-min">rtt min <m/time/ s|ms</tag>
2357 The minimum RTT above which the RTT cost will start to be applied (scaling
2358 linearly from zero up to the full cost). Default: 10 ms
2360 <tag><label id="babel-rtt-max">rtt max <m/time/ s|ms</tag>
2361 The maximum RTT above which the full RTT cost will start be applied.
2364 <tag><label id="babel-rtt-decay">rtt decay <m/number/</tag>
2365 The decay factor used for the exponentional moving average of the RTT
2366 samples from each neighbour, in units of 1/256. Higher values discards old
2367 RTT samples faster. Must be between 1 and 256. Default: 42
2369 <tag><label id="babel-send-timestamps">send timestamps <m/switch/</tag>
2370 Whether to send the timestamps used for RTT calculation on this interface.
2371 Sending the timestamps enables peers to calculate an RTT to this node,
2372 even if no RTT cost is applied to the route metrics. Default: yes.
2374 <tag><label id="babel-authentication">authentication none|mac [permissive]</tag>
2375 Selects authentication method to be used. <cf/none/ means that packets
2376 are not authenticated at all, <cf/mac/ means MAC authentication is
2377 performed as described in <rfc id="8967">. If MAC authentication is
2378 selected, the <cf/permissive/ suffix can be used to select an operation
2379 mode where outgoing packets are signed, but incoming packets will be
2380 accepted even if they fail authentication. This can be useful for
2381 incremental deployment of MAC authentication across a network. If MAC
2382 authentication is selected, a key must be specified with the
2383 <cf/password/ configuration option. Default: none.
2385 <tag><label id="babel-password">password "<m/text/"</tag>
2386 Specifies a password used for authentication. See the <ref id="proto-pass"
2387 name="password"> common option for a detailed description. The Babel
2388 protocol will only accept HMAC-based algorithms or one of the Blake
2389 algorithms, and the length of the supplied password string must match the
2390 key size used by the selected algorithm.
2394 <label id="babel-attr">
2396 <p>Babel defines just one attribute: the internal babel metric of the route. It
2397 is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
2401 <label id="babel-exam">
2408 interface "wlan0", "wlan1" {
2415 # This matches the default of babeld: redistribute all addresses
2416 # configured on local interfaces, plus re-distribute all routes received
2417 # from other babel peers.
2420 export where (source = RTS_DEVICE) || (source = RTS_BABEL);
2423 export where (source = RTS_DEVICE) || (source = RTS_BABEL);
2429 <label id="babel-issues">
2431 <p>When retracting a route, Babel generates an unreachable route for a little
2432 while (according to RFC). The interaction of this behavior with other protocols
2433 is not well tested and strange things may happen.
2440 <label id="bfd-intro">
2442 <p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
2443 is an independent tool providing liveness and failure detection. Routing
2444 protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
2445 liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
2446 seconds by default in OSPF, could be set down to several seconds). BFD offers
2447 universal, fast and low-overhead mechanism for failure detection, which could be
2448 attached to any routing protocol in an advisory role.
2450 <p>BFD consists of mostly independent BFD sessions. Each session monitors an
2451 unicast bidirectional path between two BFD-enabled routers. This is done by
2452 periodically sending control packets in both directions. BFD does not handle
2453 neighbor discovery, BFD sessions are created on demand by request of other
2454 protocols (like OSPF or BGP), which supply appropriate information like IP
2455 addresses and associated interfaces. When a session changes its state, these
2456 protocols are notified and act accordingly (e.g. break an OSPF adjacency when
2457 the BFD session went down).
2459 <p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
2460 advanced features like the echo mode or authentication are not implemented), IP
2461 transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
2462 interaction with client protocols as defined in <rfc id="5882">.
2464 <p>BFD packets are sent with a dynamic source port number. Linux systems use by
2465 default a bit different dynamic port range than the IANA approved one
2466 (49152-65535). If you experience problems with compatibility, please adjust
2467 <cf>/proc/sys/net/ipv4/ip_local_port_range</cf>.
2469 <sect1>Configuration
2470 <label id="bfd-config">
2472 <p>BFD configuration consists mainly of multiple definitions of interfaces.
2473 Most BFD config options are session specific. When a new session is requested
2474 and dynamically created, it is configured from one of these definitions. For
2475 sessions to directly connected neighbors, <cf/interface/ definitions are chosen
2476 based on the interface associated with the session, while <cf/multihop/
2477 definition is used for multihop sessions. If no definition is relevant, the
2478 session is just created with the default configuration. Therefore, an empty BFD
2479 configuration is often sufficient.
2481 <p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
2482 also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
2483 In BGP case, it is also possible to specify per-peer BFD session options (e.g.
2484 rx/tx intervals) as a part of the <cf/bfd/ option.
2486 <p>A BFD instance not associated with any VRF handles session requests from all
2487 other protocols, even ones associated with a VRF. Such setup would work for
2488 single-hop BFD sessions if <cf/net.ipv4.udp_l3mdev_accept/ sysctl is enabled,
2489 but does not currently work for multihop sessions. Another approach is to
2490 configure multiple BFD instances, one for each VRF (including the default VRF).
2491 Each BFD instance associated with a VRF (regular or default) only handles
2492 session requests from protocols in the same VRF.
2494 <p>Some of BFD session options require <m/time/ value, which has to be specified
2495 with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
2496 are allowed as units, practical minimum values are usually in order of tens of
2500 protocol bfd [<name>] {
2501 accept [ipv4|ipv6] [direct|multihop];
2502 interface <interface pattern> {
2503 interval <time>;
2504 min rx interval <time>;
2505 min tx interval <time>;
2506 idle tx interval <time>;
2507 multiplier <num>;
2508 passive <switch>;
2509 authentication none;
2510 authentication simple;
2511 authentication [meticulous] keyed md5|sha1;
2512 password "<text>";
2513 password "<text>" {
2515 generate from "<date>";
2516 generate to "<date>";
2517 accept from "<date>";
2518 accept to "<date>";
2519 from "<date>";
2524 interval <time>;
2525 min rx interval <time>;
2526 min tx interval <time>;
2527 idle tx interval <time>;
2528 multiplier <num>;
2529 passive <switch>;
2531 neighbor <ip> [dev "<interface>"] [local <ip>] [multihop <switch>];
2536 <tag><label id="bfd-accept">accept [ipv4|ipv6] [direct|multihop]</tag>
2537 A BFD protocol instance accepts (by default) all BFD session requests
2538 (with regard to VRF restrictions, see above). This option controls
2539 whether IPv4 / IPv6 and direct / multihop session requests are accepted
2540 (and which listening sockets are opened). It can be used, for example,
2541 to configure separate BFD protocol instances for IPv4 and for IPv6
2544 <tag><label id="bfd-strict-bind">strict bind <m/switch/</tag>
2545 Specify whether each BFD interface should use a separate listening
2546 socket bound to its local address, or just use a shared listening socket
2547 accepting all addresses. Binding to a specific address could be useful
2548 in cases like running multiple BIRD instances on a machine, each
2549 handling a different set of interfaces. Default: disabled.
2551 <tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
2552 Interface definitions allow to specify options for sessions associated
2553 with such interfaces and also may contain interface specific options.
2554 See <ref id="proto-iface" name="interface"> common option for a detailed
2555 description of interface patterns. Note that contrary to the behavior of
2556 <cf/interface/ definitions of other protocols, BFD protocol would accept
2557 sessions (in default configuration) even on interfaces not covered by
2560 <tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
2561 Multihop definitions allow to specify options for multihop BFD sessions,
2562 in the same manner as <cf/interface/ definitions are used for directly
2563 connected sessions. Currently only one such definition (for all multihop
2564 sessions) could be used.
2566 <tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
2567 BFD sessions are usually created on demand as requested by other
2568 protocols (like OSPF or BGP). This option allows to explicitly add
2569 a BFD session to the specified neighbor regardless of such requests.
2571 The session is identified by the IP address of the neighbor, with
2572 optional specification of used interface and local IP. By default
2573 the neighbor must be directly connected, unless the session is
2574 configured as multihop. Note that local IP must be specified for
2578 <p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
2581 <tag><label id="bfd-interval">interval <m/time/</tag>
2582 BFD ensures availability of the forwarding path associated with the
2583 session by periodically sending BFD control packets in both
2584 directions. The rate of such packets is controlled by two options,
2585 <cf/min rx interval/ and <cf/min tx interval/ (see below). This option
2586 is just a shorthand to set both of these options together.
2588 <tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
2589 This option specifies the minimum RX interval, which is announced to the
2590 neighbor and used there to limit the neighbor's rate of generated BFD
2591 control packets. Default: 10 ms.
2593 <tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
2594 This option specifies the desired TX interval, which controls the rate
2595 of generated BFD control packets (together with <cf/min rx interval/
2596 announced by the neighbor). Note that this value is used only if the BFD
2597 session is up, otherwise the value of <cf/idle tx interval/ is used
2598 instead. Default: 100 ms.
2600 <tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
2601 In order to limit unnecessary traffic in cases where a neighbor is not
2602 available or not running BFD, the rate of generated BFD control packets
2603 is lower when the BFD session is not up. This option specifies the
2604 desired TX interval in such cases instead of <cf/min tx interval/.
2607 <tag><label id="bfd-multiplier">multiplier <m/num/</tag>
2608 Failure detection time for BFD sessions is based on established rate of
2609 BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
2610 multiplier, which is essentially (ignoring jitter) a number of missed
2611 packets after which the session is declared down. Note that rates and
2612 multipliers could be different in each direction of a BFD session.
2615 <tag><label id="bfd-passive">passive <m/switch/</tag>
2616 Generally, both BFD session endpoints try to establish the session by
2617 sending control packets to the other side. This option allows to enable
2618 passive mode, which means that the router does not send BFD packets
2619 until it has received one from the other side. Default: disabled.
2621 <tag>authentication none</tag>
2622 No passwords are sent in BFD packets. This is the default value.
2624 <tag>authentication simple</tag>
2625 Every packet carries 16 bytes of password. Received packets lacking this
2626 password are ignored. This authentication mechanism is very weak.
2628 <tag>authentication [meticulous] keyed md5|sha1</tag>
2629 An authentication code is appended to each packet. The cryptographic
2630 algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
2631 for all keys (on one interface), in contrast to OSPF or RIP, where it
2632 is a per-key option. Passwords (keys) are not sent open via network.
2634 The <cf/meticulous/ variant means that cryptographic sequence numbers
2635 are increased for each sent packet, while in the basic variant they are
2636 increased about once per second. Generally, the <cf/meticulous/ variant
2637 offers better resistance to replay attacks but may require more
2640 <tag>password "<M>text</M>"</tag>
2641 Specifies a password used for authentication. See <ref id="proto-pass"
2642 name="password"> common option for detailed description. Note that
2643 password option <cf/algorithm/ is not available in BFD protocol. The
2644 algorithm is selected by <cf/authentication/ option for all passwords.
2649 <label id="bfd-exam">
2654 min rx interval 20 ms;
2655 min tx interval 50 ms;
2656 idle tx interval 300 ms;
2668 neighbor 192.168.1.10;
2669 neighbor 192.168.2.2 dev "eth2";
2670 neighbor 192.168.10.1 local 192.168.1.1 multihop;
2678 <p>The Border Gateway Protocol is the routing protocol used for backbone level
2679 routing in the today's Internet. Contrary to other protocols, its convergence
2680 does not rely on all routers following the same rules for route selection,
2681 making it possible to implement any routing policy at any router in the network,
2682 the only restriction being that if a router advertises a route, it must accept
2683 and forward packets according to it.
2685 <p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
2686 is a part of the network with common management and common routing policy. It is
2687 identified by a unique 16-bit number (ASN). Routers within each AS usually
2688 exchange AS-internal routing information with each other using an interior
2689 gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
2690 the AS communicate global (inter-AS) network reachability information with their
2691 neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
2692 received information to other routers in the AS via interior BGP (iBGP).
2694 <p>Each BGP router sends to its neighbors updates of the parts of its routing
2695 table it wishes to export along with complete path information (a list of AS'es
2696 the packet will travel through if it uses the particular route) in order to
2697 avoid routing loops.
2699 <sect1>Supported standards
2700 <label id="bgp-standards">
2704 <item> <rfc id="4271"> - Border Gateway Protocol 4 (BGP)
2705 <item> <rfc id="1997"> - BGP Communities Attribute
2706 <item> <rfc id="2385"> - Protection of BGP Sessions via TCP MD5 Signature
2707 <item> <rfc id="2545"> - Use of BGP Multiprotocol Extensions for IPv6
2708 <item> <rfc id="2918"> - Route Refresh Capability
2709 <item> <rfc id="3107"> - Carrying Label Information in BGP
2710 <item> <rfc id="4360"> - BGP Extended Communities Attribute
2711 <item> <rfc id="4364"> - BGP/MPLS IPv4 Virtual Private Networks
2712 <item> <rfc id="4456"> - BGP Route Reflection
2713 <item> <rfc id="4486"> - Subcodes for BGP Cease Notification Message
2714 <item> <rfc id="4659"> - BGP/MPLS IPv6 Virtual Private Networks
2715 <item> <rfc id="4724"> - Graceful Restart Mechanism for BGP
2716 <item> <rfc id="4760"> - Multiprotocol extensions for BGP
2717 <item> <rfc id="4798"> - Connecting IPv6 Islands over IPv4 MPLS
2718 <item> <rfc id="5065"> - AS confederations for BGP
2719 <item> <rfc id="5082"> - Generalized TTL Security Mechanism
2720 <item> <rfc id="5492"> - Capabilities Advertisement with BGP
2721 <item> <rfc id="5575"> - Dissemination of Flow Specification Rules
2722 <item> <rfc id="5668"> - 4-Octet AS Specific BGP Extended Community
2723 <item> <rfc id="6286"> - AS-Wide Unique BGP Identifier
2724 <item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error
2725 <item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers
2726 <item> <rfc id="7311"> - Accumulated IGP Metric Attribute for BGP
2727 <item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP
2728 <item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages
2729 <item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP
2730 <item> <rfc id="7947"> - Internet Exchange BGP Route Server
2731 <item> <rfc id="8092"> - BGP Large Communities Attribute
2732 <item> <rfc id="8203"> - BGP Administrative Shutdown Communication
2733 <item> <rfc id="8212"> - Default EBGP Route Propagation Behavior without Policies
2734 <item> <rfc id="8654"> - Extended Message Support for BGP
2735 <item> <rfc id="8950"> - Advertising IPv4 NLRI with an IPv6 Next Hop
2736 <item> <rfc id="9072"> - Extended Optional Parameters Length for BGP OPEN Message
2737 <item> <rfc id="9117"> - Revised Validation Procedure for BGP Flow Specifications
2738 <item> <rfc id="9234"> - Route Leak Prevention and Detection Using Roles
2741 <sect1>Route selection rules
2742 <label id="bgp-route-select-rules">
2744 <p>BGP doesn't have any simple metric, so the rules for selection of an optimal
2745 route among multiple BGP routes with the same preference are a bit more complex
2746 and they are implemented according to the following algorithm. It starts the
2747 first rule, if there are more "best" routes, then it uses the second rule to
2748 choose among them and so on.
2751 <item>Prefer route with the highest Local Preference attribute.
2752 <item>Prefer route with the shortest AS path.
2753 <item>Prefer IGP origin over EGP and EGP origin over incomplete.
2754 <item>Prefer the lowest value of the Multiple Exit Discriminator.
2755 <item>Prefer routes received via eBGP over ones received via iBGP.
2756 <item>Prefer routes with lower internal distance to a boundary router.
2757 <item>Prefer the route with the lowest value of router ID of the
2761 <sect1>IGP routing table
2762 <label id="bgp-igp-routing-table">
2764 <p>BGP is mainly concerned with global network reachability and with routes to
2765 other autonomous systems. When such routes are redistributed to routers in the
2766 AS via BGP, they contain IP addresses of a boundary routers (in route attribute
2767 NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
2768 determine immediate next hops for routes and to know their internal distances to
2769 boundary routers for the purpose of BGP route selection. In BIRD, there is
2770 usually one routing table used for both IGP routes and BGP routes.
2772 <sect1>Protocol configuration
2773 <label id="bgp-proto-config">
2775 <p>Each instance of the BGP corresponds to one neighboring router. This allows
2776 to set routing policy and all the other parameters differently for each neighbor
2777 using the following configuration parameters:
2780 <tag><label id="bgp-local">local [<m/ip/] [port <m/number/] [as <m/number/]</tag>
2781 Define which AS we are part of. (Note that contrary to other IP routers,
2782 BIRD is able to act as a router located in multiple AS'es simultaneously,
2783 but in such cases you need to tweak the BGP paths manually in the filters
2784 to get consistent behavior.) Optional <cf/ip/ argument specifies a source
2785 address, equivalent to the <cf/source address/ option (see below).
2786 Optional <cf/port/ argument specifies the local BGP port instead of
2787 standard port 179. The parameter may be used multiple times with
2788 different sub-options (e.g., both <cf/local 10.0.0.1 as 65000;/ and
2789 <cf/local 10.0.0.1; local as 65000;/ are valid). This parameter is
2792 <tag><label id="bgp-neighbor">neighbor [<m/ip/ | range <m/prefix/] [port <m/number/] [as <m/number/] [internal|external]</tag>
2793 Define neighboring router this instance will be talking to and what AS
2794 it is located in. In case the neighbor is in the same AS as we are, we
2795 automatically switch to IBGP. Alternatively, it is possible to specify
2796 just <cf/internal/ or <cf/external/ instead of AS number, in that case
2797 either local AS number, or any external AS number is accepted.
2798 Optionally, the remote port may also be specified. Like <cf/local/
2799 parameter, this parameter may also be used multiple times with different
2800 sub-options. This parameter is mandatory.
2802 It is possible to specify network prefix (with <cf/range/ keyword)
2803 instead of explicit neighbor IP address. This enables dynamic BGP
2804 behavior, where the BGP instance listens on BGP port, but new BGP
2805 instances are spawned for incoming BGP connections (if source address
2806 matches the network prefix). It is possible to mix regular BGP instances
2807 with dynamic BGP instances and have multiple dynamic BGP instances with
2810 <tag><label id="bgp-iface">interface <m/string/</tag>
2811 Define interface we should use for link-local BGP IPv6 sessions.
2812 Interface can also be specified as a part of <cf/neighbor address/
2813 (e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). The option may also be
2814 used for non link-local sessions when it is necessary to explicitly
2815 specify an interface, but only for direct (not multihop) sessions.
2817 <tag><label id="bgp-direct">direct</tag>
2818 Specify that the neighbor is directly connected. The IP address of the
2819 neighbor must be from a directly reachable IP range (i.e. associated
2820 with one of your router's interfaces), otherwise the BGP session
2821 wouldn't start but it would wait for such interface to appear. The
2822 alternative is the <cf/multihop/ option. Default: enabled for eBGP.
2824 <tag><label id="bgp-multihop">multihop [<m/number/]</tag>
2825 Configure multihop BGP session to a neighbor that isn't directly
2826 connected. Accurately, this option should be used if the configured
2827 neighbor IP address does not match with any local network subnets. Such
2828 IP address have to be reachable through system routing table. The
2829 alternative is the <cf/direct/ option. For multihop BGP it is
2830 recommended to explicitly configure the source address to have it
2831 stable. Optional <cf/number/ argument can be used to specify the number
2832 of hops (used for TTL). Note that the number of networks (edges) in a
2833 path is counted; i.e., if two BGP speakers are separated by one router,
2834 the number of hops is 2. Default: enabled for iBGP.
2836 <tag><label id="bgp-source-address">source address <m/ip/</tag>
2837 Define local address we should use as a source address for the BGP
2838 session. Default: the address of the local end of the interface our
2839 neighbor is connected to.
2841 <tag><label id="bgp-dynamic-name">dynamic name "<m/text/"</tag>
2842 Define common prefix of names used for new BGP instances spawned when
2843 dynamic BGP behavior is active. Actual names also contain numeric
2844 index to distinguish individual instances. Default: "dynbgp".
2846 <tag><label id="bgp-dynamic-name-digits">dynamic name digits <m/number/</tag>
2847 Define minimum number of digits for index in names of spawned dynamic
2848 BGP instances. E.g., if set to 2, then the first name would be
2849 "dynbgp01". Default: 0.
2851 <tag><label id="bgp-strict-bind">strict bind <m/switch/</tag>
2852 Specify whether BGP listening socket should be bound to a specific local
2853 address (the same as the <cf/source address/) and associated interface,
2854 or to all addresses. Binding to a specific address could be useful in
2855 cases like running multiple BIRD instances on a machine, each using its
2856 IP address. Note that listening sockets bound to a specific address and
2857 to all addresses collide, therefore either all BGP protocols (of the
2858 same address family and using the same local port) should have set
2859 <cf/strict bind/, or none of them. Default: disabled.
2861 <tag><label id="bgp-free-bind">free bind <m/switch/</tag>
2862 Use IP_FREEBIND socket option for the listening socket, which allows
2863 binding to an IP address not (yet) assigned to an interface. Note that
2864 all BGP instances that share a listening socket should have the same
2865 value of the <cf/freebind/ option. Default: disabled.
2867 <tag><label id="bgp-check-link">check link <M>switch</M></tag>
2868 BGP could use hardware link state into consideration. If enabled,
2869 BIRD tracks the link state of the associated interface and when link
2870 disappears (e.g. an ethernet cable is unplugged), the BGP session is
2871 immediately shut down. Note that this option cannot be used with
2872 multihop BGP. Default: enabled for direct BGP, disabled otherwise.
2874 <tag><label id="bgp-bfd">bfd <M>switch</M>|graceful| { <m/options/ }</tag>
2875 BGP could use BFD protocol as an advisory mechanism for neighbor
2876 liveness and failure detection. If enabled, BIRD setups a BFD session
2877 for the BGP neighbor and tracks its liveness by it. This has an
2878 advantage of an order of magnitude lower detection times in case of
2879 failure. When a neighbor failure is detected, the BGP session is
2880 restarted. Optionally, it can be configured (by <cf/graceful/ argument)
2881 to trigger graceful restart instead of regular restart. It is also
2882 possible to specify section with per-peer BFD session options instead of
2883 just the switch argument. All BFD session-specific options are allowed
2884 here. Note that BFD protocol also has to be configured, see
2885 <ref id="bfd" name="BFD"> section for details. Default: disabled.
2887 <tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
2888 Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
2889 protects against spoofed packets by ignoring received packets with a
2890 smaller than expected TTL. To work properly, GTSM have to be enabled on
2891 both sides of a BGP session. If both <cf/ttl security/ and
2892 <cf/multihop/ options are enabled, <cf/multihop/ option should specify
2893 proper hop value to compute expected TTL. Kernel support required:
2894 Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
2895 Note that full (ICMP protection, for example) <rfc id="5082"> support is
2896 provided by Linux only. Default: disabled.
2898 <tag><label id="bgp-password">password <m/string/</tag>
2899 Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
2900 used on BSD systems, see also <cf/setkey/ option below. Default: no
2903 <tag><label id="bgp-setkey">setkey <m/switch/</tag>
2904 On BSD systems, keys for TCP MD5 authentication are stored in the global
2905 SA/SP database, which can be accessed by external utilities (e.g.
2906 setkey(8)). BIRD configures security associations in the SA/SP database
2907 automatically based on <cf/password/ options (see above), this option
2908 allows to disable automatic updates by BIRD when manual configuration by
2909 external utilities is preferred. Note that automatic SA/SP database
2910 updates are currently implemented only for FreeBSD. Passwords have to be
2911 set manually by an external utility on NetBSD and OpenBSD. Default:
2912 enabled (ignored on non-FreeBSD).
2914 <tag><label id="bgp-passive">passive <m/switch/</tag>
2915 Standard BGP behavior is both initiating outgoing connections and
2916 accepting incoming connections. In passive mode, outgoing connections
2917 are not initiated. Default: off.
2919 <tag><label id="bgp-confederation">confederation <m/number/</tag>
2920 BGP confederations (<rfc id="5065">) are collections of autonomous
2921 systems that act as one entity to external systems, represented by one
2922 confederation identifier (instead of AS numbers). This option allows to
2923 enable BGP confederation behavior and to specify the local confederation
2924 identifier. When BGP confederations are used, all BGP speakers that are
2925 members of the BGP confederation should have the same confederation
2926 identifier configured. Default: 0 (no confederation).
2928 <tag><label id="bgp-confederation-member">confederation member <m/switch/</tag>
2929 When BGP confederations are used, this option allows to specify whether
2930 the BGP neighbor is a member of the same confederation as the local BGP
2931 speaker. The option is unnecessary (and ignored) for IBGP sessions, as
2932 the same AS number implies the same confederation. Default: no.
2934 <tag><label id="bgp-rr-client">rr client</tag>
2935 Be a route reflector and treat the neighbor as a route reflection
2936 client. Default: disabled.
2938 <tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2939 Route reflectors use cluster id to avoid route reflection loops. When
2940 there is one route reflector in a cluster it usually uses its router id
2941 as a cluster id, but when there are more route reflectors in a cluster,
2942 these need to be configured (using this option) to use a common cluster
2943 id. Clients in a cluster need not know their cluster id and this option
2944 is not allowed for them. Default: the same as router id.
2946 <tag><label id="bgp-rs-client">rs client</tag>
2947 Be a route server and treat the neighbor as a route server client.
2948 A route server is used as a replacement for full mesh EBGP routing in
2949 Internet exchange points in a similar way to route reflectors used in
2950 IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2951 uses ad-hoc implementation, which behaves like plain EBGP but reduces
2952 modifications to advertised route attributes to be transparent (for
2953 example does not prepend its AS number to AS PATH attribute and
2954 keeps MED attribute). Default: disabled.
2956 <tag><label id="bgp-allow-local-pref">allow bgp_local_pref <m/switch/</tag>
2957 Standard BGP implementations do not send the Local Preference attribute
2958 to EBGP neighbors and ignore this attribute if received from EBGP
2959 neighbors, as per <rfc id="4271">. When this option is enabled on an
2960 EBGP session, this attribute will be sent to and accepted from the peer,
2961 which is useful for example if you have a setup like in <rfc id="7938">.
2962 The option does not affect IBGP sessions. Default: off.
2964 <tag><label id="bgp-allow-med">allow bgp_med <m/switch/</tag>
2965 Standard BGP implementations do not propagate the MULTI_EXIT_DESC
2966 attribute unless it is configured locally. When this option is enabled
2967 on an EBGP session, this attribute will be sent to the peer regardless,
2968 which is useful for example if you have a setup like in <rfc id="7938">.
2969 The option does not affect IBGP sessions. Default: off.
2971 <tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2972 BGP prevents routing loops by rejecting received routes with the local
2973 AS number in the AS path. This option allows to loose or disable the
2974 check. Optional <cf/number/ argument can be used to specify the maximum
2975 number of local ASNs in the AS path that is allowed for received
2976 routes. When the option is used without the argument, the check is
2977 completely disabled and you should ensure loop-free behavior by some
2978 other means. Default: 0 (no local AS number allowed).
2980 <tag><label id="bgp-allow-as-sets">allow as sets [<m/switch/]</tag>
2981 AS path attribute received with BGP routes may contain not only
2982 sequences of AS numbers, but also sets of AS numbers. These rarely used
2983 artifacts are results of inter-AS route aggregation. AS sets are
2984 deprecated (<rfc id="6472">), and likely to be rejected in the future,
2985 as they complicate security features like RPKI validation. When this
2986 option is disabled, then received AS paths with AS sets are rejected as
2987 malformed and corresponding BGP updates are treated as withdraws.
2990 <tag><label id="bgp-enforce-first-as">enforce first as [<m/switch/]</tag>
2991 Routes received from an EBGP neighbor are generally expected to have the
2992 first (leftmost) AS number in their AS path equal to the neighbor AS
2993 number. This is not enforced by default as there are legitimate cases
2994 where it is not true, e.g. connections to route servers. When this
2995 option is enabled, routes with non-matching first AS number are rejected
2996 and corresponding updates are treated as withdraws. The option is valid
2997 on EBGP sessions only. Default: off.
2999 <tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
3000 After the initial route exchange, BGP protocol uses incremental updates
3001 to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
3002 changes its import filter, or if there is suspicion of inconsistency) it
3003 is necessary to do a new complete route exchange. BGP protocol extension
3004 Route Refresh (<rfc id="2918">) allows BGP speaker to request
3005 re-advertisement of all routes from its neighbor. This option
3006 specifies whether BIRD advertises this capability and supports
3007 related procedures. Note that even when disabled, BIRD can send route
3008 refresh requests. Disabling Route Refresh also disables Enhanced Route Refresh.
3011 <tag><label id="bgp-require-route-refresh">require route refresh <m/switch/</tag>
3012 If enabled, the BGP Route Refresh capability (<rfc id="2918">) must be
3013 announced by the BGP neighbor, otherwise the BGP session will not be
3014 established. Default: off.
3016 <tag><label id="bgp-enable-enhanced-route-refresh">enable enhanced route refresh <m/switch/</tag>
3017 BGP protocol extension Enhanced Route Refresh (<rfc id="7313">)
3018 specifies explicit begin and end for Route Refresh (see previous
3019 option), therefore the receiver can remove stale routes that were not
3020 advertised during the exchange. This option specifies whether BIRD
3021 advertises this capability and supports related procedures. Default: on.
3023 <tag><label id="bgp-require-enhanced-route-refresh">require enhanced route refresh <m/switch/</tag>
3024 If enabled, the BGP Enhanced Route Refresh capability (<rfc id="7313">)
3025 must be announced by the BGP neighbor, otherwise the BGP session
3026 will not be established. Default: off.
3028 <tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
3029 When a BGP speaker restarts or crashes, neighbors will discard all
3030 received paths from the speaker, which disrupts packet forwarding even
3031 when the forwarding plane of the speaker remains intact. <rfc id="4724">
3032 specifies an optional graceful restart mechanism to alleviate this
3033 issue. This option controls the mechanism. It has three states:
3034 Disabled, when no support is provided. Aware, when the graceful restart
3035 support is announced and the support for restarting neighbors is
3036 provided, but no local graceful restart is allowed (i.e. receiving-only
3037 role). Enabled, when the full graceful restart support is provided
3038 (i.e. both restarting and receiving role). Restarting role could be also
3039 configured per-channel. Note that proper support for local graceful
3040 restart requires also configuration of other protocols. Default: aware.
3042 <tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
3043 The restart time is announced in the BGP Graceful Restart capability
3044 and specifies how long the neighbor would wait for the BGP session to
3045 re-establish after a restart before deleting stale routes. Default:
3048 <tag><label id="bgp-require-graceful-restart">require graceful restart <m/switch/</tag>
3049 If enabled, the BGP Graceful Restart capability (<rfc id="4724">)
3050 must be announced by the BGP neighbor, otherwise the BGP session
3051 will not be established. Default: off.
3053 <tag><label id="bgp-long-lived-graceful-restart">long lived graceful restart <m/switch/|aware</tag>
3054 The long-lived graceful restart is an extension of the traditional
3055 <ref id="bgp-graceful-restart" name="BGP graceful restart">, where stale
3056 routes are kept even after the <ref id="bgp-graceful-restart-time"
3057 name="restart time"> expires for additional long-lived stale time, but
3058 they are marked with the LLGR_STALE community, depreferenced, and
3059 withdrawn from routers not supporting LLGR. Like traditional BGP
3060 graceful restart, it has three states: disabled, aware (receiving-only),
3061 and enabled. Note that long-lived graceful restart requires at least
3062 aware level of traditional BGP graceful restart. Default: aware, unless
3063 graceful restart is disabled.
3065 <tag><label id="bgp-long-lived-stale-time">long lived stale time <m/number/</tag>
3066 The long-lived stale time is announced in the BGP Long-lived Graceful
3067 Restart capability and specifies how long the neighbor would keep stale
3068 routes depreferenced during long-lived graceful restart until either the
3069 session is re-stablished and synchronized or the stale time expires and
3070 routes are removed. Default: 3600 seconds.
3072 <tag><label id="bgp-require-long-lived-graceful-restart">require long lived graceful restart <m/switch/</tag>
3073 If enabled, the BGP Long-lived Graceful Restart capability (draft)
3074 must be announced by the BGP neighbor, otherwise the BGP session
3075 will not be established. Default: off.
3077 <tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
3078 <rfc id="1997"> demands that BGP speaker should process well-known
3079 communities like no-export (65535, 65281) or no-advertise (65535,
3080 65282). For example, received route carrying a no-adverise community
3081 should not be advertised to any of its neighbors. If this option is
3082 enabled (which is by default), BIRD has such behavior automatically (it
3083 is evaluated when a route is exported to the BGP protocol just before
3084 the export filter). Otherwise, this integrated processing of
3085 well-known communities is disabled. In that case, similar behavior can
3086 be implemented in the export filter. Default: on.
3088 <tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
3089 BGP protocol was designed to use 2B AS numbers and was extended later to
3090 allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
3091 option it can be persuaded not to advertise it and to maintain old-style
3092 sessions with its neighbors. This might be useful for circumventing bugs
3093 in neighbor's implementation of 4B AS extension. Even when disabled
3094 (off), BIRD behaves internally as AS4-aware BGP router. Default: on.
3096 <tag><label id="bgp-require-as4">require as4 <m/switch/</tag>
3097 If enabled, the BGP 4B AS number capability (<rfc id="6793">) must be
3098 announced by the BGP neighbor, otherwise the BGP session will not be
3099 established. Default: off.
3101 <tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
3102 The BGP protocol uses maximum message length of 4096 bytes. This option
3103 provides an extension (<rfc id="8654">) to allow extended messages with
3104 length up to 65535 bytes. Default: off.
3106 <tag><label id="bgp-require-extended-messages">require extended messages <m/switch/</tag>
3107 If enabled, the BGP Extended Message capability (<rfc id="8654">) must
3108 be announced by the BGP neighbor, otherwise the BGP session will not be
3109 established. Default: off.
3111 <tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
3112 Use capability advertisement to advertise optional capabilities. This is
3113 standard behavior for newer BGP implementations, but there might be some
3114 older BGP implementations that reject such connection attempts. When
3115 disabled (off), features that request it (4B AS support) are also
3116 disabled. Default: on, with automatic fallback to off when received
3117 capability-related error.
3119 <tag><label id="bgp-advertise-hostname">advertise hostname <m/switch/</tag>
3120 Advertise the hostname capability along with the hostname. Default: off.
3122 <tag><label id="bgp-require-hostname">require hostname <m/switch/</tag>
3123 If enabled, the hostname capability must be announced by the BGP
3124 neighbor, otherwise the BGP session negotiation fails. Default: off.
3126 <tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
3127 When an error is encountered (either locally or by the other side),
3128 disable the instance automatically and wait for an administrator to fix
3129 the problem manually. Default: off.
3131 <tag><label id="bgp-disable-after-cease">disable after cease <m/switch/|<m/set-of-flags/</tag>
3132 When a Cease notification is received, disable the instance
3133 automatically and wait for an administrator to fix the problem manually.
3134 When used with <m/switch/ argument, it means handle every Cease subtype
3135 with the exception of <cf/connection collision/. Default: off.
3137 The <m/set-of-flags/ allows to narrow down relevant Cease subtypes. The
3138 syntax is <cf>{<m/flag/ [, <m/.../] }</cf>, where flags are: <cf/cease/,
3139 <cf/prefix limit hit/, <cf/administrative shutdown/,
3140 <cf/peer deconfigured/, <cf/administrative reset/,
3141 <cf/connection rejected/, <cf/configuration change/,
3142 <cf/connection collision/, <cf/out of resources/.
3144 <tag><label id="bgp-hold-time">hold time <m/number/</tag>
3145 Time in seconds to wait for a Keepalive message from the other side
3146 before considering the connection stale. The effective value is
3147 negotiated during session establishment and it is a minimum of this
3148 configured value and the value proposed by the peer. The zero value has
3149 a special meaning, signifying that no keepalives are used. Default: 240
3152 <tag><label id="bgp-min-hold-time">min hold time <m/number/</tag>
3153 Minimum value of the hold time that is accepted during session negotiation.
3154 If the peer proposes a lower value, the session is rejected with error.
3157 <tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
3158 Value of the hold timer used before the routers have a chance to exchange
3159 open messages and agree on the real value. Default: 240 seconds.
3161 <tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
3162 Delay in seconds between sending of two consecutive Keepalive messages.
3163 The effective value depends on the negotiated hold time, as it is scaled
3164 to maintain proportion between the keepalive time and the hold time.
3165 Default: One third of the hold time.
3167 <tag><label id="bgp-min-keepalive-time">min keepalive time <m/number/</tag>
3168 Minimum value of the keepalive time that is accepted during session
3169 negotiation. If the proposed hold time would lead to a lower value of
3170 the keepalive time, the session is rejected with error. Default: none.
3172 <tag><label id="bgp-send-hold-time">send hold time <m/number/</tag>
3173 Maximum time in seconds betweeen successfull transmissions of BGP messages.
3174 Send hold timer drops the session if the neighbor is sending keepalives,
3175 but does not receive our messages, causing the TCP connection to stall.
3176 This may happen due to malfunctioning or overwhelmed neighbor. See
3177 <HTMLURL URL="https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-sendholdtimer/"
3178 name="draft-ietf-idr-bgp-sendholdtimer"> for more details.
3180 Like the option <cf/keepalive time/, the effective value depends on the
3181 negotiated hold time, as it is scaled to maintain proportion between the
3182 send hold time and the keepalive time. If it is set to zero, the timer
3183 is disabled. Default: double of the hold timer limit.
3185 The option <cf/disable rx/ is intended only for testing this feature and
3186 should not be used anywhere else. It discards received messages and
3187 disables the hold timer.
3189 <tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
3190 Delay in seconds between protocol startup and the first attempt to
3191 connect. Default: 5 seconds.
3193 <tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
3194 Time in seconds to wait before retrying a failed attempt to connect.
3195 Default: 120 seconds.
3197 <tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
3198 Minimum and maximum delay in seconds between a protocol failure (either
3199 local or reported by the peer) and automatic restart. Doesn not apply
3200 when <cf/disable after error/ is configured. If consecutive errors
3201 happen, the delay is increased exponentially until it reaches the
3202 maximum. Default: 60, 300.
3204 <tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
3205 Maximum time in seconds between two protocol failures to treat them as a
3206 error sequence which makes <cf/error wait time/ increase exponentially.
3207 Default: 300 seconds.
3209 <tag><label id="bgp-path-metric">path metric <m/switch/</tag>
3210 Enable comparison of path lengths when deciding which BGP route is the
3211 best one. Default: on.
3213 <tag><label id="bgp-med-metric">med metric <m/switch/</tag>
3214 Enable comparison of MED attributes (during best route selection) even
3215 between routes received from different ASes. This may be useful if all
3216 MED attributes contain some consistent metric, perhaps enforced in
3217 import filters of AS boundary routers. If this option is disabled, MED
3218 attributes are compared only if routes are received from the same AS
3219 (which is the standard behavior). Default: off.
3221 <tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
3222 BGP route selection algorithm is often viewed as a comparison between
3223 individual routes (e.g. if a new route appears and is better than the
3224 current best one, it is chosen as the new best one). But the proper
3225 route selection, as specified by <rfc id="4271">, cannot be fully
3226 implemented in that way. The problem is mainly in handling the MED
3227 attribute. BIRD, by default, uses an simplification based on individual
3228 route comparison, which in some cases may lead to temporally dependent
3229 behavior (i.e. the selection is dependent on the order in which routes
3230 appeared). This option enables a different (and slower) algorithm
3231 implementing proper <rfc id="4271"> route selection, which is
3232 deterministic. Alternative way how to get deterministic behavior is to
3233 use <cf/med metric/ option. This option is incompatible with <ref
3234 id="dsc-table-sorted" name="sorted tables">. Default: off.
3236 <tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
3237 Enable comparison of internal distances to boundary routers during best
3238 route selection. Default: on.
3240 <tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
3241 Standard route selection algorithm breaks ties by comparing router IDs.
3242 This changes the behavior to prefer older routes (when both are external
3243 and from different peer). For details, see <rfc id="5004">. Default: off.
3245 <tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
3246 Value of the Multiple Exit Discriminator to be used during route
3247 selection when the MED attribute is missing. Default: 0.
3249 <tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
3250 A default value for the Local Preference attribute. It is used when
3251 a new Local Preference attribute is attached to a route by the BGP
3252 protocol itself (for example, if a route is received through eBGP and
3253 therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
3256 <tag><label id="bgp-local-role">local role <m/role-name/</tag>
3257 BGP roles are a mechanism for route leak prevention and automatic route
3258 filtering based on common BGP topology relationships. They are defined
3259 in <rfc id="9234">. Instead of manually configuring filters and
3260 communities, automatic filtering is done with the help of the OTC
3261 attribute - a flag for routes that should be sent only to customers.
3262 The same attribute is also used to automatically detect and filter route
3263 leaks created by third parties.
3265 This option is valid for EBGP sessions, but it is not recommended to be
3266 used within AS confederations (which would require manual filtering of
3267 <cf/bgp_otc/ attribute on confederation boundaries).
3269 Possible <cf><m/role-name/</cf> values are: <cf/provider/,
3270 <cf/rs_server/, <cf/rs_client/, <cf/customer/ and <cf/peer/.
3271 Default: No local role assigned.
3273 <tag><label id="bgp-require-roles">require roles <m/switch/</tag>
3274 If this option is set, the BGP roles must be defined on both sides,
3275 otherwise the session will not be established. This behavior is defined
3276 in <rfc id="9234"> as "strict mode" and is used to enforce corresponding
3277 configuration at your conterpart side. Default: disabled.
3280 <sect1>Channel configuration
3281 <label id="bgp-channel-config">
3283 <p>BGP supports several AFIs and SAFIs over one connection. Every AFI/SAFI
3284 announced to the peer corresponds to one channel. The table of supported AFI/SAFIs
3285 together with their appropriate channels follows.
3288 <tabular ca="l|l|l|r|r">
3289 <bf/Channel name/ | <bf/Table nettype/ | <bf/IGP table allowed/ | <bf/AFI/ | <bf/SAFI/
3291 <cf/ipv4/ | <cf/ipv4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 1
3292 @ <cf/ipv6/ | <cf/ipv6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 1
3293 @ <cf/ipv4 multicast/ | <cf/ipv4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 2
3294 @ <cf/ipv6 multicast/ | <cf/ipv6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 2
3295 @ <cf/ipv4 mpls/ | <cf/ipv4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 4
3296 @ <cf/ipv6 mpls/ | <cf/ipv6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 4
3297 @ <cf/vpn4 mpls/ | <cf/vpn4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 128
3298 @ <cf/vpn6 mpls/ | <cf/vpn6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 128
3299 @ <cf/vpn4 multicast/ | <cf/vpn4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 129
3300 @ <cf/vpn6 multicast/ | <cf/vpn6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 129
3301 @ <cf/flow4/ | <cf/flow4/ | --- | 1 | 133
3302 @ <cf/flow6/ | <cf/flow6/ | --- | 2 | 133
3306 <p>The BGP protocol can be configured as MPLS-aware (by defining both AFI/SAFI
3307 channels and the MPLS channel). In such case the BGP protocol assigns labels to
3308 routes imported from MPLS-aware SAFIs (i.e. <cf/ipvX mpls/ and <cf/vpnX mpls/)
3309 and automatically announces corresponding MPLS route for each labeled route. As
3310 BGP generally processes a large amount of routes, it is suggested to set MPLS
3311 label policy to <cf/aggregate/.
3313 <p>Note that even BGP instances without MPLS channel and without local MPLS
3314 configuration can still propagate third-party MPLS labels, e.g. as route
3315 reflectors, they just will not assign local labels to imported routes and will
3316 not announce MPLS routes for local MPLS forwarding.
3318 <p>Due to <rfc id="8212">, external BGP protocol requires explicit configuration
3319 of import and export policies (in contrast to other protocols, where default
3320 policies of <cf/import all/ and <cf/export none/ are used in absence of explicit
3321 configuration). Note that blanket policies like <cf/all/ or <cf/none/ can still
3322 be used in explicit configuration.
3324 <p>BGP channels have additional config options (together with the common ones):
3327 <tag><label id="bgp-mandatory">mandatory <m/switch/</tag>
3328 When local and neighbor sets of configured AFI/SAFI pairs differ,
3329 capability negotiation ensures that a common subset is used. For
3330 mandatory channels their associated AFI/SAFI must be negotiated
3331 (i.e., also announced by the neighbor), otherwise BGP session
3332 negotiation fails with <it/'Required capability missing'/ error.
3333 Regardless, at least one AFI/SAFI must be negotiated in order to BGP
3334 session be successfully established. Default: off.
3336 <tag><label id="bgp-next-hop-keep">next hop keep <m/switch/|ibgp|ebgp</tag>
3337 Do not modify the Next Hop attribute and advertise the current one
3338 unchanged even in cases where our own local address should be used
3339 instead. This is necessary when the BGP speaker does not forward network
3340 traffic (route servers and some route reflectors) and also can be useful
3341 in some other cases (e.g. multihop EBGP sessions). Can be enabled for
3342 all routes, or just for routes received from IBGP / EBGP neighbors.
3343 Default: disabled for regular BGP, enabled for route servers,
3344 <cf/ibgp/ for route reflectors.
3346 <tag><label id="bgp-next-hop-self">next hop self <m/switch/|ibgp|ebgp</tag>
3347 Always advertise our own local address as a next hop, even in cases
3348 where the current Next Hop attribute should be used unchanged. This is
3349 sometimes used for routes propagated from EBGP to IBGP when IGP routing
3350 does not cover inter-AS links, therefore IP addreses of EBGP neighbors
3351 are not resolvable through IGP. Can be enabled for all routes, or just
3352 for routes received from IBGP / EBGP neighbors. Default: disabled.
3354 <tag><label id="bgp-next-hop-address">next hop address <m/ip/</tag>
3355 Specify which address to use when our own local address should be
3356 announced in the Next Hop attribute. Default: the source address of the
3357 BGP session (if acceptable), or the preferred address of an associated
3360 <tag><label id="bgp-next-hop-prefer">next hop prefer global</tag>
3361 Prefer global IPv6 address to link-local IPv6 address for immediate next
3362 hops of received routes. For IPv6 routes, the Next Hop attribute may
3363 contain both a global IP address and a link-local IP address. For IBGP
3364 sessions, the global IP address is resolved (<ref id="bgp-gateway"
3365 name="gateway recursive">) through an IGP routing table
3366 (<ref id="bgp-igp-table" name="igp table">) to get an immediate next
3367 hop. If the resulting IGP route is a direct route (i.e., the next hop is
3368 a direct neighbor), then the link-local IP address from the Next Hop
3369 attribute is used as the immediate next hop. This option change it to
3370 use the global IP address instead. Note that even with this option
3371 enabled a route may end with a link-local immediate next hop when the
3372 IGP route has one. Default: disabled.
3374 <tag><label id="bgp-gateway">gateway direct|recursive</tag>
3375 For received routes, their <cf/gw/ (immediate next hop) attribute is
3376 computed from received <cf/bgp_next_hop/ attribute. This option
3377 specifies how it is computed. Direct mode means that the IP address from
3378 <cf/bgp_next_hop/ is used and must be directly reachable. Recursive mode
3379 means that the gateway is computed by an IGP routing table lookup for
3380 the IP address from <cf/bgp_next_hop/. Note that there is just one level
3381 of indirection in recursive mode - the route obtained by the lookup must
3382 not be recursive itself, to prevent mutually recursive routes.
3384 Recursive mode is the behavior specified by the BGP
3385 standard. Direct mode is simpler, does not require any routes in a
3386 routing table, and was used in older versions of BIRD, but does not
3387 handle well nontrivial iBGP setups and multihop. Recursive mode is
3388 incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
3389 <cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
3391 <tag><label id="bgp-igp-table">igp table <m/name/</tag>
3392 Specifies a table that is used as an IGP routing table. The type of this
3393 table must be as allowed in the table above. This option is allowed once
3394 for every allowed table type. Default: the same as the main table
3395 the channel is connected to (if eligible).
3397 <tag><label id="bgp-import-table">import table <m/switch/</tag>
3398 A BGP import table contains all received routes from given BGP neighbor,
3399 before application of import filters. It is also called <em/Adj-RIB-In/
3400 in BGP terminology. BIRD BGP by default operates without import tables,
3401 in which case received routes are just processed by import filters,
3402 accepted ones are stored in the master table, and the rest is forgotten.
3403 Enabling <cf/import table/ allows to store unprocessed routes, which can
3404 be examined later by <cf/show route/, and can be used to reconfigure
3405 import filters without full route refresh. Default: off.
3407 Note that currently the import table breaks routes with recursive
3408 nexthops (e.g. ones from IBGP, see <ref id="bgp-gateway" name="gateway
3409 recursive">), they are not properly updated after next hop change. For
3410 the same reason, it also breaks re-evaluation of flowspec routes with
3411 <ref id="bgp-validate" name="flowspec validation"> option enabled on
3414 <tag><label id="bgp-export-table">export table <m/switch/</tag>
3415 A BGP export table contains all routes sent to given BGP neighbor, after
3416 application of export filters. It is also called <em/Adj-RIB-Out/ in BGP
3417 terminology. BIRD BGP by default operates without export tables, in
3418 which case routes from master table are just processed by export filters
3419 and then announced by BGP. Enabling <cf/export table/ allows to store
3420 routes after export filter processing, so they can be examined later by
3421 <cf/show route/, and can be used to eliminate unnecessary updates or
3422 withdraws. Default: off.
3424 <tag><label id="bgp-secondary">secondary <m/switch/</tag>
3425 Usually, if an export filter rejects a selected route, no other route is
3426 propagated for that network. This option allows to try the next route in
3427 order until one that is accepted is found or all routes for that network
3428 are rejected. This can be used for route servers that need to propagate
3429 different tables to each client but do not want to have these tables
3430 explicitly (to conserve memory). This option requires that the connected
3431 routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
3433 <tag><label id="bgp-validate">validate <m/switch/</tag>
3434 Apply flowspec validation procedure as described in <rfc id="8955">
3435 section 6 and <rfc id="9117">. The Validation procedure enforces that
3436 only routers in the forwarding path for a network can originate flowspec
3437 rules for that network. The validation procedure should be used for EBGP
3438 to prevent injection of malicious flowspec rules from outside, but it
3439 should also be used for IBGP to ensure that selected flowspec rules are
3440 consistent with selected IP routes. The validation procedure uses an IP
3441 routing table (<ref id="bgp-base-table" name="base table">, see below)
3442 against which flowspec rules are validated. This option is limited to
3443 flowspec channels. Default: off (for compatibility reasons).
3445 Note that currently the flowspec validation does not work reliably
3446 together with <ref id="bgp-import-table" name="import table"> option
3447 enabled on flowspec channels.
3449 <tag><label id="bgp-base-table">base table <m/name/</tag>
3450 Specifies an IP table used for the flowspec validation procedure. The
3451 table must have enabled <cf/trie/ option, otherwise the validation
3452 procedure would not work. The type of the table must be <cf/ipv4/ for
3453 <cf/flow4/ channels and <cf/ipv6/ for <cf/flow6/ channels. This option
3454 is limited to flowspec channels. Default: the main table of the
3455 <cf/ipv4/ / <cf/ipv6/ channel of the same BGP instance, or the
3456 <cf/master4/ / <cf/master6/ table if there is no such channel.
3458 <tag><label id="bgp-extended-next-hop">extended next hop <m/switch/</tag>
3459 BGP expects that announced next hops have the same address family as
3460 associated network prefixes. This option provides an extension to use
3461 IPv4 next hops with IPv6 prefixes and vice versa. For IPv4 / VPNv4
3462 channels, the behavior is controlled by the Extended Next Hop Encoding
3463 capability, as described in <rfc id="8950">. For IPv6 / VPNv6 channels,
3464 just IPv4-mapped IPv6 addresses are used, as described in
3465 <rfc id="4798"> and <rfc id="4659">. Default: off.
3467 <tag><label id="bgp-require-extended-next-hop">require extended next hop <m/switch/</tag>
3468 If enabled, the BGP Extended Next Hop Encoding capability (<rfc id="8950">)
3469 must be announced by the BGP neighbor, otherwise the BGP session will
3470 not be established. Note that this option is relevant just for IPv4 /
3471 VPNv4 channels, as IPv6 / VPNv6 channels use a different mechanism not
3472 signalled by a capability. Default: off.
3474 <tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
3475 Standard BGP can propagate only one path (route) per destination network
3476 (usually the selected one). This option controls the ADD-PATH protocol
3477 extension, which allows to advertise any number of paths to a
3478 destination. Note that to be active, ADD-PATH has to be enabled on both
3479 sides of the BGP session, but it could be enabled separately for RX and
3480 TX direction. When active, all available routes accepted by the export
3481 filter are advertised to the neighbor. Default: off.
3483 <tag><label id="bgp-require-add-paths">require add paths <m/switch/</tag>
3484 If enabled, the BGP ADD-PATH capability (<rfc id="7911">) must be
3485 announced by the BGP neighbor, otherwise the BGP session will not be
3486 established. Announced directions in the capability must be compatible
3487 with locally configured directions. E.g., If <cf/add path tx/ is
3488 configured locally, then the neighbor capability must announce RX.
3491 <tag><label id="bgp-aigp">aigp <m/switch/|originate</tag>
3492 The BGP protocol does not use a common metric like other routing
3493 protocols, instead it uses a set of criteria for route selection
3494 consisting both overall AS path length and a distance to the nearest AS
3495 boundary router. Assuming that metrics of different autonomous systems
3496 are incomparable, once a route is propagated from an AS to a next one,
3497 the distance in the old AS does not matter.
3499 The AIGP extension (<rfc id="7311">) allows to propagate accumulated
3500 IGP metric (in the AIGP attribute) through both IBGP and EBGP links,
3501 computing total distance through multiple autonomous systems (assuming
3502 they use comparable IGP metric). The total AIGP metric is compared in
3503 the route selection process just after Local Preference comparison (and
3504 before AS path length comparison).
3506 This option controls whether AIGP attribute propagation is allowed on
3507 the session. Optionally, it can be set to <cf/originate/, which not only
3508 allows AIGP attribute propagation, but also new AIGP attributes are
3509 automatically attached to non-BGP routes with valid IGP metric (e.g.
3510 <cf/ospf_metric1/) as they are exported to the BGP session. Default:
3511 enabled for IBGP (and intra-confederation EBGP), disabled for regular
3514 <tag><label id="bgp-cost">cost <m/number/</tag>
3515 When BGP <ref id="bgp-gateway" name="gateway mode"> is <cf/recursive/
3516 (mainly multihop IBGP sessions), then the distance to BGP next hop is
3517 based on underlying IGP metric. This option specifies the distance to
3518 BGP next hop for BGP sessions in direct gateway mode (mainly direct
3521 <tag><label id="bgp-graceful-restart-c">graceful restart <m/switch/</tag>
3522 Although BGP graceful restart is configured mainly by protocol-wide
3523 <ref id="bgp-graceful-restart" name="options">, it is possible to
3524 configure restarting role per AFI/SAFI pair by this channel option.
3525 The option is ignored if graceful restart is disabled by protocol-wide
3526 option. Default: off in aware mode, on in full mode.
3528 <tag><label id="bgp-long-lived-graceful-restart-c">long lived graceful restart <m/switch/</tag>
3529 BGP long-lived graceful restart is configured mainly by protocol-wide
3530 <ref id="bgp-long-lived-graceful-restart" name="options">, but the
3531 restarting role can be set per AFI/SAFI pair by this channel option.
3532 The option is ignored if long-lived graceful restart is disabled by
3533 protocol-wide option. Default: off in aware mode, on in full mode.
3535 <tag><label id="bgp-long-lived-stale-time-c">long lived stale time <m/number/</tag>
3536 Like previous graceful restart channel options, this option allows to
3537 set <ref id="bgp-long-lived-stale-time" name="long lived stale time">
3538 per AFI/SAFI pair instead of per protocol. Default: set by protocol-wide
3543 <label id="bgp-attr">
3545 <p>BGP defines several route attributes. Some of them (those marked with
3546 `<tt/I/' in the table below) are available on internal BGP connections only,
3547 some of them (marked with `<tt/O/') are optional.
3550 <tag><label id="rta-bgp-path">bgppath bgp_path</tag>
3551 Sequence of AS numbers describing the AS path the packet will travel
3552 through when forwarded according to the particular route. In case of
3553 internal BGP it doesn't contain the number of the local AS.
3555 <tag><label id="rta-bgp-local-pref">int bgp_local_pref [I]</tag>
3556 Local preference value used for selection among multiple BGP routes (see
3557 the selection rules above). It's used as an additional metric which is
3558 propagated through the whole local AS.
3560 <tag><label id="rta-bgp-med">int bgp_med [O]</tag>
3561 The Multiple Exit Discriminator of the route is an optional attribute
3562 which is used on external (inter-AS) links to convey to an adjacent AS
3563 the optimal entry point into the local AS. The received attribute is
3564 also propagated over internal BGP links. The attribute value is zeroed
3565 when a route is exported to an external BGP instance to ensure that the
3566 attribute received from a neighboring AS is not propagated to other
3567 neighboring ASes. A new value might be set in the export filter of an
3568 external BGP instance. See <rfc id="4451"> for further discussion of
3571 <tag><label id="rta-bgp-origin">enum bgp_origin</tag>
3572 Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
3573 in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
3574 from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
3575 <cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
3577 <tag><label id="rta-bgp-next-hop">ip bgp_next_hop</tag>
3578 Next hop to be used for forwarding of packets to this destination. On
3579 internal BGP connections, it's an address of the originating router if
3580 it's inside the local AS or a boundary router the packet will leave the
3581 AS through if it's an exterior route, so each BGP speaker within the AS
3582 has a chance to use the shortest interior path possible to this point.
3584 <tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr [O]</tag>
3585 This is an optional attribute which carries no value, but the sole
3586 presence of which indicates that the route has been aggregated from
3587 multiple routes by some router on the path from the originator.
3589 <tag><label id="rta-bgp-aggregator">void bgp_aggregator [O]</tag>
3590 This is an optional attribute specifying AS number and IP address of the
3591 BGP router that created the route by aggregating multiple BGP routes.
3592 Currently, the attribute is not accessible from filters.
3594 <tag><label id="rta-bgp-community">clist bgp_community [O]</tag>
3595 List of community values associated with the route. Each such value is a
3596 pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
3597 integers, the first of them containing the number of the AS which
3598 defines the community and the second one being a per-AS identifier.
3599 There are lots of uses of the community mechanism, but generally they
3600 are used to carry policy information like "don't export to USA peers".
3601 As each AS can define its own routing policy, it also has a complete
3602 freedom about which community attributes it defines and what will their
3605 <tag><label id="rta-bgp-ext-community">eclist bgp_ext_community [O]</tag>
3606 List of extended community values associated with the route. Extended
3607 communities have similar usage as plain communities, but they have an
3608 extended range (to allow 4B ASNs) and a nontrivial structure with a type
3609 field. Individual community values are represented using an <cf/ec/ data
3610 type inside the filters.
3612 <tag><label id="rta-bgp-large-community">lclist bgp_large_community [O]</tag>
3613 List of large community values associated with the route. Large BGP
3614 communities is another variant of communities, but contrary to extended
3615 communities they behave very much the same way as regular communities,
3616 just larger -- they are uniform untyped triplets of 32bit numbers.
3617 Individual community values are represented using an <cf/lc/ data type
3620 <tag><label id="rta-bgp-originator-id">quad bgp_originator_id [I, O]</tag>
3621 This attribute is created by the route reflector when reflecting the
3622 route and contains the router ID of the originator of the route in the
3625 <tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list [I, O]</tag>
3626 This attribute contains a list of cluster IDs of route reflectors. Each
3627 route reflector prepends its cluster ID when reflecting the route.
3629 <tag><label id="rta-bgp-aigp">void bgp_aigp [O]</tag>
3630 This attribute contains accumulated IGP metric, which is a total
3631 distance to the destination through multiple autonomous systems.
3632 Currently, the attribute is not accessible from filters.
3634 <tag><label id="bgp-otc">int bgp_otc [O]</tag>
3635 This attribute is defined in <rfc id="9234">. OTC is a flag that marks
3636 routes that should be sent only to customers. If <ref id="bgp-local-role"
3637 name="local role"> is configured it set automatically.
3640 <p>For attributes unknown by BIRD, the user can assign a name (on top level) to
3641 an attribute by its number. This defined name can be used then to get, set (as a
3642 bytestring, transitive) or unset the given attribute even though BIRD knows
3645 <p>Note that it is not possible to define an attribute with the same number
3646 as one known by BIRD, therefore use of this statement carries a risk of
3647 incompatibility with future BIRD versions.
3649 <tt><label id="bgp-attribute-custom">attribute bgp <m/number/ bytestring <m/name/;</tt>
3652 <label id="bgp-exam">
3656 local 198.51.100.14 as 65000; # Use a private AS number
3657 neighbor 198.51.100.130 as 64496; # Our neighbor ...
3658 multihop; # ... which is connected indirectly
3660 export filter { # We use non-trivial export rules
3661 if source = RTS_STATIC then { # Export only static routes
3662 # Assign our community
3663 bgp_community.add((65000,64501));
3664 # Artificially increase path length
3665 # by advertising local AS number twice
3666 if bgp_path ~ [= 65000 =] then
3667 bgp_path.prepend(65000);
3673 next hop self; # advertise this router as next hop
3674 igp table myigptable4; # IGP table for routes with IPv4 nexthops
3675 igp table myigptable6; # IGP table for routes with IPv6 nexthops
3678 export filter mylargefilter; # We use a named filter
3680 missing lladdr self;
3681 igp table myigptable4; # IGP table for routes with IPv4 nexthops
3682 igp table myigptable6; # IGP table for routes with IPv6 nexthops
3686 export filter someotherfilter;
3687 table mymulticasttable4; # Another IPv4 table, dedicated for multicast
3688 igp table myigptable4;
3697 <p>The BGP Monitoring Protocol is used for monitoring BGP sessions and obtaining
3698 routing table data. The current implementation in BIRD is a preliminary release
3699 with a limited feature set, it will be subject to significant changes in the
3700 future. It is not ready for production usage and therefore it is not compiled
3701 by default and have to be enabled during installation by the configure option
3702 <tt/--with-protocols=/.
3704 <p>The implementation supports monitoring protocol state changes, pre-policy
3705 routes (in <ref id="bgp-import-table" name="BGP import tables">) and post-policy
3706 routes (in regular routing tables). All BGP protocols are monitored automatically.
3709 <label id="bmp-exam">
3713 # The monitoring station to connect to
3714 station address ip 198.51.100.10 port 1790;
3716 # Monitor received routes (in import table)
3717 monitoring rib in pre_policy;
3719 # Monitor accepted routes (passed import filters)
3720 monitoring rib in post_policy;
3728 <p>The Device protocol is not a real routing protocol. It doesn't generate any
3729 routes and it only serves as a module for getting information about network
3730 interfaces from the kernel. This protocol supports no channel.
3732 <p>Except for very unusual circumstances, you probably should include this
3733 protocol in the configuration since almost all other protocols require network
3734 interfaces to be defined for them to work with.
3736 <sect1>Configuration
3737 <label id="device-config">
3740 <tag><label id="device-scan-time">scan time <m/number/</tag>
3741 Time in seconds between two scans of the network interface list. On
3742 systems where we are notified about interface status changes
3743 asynchronously (such as newer versions of Linux), we need to scan the
3744 list only in order to avoid confusion by lost notification messages,
3745 so the default time is set to a large value.
3747 <tag><label id="device-iface">interface <m/pattern/ [, <m/.../]</tag>
3748 By default, the Device protocol handles all interfaces without any
3749 configuration. Interface definitions allow to specify optional
3750 parameters for specific interfaces. See <ref id="proto-iface"
3751 name="interface"> common option for detailed description. Currently only
3752 one interface option is available:
3754 <tag><label id="device-preferred">preferred <m/ip/</tag>
3755 If a network interface has more than one IP address, BIRD chooses one of
3756 them as a preferred one. Preferred IP address is used as source address
3757 for packets or announced next hop by routing protocols. Precisely, BIRD
3758 chooses one preferred IPv4 address, one preferred IPv6 address and one
3759 preferred link-local IPv6 address. By default, BIRD chooses the first
3760 found IP address as the preferred one.
3762 This option allows to specify which IP address should be preferred. May
3763 be used multiple times for different address classes (IPv4, IPv6, IPv6
3764 link-local). In all cases, an address marked by operating system as
3765 secondary cannot be chosen as the primary one.
3768 <p>As the Device protocol doesn't generate any routes, it cannot have
3769 any attributes. Example configuration looks like this:
3773 scan time 10; # Scan the interfaces often
3775 preferred 192.168.1.1;
3776 preferred 2001:db8:1:10::1;
3785 <p>The Direct protocol is a simple generator of device routes for all the
3786 directly connected networks according to the list of interfaces provided by the
3787 kernel via the Device protocol. The Direct protocol supports both IPv4 and IPv6
3788 channels; both can be configured simultaneously. It can also be configured with
3789 <ref id="ip-sadr-routes" name="IPv6 SADR"> channel instead of regular IPv6
3790 channel in order to be used together with SADR-enabled Babel protocol.
3792 <p>The question is whether it is a good idea to have such device routes in BIRD
3793 routing table. OS kernel usually handles device routes for directly connected
3794 networks by itself so we don't need (and don't want) to export these routes to
3795 the kernel protocol. OSPF protocol creates device routes for its interfaces
3796 itself and BGP protocol is usually used for exporting aggregate routes. But the
3797 Direct protocol is necessary for distance-vector protocols like RIP or Babel to
3798 announce local networks.
3800 <p>There are just few configuration options for the Direct protocol:
3803 <tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
3804 By default, the Direct protocol will generate device routes for all the
3805 interfaces available. If you want to restrict it to some subset of
3806 interfaces or addresses (e.g. if you're using multiple routing tables
3807 for policy routing and some of the policy domains don't contain all
3808 interfaces), just use this clause. See <ref id="proto-iface" name="interface">
3809 common option for detailed description. The Direct protocol uses
3810 extended interface clauses.
3812 <tag><label id="direct-check-link">check link <m/switch/</tag>
3813 If enabled, a hardware link state (reported by OS) is taken into
3814 consideration. Routes for directly connected networks are generated only
3815 if link up is reported and they are withdrawn when link disappears
3816 (e.g., an ethernet cable is unplugged). Default value is no.
3819 <p>Direct device routes don't contain any specific attributes.
3821 <p>Example config might look like this:
3827 interface "-arc*", "*"; # Exclude the ARCnets
3835 <p>The Kernel protocol is not a real routing protocol. Instead of communicating
3836 with other routers in the network, it performs synchronization of BIRD's routing
3837 tables with the OS kernel. Basically, it sends all routing table updates to the
3838 kernel and from time to time it scans the kernel tables to see whether some
3839 routes have disappeared (for example due to unnoticed up/down transition of an
3840 interface) or whether an `alien' route has been added by someone else (depending
3841 on the <cf/learn/ switch, such routes are either ignored or accepted to our
3844 <p>Note that routes created by OS kernel itself, namely direct routes
3845 representing IP subnets of associated interfaces, are imported only with
3846 <cf/learn all/ enabled.
3848 <p>If your OS supports only a single routing table, you can configure only one
3849 instance of the Kernel protocol. If it supports multiple tables (in order to
3850 allow policy routing; such an OS is for example Linux), you can run as many
3851 instances as you want, but each of them must be connected to a different BIRD
3852 routing table and to a different kernel table.
3854 <p>Because the kernel protocol is partially integrated with the connected
3855 routing table, there are two limitations - it is not possible to connect more
3856 kernel protocols to the same routing table and changing route destination
3857 (gateway) in an export filter of a kernel protocol does not work. Both
3858 limitations can be overcome using another routing table and the pipe protocol.
3860 <p>The Kernel protocol supports both IPv4 and IPv6 channels; only one channel
3861 can be configured in each protocol instance. On Linux, it also supports <ref
3862 id="ip-sadr-routes" name="IPv6 SADR"> and <ref id="mpls-routes" name="MPLS">
3865 <sect1>Configuration
3866 <label id="krt-config">
3869 <tag><label id="krt-persist">persist <m/switch/</tag>
3870 Tell BIRD to leave all its routes in the routing tables when it exits
3871 (instead of cleaning them up).
3873 <tag><label id="krt-scan-time">scan time <m/number/</tag>
3874 Time in seconds between two consecutive scans of the kernel routing
3877 <tag><label id="krt-learn">learn <m/switch/|all</tag>
3878 Enable learning of routes added to the kernel routing tables by other
3879 routing daemons or by the system administrator. This is possible only on
3880 systems which support identification of route authorship. By default,
3881 routes created by kernel (marked as "proto kernel") are not imported.
3882 Use <cf/learn all/ option to import even these routes.
3884 <tag><label id="krt-kernel-table">kernel table <m/number/</tag>
3885 Select which kernel table should this particular instance of the Kernel
3886 protocol work with. Available only on systems supporting multiple
3889 <tag><label id="krt-metric">metric <m/number/</tag> (Linux)
3890 Use specified value as a kernel metric (priority) for all routes sent to
3891 the kernel. When multiple routes for the same network are in the kernel
3892 routing table, the Linux kernel chooses one with lower metric. Also,
3893 routes with different metrics do not clash with each other, therefore
3894 using dedicated metric value is a reliable way to avoid overwriting
3895 routes from other sources (e.g. kernel device routes). Metric 0 has a
3896 special meaning of undefined metric, in which either OS default is used,
3897 or per-route metric can be set using <cf/krt_metric/ attribute. Default:
3900 <tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
3901 Participate in graceful restart recovery. If this option is enabled and
3902 a graceful restart recovery is active, the Kernel protocol will defer
3903 synchronization of routing tables until the end of the recovery. Note
3904 that import of kernel routes to BIRD is not affected.
3906 <tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
3907 Usually, only best routes are exported to the kernel protocol. With path
3908 merging enabled, both best routes and equivalent non-best routes are
3909 merged during export to generate one ECMP (equal-cost multipath) route
3910 for each network. This is useful e.g. for BGP multipath. Note that best
3911 routes are still pivotal for route export (responsible for most
3912 properties of resulting ECMP routes), while exported non-best routes are
3913 responsible just for additional multipath next hops. This option also
3914 allows to specify a limit on maximal number of nexthops in one route. By
3915 default, multipath merging is disabled. If enabled, default value of the
3918 <tag><label id="krt-netlink-rx-buffer">netlink rx buffer <m/number/</tag> (Linux)
3919 Set kernel receive buffer size (in bytes) for the netlink socket. The default
3920 value is OS-dependent (from the <file>/proc/sys/net/core/rmem_default</file>
3921 file), If you get some "Kernel dropped some netlink message ..." warnings,
3922 you may increase this value.
3926 <label id="krt-attr">
3928 <p>The Kernel protocol defines several attributes. These attributes are
3929 translated to appropriate system (and OS-specific) route attributes. We support
3933 <tag><label id="rta-krt-source">int krt_source</tag>
3934 The original source of the imported kernel route. The value is
3935 system-dependent. On Linux, it is a value of the protocol field of the
3936 route. See /etc/iproute2/rt_protos for common values. On BSD, it is
3937 based on STATIC and PROTOx flags. The attribute is read-only.
3939 <tag><label id="rta-krt-metric">int krt_metric</tag> (Linux)
3940 The kernel metric of the route. When multiple same routes are in a
3941 kernel routing table, the Linux kernel chooses one with lower metric.
3942 Note that preferred way to set kernel metric is to use protocol option
3943 <cf/metric/, unless per-route metric values are needed.
3945 <tag><label id="rta-krt-prefsrc">ip krt_prefsrc</tag> (Linux)
3946 The preferred source address. Used in source address selection for
3947 outgoing packets. Has to be one of the IP addresses of the router.
3949 <tag><label id="rta-krt-realm">int krt_realm</tag> (Linux)
3950 The realm of the route. Can be used for traffic classification.
3952 <tag><label id="rta-krt-scope">int krt_scope</tag> (Linux IPv4)
3953 The scope of the route. Valid values are 0-254, although Linux kernel
3954 may reject some values depending on route type and nexthop. It is
3955 supposed to represent `indirectness' of the route, where nexthops of
3956 routes are resolved through routes with a higher scope, but in current
3957 kernels anything below <it/link/ (253) is treated as <it/global/ (0).
3958 When not present, global scope is implied for all routes except device
3959 routes, where link scope is used by default.
3962 <p>In Linux, there is also a plenty of obscure route attributes mostly focused
3963 on tuning TCP performance of local connections. BIRD supports most of these
3964 attributes, see Linux or iproute2 documentation for their meaning. Attributes
3965 <cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, <cf/krt_congctl/ has type
3966 string, others have type int. Supported attributes are:
3968 <cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
3969 <cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
3970 <cf/krt_ssthresh/, <cf/krt_lock_ssthresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
3971 <cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
3972 <cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
3973 <cf/krt_initcwnd/, <cf/krt_lock_initcwnd/, <cf/krt_initrwnd/, <cf/krt_lock_initrwnd/,
3974 <cf/krt_quickack/, <cf/krt_lock_quickack/, <cf/krt_congctl/, <cf/krt_lock_congctl/,
3975 <cf/krt_fastopen_no_cookie/, <cf/krt_lock_fastopen_no_cookie/,
3976 <cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
3979 <label id="krt-exam">
3981 <p>A simple configuration can look this way:
3989 <p>Or for a system with two routing tables:
3992 protocol kernel { # Primary routing table
3993 learn; # Learn alien routes from the kernel
3994 persist; # Do not remove routes on bird shutdown
3995 scan time 10; # Scan kernel routing table every 10 seconds
4002 protocol kernel { # Secondary routing table
4016 <label id="l3vpn-intro">
4018 <p>The L3VPN protocol serves as a translator between IP routes and VPN
4019 routes. It is a component for BGP/MPLS IP VPNs (<rfc id="4364">) and implements
4020 policies defined there. In import direction (VPN -> IP), VPN routes matching
4021 import target specification are stripped of route distinguisher and MPLS labels
4022 and announced as IP routes, In export direction (IP -> VPN), IP routes are
4023 expanded with specific route distinguisher, export target communities and MPLS
4024 label and announced as labeled VPN routes. Unlike the Pipe protocol, the L3VPN
4025 protocol propagates just the best route for each network.
4027 <p>In BGP/MPLS IP VPNs, route distribution is controlled by Route Targets (RT).
4028 VRFs are associated with one or more RTs. Routes are also associated with one or
4029 more RTs, which are encoded as route target extended communities
4030 in <ref id="rta-bgp-ext-community" name="bgp_ext_community">. A route is then
4031 imported into each VRF that shares an associated Route Target. The L3VPN
4032 protocol implements this mechanism through mandatory <cf/import target/ and
4033 <cf/export target/ protocol options.
4035 <sect1>Configuration
4036 <label id="l3vpn-config">
4038 <p>L3VPN configuration consists of a few mandatory options and multiple channel
4039 definitions. For convenience, the default export filter in L3VPN channels is
4040 <cf/all/, as the primary way to control import and export of routes is through
4041 protocol options <cf/import target/ and <cf/export target/. If custom filters
4042 are used, note that the export filter of the input channel is applied before
4043 the route translation, while the import filter of the output channel is applied
4046 <p>In contrast to the Pipe protocol, the L3VPN protocol can handle both IPv4 and
4047 IPv6 routes in one instance, also both IP side and VPN side are represented as
4048 separate channels, although that may change in the future. The L3VPN is always
4049 MPLS-aware protocol, therefore a MPLS channel is mandatory. Altogether, L3VPN
4050 could have up to 5 channels: <cf/ipv4/, <cf/ipv6/, <cf/vpn4/, <cf/vpn6/, and
4054 <tag><label id="l3vpn-route-distinguisher">route distinguisher <m/vpnrd/</tag>
4055 The route distinguisher that is attached to routes in the export
4056 direction. Mandatory.
4058 <tag><label id="l3vpn-rd">rd <m/vpnrd/</tag>
4059 A shorthand for the option <cf/route distinguisher/.
4061 <tag><label id="l3vpn-import-target">import target <m/ec/|<m/ec-set/</tag>
4062 Route target extended communities specifying which routes should be
4063 imported. Either one community or a set. A route is imported if there is
4064 non-empty intersection between extended communities of the route and the
4065 import target of the L3VPN protocol. Mandatory.
4067 <tag><label id="l3vpn-export-target">export target <m/ec/|<m/ec-set/</tag>
4068 Route target extended communities that are attached to the route in the
4069 export direction. Either one community or a set. Other route target
4070 extended communities are removed. Mandatory.
4072 <tag><label id="l3vpn-route-target">route target <m/ec/|<m/ec-set/</tag>
4073 A shorthand for both <cf/import target/ and <cf/export target/.
4077 <label id="l3vpn-attr">
4079 <p>The L3VPN protocol does not define any route attributes.
4082 <label id="l3vpn-exam">
4084 <p>Here is an example of L3VPN setup with one VPN and BGP uplink. IP routes
4085 learned from a customer in the VPN are stored in <cf/vrf0vX/ tables, which are
4086 mapped to kernel VRF vrf0. Routes can also be exchanged through BGP with
4087 different sites hosting that VPN. Forwarding of VPN traffic through the network
4090 <p>Omitted from the example are some routing protocol to exchange routes with
4091 the customer and some sort of MPLS-aware IGP to resolve next hops for BGP VPN
4099 protocol kernel krt_mpls {
4100 mpls { table mtab; export all; };
4106 # Exchange VPN routes through BGP
4108 vpn4 { table vpntab4; import all; export all; };
4109 vpn6 { table vpntab6; import all; export all; };
4110 mpls { label policy aggregate; };
4111 local 10.0.0.1 as 10;
4112 neighbor 10.0.0.2 as 10;
4119 protocol kernel kernel0v4 {
4121 ipv4 { table vrf0v4; export all; };
4125 protocol kernel kernel0v6 {
4127 ipv6 { table vrf0v6; export all; };
4131 protocol l3vpn l3vpn0 {
4133 ipv4 { table vrf0v4; };
4134 ipv6 { table vrf0v6; };
4135 vpn4 { table vpntab4; };
4136 vpn6 { table vpntab6; };
4137 mpls { label policy vrf; };
4140 import target [(rt, 10, 32..40)];
4141 export target [(rt, 10, 30), (rt, 10, 31)];
4150 <label id="mrt-intro">
4152 <p>The MRT protocol is a component responsible for handling the Multi-Threaded
4153 Routing Toolkit (MRT) routing information export format, which is mainly used
4154 for collecting and analyzing of routing information from BGP routers. The MRT
4155 protocol can be configured to do periodic dumps of routing tables, created MRT
4156 files can be analyzed later by other tools. Independent MRT table dumps can also
4157 be requested from BIRD client. There is also a feature to save incoming BGP
4158 messages in MRT files, but it is controlled by <ref id="proto-mrtdump"
4159 name="mrtdump"> options independently of MRT protocol, although that might
4160 change in the future.
4162 BIRD implements the main MRT format specification as defined in <rfc id="6396">
4163 and the ADD_PATH extension (<rfc id="8050">).
4165 <sect1>Configuration
4166 <label id="mrt-config">
4168 <p>MRT configuration consists of several statements describing routing table
4169 dumps. Multiple independent periodic dumps can be done as multiple MRT protocol
4170 instances. The MRT protocol does not use channels. There are two mandatory
4171 statements: <cf/filename/ and <cf/period/.
4173 The behavior can be modified by following configuration parameters:
4176 <tag><label id="mrt-table">table <m/name/ | "<m/pattern/"</tag>
4177 Specify a routing table (or a set of routing tables described by a
4178 wildcard pattern) that are to be dumped by the MRT protocol instance.
4179 Default: the master table.
4181 <tag><label id="mrt-filter">filter { <m/filter commands/ }</tag>
4182 The MRT protocol allows to specify a filter that is applied to routes as
4183 they are dumped. Rejected routes are ignored and not saved to the MRT
4184 dump file. Default: no filter.
4186 <tag><label id="mrt-where">where <m/filter expression/</tag>
4187 An alternative way to specify a filter for the MRT protocol.
4189 <tag><label id="mrt-filename">filename "<m/filename/"</tag>
4190 Specify a filename for MRT dump files. The filename may contain time
4191 format sequences with <it/strftime(3)/ notation (see <it/man strftime/
4192 for details), there is also a sequence "%N" that is expanded to the name
4193 of dumped table. Therefore, each periodic dump of each table can be
4194 saved to a different file. Mandatory, see example below.
4196 <tag><label id="mrt-period">period <m/number/</tag>
4197 Specify the time interval (in seconds) between periodic dumps.
4200 <tag><label id="mrt-always-add-path">always add path <m/switch/</tag>
4201 The MRT format uses special records (specified in <rfc id="8050">) for
4202 routes received using BGP ADD_PATH extension to keep Path ID, while
4203 other routes use regular records. This has advantage of better
4204 compatibility with tools that do not know special records, but it loses
4205 information about which route is the best route. When this option is
4206 enabled, both ADD_PATH and non-ADD_PATH routes are stored in ADD_PATH
4207 records and order of routes for network is preserved. Default: disabled.
4211 <label id="mrt-exam">
4216 where source = RTS_BGP;
4217 filename "/var/log/bird/%N_%F_%T.mrt";
4227 <label id="ospf-intro">
4229 <p>Open Shortest Path First (OSPF) is a quite complex interior gateway
4230 protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
4231 the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
4232 state (a.k.a. shortest path first) protocol -- each router maintains a database
4233 describing the autonomous system's topology. Each participating router has an
4234 identical copy of the database and all routers run the same algorithm
4235 calculating a shortest path tree with themselves as a root. OSPF chooses the
4236 least cost path as the best path.
4238 <p>In OSPF, the autonomous system can be split to several areas in order to
4239 reduce the amount of resources consumed for exchanging the routing information
4240 and to protect the other areas from incorrect routing data. Topology of the area
4241 is hidden to the rest of the autonomous system.
4243 <p>Another very important feature of OSPF is that it can keep routing information
4244 from other protocols (like Static or BGP) in its link state database as external
4245 routes. Each external route can be tagged by the advertising router, making it
4246 possible to pass additional information between routers on the boundary of the
4249 <p>OSPF quickly detects topological changes in the autonomous system (such as
4250 router interface failures) and calculates new loop-free routes after a short
4251 period of convergence. Only a minimal amount of routing traffic is involved.
4253 <p>Each router participating in OSPF routing periodically sends Hello messages
4254 to all its interfaces. This allows neighbors to be discovered dynamically. Then
4255 the neighbors exchange theirs parts of the link state database and keep it
4256 identical by flooding updates. The flooding process is reliable and ensures that
4257 each router detects all changes.
4259 <sect1>Configuration
4260 <label id="ospf-config">
4262 <p>First, the desired OSPF version can be specified by using <cf/ospf v2/ or
4263 <cf/ospf v3/ as a protocol type. By default, OSPFv2 is used. In the main part of
4264 configuration, there can be multiple definitions of OSPF areas, each with a
4265 different id. These definitions includes many other switches and multiple
4266 definitions of interfaces. Definition of interface may contain many switches and
4267 constant definitions and list of neighbors on nonbroadcast networks.
4269 <p>OSPFv2 needs one IPv4 channel. OSPFv3 needs either one IPv6 channel, or one
4270 IPv4 channel (<rfc id="5838">). Therefore, it is possible to use OSPFv3 for both
4271 IPv4 and Pv6 routing, but it is necessary to have two protocol instances anyway.
4272 If no channel is configured, appropriate channel is defined with default
4276 protocol ospf [v2|v3] <name> {
4277 rfc1583compat <switch>;
4278 rfc5838 <switch>;
4279 instance id <num>;
4280 stub router <switch>;
4282 ecmp <switch> [limit <num>];
4283 merge external <switch>;
4284 graceful restart <switch>|aware;
4285 graceful restart time <num>;
4289 summary <switch>;
4290 default nssa <switch>;
4291 default cost <num>;
4292 default cost2 <num>;
4293 translator <switch>;
4294 translator stability <num>;
4298 <prefix> hidden;
4302 <prefix> hidden;
4303 <prefix> tag <num>;
4305 stubnet <prefix>;
4306 stubnet <prefix> {
4307 hidden <switch>;
4308 summary <switch>;
4311 interface <interface pattern> [instance <num>] {
4313 stub <switch>;
4316 retransmit <num>;
4317 priority <num>;
4319 dead count <num>;
4321 secondary <switch>;
4322 rx buffer [normal|large|<num>];
4323 tx length <num>;
4324 type [broadcast|bcast|pointopoint|ptp|
4325 nonbroadcast|nbma|pointomultipoint|ptmp];
4326 link lsa suppression <switch>;
4327 strict nonbroadcast <switch>;
4328 real broadcast <switch>;
4329 ptp netmask <switch>;
4330 ptp address <switch>;
4331 check link <switch>;
4333 ecmp weight <num>;
4334 ttl security [<switch>; | tx only]
4335 tx class|dscp <num>;
4336 tx priority <num>;
4337 authentication none|simple|cryptographic;
4338 password "<text>";
4339 password "<text>" {
4341 generate from "<date>";
4342 generate to "<date>";
4343 accept from "<date>";
4344 accept to "<date>";
4345 from "<date>";
4347 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
4351 <ip> eligible;
4354 virtual link <id> [instance <num>] {
4356 retransmit <num>;
4358 dead count <num>;
4360 authentication none|simple|cryptographic;
4361 password "<text>";
4362 password "<text>" {
4364 generate from "<date>";
4365 generate to "<date>";
4366 accept from "<date>";
4367 accept to "<date>";
4368 from "<date>";
4370 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
4378 <tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
4379 This option controls compatibility of routing table calculation with
4380 <rfc id="1583">. Default value is no.
4382 <tag><label id="ospf-rfc5838">rfc5838 <m/switch/</tag>
4383 Basic OSPFv3 is limited to IPv6 unicast routing. The <rfc id="5838">
4384 extension defines support for more address families (IPv4, IPv6, both
4385 unicast and multicast). The extension is enabled by default, but can be
4386 disabled if necessary, as it restricts the range of available instance
4387 IDs. Default value is yes.
4389 <tag><label id="ospf-instance-id">instance id <m/num/</tag>
4390 When multiple OSPF protocol instances are active on the same links, they
4391 should use different instance IDs to distinguish their packets. Although
4392 it could be done on per-interface basis, it is often preferred to set
4393 one instance ID to whole OSPF domain/topology (e.g., when multiple
4394 instances are used to represent separate logical topologies on the same
4395 physical network). This option specifies the instance ID for all
4396 interfaces of the OSPF instance, but can be overridden by
4397 <cf/interface/ option. Default value is 0 unless OSPFv3-AF extended
4398 address families are used, see <rfc id="5838"> for that case.
4400 <tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
4401 This option configures the router to be a stub router, i.e., a router
4402 that participates in the OSPF topology but does not allow transit
4403 traffic. In OSPFv2, this is implemented by advertising maximum metric
4404 for outgoing links. In OSPFv3, the stub router behavior is announced by
4405 clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
4406 Default value is no.
4408 <tag><label id="ospf-tick">tick <M>num</M></tag>
4409 The routing table calculation and clean-up of areas' databases is not
4410 performed when a single link state change arrives. To lower the CPU
4411 utilization, it's processed later at periodical intervals of <m/num/
4412 seconds. The default value is 1.
4414 <tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
4415 This option specifies whether OSPF is allowed to generate ECMP
4416 (equal-cost multipath) routes. Such routes are used when there are
4417 several directions to the destination, each with the same (computed)
4418 cost. This option also allows to specify a limit on maximum number of
4419 nexthops in one route. By default, ECMP is enabled if supported by
4420 Kernel. Default value of the limit is 16.
4422 <tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
4423 This option specifies whether OSPF should merge external routes from
4424 different routers/LSAs for the same destination. When enabled together
4425 with <cf/ecmp/, equal-cost external routes will be combined to multipath
4426 routes in the same way as regular routes. When disabled, external routes
4427 from different LSAs are treated as separate even if they represents the
4428 same destination. Default value is no.
4430 <tag><label id="ospf-graceful-restart">graceful restart <m/switch/|aware</tag>
4431 When an OSPF instance is restarted, neighbors break adjacencies and
4432 recalculate their routing tables, which disrupts packet forwarding even
4433 when the forwarding plane of the restarting router remains intact.
4434 <rfc id="3623"> specifies a graceful restart mechanism to alleviate this
4435 issue. For OSPF graceful restart, restarting router originates
4436 Grace-LSAs, announcing intent to do graceful restart. Neighbors
4437 receiving these LSAs enter helper mode, in which they ignore breakdown
4438 of adjacencies, behave as if nothing is happening and keep old routes.
4439 When adjacencies are reestablished, the restarting router flushes
4440 Grace-LSAs and graceful restart is ended.
4442 This option controls the graceful restart mechanism. It has three
4443 states: Disabled, when no support is provided. Aware, when graceful
4444 restart helper mode is supported, but no local graceful restart is
4445 allowed (i.e. helper-only role). Enabled, when the full graceful restart
4446 support is provided (i.e. both restarting and helper role). Note that
4447 proper support for local graceful restart requires also configuration of
4448 other protocols. Default: aware.
4450 <tag><label id="ospf-graceful-restart-time">graceful restart time <m/num/</tag>
4451 The restart time is announced in the Grace-LSA and specifies how long
4452 neighbors should wait for proper end of the graceful restart before
4453 exiting helper mode prematurely. Default: 120 seconds.
4455 <tag><label id="ospf-area">area <M>id</M></tag>
4456 This defines an OSPF area with given area ID (an integer or an IPv4
4457 address, similarly to a router ID). The most important area is the
4458 backbone (ID 0) to which every other area must be connected.
4460 <tag><label id="ospf-stub">stub</tag>
4461 This option configures the area to be a stub area. External routes are
4462 not flooded into stub areas. Also summary LSAs can be limited in stub
4463 areas (see option <cf/summary/). By default, the area is not a stub
4466 <tag><label id="ospf-nssa">nssa</tag>
4467 This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
4468 is a variant of a stub area which allows a limited way of external route
4469 propagation. Global external routes are not propagated into a NSSA, but
4470 an external route can be imported into NSSA as a (area-wide) NSSA-LSA
4471 (and possibly translated and/or aggregated on area boundary). By
4472 default, the area is not NSSA.
4474 <tag><label id="ospf-summary">summary <M>switch</M></tag>
4475 This option controls propagation of summary LSAs into stub or NSSA
4476 areas. If enabled, summary LSAs are propagated as usual, otherwise just
4477 the default summary route (0.0.0.0/0) is propagated (this is sometimes
4478 called totally stubby area). If a stub area has more area boundary
4479 routers, propagating summary LSAs could lead to more efficient routing
4480 at the cost of larger link state database. Default value is no.
4482 <tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
4483 When <cf/summary/ option is enabled, default summary route is no longer
4484 propagated to the NSSA. In that case, this option allows to originate
4485 default route as NSSA-LSA to the NSSA. Default value is no.
4487 <tag><label id="ospf-default-cost">default cost <M>num</M></tag>
4488 This option controls the cost of a default route propagated to stub and
4489 NSSA areas. Default value is 1000.
4491 <tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
4492 When a default route is originated as NSSA-LSA, its cost can use either
4493 type 1 or type 2 metric. This option allows to specify the cost of a
4494 default route in type 2 metric. By default, type 1 metric (option
4495 <cf/default cost/) is used.
4497 <tag><label id="ospf-translator">translator <M>switch</M></tag>
4498 This option controls translation of NSSA-LSAs into external LSAs. By
4499 default, one translator per NSSA is automatically elected from area
4500 boundary routers. If enabled, this area boundary router would
4501 unconditionally translate all NSSA-LSAs regardless of translator
4502 election. Default value is no.
4504 <tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
4505 This option controls the translator stability interval (in seconds).
4506 When the new translator is elected, the old one keeps translating until
4507 the interval is over. Default value is 40.
4509 <tag><label id="ospf-networks">networks { <m/set/ }</tag>
4510 Definition of area IP ranges. This is used in summary LSA origination.
4511 Hidden networks are not propagated into other areas.
4513 <tag><label id="ospf-external">external { <m/set/ }</tag>
4514 Definition of external area IP ranges for NSSAs. This is used for
4515 NSSA-LSA translation. Hidden networks are not translated into external
4516 LSAs. Networks can have configured route tag.
4518 <tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
4519 Stub networks are networks that are not transit networks between OSPF
4520 routers. They are also propagated through an OSPF area as a part of a
4521 link state database. By default, BIRD generates a stub network record
4522 for each primary network address on each OSPF interface that does not
4523 have any OSPF neighbors, and also for each non-primary network address
4524 on each OSPF interface. This option allows to alter a set of stub
4525 networks propagated by this router.
4527 Each instance of this option adds a stub network with given network
4528 prefix to the set of propagated stub network, unless option <cf/hidden/
4529 is used. It also suppresses default stub networks for given network
4530 prefix. When option <cf/summary/ is used, also default stub networks
4531 that are subnetworks of given stub network are suppressed. This might be
4532 used, for example, to aggregate generated stub networks.
4534 <tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
4535 Defines that the specified interfaces belong to the area being defined.
4536 See <ref id="proto-iface" name="interface"> common option for detailed
4537 description. In OSPFv2, extended interface clauses are used, because
4538 each network prefix is handled as a separate virtual interface.
4540 You can specify alternative instance ID for the interface definition,
4541 therefore it is possible to have several instances of that interface
4542 with different options or even in different areas. For OSPFv2, instance
4543 ID support is an extension (<rfc id="6549">) and is supposed to be set
4544 per-protocol. For OSPFv3, it is an integral feature.
4546 <tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
4547 Virtual link to router with the router id. Virtual link acts as a
4548 point-to-point interface belonging to backbone. The actual area is used
4549 as a transport area. This item cannot be in the backbone. Like with
4550 <cf/interface/ option, you could also use several virtual links to one
4551 destination with different instance IDs.
4553 <tag><label id="ospf-cost">cost <M>num</M></tag>
4554 Specifies output cost (metric) of an interface. Default value is 10.
4556 <tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
4557 If set to interface it does not listen to any packet and does not send
4558 any hello. Default value is no.
4560 <tag><label id="ospf-hello">hello <M>num</M></tag>
4561 Specifies interval in seconds between sending of Hello messages. Beware,
4562 all routers on the same network need to have the same hello interval.
4563 Default value is 10.
4565 <tag><label id="ospf-poll">poll <M>num</M></tag>
4566 Specifies interval in seconds between sending of Hello messages for some
4567 neighbors on NBMA network. Default value is 20.
4569 <tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
4570 Specifies interval in seconds between retransmissions of unacknowledged
4571 updates. Default value is 5.
4573 <tag><label id="ospf-transmit-delay">transmit delay <M>num</M></tag>
4574 Specifies estimated transmission delay of link state updates send over
4575 the interface. The value is added to LSA age of LSAs propagated through
4576 it. Default value is 1.
4578 <tag><label id="ospf-priority">priority <M>num</M></tag>
4579 On every multiple access network (e.g., the Ethernet) Designated Router
4580 and Backup Designated router are elected. These routers have some special
4581 functions in the flooding process. Higher priority increases preferences
4582 in this election. Routers with priority 0 are not eligible. Default
4585 <tag><label id="ospf-wait">wait <M>num</M></tag>
4586 After start, router waits for the specified number of seconds between
4587 starting election and building adjacency. Default value is 4*<m/hello/.
4589 <tag><label id="ospf-dead-count">dead count <M>num</M></tag>
4590 When the router does not receive any messages from a neighbor in
4591 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
4593 <tag><label id="ospf-dead">dead <M>num</M></tag>
4594 When the router does not receive any messages from a neighbor in
4595 <m/dead/ seconds, it will consider the neighbor down. If both directives
4596 <cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
4598 <tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
4599 This option allows to specify the size of buffers used for packet
4600 processing. The buffer size should be bigger than maximal size of any
4601 packets. By default, buffers are dynamically resized as needed, but a
4602 fixed value could be specified. Value <cf/large/ means maximal allowed
4603 packet size - 65535.
4605 <tag><label id="ospf-tx-length">tx length <M>num</M></tag>
4606 Transmitted OSPF messages that contain large amount of information are
4607 segmented to separate OSPF packets to avoid IP fragmentation. This
4608 option specifies the soft ceiling for the length of generated OSPF
4609 packets. Default value is the MTU of the network interface. Note that
4610 larger OSPF packets may still be generated if underlying OSPF messages
4611 cannot be splitted (e.g. when one large LSA is propagated).
4613 <tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
4614 BIRD detects a type of a connected network automatically, but sometimes
4615 it's convenient to force use of a different type manually. On broadcast
4616 networks (like ethernet), flooding and Hello messages are sent using
4617 multicasts (a single packet for all the neighbors). A designated router
4618 is elected and it is responsible for synchronizing the link-state
4619 databases and originating network LSAs. This network type cannot be used
4620 on physically NBMA networks and on unnumbered networks (networks without
4623 <tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
4624 Point-to-point networks connect just 2 routers together. No election is
4625 performed and no network LSA is originated, which makes it simpler and
4626 faster to establish. This network type is useful not only for physically
4627 PtP ifaces (like PPP or tunnels), but also for broadcast networks used
4628 as PtP links. This network type cannot be used on physically NBMA
4631 <tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
4632 On NBMA networks, the packets are sent to each neighbor separately
4633 because of lack of multicast capabilities. Like on broadcast networks,
4634 a designated router is elected, which plays a central role in propagation
4635 of LSAs. This network type cannot be used on unnumbered networks.
4637 <tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
4638 This is another network type designed to handle NBMA networks. In this
4639 case the NBMA network is treated as a collection of PtP links. This is
4640 useful if not every pair of routers on the NBMA network has direct
4641 communication, or if the NBMA network is used as an (possibly
4642 unnumbered) PtP link.
4644 <tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
4645 In OSPFv3, link LSAs are generated for each link, announcing link-local
4646 IPv6 address of the router to its local neighbors. These are useless on
4647 PtP or PtMP networks and this option allows to suppress the link LSA
4648 origination for such interfaces. The option is ignored on other than PtP
4649 or PtMP interfaces. Default value is no.
4651 <tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
4652 If set, don't send hello to any undefined neighbor. This switch is
4653 ignored on other than NBMA or PtMP interfaces. Default value is no.
4655 <tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
4656 In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
4657 packets are sent as IP multicast packets. This option changes the
4658 behavior to using old-fashioned IP broadcast packets. This may be useful
4659 as a workaround if IP multicast for some reason does not work or does
4660 not work reliably. This is a non-standard option and probably is not
4661 interoperable with other OSPF implementations. Default value is no.
4663 <tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
4664 In <cf/type ptp/ network configurations, OSPFv2 implementations should
4665 ignore received netmask field in hello packets and should send hello
4666 packets with zero netmask field on unnumbered PtP links. But some OSPFv2
4667 implementations perform netmask checking even for PtP links.
4669 This option specifies whether real netmask will be used in hello packets
4670 on <cf/type ptp/ interfaces. You should ignore this option unless you
4671 meet some compatibility problems related to this issue. Default value is
4672 no for unnumbered PtP links, yes otherwise.
4674 <tag><label id="ospf-ptp-address">ptp address <m/switch/</tag>
4675 In <cf/type ptp/ network configurations, OSPFv2 implementations should
4676 use IP address for regular PtP links and interface id for unnumbered PtP
4677 links in data field of link description records in router LSA. This data
4678 field has only local meaning for PtP links, but some broken OSPFv2
4679 implementations assume there is an IP address and use it as a next hop
4680 in SPF calculations. Note that interface id for unnumbered PtP links is
4681 necessary when graceful restart is enabled to distinguish PtP links with
4682 the same local IP address.
4684 This option specifies whether an IP address will be used in data field
4685 for <cf/type ptp/ interfaces, it is ignored for other interfaces. You
4686 should ignore this option unless you meet some compatibility problems
4687 related to this issue. Default value is no for unnumbered PtP links when
4688 graceful restart is enabled, yes otherwise.
4690 <tag><label id="ospf-check-link">check link <M>switch</M></tag>
4691 If set, a hardware link state (reported by OS) is taken into consideration.
4692 When a link disappears (e.g. an ethernet cable is unplugged), neighbors
4693 are immediately considered unreachable and only the address of the iface
4694 (instead of whole network prefix) is propagated. It is possible that
4695 some hardware drivers or platforms do not implement this feature.
4696 Default value is yes.
4698 <tag><label id="ospf-bfd">bfd <M>switch</M></tag>
4699 OSPF could use BFD protocol as an advisory mechanism for neighbor
4700 liveness and failure detection. If enabled, BIRD setups a BFD session
4701 for each OSPF neighbor and tracks its liveness by it. This has an
4702 advantage of an order of magnitude lower detection times in case of
4703 failure. Note that BFD protocol also has to be configured, see
4704 <ref id="bfd" name="BFD"> section for details. Default value is no.
4706 <tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
4707 TTL security is a feature that protects routing protocols from remote
4708 spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
4709 destined to neighbors. Because TTL is decremented when packets are
4710 forwarded, it is non-trivial to spoof packets with TTL 255 from remote
4711 locations. Note that this option would interfere with OSPF virtual
4714 If this option is enabled, the router will send OSPF packets with TTL
4715 255 and drop received packets with TTL less than 255. If this option si
4716 set to <cf/tx only/, TTL 255 is used for sent packets, but is not
4717 checked for received packets. Default value is no.
4719 <tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
4720 These options specify the ToS/DiffServ/Traffic class/Priority of the
4721 outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
4722 option for detailed description.
4724 <tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
4725 When ECMP (multipath) routes are allowed, this value specifies a
4726 relative weight used for nexthops going through the iface. Allowed
4727 values are 1-256. Default value is 1.
4729 <tag><label id="ospf-auth-none">authentication none</tag>
4730 No passwords are sent in OSPF packets. This is the default value.
4732 <tag><label id="ospf-auth-simple">authentication simple</tag>
4733 Every packet carries 8 bytes of password. Received packets lacking this
4734 password are ignored. This authentication mechanism is very weak.
4735 This option is not available in OSPFv3.
4737 <tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
4738 An authentication code is appended to every packet. The specific
4739 cryptographic algorithm is selected by option <cf/algorithm/ for each
4740 key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
4741 and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
4742 network, so this mechanism is quite secure. Packets can still be read by
4745 <tag><label id="ospf-pass">password "<M>text</M>"</tag>
4746 Specifies a password used for authentication. See
4747 <ref id="proto-pass" name="password"> common option for detailed
4750 <tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
4751 A set of neighbors to which Hello messages on NBMA or PtMP networks are
4752 to be sent. For NBMA networks, some of them could be marked as eligible.
4753 In OSPFv3, link-local addresses should be used, using global ones is
4754 possible, but it is nonstandard and might be problematic. And definitely,
4755 link-local and global addresses should not be mixed.
4759 <label id="ospf-attr">
4761 <p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
4763 <p>Metric is ranging from 1 to infinity (65535). External routes use
4764 <cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
4765 with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
4766 <cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
4767 <cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
4768 2/ is stored in attribute <cf/ospf_metric2/.
4770 When both metrics are specified then <cf/metric of type 2/ is used. This is
4771 relevant e.g. when a type 2 external route is propagated from one OSPF domain to
4772 another and <cf/ospf_metric1/ is an internal distance to the original ASBR,
4773 while <cf/ospf_metric2/ stores the type 2 metric. Note that in such cases if
4774 <cf/ospf_metric1/ is non-zero then <cf/ospf_metric2/ is increased by one to
4775 ensure monotonicity of metric, as internal distance is reset to zero when an
4776 external route is announced.
4778 <p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
4779 integer which is used when exporting routes to other protocols; otherwise, it
4780 doesn't affect routing inside the OSPF domain at all. The fourth attribute
4781 <cf/ospf_router_id/ is a router ID of the router advertising that route /
4782 network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
4786 <label id="ospf-exam">
4789 protocol ospf MyOSPF {
4792 if source = RTS_BGP then {
4805 authentication simple;
4810 authentication cryptographic;
4813 generate to "2023-04-22 11:00:06";
4814 accept from "2021-01-17 12:01:05";
4815 algorithm hmac sha384;
4819 generate to "2025-07-22";
4820 accept from "2021-02-22";
4821 algorithm hmac sha512;
4834 172.16.2.0/24 hidden;
4836 interface "-arc0" , "arc*" {
4838 authentication none;
4839 strict nonbroadcast yes;
4844 192.168.120.1 eligible;
4857 <label id="perf-intro">
4859 <p>The Perf protocol is a generator of fake routes together with a time measurement
4860 framework. Its purpose is to check BIRD performance and to benchmark filters.
4862 <p>Import mode of this protocol runs in several steps. In each step, it generates 2^x routes,
4863 imports them into the appropriate table and withdraws them. The exponent x is configurable.
4864 It runs the benchmark several times for the same x, then it increases x by one
4865 until it gets too high, then it stops.
4867 <p>Export mode of this protocol repeats route refresh from table and measures how long it takes.
4869 <p>Output data is logged on info level. There is a Perl script <cf>proto/perf/parse.pl</cf>
4870 which may be handy to parse the data and draw some plots.
4872 <p>Implementation of this protocol is experimental. Use with caution and do not keep
4873 any instance of Perf in production configs for long time. The config interface is also unstable
4874 and may change in future versions without warning.
4876 <sect1>Configuration
4877 <label id="perf-config">
4880 <tag><label id="perf-mode">mode import|export</tag>
4881 Set perf mode. Default: import
4883 <tag><label id="perf-repeat">repeat <m/number/</tag>
4884 Run this amount of iterations of the benchmark for every amount step. Default: 4
4886 <tag><label id="perf-from">exp from <m/number/</tag>
4887 Begin benchmarking on this exponent for number of generated routes in one step.
4890 <tag><label id="perf-to">exp to <m/number/</tag>
4891 Stop benchmarking on this exponent. Default: 20
4893 <tag><label id="perf-threshold-min">threshold min <m/time/</tag>
4894 If a run for the given exponent took less than this time for route import,
4895 increase the exponent immediately. Default: 1 ms
4897 <tag><label id="perf-threshold-max">threshold max <m/time/</tag>
4898 If every run for the given exponent took at least this time for route import,
4899 stop benchmarking. Default: 500 ms
4906 <label id="pipe-intro">
4908 <p>The Pipe protocol serves as a link between two routing tables, allowing
4909 routes to be passed from a table declared as primary (i.e., the one the pipe is
4910 connected to using the <cf/table/ configuration keyword) to the secondary one
4911 (declared using <cf/peer table/) and vice versa, depending on what's allowed by
4912 the filters. Export filters control export of routes from the primary table to
4913 the secondary one, import filters control the opposite direction. Both tables
4914 must be of the same nettype.
4916 <p>The Pipe protocol retransmits all routes from one table to the other table,
4917 retaining their original source and attributes. If import and export filters
4918 are set to accept, then both tables would have the same content.
4920 <p>The primary use of multiple routing tables and the Pipe protocol is for
4921 policy routing, where handling of a single packet doesn't depend only on its
4922 destination address, but also on its source address, source interface, protocol
4923 type and other similar parameters. In many systems (Linux being a good example),
4924 the kernel allows to enforce routing policies by defining routing rules which
4925 choose one of several routing tables to be used for a packet according to its
4926 parameters. Setting of these rules is outside the scope of BIRD's work (on
4927 Linux, you can use the <tt/ip/ command), but you can create several routing
4928 tables in BIRD, connect them to the kernel ones, use filters to control which
4929 routes appear in which tables and also you can employ the Pipe protocol for
4930 exporting a selected subset of one table to another one.
4932 <sect1>Configuration
4933 <label id="pipe-config">
4935 <p>Essentially, the Pipe protocol is just a channel connected to a table on both
4936 sides. Therefore, the configuration block for <cf/protocol pipe/ shall directly
4937 include standard channel config options; see the example below.
4940 <tag><label id="pipe-peer-table">peer table <m/table/</tag>
4941 Defines secondary routing table to connect to. The primary one is
4942 selected by the <cf/table/ keyword.
4946 <label id="pipe-attr">
4948 <p>The Pipe protocol doesn't define any route attributes.
4951 <label id="pipe-exam">
4953 <p>Let's consider a router which serves as a boundary router of two different
4954 autonomous systems, each of them connected to a subset of interfaces of the
4955 router, having its own exterior connectivity and wishing to use the other AS as
4956 a backup connectivity in case of outage of its own exterior line.
4958 <p>Probably the simplest solution to this situation is to use two routing tables
4959 (we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
4960 packets having arrived from interfaces belonging to the first AS will be routed
4961 according to <cf/as1/ and similarly for the second AS. Thus we have split our
4962 router to two logical routers, each one acting on its own routing table, having
4963 its own routing protocols on its own interfaces. In order to use the other AS's
4964 routes for backup purposes, we can pass the routes between the tables through a
4965 Pipe protocol while decreasing their preferences and correcting their BGP paths
4966 to reflect the AS boundary crossing.
4969 ipv4 table as1; # Define the tables
4972 protocol kernel kern1 { # Synchronize them with the kernel
4973 ipv4 { table as1; export all; };
4977 protocol kernel kern2 {
4978 ipv4 { table as2; export all; };
4982 protocol bgp bgp1 { # The outside connections
4983 ipv4 { table as1; import all; export all; };
4985 neighbor 192.168.0.1 as 1001;
4989 ipv4 { table as2; import all; export all; };
4991 neighbor 10.0.0.1 as 1002;
4994 protocol pipe { # The Pipe
4998 if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks
4999 if preference>10 then preference = preference-10;
5000 if source=RTS_BGP then bgp_path.prepend(1);
5006 if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks
5007 if preference>10 then preference = preference-10;
5008 if source=RTS_BGP then bgp_path.prepend(2);
5021 <label id="radv-intro">
5023 <p>The RAdv protocol is an implementation of Router Advertisements, which are
5024 used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
5025 time intervals or as an answer to a request) advertisement packets to connected
5026 networks. These packets contain basic information about a local network (e.g. a
5027 list of network prefixes), which allows network hosts to autoconfigure network
5028 addresses and choose a default route. BIRD implements router behavior as defined
5029 in <rfc id="4861">, router preferences and specific routes (<rfc id="4191">),
5030 and DNS extensions (<rfc id="6106">).
5032 <p>The RAdv protocols supports just IPv6 channel.
5034 <sect1>Configuration
5035 <label id="radv-config">
5037 <p>There are several classes of definitions in RAdv configuration -- interface
5038 definitions, prefix definitions and DNS definitions:
5041 <tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
5042 Interface definitions specify a set of interfaces on which the
5043 protocol is activated and contain interface specific options.
5044 See <ref id="proto-iface" name="interface"> common options for
5045 detailed description.
5047 <tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
5048 Prefix definitions allow to modify a list of advertised prefixes. By
5049 default, the advertised prefixes are the same as the network prefixes
5050 assigned to the interface. For each network prefix, the matching prefix
5051 definition is found and its options are used. If no matching prefix
5052 definition is found, the prefix is used with default options.
5054 Prefix definitions can be either global or interface-specific. The
5055 second ones are part of interface options. The prefix definition
5056 matching is done in the first-match style, when interface-specific
5057 definitions are processed before global definitions. As expected, the
5058 prefix definition is matching if the network prefix is a subnet of the
5059 prefix in prefix definition.
5061 <tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
5062 RDNSS definitions allow to specify a list of advertised recursive DNS
5063 servers together with their options. As options are seldom necessary,
5064 there is also a short variant <cf>rdnss <m/address/</cf> that just
5065 specifies one DNS server. Multiple definitions are cumulative. RDNSS
5066 definitions may also be interface-specific when used inside interface
5067 options. By default, interface uses both global and interface-specific
5068 options, but that can be changed by <cf/rdnss local/ option.
5070 <tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
5071 DNSSL definitions allow to specify a list of advertised DNS search
5072 domains together with their options. Like <cf/rdnss/ above, multiple
5073 definitions are cumulative, they can be used also as interface-specific
5074 options and there is a short variant <cf>dnssl <m/domain/</cf> that just
5075 specifies one DNS search domain.
5077 <tag><label id="radv-custom-option">custom option type <m/number/ value <m/bytestring/</tag>
5078 Custom option definitions allow to define an arbitrary option to
5079 advertise. You need to specify the option type number and the binary
5080 payload of the option. The length field is calculated automatically.
5081 Like <cf/rdnss/ above, multiple definitions are cumulative, they can
5082 be used also as interface-specific options.
5084 The following example advertises PREF64 option (<rfc id="8781">) with
5085 prefix <cf>2001:db8:a:b::/96</cf> and the lifetime of <cf/1 hour/:
5087 <label id="radv-custom-option-exam">
5089 custom option type 38 value hex:0e:10:20:01:0d:b8:00:0a:00:0b:00:00:00:00;
5092 <tag><label id="radv-trigger">trigger <m/prefix/</tag>
5093 RAdv protocol could be configured to change its behavior based on
5094 availability of routes. When this option is used, the protocol waits in
5095 suppressed state until a <it/trigger route/ (for the specified network)
5096 is exported to the protocol, the protocol also returns to suppressed
5097 state if the <it/trigger route/ disappears. Note that route export
5098 depends on specified export filter, as usual. This option could be used,
5099 e.g., for handling failover in multihoming scenarios.
5101 During suppressed state, router advertisements are generated, but with
5102 some fields zeroed. Exact behavior depends on which fields are zeroed,
5103 this can be configured by <cf/sensitive/ option for appropriate
5104 fields. By default, just <cf/default lifetime/ (also called <cf/router
5105 lifetime/) is zeroed, which means hosts cannot use the router as a
5106 default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
5107 also be configured as <cf/sensitive/ for a prefix, which would cause
5108 autoconfigured IPs to be deprecated or even removed.
5110 <tag><label id="radv-propagate-routes">propagate routes <m/switch/</tag>
5111 This option controls propagation of more specific routes, as defined in
5112 <rfc id="4191">. If enabled, all routes exported to the RAdv protocol,
5113 with the exception of the trigger prefix, are added to advertisments as
5114 additional options. The lifetime and preference of advertised routes can
5115 be set individually by <cf/ra_lifetime/ and <cf/ra_preference/ route
5116 attributes, or per interface by <cf/route lifetime/ and
5117 <cf/route preference/ options. Default: disabled.
5119 Note that the RFC discourages from sending more than 17 routes and
5120 recommends the routes to be configured manually.
5123 <p>Interface specific options:
5126 <tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
5127 Unsolicited router advertisements are sent in irregular time intervals.
5128 This option specifies the maximum length of these intervals, in seconds.
5129 Valid values are 4-1800. Default: 600
5131 <tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
5132 This option specifies the minimum length of that intervals, in seconds.
5133 Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
5134 about 1/3 * <cf/max ra interval/.
5136 <tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
5137 The minimum delay between two consecutive router advertisements, in
5140 <tag><label id="radv-solicited-ra-unicast">solicited ra unicast <m/switch/</tag>
5141 Solicited router advertisements are usually sent to all-nodes multicast
5142 group like unsolicited ones, but the router can be configured to send
5143 them as unicast directly to soliciting nodes instead. This is especially
5144 useful on wireless networks (see <rfc id="7772">). Default: no
5146 <tag><label id="radv-iface-managed">managed <m/switch/</tag>
5147 This option specifies whether hosts should use DHCPv6 for IP address
5148 configuration. Default: no
5150 <tag><label id="radv-iface-other-config">other config <m/switch/</tag>
5151 This option specifies whether hosts should use DHCPv6 to receive other
5152 configuration information. Default: no
5154 <tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
5155 This option specifies which value of MTU should be used by hosts. 0
5156 means unspecified. Default: 0
5158 <tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
5159 This option specifies the time (in milliseconds) how long hosts should
5160 assume a neighbor is reachable (from the last confirmation). Maximum is
5161 3600000, 0 means unspecified. Default 0.
5163 <tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
5164 This option specifies the time (in milliseconds) how long hosts should
5165 wait before retransmitting Neighbor Solicitation messages. 0 means
5166 unspecified. Default 0.
5168 <tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
5169 This option specifies which value of Hop Limit should be used by
5170 hosts. Valid values are 0-255, 0 means unspecified. Default: 64
5172 <tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
5173 This option specifies the time (in seconds) how long (since the receipt
5174 of RA) hosts may use the router as a default router. 0 means do not use
5175 as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
5176 Default: 3 * <cf/max ra interval/, <cf/sensitive/ yes.
5178 <tag><label id="radv-iface-default-preference">default preference low|medium|high</tag>
5179 This option specifies the Default Router Preference value to advertise
5180 to hosts. Default: medium.
5182 <tag><label id="radv-iface-route-lifetime">route lifetime <m/expr/ [sensitive <m/switch/]</tag>
5183 This option specifies the default value of advertised lifetime for
5184 specific routes; i.e., the time (in seconds) for how long (since the
5185 receipt of RA) hosts should consider these routes valid. A special value
5186 0xffffffff represents infinity. The lifetime can be overriden on a per
5187 route basis by the <ref id="rta-ra-lifetime" name="ra_lifetime"> route
5188 attribute. Default: 3 * <cf/max ra interval/, <cf/sensitive/ no.
5190 For the <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
5191 If <cf/sensitive/ is enabled, even the routes with the <cf/ra_lifetime/
5192 attribute become sensitive to the trigger.
5194 <tag><label id="radv-iface-route-preference">route preference low|medium|high</tag>
5195 This option specifies the default value of advertised route preference
5196 for specific routes. The value can be overriden on a per route basis by
5197 the <ref id="rta-ra-preference" name="ra_preference"> route attribute.
5200 <tag><label id="radv-prefix-linger-time">prefix linger time <m/expr/</tag>
5201 When a prefix or a route disappears, it is advertised for some time with
5202 zero lifetime, to inform clients it is no longer valid. This option
5203 specifies the time (in seconds) for how long prefixes are advertised
5204 that way. Default: 3 * <cf/max ra interval/.
5206 <tag><label id="radv-route-linger-time">route linger time <m/expr/</tag>
5207 When a prefix or a route disappears, it is advertised for some time with
5208 zero lifetime, to inform clients it is no longer valid. This option
5209 specifies the time (in seconds) for how long routes are advertised
5210 that way. Default: 3 * <cf/max ra interval/.
5212 <tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
5213 Use only local (interface-specific) RDNSS definitions for this
5214 interface. Otherwise, both global and local definitions are used. Could
5215 also be used to disable RDNSS for given interface if no local definitons
5216 are specified. Default: no.
5218 <tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
5219 Use only local DNSSL definitions for this interface. See <cf/rdnss local/
5220 option above. Default: no.
5222 <tag><label id="radv-iface-custom-local">custom option local <m/switch/</tag>
5223 Use only local custom option definitions for this interface. See <cf/rdnss local/
5224 option above. Default: no.
5227 <p>Prefix specific options
5230 <tag><label id="radv-prefix-skip">skip <m/switch/</tag>
5231 This option allows to specify that given prefix should not be
5232 advertised. This is useful for making exceptions from a default policy
5233 of advertising all prefixes. Note that for withdrawing an already
5234 advertised prefix it is more useful to advertise it with zero valid
5235 lifetime. Default: no
5237 <tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
5238 This option specifies whether hosts may use the advertised prefix for
5239 onlink determination. Default: yes
5241 <tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
5242 This option specifies whether hosts may use the advertised prefix for
5243 stateless autoconfiguration. Default: yes
5245 <tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
5246 This option specifies the time (in seconds) how long (after the
5247 receipt of RA) the prefix information is valid, i.e., autoconfigured
5248 IP addresses can be assigned and hosts with that IP addresses are
5249 considered directly reachable. 0 means the prefix is no longer
5250 valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
5251 Default: 86400 (1 day), <cf/sensitive/ no.
5253 <tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
5254 This option specifies the time (in seconds) how long (after the
5255 receipt of RA) IP addresses generated from the prefix using stateless
5256 autoconfiguration remain preferred. For <cf/sensitive/ option,
5257 see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
5261 <p>RDNSS specific options:
5264 <tag><label id="radv-rdnss-ns">ns <m/address/</tag>
5265 This option specifies one recursive DNS server. Can be used multiple
5266 times for multiple servers. It is mandatory to have at least one
5267 <cf/ns/ option in <cf/rdnss/ definition.
5269 <tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
5270 This option specifies the time how long the RDNSS information may be
5271 used by clients after the receipt of RA. It is expressed either in
5272 seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
5273 interval/. Note that RDNSS information is also invalidated when
5274 <cf/default lifetime/ expires. 0 means these addresses are no longer
5275 valid DNS servers. Default: 3 * <cf/max ra interval/.
5278 <p>DNSSL specific options:
5281 <tag><label id="radv-dnssl-domain">domain <m/address/</tag>
5282 This option specifies one DNS search domain. Can be used multiple times
5283 for multiple domains. It is mandatory to have at least one <cf/domain/
5284 option in <cf/dnssl/ definition.
5286 <tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
5287 This option specifies the time how long the DNSSL information may be
5288 used by clients after the receipt of RA. Details are the same as for
5289 RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
5293 <label id="radv-attr">
5295 <p>RAdv defines two route attributes:
5298 <tag><label id="rta-ra-preference">enum ra_preference</tag>
5299 The preference of the route. The value can be <it/RA_PREF_LOW/,
5300 <it/RA_PREF_MEDIUM/ or <it/RA_PREF_HIGH/. If the attribute is not set,
5301 the <ref id="radv-iface-route-preference" name="route preference">
5304 <tag><label id="rta-ra-lifetime">int ra_lifetime</tag>
5305 The advertised lifetime of the route, in seconds. The special value of
5306 0xffffffff represents infinity. If the attribute is not set, the
5307 <ref id="radv-iface-route-lifetime" name="route lifetime">
5312 <label id="radv-exam">
5315 ipv6 table radv_routes; # Manually configured routes go here
5318 ipv6 { table radv_routes; };
5320 route 2001:0DB8:4000::/48 unreachable;
5321 route 2001:0DB8:4010::/48 unreachable;
5323 route 2001:0DB8:4020::/48 unreachable {
5324 ra_preference = RA_PREF_HIGH;
5330 propagate routes yes; # Propagate the routes from the radv_routes table
5331 ipv6 { table radv_routes; export all; };
5334 max ra interval 5; # Fast failover with more routers
5335 managed yes; # Using DHCPv6 on eth2
5337 autonomous off; # So do not autoconfigure any IP
5341 interface "eth*"; # No need for any other options
5343 prefix 2001:0DB8:1234::/48 {
5344 preferred lifetime 0; # Deprecated address range
5347 prefix 2001:0DB8:2000::/48 {
5348 autonomous off; # Do not autoconfigure
5351 rdnss 2001:0DB8:1234::10; # Short form of RDNSS
5355 ns 2001:0DB8:1234::11;
5356 ns 2001:0DB8:1234::12;
5372 <label id="rip-intro">
5374 <p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
5375 where each router broadcasts (to all its neighbors) distances to all networks it
5376 can reach. When a router hears distance to another network, it increments it and
5377 broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
5378 network goes unreachable, routers keep telling each other that its distance is
5379 the original distance plus 1 (actually, plus interface metric, which is usually
5380 one). After some time, the distance reaches infinity (that's 15 in RIP) and all
5381 routers know that network is unreachable. RIP tries to minimize situations where
5382 counting to infinity is necessary, because it is slow. Due to infinity being 16,
5383 you can't use RIP on networks where maximal distance is higher than 15
5386 <p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
5387 id="2080">), Triggered RIP for demand circuits (<rfc id="2091">), and RIP
5388 cryptographic authentication (<rfc id="4822">).
5390 <p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
5391 convergence, big network load and inability to handle larger networks makes it
5392 pretty much obsolete. It is still usable on very small networks.
5394 <sect1>Configuration
5395 <label id="rip-config">
5397 <p>RIP configuration consists mainly of common protocol options and interface
5398 definitions, most RIP options are interface specific. RIPng (RIP for IPv6)
5399 protocol instance can be configured by using <cf/rip ng/ instead of just
5400 <cf/rip/ as a protocol type.
5402 <p>RIP needs one IPv4 channel. RIPng needs one IPv6 channel. If no channel is
5403 configured, appropriate channel is defined with default parameters.
5406 protocol rip [ng] [<name>] {
5407 infinity <number>;
5408 ecmp <switch> [limit <number>];
5409 interface <interface pattern> {
5410 metric <number>;
5411 mode multicast|broadcast;
5412 passive <switch>;
5414 port <number>;
5416 split horizon <switch>;
5417 poison reverse <switch>;
5418 demand circuit <switch>;
5419 check zero <switch>;
5420 update time <number>;
5421 timeout time <number>;
5422 garbage time <number>;
5423 ecmp weight <number>;
5424 ttl security <switch>; | tx only;
5425 tx class|dscp <number>;
5426 tx priority <number>;
5427 rx buffer <number>;
5428 tx length <number>;
5429 check link <switch>;
5430 authentication none|plaintext|cryptographic;
5431 password "<text>";
5432 password "<text>" {
5434 generate from "<date>";
5435 generate to "<date>";
5436 accept from "<date>";
5437 accept to "<date>";
5438 from "<date>";
5440 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
5447 <tag><label id="rip-infinity">infinity <M>number</M></tag>
5448 Selects the distance of infinity. Bigger values will make
5449 protocol convergence even slower. The default value is 16.
5451 <tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
5452 This option specifies whether RIP is allowed to generate ECMP
5453 (equal-cost multipath) routes. Such routes are used when there are
5454 several directions to the destination, each with the same (computed)
5455 cost. This option also allows to specify a limit on maximum number of
5456 nexthops in one route. By default, ECMP is enabled if supported by
5457 Kernel. Default value of the limit is 16.
5459 <tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
5460 Interface definitions specify a set of interfaces on which the
5461 protocol is activated and contain interface specific options.
5462 See <ref id="proto-iface" name="interface"> common options for
5463 detailed description.
5466 <p>Interface specific options:
5469 <tag><label id="rip-iface-metric">metric <m/num/</tag>
5470 This option specifies the metric of the interface. When a route is
5471 received from the interface, its metric is increased by this value
5472 before further processing. Valid values are 1-255, but values higher
5473 than infinity has no further meaning. Default: 1.
5475 <tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
5476 This option selects the mode for RIP to use on the interface. The
5477 default is multicast mode for RIPv2 and broadcast mode for RIPv1.
5478 RIPng always uses the multicast mode.
5480 <tag><label id="rip-iface-passive">passive <m/switch/</tag>
5481 Passive interfaces receive routing updates but do not transmit any
5482 messages. Default: no.
5484 <tag><label id="rip-iface-address">address <m/ip/</tag>
5485 This option specifies a destination address used for multicast or
5486 broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
5487 (ff02::9) multicast address, or an appropriate broadcast address in the
5490 <tag><label id="rip-iface-port">port <m/number/</tag>
5491 This option selects an UDP port to operate on, the default is the
5492 official RIP (520) or RIPng (521) port.
5494 <tag><label id="rip-iface-version">version 1|2</tag>
5495 This option selects the version of RIP used on the interface. For RIPv1,
5496 automatic subnet aggregation is not implemented, only classful network
5497 routes and host routes are propagated. Note that BIRD allows RIPv1 to be
5498 configured with features that are defined for RIPv2 only, like
5499 authentication or using multicast sockets. The default is RIPv2 for IPv4
5500 RIP, the option is not supported for RIPng, as no further versions are
5503 <tag><label id="rip-iface-version-only">version only <m/switch/</tag>
5504 Regardless of RIP version configured for the interface, BIRD accepts
5505 incoming packets of any RIP version. This option restrict accepted
5506 packets to the configured version. Default: no.
5508 <tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
5509 Split horizon is a scheme for preventing routing loops. When split
5510 horizon is active, routes are not regularly propagated back to the
5511 interface from which they were received. They are either not propagated
5512 back at all (plain split horizon) or propagated back with an infinity
5513 metric (split horizon with poisoned reverse). Therefore, other routers
5514 on the interface will not consider the router as a part of an
5515 independent path to the destination of the route. Default: yes.
5517 <tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
5518 When split horizon is active, this option specifies whether the poisoned
5519 reverse variant (propagating routes back with an infinity metric) is
5520 used. The poisoned reverse has some advantages in faster convergence,
5521 but uses more network traffic. Default: yes.
5523 <tag><label id="rip-iface-demand-circuit">demand circuit <m/switch/</tag>
5524 Regular RIP sends periodic full updates on an interface. There is the
5525 Triggered RIP extension for demand circuits (<rfc id="2091">), which
5526 removes periodic updates and introduces update acknowledgments. When
5527 enabled, there is no RIP communication in steady-state network. Note
5528 that in order to work, it must be enabled on both sides. As there are
5529 no hello packets, it depends on hardware link state to detect neighbor
5530 failures. Also, it is designed for PtP links and it does not work
5531 properly with multiple RIP neighbors on an interface. Default: no.
5533 <tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
5534 Received RIPv1 packets with non-zero values in reserved fields should
5535 be discarded. This option specifies whether the check is performed or
5536 such packets are just processed as usual. Default: yes.
5538 <tag><label id="rip-iface-update-time">update time <m/number/</tag>
5539 Specifies the number of seconds between periodic updates. A lower number
5540 will mean faster convergence but bigger network load. Default: 30.
5542 <tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
5543 Specifies the time interval (in seconds) between the last received route
5544 announcement and the route expiration. After that, the network is
5545 considered unreachable, but still is propagated with infinity distance.
5548 <tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
5549 Specifies the time interval (in seconds) between the route expiration
5550 and the removal of the unreachable network entry. The garbage interval,
5551 when a route with infinity metric is propagated, is used for both
5552 internal (after expiration) and external (after withdrawal) routes.
5555 <tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
5556 When ECMP (multipath) routes are allowed, this value specifies a
5557 relative weight used for nexthops going through the iface. Valid
5558 values are 1-256. Default value is 1.
5560 <tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
5561 Selects authentication method to be used. <cf/none/ means that packets
5562 are not authenticated at all, <cf/plaintext/ means that a plaintext
5563 password is embedded into each packet, and <cf/cryptographic/ means that
5564 packets are authenticated using some cryptographic hash function
5565 selected by option <cf/algorithm/ for each key. The default
5566 cryptographic algorithm for RIP keys is Keyed-MD5. If you set
5567 authentication to not-none, it is a good idea to add <cf>password</cf>
5568 section. Default: none.
5570 <tag><label id="rip-iface-pass">password "<m/text/"</tag>
5571 Specifies a password used for authentication. See <ref id="proto-pass"
5572 name="password"> common option for detailed description.
5574 <tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
5575 TTL security is a feature that protects routing protocols from remote
5576 spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
5577 destined to neighbors. Because TTL is decremented when packets are
5578 forwarded, it is non-trivial to spoof packets with TTL 255 from remote
5581 If this option is enabled, the router will send RIP packets with TTL 255
5582 and drop received packets with TTL less than 255. If this option si set
5583 to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
5584 for received packets. Such setting does not offer protection, but offers
5585 compatibility with neighbors regardless of whether they use ttl
5588 For RIPng, TTL security is a standard behavior (required by <rfc
5589 id="2080">) and therefore default value is yes. For IPv4 RIP, default
5592 <tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
5593 These options specify the ToS/DiffServ/Traffic class/Priority of the
5594 outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
5595 option for detailed description.
5597 <tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
5598 This option specifies the size of buffers used for packet processing.
5599 The buffer size should be bigger than maximal size of received packets.
5600 The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
5602 <tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
5603 This option specifies the maximum length of generated RIP packets. To
5604 avoid IP fragmentation, it should not exceed the interface MTU value.
5605 The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
5607 <tag><label id="rip-iface-check-link">check link <m/switch/</tag>
5608 If set, the hardware link state (as reported by OS) is taken into
5609 consideration. When the link disappears (e.g. an ethernet cable is
5610 unplugged), neighbors are immediately considered unreachable and all
5611 routes received from them are withdrawn. It is possible that some
5612 hardware drivers or platforms do not implement this feature.
5617 <label id="rip-attr">
5619 <p>RIP defines two route attributes:
5622 <tag><label id="rta-rip-metric">int rip_metric</tag>
5623 RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
5624 from different RIP instances are available and all of them have the same
5625 preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
5626 non-RIP route is exported to RIP, the default metric is 1.
5628 <tag><label id="rta-rip-tag">int rip_tag</tag>
5629 RIP route tag: a 16-bit number which can be used to carry additional
5630 information with the route (for example, an originating AS number in
5631 case of external routes). When a non-RIP route is exported to RIP, the
5636 <label id="rip-exam">
5650 authentication cryptographic;
5651 password "secret" { algorithm hmac sha256; };
5662 <p>The Resource Public Key Infrastructure (RPKI) is mechanism for origin
5663 validation of BGP routes (<rfc id="6480">). BIRD supports only so-called
5664 RPKI-based origin validation. There is implemented RPKI to Router (RPKI-RTR)
5665 protocol (<rfc id="6810">). It uses some of the RPKI data to allow a router to
5666 verify that the autonomous system announcing an IP address prefix is in fact
5667 authorized to do so. This is not crypto checked so can be violated. But it
5668 should prevent the vast majority of accidental hijackings on the Internet today,
5669 e.g. the famous Pakistani accidental announcement of YouTube's address space.
5671 <p>The RPKI-RTR protocol receives and maintains a set of ROAs from a cache
5672 server (also called validator). You can validate routes (<rfc id="6483">,
5673 <rfc id="6811">) using function <cf/roa_check()/ in filter and set it as import
5674 filter at the BGP protocol. BIRD offers crude automatic re-validating of
5675 affected routes after RPKI update, see option <ref id="proto-rpki-reload"
5676 name="rpki reload">. Or you can use a BIRD client command <cf>reload in
5677 <m/bgp_protocol_name/</cf> for manual call of revalidation of all routes.
5679 <sect1>Supported transports
5682 <item>Unprotected transport over TCP uses a port 323. The cache server
5683 and BIRD router should be on the same trusted and controlled network
5684 for security reasons.
5685 <item>SSHv2 encrypted transport connection uses the normal SSH port
5689 <sect1>Configuration
5691 <p>We currently support just one cache server per protocol. However you can
5692 define more RPKI protocols generally.
5695 protocol rpki [<name>] {
5696 roa4 { table <tab>; };
5697 roa6 { table <tab>; };
5698 remote <ip> | "<domain>" [port <num>];
5700 local address <ip>;
5701 refresh [keep] <num>;
5702 retry [keep] <num>;
5703 expire [keep] <num>;
5706 bird private key "</path/to/id_rsa>";
5707 remote public key "</path/to/known_host>";
5708 user "<name>";
5713 <p>Alse note that you have to specify the ROA channel. If you want to import
5714 only IPv4 prefixes you have to specify only roa4 channel. Similarly with IPv6
5715 prefixes only. If you want to fetch both IPv4 and even IPv6 ROAs you have to
5716 specify both channels.
5718 <sect2>RPKI protocol options
5721 <tag>remote <m/ip/ | "<m/hostname/" [port <m/num/]</tag> Specifies
5722 a destination address of the cache server. Can be specified by an IP
5723 address or by full domain name string. Only one cache can be specified
5724 per protocol. This option is required.
5726 <tag>port <m/num/</tag> Specifies the port number. The default port
5727 number is 323 for transport without any encryption and 22 for transport
5728 with SSH encryption.
5730 <tag>local address <m/ip/</tag>
5731 Define local address we should use as a source address for the RTR session.
5733 <tag>refresh [keep] <m/num/</tag> Time period in seconds. Tells how
5734 long to wait before next attempting to poll the cache using a Serial
5735 Query or a Reset Query packet. Must be lower than 86400 seconds (one
5736 day). Too low value can caused a false positive detection of
5737 network connection problems. A keyword <cf/keep/ suppresses updating
5738 this value by a cache server.
5739 Default: 3600 seconds
5741 <tag>retry [keep] <m/num/</tag> Time period in seconds between a failed
5742 Serial/Reset Query and a next attempt. Maximum allowed value is 7200
5743 seconds (two hours). Too low value can caused a false positive
5744 detection of network connection problems. A keyword <cf/keep/
5745 suppresses updating this value by a cache server.
5746 Default: 600 seconds
5748 <tag>expire [keep] <m/num/</tag> Time period in seconds. Received
5749 records are deleted if the client was unable to successfully refresh
5750 data for this time period. Must be in range from 600 seconds (ten
5751 minutes) to 172800 seconds (two days). A keyword <cf/keep/
5752 suppresses updating this value by a cache server.
5753 Default: 7200 seconds
5755 <tag>ignore max length <m/switch/</tag>
5756 Ignore received max length in ROA records and use max value (32 or 128)
5757 instead. This may be useful for implementing loose RPKI check for
5758 blackholes. Default: disabled.
5760 <tag>transport tcp</tag> Unprotected transport over TCP. It's a default
5761 transport. Should be used only on secure private networks.
5764 <tag>transport ssh { <m/SSH transport options.../ }</tag> It enables a
5765 SSHv2 transport encryption. Cannot be combined with a TCP transport.
5769 <sect3>SSH transport options
5772 <tag>bird private key "<m>/path/to/id_rsa</m>"</tag>
5773 A path to the BIRD's private SSH key for authentication.
5774 It can be a <cf><m>id_rsa</m></cf> file.
5776 <tag>remote public key "<m>/path/to/known_host</m>"</tag>
5777 A path to the cache's public SSH key for verification identity
5778 of the cache server. It could be a path to <cf><m>known_host</m></cf> file.
5780 <tag>user "<m/name/"</tag>
5781 A SSH user name for authentication. This option is a required.
5785 <sect2>BGP origin validation
5786 <p>Policy: Don't import <cf/ROA_INVALID/ routes.
5797 # Please, do not use rpki-validator.realmv6.org in production
5798 remote "rpki-validator.realmv6.org" port 8282;
5806 if (roa_check(r4, net, bgp_path.last) = ROA_INVALID) then
5808 print "Ignore RPKI invalid ", net, " for ASN ", bgp_path.last;
5817 neighbor 192.168.2.1 as 65001;
5819 import filter peer_in_v4;
5825 <sect2>SSHv2 transport encryption
5837 remote 127.0.0.1 port 2345;
5839 bird private key "/home/birdgeek/.ssh/id_rsa";
5840 remote public key "/home/birdgeek/.ssh/known_hosts";
5844 # Default interval values
5852 <p>The Static protocol doesn't communicate with other routers in the network,
5853 but instead it allows you to define routes manually. This is often used for
5854 specifying how to forward packets to parts of the network which don't use
5855 dynamic routing at all and also for defining sink routes (i.e., those telling to
5856 return packets as undeliverable if they are in your IP block, you don't have any
5857 specific destination for them and you don't want to send them out through the
5858 default route to prevent routing loops).
5860 <p>There are three classes of definitions in Static protocol configuration --
5861 global options, static route definitions, and per-route options. Usually, the
5862 definition of the protocol contains mainly a list of static routes. Static
5863 routes have no specific attributes, but <ref id="rta-igp-metric" name="igp_metric">
5864 attribute is used to compare static routes with the same preference.
5866 <p>The list of static routes may contain multiple routes for the same network
5867 (usually, but not necessary, distinquished by <cf/preference/ or <cf/igp_metric/),
5868 but only routes of the same network type are allowed, as the static protocol
5869 has just one channel. E.g., to have both IPv4 and IPv6 static routes, define two
5870 static protocols, each with appropriate routes and channel.
5872 <p>The Static protocol can be configured as MPLS-aware (by defining both the
5873 primary channel and MPLS channel). In that case the Static protocol assigns
5874 labels to IP routes and automatically announces corresponding MPLS route for
5880 <tag><label id="static-check-link">check link <m/switch/</tag>
5881 If set, hardware link states of network interfaces are taken into
5882 consideration. When link disappears (e.g. ethernet cable is unplugged),
5883 static routes directing to that interface are removed. It is possible
5884 that some hardware drivers or platforms do not implement this feature.
5887 <tag><label id="static-igp-table">igp table <m/name/</tag>
5888 Specifies a table that is used for route table lookups of recursive
5889 routes. Default: the same table as the protocol is connected to.
5892 <p>Route definitions (each may also contain a block of per-route options):
5894 <sect1>Regular routes; MPLS switching rules
5896 <p>There exist several types of routes; keep in mind that <m/prefix/ syntax is
5897 <ref id="type-prefix" name="dependent on network type">.
5900 <tag>route <m/prefix/ [mpls <m/number/] via <m/ip/|<m/"interface"/ [<m/per-nexthop options/] [via ...]</tag>
5901 Regular routes may bear one or more <ref id="route-next-hop" name="next
5902 hops">. Every next hop is preceded by <cf/via/ and configured as shown.
5904 When the Static protocol is MPLS-aware, the optional <cf/mpls/ statement
5905 after <m/prefix/ specifies a static label for the labeled route, instead
5906 of using dynamically allocated label.
5908 <tag>route <m/prefix/ [mpls <m/number/] recursive <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
5909 Recursive nexthop resolves the given IP in the configured IGP table and
5910 uses that route's next hop. The MPLS stacks are concatenated; on top is
5911 the IGP's nexthop stack and on bottom is this route's stack.
5913 <tag>route <m/prefix/ [mpls <m/number/] blackhole|unreachable|prohibit</tag>
5914 Special routes specifying to silently drop the packet, return it as
5915 unreachable or return it as administratively prohibited. First two
5916 targets are also known as <cf/drop/ and <cf/reject/.
5919 <p>When the particular destination is not available (the interface is down or
5920 the next hop of the route is not a neighbor at the moment), Static just
5921 uninstalls the route from the table it is connected to and adds it again as soon
5922 as the destination becomes adjacent again.
5924 <sect2>Per-nexthop options
5926 <p>There are several options that in a case of multipath route are per-nexthop
5927 (i.e., they can be used multiple times for a route, one time for each nexthop).
5928 Syntactically, they are not separate options but just parts of <cf/route/
5929 statement after each <cf/via/ statement, not separated by semicolons. E.g.,
5930 statement <cf>route 10.0.0.0/8 via 192.0.2.1 bfd weight 1 via 192.0.2.2 weight
5931 2;</cf> describes a route with two nexthops, the first nexthop has two per-nexthop
5932 options (<cf/bfd/ and <cf/weight 1/), the second nexthop has just <cf/weight 2/.
5935 <tag><label id="static-route-bfd">bfd <m/switch/</tag>
5936 The Static protocol could use BFD protocol for next hop liveness
5937 detection. If enabled, a BFD session to the route next hop is created
5938 and the static route is BFD-controlled -- the static route is announced
5939 only if the next hop liveness is confirmed by BFD. If the BFD session
5940 fails, the static route (or just the affected nexthop from multiple
5941 ones) is removed. Note that this is a bit different compared to other
5942 protocols, which may use BFD as an advisory mechanism for fast failure
5943 detection but ignore it if a BFD session is not even established. Note
5944 that BFD protocol also has to be configured, see <ref id="bfd" name="BFD">
5945 section for details. Default value is no.
5947 <tag><label id="static-route-dev">dev <m/text/</tag>
5948 The outgoing interface associated with the nexthop. Useful for
5949 link-local nexthop addresses or when multiple interfaces use the same
5950 network prefix. By default, the outgoing interface is resolved from the
5953 <tag><label id="static-route-mpls">mpls <m/num/[/<m/num/[/<m/num/[...]]]</tag>
5954 MPLS labels that should be pushed to packets forwarded by the route.
5955 The option could be used for both IP routes (on MPLS ingress routers)
5956 and MPLS switching rules (on MPLS transit routers). Default value is
5959 <tag><label id="static-route-onlink">onlink <m/switch/</tag>
5960 Onlink flag means that the specified nexthop is accessible on the
5961 (specified) interface regardless of IP prefixes of the interface. The
5962 interface must be attached to nexthop IP address using link-local-scope
5963 format (e.g. <cf/192.0.2.1%eth0/). Default value is no.
5965 <tag><label id="static-route-weight">weight <m/switch/</tag>
5966 For multipath routes, this value specifies a relative weight of the
5967 nexthop. Allowed values are 1-256. Default value is 1.
5970 <sect1>Route Origin Authorization
5972 <p>The ROA config is just <cf>route <m/prefix/ max <m/int/ as <m/int/</cf> with no nexthop.
5974 <sect1>Autonomous System Provider Authorization
5976 <p>The ASPA config is <cf>route aspa <m/int/ providers <m/int/ [, <m/int/ ...]</cf> with no nexthop.
5977 The first ASN is client and the following are a list of providers.
5978 For a transit, you can also write <cf>route aspa <m/int/ transit</cf> to get
5979 the no-provider ASPA.
5982 <label id="flowspec-network-type">
5984 <p>The flow specification are rules for routers and firewalls for filtering
5985 purpose. It is described by <rfc id="5575">. There are 3 types of arguments:
5986 <m/inet4/ or <m/inet6/ prefixes, numeric matching expressions and bitmask
5987 matching expressions.
5989 Numeric matching is a matching sequence of numbers and ranges separeted by a
5990 commas (<cf/,/) (e.g. <cf/10,20,30/). Ranges can be written using double dots
5991 <cf/../ notation (e.g. <cf/80..90,120..124/). An alternative notation are
5992 sequence of one or more pairs of relational operators and values separated by
5993 logical operators <cf/&&/ or <cf/||/. Allowed relational operators are <cf/=/,
5994 <cf/!=/, <cf/</, <cf/<=/, <cf/>/, <cf/>=/, <cf/true/ and <cf/false/.
5996 Bitmask matching is written using <m/value/<cf>/</cf><m/mask/ or
5997 <cf/!/<m/value/<cf>/</cf><m/mask/ pairs. It means that <cf/(/<m/data/ <cf/&/
5998 <m/mask/<cf/)/ is or is not equal to <m/value/. It is also possible to use
5999 multiple value/mask pairs connected by logical operators <cf/&&/ or <cf/||/.
6000 Note that for negated matches, value must be either zero or equal to bitmask
6001 (e.g. !0x0/0xf or !0xf/0xf, but not !0x3/0xf).
6003 <sect2>IPv4 Flowspec
6006 <tag><label id="flow-dst">dst <m/inet4/</tag>
6007 Set a matching destination prefix (e.g. <cf>dst 192.168.0.0/16</cf>).
6008 Only this option is mandatory in IPv4 Flowspec.
6010 <tag><label id="flow-src">src <m/inet4/</tag>
6011 Set a matching source prefix (e.g. <cf>src 10.0.0.0/8</cf>).
6013 <tag><label id="flow-proto">proto <m/numbers-match/</tag>
6014 Set a matching IP protocol numbers (e.g. <cf/proto 6/).
6016 <tag><label id="flow-port">port <m/numbers-match/</tag>
6017 Set a matching source or destination TCP/UDP port numbers (e.g.
6018 <cf>port 1..1023,1194,3306</cf>).
6020 <tag><label id="flow-dport">dport <m/numbers-match/</tag>
6021 Set a matching destination port numbers (e.g. <cf>dport 49151</cf>).
6023 <tag><label id="flow-sport">sport <m/numbers-match/</tag>
6024 Set a matching source port numbers (e.g. <cf>sport = 0</cf>).
6026 <tag><label id="flow-icmp-type">icmp type <m/numbers-match/</tag>
6027 Set a matching type field number of an ICMP packet (e.g. <cf>icmp type
6030 <tag><label id="flow-icmp-code">icmp code <m/numbers-match/</tag>
6031 Set a matching code field number of an ICMP packet (e.g. <cf>icmp code
6034 <tag><label id="flow-tcp-flags">tcp flags <m/bitmask-match/</tag>
6035 Set a matching bitmask for TCP header flags (aka control bits) (e.g.
6036 <cf>tcp flags 0x03/0x0f;</cf>). The maximum length of mask is 12 bits
6039 <tag><label id="flow-length">length <m/numbers-match/</tag>
6040 Set a matching packet length (e.g. <cf>length > 1500</cf>)
6042 <tag><label id="flow-dscp">dscp <m/numbers-match/</tag>
6043 Set a matching DiffServ Code Point number (e.g. <cf>dscp 8..15</cf>).
6045 <tag><label id="flow-fragment">fragment <m/fragmentation-type/</tag>
6046 Set a matching type of packet fragmentation. Allowed fragmentation
6047 types are <cf/dont_fragment/, <cf/is_fragment/, <cf/first_fragment/,
6048 <cf/last_fragment/ (e.g. <cf>fragment is_fragment &&
6049 !dont_fragment</cf>).
6058 port > 24 && < 30 || 40..50,60..70,80 && >= 90;
6059 tcp flags 0x03/0x0f;
6062 fragment dont_fragment, is_fragment || !first_fragment;
6067 <sect2>Differences for IPv6 Flowspec
6069 <p>Flowspec IPv6 are same as Flowspec IPv4 with a few exceptions.
6071 <item>Prefixes <m/inet6/ can be specified not only with prefix length,
6072 but with prefix <cf/offset/ <m/num/ too (e.g.
6073 <cf>::1234:5678:9800:0000/101 offset 64</cf>). Offset means to don't
6074 care of <m/num/ first bits.
6075 <item>IPv6 Flowspec hasn't mandatory any flowspec component.
6076 <item>In IPv6 packets, there is a matching the last next header value
6077 for a matching IP protocol number (e.g. <cf>next header 6</cf>).
6078 <item>It is not possible to set <cf>dont_fragment</cf> as a type of
6079 packet fragmentation.
6083 <tag><label id="flow6-dst">dst <m/inet6/ [offset <m/num/]</tag>
6084 Set a matching destination IPv6 prefix (e.g. <cf>dst
6085 ::1c77:3769:27ad:a11a/128 offset 64</cf>).
6087 <tag><label id="flow6-src">src <m/inet6/ [offset <m/num/]</tag>
6088 Set a matching source IPv6 prefix (e.g. <cf>src fe80::/64</cf>).
6090 <tag><label id="flow6-next-header">next header <m/numbers-match/</tag>
6091 Set a matching IP protocol numbers (e.g. <cf>next header != 6</cf>).
6093 <tag><label id="flow6-label">label <m/bitmask-match/</tag>
6094 Set a 20-bit bitmask for matching Flow Label field in IPv6 packets
6095 (e.g. <cf>label 0x8e5/0x8e5</cf>).
6100 flow6 { table myflow6; };
6103 dst fec0:1122:3344:5566:7788:99aa:bbcc:ddee/128;
6104 src 0000:0000:0000:0001:1234:5678:9800:0000/101 offset 63;
6106 sport > 24 && < 30 || = 40 || 50,60,70..80;
6108 tcp flags 0x03/0x0f && !0/0xff || 0x33/0x33;
6109 fragment !is_fragment || !first_fragment;
6110 label 0xaaaa/0xaaaa && 0x33/0x33;
6115 <sect1>Per-route options
6118 <tag><label id="static-route-filter"><m/filter expression/</tag>
6119 This is a special option that allows filter expressions to be configured
6120 on per-route basis. Can be used multiple times. These expressions are
6121 evaluated when the route is originated, similarly to the import filter
6122 of the static protocol. This is especially useful for configuring route
6123 attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
6124 exported to the OSPF protocol.
6127 <sect1>Example static configs
6128 <label id="static-example">
6132 ipv4 { table testable; }; # Connect to a non-default routing table
6133 check link; # Advertise routes only if link is up
6134 route 0.0.0.0/0 via 198.51.100.130; # Default route
6135 route 10.0.0.0/8 # Multipath route
6136 via 198.51.100.10 weight 2
6137 via 198.51.100.20 bfd # BFD-controlled next hop
6139 route 203.0.113.0/24 blackhole; # Sink route
6140 route 10.2.0.0/24 via "arc0"; # Direct route
6141 route 10.2.2.0/24 via 192.0.2.1 dev "eth0" onlink; # Route with both nexthop and iface
6142 route 192.168.10.0/24 via 198.51.100.100 {
6143 ospf_metric1 = 20; # Set extended attribute
6145 route 192.168.11.0/24 via 198.51.100.100 {
6146 ospf_metric2 = 100; # Set extended attribute
6147 ospf_tag = 2; # Set extended attribute
6149 route 192.168.12.0/24 via 198.51.100.100 {
6150 bgp_community.add((65535, 65281)); # Set extended BGP attribute
6151 bgp_large_community.add((64512, 1, 1)); # Set extended BGP attribute
6156 ipv6; # Channel is mandatory
6157 route 2001:db8:10::/48 via 2001:db8:1::1; # Route with global nexthop
6158 route 2001:db8:20::/48 via fe80::10%eth0; # Route with link-local nexthop
6159 route 2001:db8:30::/48 via fe80::20%'eth1.60'; # Iface with non-alphanumeric characters
6160 route 2001:db8:40::/48 via fe80::30 dev "eth1"; # Another link-local nexthop
6161 route 2001:db8:50::/48 via "eth2"; # Direct route to eth2
6162 route 2001:db8::/32 unreachable; # Unreachable route
6163 route ::/0 via 2001:db8:1::1 bfd; # BFD-controlled default route
6169 <label id="conclusion">
6172 <label id="future-work">
6174 <p>Although BIRD supports all the commonly used routing protocols, there are
6175 still some features which would surely deserve to be implemented in future
6180 <item>Route aggregation and flap dampening
6181 <item>Multicast routing protocols
6182 <item>Ports to other systems
6186 <sect>Getting more help
6189 <p>If you use BIRD, you're welcome to join the bird-users mailing list
6190 (<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
6191 where you can share your experiences with the other users and consult
6192 your problems with the authors. To subscribe to the list, visit
6193 <HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
6194 The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
6196 <p>BIRD is a relatively young system and it probably contains some bugs. You can
6197 report any problems to the bird-users list and the authors will be glad to solve
6198 them, but before you do so, please make sure you have read the available
6199 documentation and that you are running the latest version (available at
6200 <HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
6201 (Of course, a patch which fixes the bug is always welcome as an attachment.)
6203 <p>If you want to understand what is going inside, Internet standards are a good
6204 and interesting reading. You can get them from
6205 <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
6206 nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
6207 name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
6214 LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools
6215 LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
6216 LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
6217 LocalWords: len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth
6218 LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP
6219 LocalWords: EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC
6220 LocalWords: OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU
6221 LocalWords: uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc
6222 LocalWords: compat multicasts nonbroadcast pointopoint loopback sym stats
6223 LocalWords: Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt
6224 LocalWords: proto wildcard