1 <!doctype birddoc system>
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10 This is a slightly modified linuxdoc dtd. Anything in <descrip> tags is
11 considered definition of configuration primitives, <cf> is fragment of
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13 configuration - something in config which is not keyword.
17 Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
23 <title>BIRD 2.0 User's Guide
25 Ondrej Filip <it/<feela@network.cz>/,
26 Pavel Machek <it/<pavel@ucw.cz>/,
27 Martin Mares <it/<mj@ucw.cz>/,
28 Jan Matejka <it/<mq@jmq.cz>/,
29 Ondrej Zajicek <it/<santiago@crfreenet.org>/
33 This document contains user documentation for the BIRD Internet Routing Daemon project.
36 <!-- Table of contents -->
39 <!-- Begin the document -->
46 <label id="what-is-bird">
48 <p>The name `BIRD' is actually an acronym standing for `BIRD Internet Routing
49 Daemon'. Let's take a closer look at the meaning of the name:
51 <p><em/BIRD/: Well, we think we have already explained that. It's an acronym
52 standing for `BIRD Internet Routing Daemon', you remember, don't you? :-)
54 <p><em/Internet Routing/: It's a program (well, a daemon, as you are going to
55 discover in a moment) which works as a dynamic router in an Internet type
56 network (that is, in a network running either the IPv4 or the IPv6 protocol).
57 Routers are devices which forward packets between interconnected networks in
58 order to allow hosts not connected directly to the same local area network to
59 communicate with each other. They also communicate with the other routers in the
60 Internet to discover the topology of the network which allows them to find
61 optimal (in terms of some metric) rules for forwarding of packets (which are
62 called routing tables) and to adapt themselves to the changing conditions such
63 as outages of network links, building of new connections and so on. Most of
64 these routers are costly dedicated devices running obscure firmware which is
65 hard to configure and not open to any changes (on the other hand, their special
66 hardware design allows them to keep up with lots of high-speed network
67 interfaces, better than general-purpose computer does). Fortunately, most
68 operating systems of the UNIX family allow an ordinary computer to act as a
69 router and forward packets belonging to the other hosts, but only according to a
70 statically configured table.
72 <p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program
73 running on background which does the dynamic part of Internet routing, that is
74 it communicates with the other routers, calculates routing tables and sends them
75 to the OS kernel which does the actual packet forwarding. There already exist
76 other such routing daemons: routed (RIP only), GateD (non-free),
77 <HTMLURL URL="http://www.zebra.org" name="Zebra"> and
78 <HTMLURL URL="http://sourceforge.net/projects/mrt" name="MRTD">,
79 but their capabilities are limited and they are relatively hard to configure
82 <p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
83 to support all the routing technology used in the today's Internet or planned to
84 be used in near future and to have a clean extensible architecture allowing new
85 routing protocols to be incorporated easily. Among other features, BIRD
89 <item>both IPv4 and IPv6 protocols
90 <item>multiple routing tables
91 <item>the Border Gateway Protocol (BGPv4)
92 <item>the Routing Information Protocol (RIPv2, RIPng)
93 <item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
94 <item>the Babel Routing Protocol
95 <item>the Router Advertisements for IPv6 hosts
96 <item>a virtual protocol for exchange of routes between different
97 routing tables on a single host
98 <item>a command-line interface allowing on-line control and inspection
99 of status of the daemon
100 <item>soft reconfiguration (no need to use complex online commands to
101 change the configuration, just edit the configuration file and
102 notify BIRD to re-read it and it will smoothly switch itself to
103 the new configuration, not disturbing routing protocols unless
104 they are affected by the configuration changes)
105 <item>a powerful language for route filtering
108 <p>BIRD has been developed at the Faculty of Math and Physics, Charles
109 University, Prague, Czech Republic as a student project. It can be freely
110 distributed under the terms of the GNU General Public License.
112 <p>BIRD has been designed to work on all UNIX-like systems. It has been
113 developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD
114 and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively
115 easy due to its highly modular architecture.
117 <p>BIRD 1.x supported either IPv4 or IPv6 protocol, but had to be compiled separately
118 for each one. BIRD~2 supports both of them with a possibility of further extension.
119 BIRD~2 supports Linux at least 3.16, FreeBSD 10, NetBSD 7.0, and OpenBSD 5.8.
120 Anyway, it will probably work well also on older systems.
122 <sect>Installing BIRD
125 <p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make)
126 and Perl, installing BIRD should be as easy as:
132 vi /usr/local/etc/bird.conf
136 <p>You can use <tt>./configure --help</tt> to get a list of configure
137 options. The most important ones are: <tt/--with-protocols=/ to produce a slightly smaller
138 BIRD executable by configuring out routing protocols you don't use, and
139 <tt/--prefix=/ to install BIRD to a place different from <file>/usr/local</file>.
145 <p>You can pass several command-line options to bird:
148 <tag><label id="argv-config">-c <m/config name/</tag>
149 use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>.
151 <tag><label id="argv-debug">-d</tag>
152 enable debug messages and run bird in foreground.
154 <tag><label id="argv-log-file">-D <m/filename of debug log/</tag>
155 log debugging information to given file instead of stderr.
157 <tag><label id="argv-foreground">-f</tag>
158 run bird in foreground.
160 <tag><label id="argv-group">-g <m/group/</tag>
161 use that group ID, see the next section for details.
163 <tag><label id="argv-help">-h, --help</tag>
164 display command-line options to bird.
166 <tag><label id="argv-local">-l</tag>
167 look for a configuration file and a communication socket in the current
168 working directory instead of in default system locations. However, paths
169 specified by options <cf/-c/, <cf/-s/ have higher priority.
171 <tag><label id="argv-parse">-p</tag>
172 just parse the config file and exit. Return value is zero if the config
173 file is valid, nonzero if there are some errors.
175 <tag><label id="argv-pid">-P <m/name of PID file/</tag>
176 create a PID file with given filename.
178 <tag><label id="argv-recovery">-R</tag>
179 apply graceful restart recovery after start.
181 <tag><label id="argv-socket">-s <m/name of communication socket/</tag>
182 use given filename for a socket for communications with the client,
183 default is <it/prefix/<file>/var/run/bird.ctl</file>.
185 <tag><label id="argv-user">-u <m/user/</tag>
186 drop privileges and use that user ID, see the next section for details.
188 <tag><label id="argv-version">--version</tag>
189 display bird version.
192 <p>BIRD writes messages about its work to log files or syslog (according to config).
196 <label id="privileges">
198 <p>BIRD, as a routing daemon, uses several privileged operations (like setting
199 routing table and using raw sockets). Traditionally, BIRD is executed and runs
200 with root privileges, which may be prone to security problems. The recommended
201 way is to use a privilege restriction (options <cf/-u/, <cf/-g/). In that case
202 BIRD is executed with root privileges, but it changes its user and group ID to
203 an unprivileged ones, while using Linux capabilities to retain just required
204 privileges (capabilities CAP_NET_*). Note that the control socket is created
205 before the privileges are dropped, but the config file is read after that. The
206 privilege restriction is not implemented in BSD port of BIRD.
208 <p>An unprivileged user (as an argument to <cf/-u/ options) may be the user
209 <cf/nobody/, but it is suggested to use a new dedicated user account (like
210 <cf/bird/). The similar considerations apply for the group option, but there is
211 one more condition -- the users in the same group can use <file/birdc/ to
214 <p>Finally, there is a possibility to use external tools to run BIRD in an
215 environment with restricted privileges. This may need some configuration, but it
216 is generally easy -- BIRD needs just the standard library, privileges to read
217 the config file and create the control socket and the CAP_NET_* capabilities.
221 <label id="architecture">
224 <label id="routing-tables">
226 <p>The heart of BIRD is a routing table. BIRD has several independent routing tables;
227 each of them contains routes of exactly one <m/nettype/ (see below). There are two
228 default tables -- <cf/master4/ for IPv4 routes and <cf/master6/ for IPv6 routes.
229 Other tables must be explicitly configured.
232 These routing tables are not kernel forwarding tables. No forwarding is done by
233 BIRD. If you want to forward packets using the routes in BIRD tables, you may
234 use the Kernel protocol (see below) to synchronize them with kernel FIBs.
237 Every nettype defines a (kind of) primary key on routes. Every route source can
238 supply one route for every possible primary key; new route announcement replaces
239 the old route from the same source, keeping other routes intact. BIRD always
240 chooses the best route for each primary key among the known routes and keeps the
241 others as suboptimal. When the best route is retracted, BIRD re-runs the best
242 route selection algorithm to find the current best route.
245 The global best route selection algorithm is (roughly) as follows:
248 <item>Preferences of the routes are compared.
249 <item>Source protocol instance preferences are compared.
250 <item>If source protocols are the same (e.g. BGP vs. BGP), the protocol's route selection algorithm is invoked.
251 <item>If source protocols are different (e.g. BGP vs. OSPF), result of the algorithm is undefined.
254 <p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected
255 route from a list of entries for one network. But if the <cf/sorted/ option is
256 activated, these lists of entries are kept completely sorted (according to
257 preference or some protocol-dependent metric). This is needed for some features
258 of some protocols (e.g. <cf/secondary/ option of BGP protocol, which allows to
259 accept not just a selected route, but the first route (in the sorted list) that
260 is accepted by filters), but it is incompatible with some other features (e.g.
261 <cf/deterministic med/ option of BGP protocol, which activates a way of choosing
262 selected route that cannot be described using comparison and ordering). Minor
263 advantage is that routes are shown sorted in <cf/show route/, minor disadvantage
264 is that it is slightly more computationally expensive.
266 <sect>Routes and network types
269 <p>BIRD works with several types of routes. Some of them are typical IP routes,
270 others are better described as forwarding rules. We call them all routes,
271 regardless of this difference.
273 <p>Every route consists of several attributes (read more about them in the
274 <ref id="route-attributes" name="Route attributes"> section); the common for all
278 <item>IP address of router which told us about this route
279 <item>Source protocol instance
280 <item>Route preference
281 <item>Optional attributes defined by protocols
284 <p>Other attributes depend on nettypes. Some of them are part of the primary key, these are marked (PK).
286 <sect1>IPv4 and IPv6 routes
287 <label id="ip-routes">
289 <p>The traditional routes. Configuration keywords are <cf/ipv4/ and <cf/ipv6/.
292 <item>(PK) Route destination (IP prefix together with its length)
293 <item>Route next hops (see below)
296 <sect1>VPN IPv4 and IPv6 routes
297 <label id="vpn-routes">
299 <p>Routes for IPv4 and IPv6 with VPN Route Distinguisher (<rfc id="4364">).
300 Configuration keywords are <cf/vpn4/ and <cf/vpn6/.
303 <item>(PK) Route destination (IP prefix together with its length)
304 <item>(PK) Route distinguisher (according to <rfc id="4364">)
305 <item>Route next hops
308 <sect1>Route Origin Authorization for IPv4 and IPv6
309 <label id="roa-routes">
311 <p>These entries can be used to validate route origination of BGP routes.
312 A ROA entry specifies prefixes which could be originated by an AS number.
313 Their keywords are <cf/roa4/ and <cf/roa6/.
316 <item>(PK) IP prefix together with its length
317 <item>(PK) Matching prefix maximal length
321 <sect1>Flowspec for IPv4 and IPv6
322 <label id="flow-routes">
324 <p>Flowspec rules are a form of firewall and traffic flow control rules
325 distributed mostly via BGP. These rules may help the operators stop various
326 network attacks in the beginning before eating up the whole bandwidth.
327 Configuration keywords are <cf/flow4/ and <cf/flow6/.
330 <item>(PK) IP prefix together with its length
331 <item>(PK) Flow definition data
332 <item>Flow action (encoded internally as BGP communities according to <rfc id="5575">)
335 <sect1>MPLS switching rules
336 <label id="mpls-routes">
338 <p>This nettype is currently a stub before implementing more support of <rfc id="3031">.
339 BIRD currently does not support any label distribution protocol nor any label assignment method.
340 Only the Kernel, Pipe and Static protocols can use MPLS tables.
341 Configuration keyword is <cf/mpls/.
344 <item>(PK) MPLS label
345 <item>Route next hops
348 <sect1>Route next hops
349 <label id="route-next-hop">
351 <p>This is not a nettype. The route next hop is a complex attribute common for many
352 nettypes as you can see before. Every next hop has its assigned device
353 (either assumed from its IP address or set explicitly). It may have also
354 an IP address and an MPLS stack (one or both independently).
355 Maximal MPLS stack depth is set (in compile time) to 8 labels.
357 <p>Every route (when eligible to have a next hop) can have more than one next hop.
358 In that case, every next hop has also its weight.
360 <sect>Protocols and channels
361 <label id="protocols-concept">
363 <p>BIRD protocol is an abstract class of producers and consumers of the routes.
364 Each protocol may run in multiple instances and bind on one side to route
365 tables via channels, on the other side to specified listen sockets (BGP),
366 interfaces (Babel, OSPF, RIP), APIs (Kernel, Direct), or nothing (Static, Pipe).
368 <p>There are also two protocols that do not have any channels -- BFD and Device.
369 Both of them are kind of service for other protocols.
371 <p>Each protocol is connected to a routing table through a channel. Some protocols
372 support only one channel (OSPF, RIP), some protocols support more channels (BGP, Direct).
373 Each channel has two filters which can accept, reject and modify the routes.
374 An <it/export/ filter is applied to routes passed from the routing table to the protocol,
375 an <it/import/ filter is applied to routes in the opposite direction.
377 <sect>Graceful restart
378 <label id="graceful-restart">
380 <p>When BIRD is started after restart or crash, it repopulates routing tables in
381 an uncoordinated manner, like after clean start. This may be impractical in some
382 cases, because if the forwarding plane (i.e. kernel routing tables) remains
383 intact, then its synchronization with BIRD would temporarily disrupt packet
384 forwarding until protocols converge. Graceful restart is a mechanism that could
385 help with this issue. Generally, it works by starting protocols and letting them
386 repopulate routing tables while deferring route propagation until protocols
387 acknowledge their convergence. Note that graceful restart behavior have to be
388 configured for all relevant protocols and requires protocol-specific support
389 (currently implemented for Kernel and BGP protocols), it is activated for
390 particular boot by option <cf/-R/.
397 <label id="config-intro">
399 <p>BIRD is configured using a text configuration file. Upon startup, BIRD reads
400 <it/prefix/<file>/etc/bird.conf</file> (unless the <tt/-c/ command line option
401 is given). Configuration may be changed at user's request: if you modify the
402 config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
403 config. Then there's the client which allows you to talk with BIRD in an
406 <p>In the config, everything on a line after <cf/#/ or inside <cf>/* */</cf> is
407 a comment, whitespace characters are treated as a single space. If there's a
408 variable number of options, they are grouped using the <cf/{ }/ brackets. Each
409 option is terminated by a <cf/;/. Configuration is case sensitive. There are two
410 ways how to name symbols (like protocol names, filter names, constants etc.).
411 You can either use a simple string starting with a letter followed by any
412 combination of letters and numbers (e.g. <cf/R123/, <cf/myfilter/, <cf/bgp5/) or
413 you can enclose the name into apostrophes (<cf/'/) and than you can use any
414 combination of numbers, letters. hyphens, dots and colons (e.g.
415 <cf/'1:strange-name'/, <cf/'-NAME-'/, <cf/'cool::name'/).
417 <p>Here is an example of a simple config file. It enables synchronization of
418 routing tables with OS kernel, learns network interfaces and runs RIP on all
419 network interfaces found.
424 export all; # Default is export none
426 persist; # Don't remove routes on BIRD shutdown
443 <label id="global-opts">
446 <tag><label id="opt-include">include "<m/filename/";</tag>
447 This statement causes inclusion of a new file. The <m/filename/ could
448 also be a wildcard, in that case matching files are included in
449 alphabetic order. The maximal depth is 8. Note that this statement can
450 be used anywhere in the config file, even inside other options, but
451 always on the beginning of line. In the following example, the first
452 semicolon belongs to the <cf/include/, the second to <cf/ipv6 table/.
453 If the <file/tablename.conf/ contains exactly one token (the name of the
454 table), this construction is correct:
457 include "tablename.conf";;
460 <tag><label id="opt-log">log "<m/filename/"|syslog [name <m/name/]|stderr all|{ <m/list of classes/ }</tag>
461 Set logging of messages having the given class (either <cf/all/ or
462 <cf/{ error|trace [, <m/.../] }/ etc.) into selected destination (a file specified
463 as a filename string, syslog with optional name argument, or the stderr
464 output). Classes are:
465 <cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
466 <cf/debug/ for debugging messages,
467 <cf/trace/ when you want to know what happens in the network,
468 <cf/remote/ for messages about misbehavior of remote machines,
469 <cf/auth/ about authentication failures,
470 <cf/bug/ for internal BIRD bugs.
471 You may specify more than one <cf/log/ line to establish logging to
472 multiple destinations. Default: log everything to the system log.
474 <tag><label id="opt-debug-protocols">debug protocols all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
475 Set global defaults of protocol debugging options. See <cf/debug/ in the
476 following section. Default: off.
478 <tag><label id="opt-debug-commands">debug commands <m/number/</tag>
479 Control logging of client connections (0 for no logging, 1 for logging
480 of connects and disconnects, 2 and higher for logging of all client
481 commands). Default: 0.
483 <tag><label id="opt-debug-latency">debug latency <m/switch/</tag>
484 Activate tracking of elapsed time for internal events. Recent events
485 could be examined using <cf/dump events/ command. Default: off.
487 <tag><label id="opt-debug-latency-limit">debug latency limit <m/time/</tag>
488 If <cf/debug latency/ is enabled, this option allows to specify a limit
489 for elapsed time. Events exceeding the limit are logged. Default: 1 s.
491 <tag><label id="opt-watchdog-warn">watchdog warning <m/time/</tag>
492 Set time limit for I/O loop cycle. If one iteration took more time to
493 complete, a warning is logged. Default: 5 s.
495 <tag><label id="opt-watchdog-timeout">watchdog timeout <m/time/</tag>
496 Set time limit for I/O loop cycle. If the limit is breached, BIRD is
497 killed by abort signal. The timeout has effective granularity of
498 seconds, zero means disabled. Default: disabled (0).
500 <tag><label id="opt-mrtdump">mrtdump "<m/filename/"</tag>
501 Set MRTdump file name. This option must be specified to allow MRTdump
502 feature. Default: no dump file.
504 <tag><label id="opt-mrtdump-protocols">mrtdump protocols all|off|{ states|messages [, <m/.../] }</tag>
505 Set global defaults of MRTdump options. See <cf/mrtdump/ in the
506 following section. Default: off.
508 <tag><label id="opt-filter">filter <m/name local variables/{ <m/commands/ }</tag>
509 Define a filter. You can learn more about filters in the following
512 <tag><label id="opt-function">function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag>
513 Define a function. You can learn more about functions in the following chapter.
515 <tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
516 Define a protocol instance called <cf><m/name/</cf> (or with a name like
517 "rip5" generated automatically if you don't specify any
518 <cf><m/name/</cf>). You can learn more about configuring protocols in
519 their own chapters. When <cf>from <m/name2/</cf> expression is used,
520 initial protocol options are taken from protocol or template
521 <cf><m/name2/</cf> You can run more than one instance of most protocols
522 (like RIP or BGP). By default, no instances are configured.
524 <tag><label id="opt-template">template rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
525 Define a protocol template instance called <m/name/ (or with a name like
526 "bgp1" generated automatically if you don't specify any <m/name/).
527 Protocol templates can be used to group common options when many
528 similarly configured protocol instances are to be defined. Protocol
529 instances (and other templates) can use templates by using <cf/from/
530 expression and the name of the template. At the moment templates (and
531 <cf/from/ expression) are not implemented for OSPF protocol.
533 <tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
534 Define a constant. You can use it later in every place you could use a
535 value of the same type. Besides, there are some predefined numeric
536 constants based on /etc/iproute2/rt_* files. A list of defined constants
537 can be seen (together with other symbols) using 'show symbols' command.
539 <tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
540 Set BIRD's router ID. It's a world-wide unique identification of your
541 router, usually one of router's IPv4 addresses. Default: the lowest
542 IPv4 address of a non-loopback interface.
544 <tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
545 Set BIRD's router ID based on an IPv4 address of an interface specified by
546 an interface pattern.
547 See <ref id="proto-iface" name="interface"> section for detailed
548 description of interface patterns with extended clauses.
550 <tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
551 During graceful restart recovery, BIRD waits for convergence of routing
552 protocols. This option allows to specify a timeout for the recovery to
553 prevent waiting indefinitely if some protocols cannot converge. Default:
556 <tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
557 This option allows to specify a format of date/time used by BIRD. The
558 first argument specifies for which purpose such format is used.
559 <cf/route/ is a format used in 'show route' command output,
560 <cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
561 used for other commands and <cf/log/ is used in a log file.
563 "<m/format1/" is a format string using <it/strftime(3)/ notation (see
564 <it/man strftime/ for details). It is extended to support sub-second
565 time part with variable precision (up to microseconds) using "%f"
566 conversion code (e.g., "%T.%3f" is hh:mm:ss.sss time). <m/limit/ and
567 "<m/format2/" allow to specify the second format string for times in
568 past deeper than <m/limit/ seconds.
570 There are several shorthands: <cf/iso long/ is a ISO 8601 date/time
571 format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F
572 %T"/. Similarly, <cf/iso long ms/ and <cf/iso long us/ are ISO 8601
573 date/time formats with millisecond or microsecond precision.
574 <cf/iso short/ is a variant of ISO 8601 that uses just the time format
575 (hh:mm:ss) for near times (up to 20 hours in the past) and the date
576 format (YYYY-MM-DD) for far times. This is a shorthand for <cf/"%T"
577 72000 "%F"/. And there are also <cf/iso short ms/ and <cf/iso short us/
578 high-precision variants of that.
580 By default, BIRD uses the <cf/iso short ms/ format for <cf/route/ and
581 <cf/protocol/ times, and the <cf/iso long ms/ format for <cf/base/ and
584 <tag><label id="opt-table"><m/nettype/ table <m/name/ [sorted]</tag>
585 Create a new routing table. The default routing tables <cf/master4/ and
586 <cf/master6/ are created implicitly, other routing tables have to be
587 added by this command. Option <cf/sorted/ can be used to enable sorting
588 of routes, see <ref id="dsc-table-sorted" name="sorted table">
589 description for details.
591 <tag><label id="opt-eval">eval <m/expr/</tag>
592 Evaluates given filter expression. It is used by the developers for testing of filters.
596 <sect>Protocol options
597 <label id="protocol-opts">
599 <p>For each protocol instance, you can configure a bunch of options. Some of
600 them (those described in this section) are generic, some are specific to the
601 protocol (see sections talking about the protocols).
603 <p>Several options use a <m/switch/ argument. It can be either <cf/on/,
604 <cf/yes/ or a numeric expression with a non-zero value for the option to be
605 enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
606 disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
610 <tag><label id="proto-disabled">disabled <m/switch/</tag>
611 Disables the protocol. You can change the disable/enable status from the
612 command line interface without needing to touch the configuration.
613 Disabled protocols are not activated. Default: protocol is enabled.
615 <tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
616 Set protocol debugging options. If asked, each protocol is capable of
617 writing trace messages about its work to the log (with category
618 <cf/trace/). You can either request printing of <cf/all/ trace messages
619 or only of the types selected: <cf/states/ for protocol state changes
620 (protocol going up, down, starting, stopping etc.), <cf/routes/ for
621 routes exchanged with the routing table, <cf/filters/ for details on
622 route filtering, <cf/interfaces/ for interface change events sent to the
623 protocol, <cf/events/ for events internal to the protocol and <cf/packets/
624 for packets sent and received by the protocol. Default: off.
626 <tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
627 Set protocol MRTdump flags. MRTdump is a standard binary format for
628 logging information from routing protocols and daemons. These flags
629 control what kind of information is logged from the protocol to the
630 MRTdump file (which must be specified by global <cf/mrtdump/ option, see
631 the previous section). Although these flags are similar to flags of
632 <cf/debug/ option, their meaning is different and protocol-specific. For
633 BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
634 received BGP messages. Other protocols does not support MRTdump yet.
636 <tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
637 This option can be used to override global router id for a given
638 protocol. Default: uses global router id.
640 <tag><label id="proto-description">description "<m/text/"</tag>
641 This is an optional description of the protocol. It is displayed as a
642 part of the output of 'show route all' command.
644 <tag><label id="proto-vrf">vrf "<m/text/"</tag>
645 Associate the protocol with specific VRF. The protocol will be
646 restricted to interfaces assigned to the VRF and will use sockets bound
647 to the VRF. Appropriate VRF interface must exist on OS level. For kernel
648 protocol, an appropriate table still must be explicitly selected by
649 <cf/table/ option. Note that the VRF support in BIRD and Linux kernel
650 (4.11) is still in development and is currently problematic outside of
653 <tag><label id="proto-channel"><m/channel name/ [{<m/channel config/}]</tag>
654 Every channel must be explicitly stated. See the protocol-specific
655 configuration for the list of supported channel names. See the
656 <ref id="channel-opts" name="channel configuration section"> for channel
660 <p>There are several options that give sense only with certain protocols:
663 <tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
664 Specifies a set of interfaces on which the protocol is activated with
665 given interface-specific options. A set of interfaces specified by one
666 interface option is described using an interface pattern. The interface
667 pattern consists of a sequence of clauses (separated by commas), each
668 clause is a mask specified as a shell-like pattern. Interfaces are
669 matched by their name.
671 An interface matches the pattern if it matches any of its clauses. If
672 the clause begins with <cf/-/, matching interfaces are excluded. Patterns
673 are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
674 means eth0 and all non-ethernets.
676 Some protocols (namely OSPFv2 and Direct) support extended clauses that
677 may contain a mask, a prefix, or both of them. An interface matches such
678 clause if its name matches the mask (if specified) and its address
679 matches the prefix (if specified). Extended clauses are used when the
680 protocol handles multiple addresses on an interface independently.
682 An interface option can be used more times with different interface-specific
683 options, in that case for given interface the first matching interface
686 This option is allowed in Babel, BFD, Device, Direct, OSPF, RAdv and RIP
687 protocols. In OSPF protocol it is used in the <cf/area/ subsection.
693 <cf>interface "*" { type broadcast; };</cf> - start the protocol on all
694 interfaces with <cf>type broadcast</cf> option.
696 <cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
697 protocol on enumerated interfaces with <cf>type ptp</cf> option.
699 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
700 on all interfaces that have address from 192.168.0.0/16, but not from
703 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
704 on all interfaces that have address from 192.168.0.0/16, but not from
707 <cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
708 ethernet interfaces that have address from 192.168.1.0/24.
710 <tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
711 This option specifies the value of ToS/DS/Class field in IP headers of
712 the outgoing protocol packets. This may affect how the protocol packets
713 are processed by the network relative to the other network traffic. With
714 <cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
715 octet (but two bits reserved for ECN are ignored). With <cf/dscp/
716 keyword, the value (0-63) is used just for the DS field in the octet.
717 Default value is 0xc0 (DSCP 0x30 - CS6).
719 <tag><label id="proto-tx-priority">tx priority <m/num/</tag>
720 This option specifies the local packet priority. This may affect how the
721 protocol packets are processed in the local TX queues. This option is
722 Linux specific. Default value is 7 (highest priority, privileged traffic).
724 <tag><label id="proto-pass">password "<m/password/" [ { <m>password options</m> } ]</tag>
725 Specifies a password that can be used by the protocol as a shared secret
726 key. Password option can be used more times to specify more passwords.
727 If more passwords are specified, it is a protocol-dependent decision
728 which one is really used. Specifying passwords does not mean that
729 authentication is enabled, authentication can be enabled by separate,
730 protocol-dependent <cf/authentication/ option.
732 This option is allowed in BFD, OSPF and RIP protocols. BGP has also
733 <cf/password/ option, but it is slightly different and described
738 <p>Password option can contain section with some (not necessary all) password sub-options:
741 <tag><label id="proto-pass-id">id <M>num</M></tag>
742 ID of the password, (1-255). If it is not used, BIRD will choose ID based
743 on an order of the password item in the interface. For example, second
744 password item in one interface will have default ID 2. ID is used by
745 some routing protocols to identify which password was used to
746 authenticate protocol packets.
748 <tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
749 The start time of the usage of the password for packet signing.
750 The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
752 <tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
753 The last time of the usage of the password for packet signing.
755 <tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
756 The start time of the usage of the password for packet verification.
758 <tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
759 The last time of the usage of the password for packet verification.
761 <tag><label id="proto-pass-from">from "<m/time/"</tag>
762 Shorthand for setting both <cf/generate from/ and <cf/accept from/.
764 <tag><label id="proto-pass-to">to "<m/time/"</tag>
765 Shorthand for setting both <cf/generate to/ and <cf/accept to/.
767 <tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 )</tag>
768 The message authentication algorithm for the password when cryptographic
769 authentication is enabled. The default value depends on the protocol.
770 For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3
771 protocol it is HMAC-SHA-256.
776 <sect>Channel options
777 <label id="channel-opts">
779 <p>Every channel belongs to a protocol and is configured inside its block. The
780 minimal channel config is empty, then it uses default values. The name of the
781 channel implies its nettype. Channel definitions can be inherited from protocol
782 templates. Multiple definitions of the same channel are forbidden, but channels
783 inherited from templates can be updated by new definitions.
786 <tag><label id="proto-table">table <m/name/</tag>
787 Specify a table to which the channel is connected. Default: the first
788 table of given nettype.
790 <tag><label id="proto-preference">preference <m/expr/</tag>
791 Sets the preference of routes generated by the protocol and imported
792 through this channel. Default: protocol dependent.
794 <tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/boolean filter expression/</tag>
795 Specify a filter to be used for filtering routes coming from the
796 protocol to the routing table. <cf/all/ is for keeping all routes,
797 <cf/none/ is for dropping all routes. Default: <cf/all/ (except for
800 <tag><label id="proto-export">export <m/filter/</tag>
801 This is similar to the <cf>import</cf> keyword, except that it works in
802 the direction from the routing table to the protocol. Default: <cf/none/
805 <tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
806 Usually, if an import filter rejects a route, the route is forgotten.
807 When this option is active, these routes are kept in the routing table,
808 but they are hidden and not propagated to other protocols. But it is
809 possible to show them using <cf/show route filtered/. Note that this
810 option does not work for the pipe protocol. Default: off.
812 <tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
813 Specify an import route limit (a maximum number of routes imported from
814 the protocol) and optionally the action to be taken when the limit is
815 hit. Warn action just prints warning log message. Block action discards
816 new routes coming from the protocol. Restart and disable actions shut
817 the protocol down like appropriate commands. Disable is the default
818 action if an action is not explicitly specified. Note that limits are
819 reset during protocol reconfigure, reload or restart. Default: <cf/off/.
821 <tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
822 Specify an receive route limit (a maximum number of routes received from
823 the protocol and remembered). It works almost identically to <cf>import
824 limit</cf> option, the only difference is that if <cf/import keep
825 filtered/ option is active, filtered routes are counted towards the
826 limit and blocked routes are forgotten, as the main purpose of the
827 receive limit is to protect routing tables from overflow. Import limit,
828 on the contrary, counts accepted routes only and routes blocked by the
829 limit are handled like filtered routes. Default: <cf/off/.
831 <tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
832 Specify an export route limit, works similarly to the <cf>import
833 limit</cf> option, but for the routes exported to the protocol. This
834 option is experimental, there are some problems in details of its
835 behavior -- the number of exported routes can temporarily exceed the
836 limit without triggering it during protocol reload, exported routes
837 counter ignores route blocking and block action also blocks route
838 updates of already accepted routes -- and these details will probably
839 change in the future. Default: <cf/off/.
842 <p>This is a trivial example of RIP configured for IPv6 on all interfaces:
850 <p>This is a non-trivial example.
855 import filter { ... };
856 export filter { ... };
863 <p>And this is even more complicated example using templates.
866 local 198.51.100.14 as 65000;
870 import filter { ... };
875 import filter { ... };
881 neighbor 198.51.100.130 as 64496;
883 # IPv4 channel is inherited as-is, while IPv6
884 # channel is adjusted by export filter option
886 export filter { ... };
892 <chapt>Remote control
893 <label id="remote-control">
895 <p>You can use the command-line client <file>birdc</file> to talk with a running
896 BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
897 changed with the <tt/-s/ option given to both the server and the client). The
898 commands can perform simple actions such as enabling/disabling of protocols,
899 telling BIRD to show various information, telling it to show routing table
900 filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
901 get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
902 client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
903 be passed to the client, to make it dump numeric return codes along with the
904 messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
905 own applications could do that, too -- the format of communication between BIRD
906 and <file/birdc/ is stable (see the programmer's documentation).
908 <p>There is also lightweight variant of BIRD client called <file/birdcl/, which
909 does not support command line editing and history and has minimal dependencies.
910 This is useful for running BIRD in resource constrained environments, where
911 Readline library (required for regular BIRD client) is not available.
913 <p>Many commands have the <m/name/ of the protocol instance as an argument.
914 This argument can be omitted if there exists only a single instance.
916 <p>Here is a brief list of supported functions:
919 <tag><label id="cli-show-status">show status</tag>
920 Show router status, that is BIRD version, uptime and time from last
923 <tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
924 Show the list of interfaces. For each interface, print its type, state,
925 MTU and addresses assigned.
927 <tag><label id="cli-show-protocols">show protocols [all]</tag>
928 Show list of protocol instances along with tables they are connected to
929 and protocol status, possibly giving verbose information, if <cf/all/ is
932 <!-- TODO: Move these protocol-specific remote control commands to the protocol sections -->
933 <tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
934 Show detailed information about OSPF interfaces.
936 <tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
937 Show a list of OSPF neighbors and a state of adjacency to them.
939 <tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
940 Show detailed information about OSPF areas based on a content of the
941 link-state database. It shows network topology, stub networks,
942 aggregated networks and routers from other areas and external routes.
943 The command shows information about reachable network nodes, use option
944 <cf/all/ to show information about all network nodes in the link-state
947 <tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
948 Show a topology of OSPF areas based on a content of the link-state
949 database. It is just a stripped-down version of 'show ospf state'.
951 <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>
952 Show contents of an OSPF LSA database. Options could be used to filter
955 <tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
956 Show detailed information about RIP interfaces.
958 <tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
959 Show a list of RIP neighbors and associated state.
961 <tag><label id="cli-show-static">show static [<m/name/]</tag>
962 Show detailed information about static routes.
964 <tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/]</tag>
965 Show information about BFD sessions.
967 <tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
968 Show the list of symbols defined in the configuration (names of
969 protocols, routing tables etc.).
971 <tag><label id="cli-show-route">show route [[for] <m/prefix/|<m/IP/] [table (<m/t/ | all)] [filter <m/f/|where <m/c/] [(export|preexport|noexport) <m/p/] [protocol <m/p/] [(stats|count)] [<m/options/]</tag>
972 Show contents of specified routing tables, that is routes, their metrics
973 and (in case the <cf/all/ switch is given) all their attributes.
975 <p>You can specify a <m/prefix/ if you want to print routes for a
976 specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
977 the entry which will be used for forwarding of packets to the given
978 destination. By default, all routes for each network are printed with
979 the selected one at the top, unless <cf/primary/ is given in which case
980 only the selected route is shown.
982 <p>The <cf/show route/ command can process one or multiple routing
983 tables. The set of selected tables is determined on three levels: First,
984 tables can be explicitly selected by <cf/table/ switch, which could be
985 used multiple times, all tables are specified by <cf/table all/. Second,
986 tables can be implicitly selected by channels or protocols that are
987 arguments of several other switches (e.g., <cf/export/, <cf/protocol/).
988 Last, the set of default tables is used: <cf/master4/, <cf/master6/ and
989 each first table of any other network type.
991 <p>You can also ask for printing only routes processed and accepted by
992 a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
993 </cf> or matching a given condition (<cf>where <m/condition/</cf>).
995 The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
996 printing of routes that are exported to the specified protocol or
997 channel. With <cf/preexport/, the export filter of the channel is
998 skipped. With <cf/noexport/, routes rejected by the export filter are
999 printed instead. Note that routes not exported for other reasons
1000 (e.g. secondary routes or routes imported from that protocol) are not
1001 printed even with <cf/noexport/. These switches also imply that
1002 associated routing tables are selected instead of default ones.
1004 <p>You can also select just routes added by a specific protocol.
1005 <cf>protocol <m/p/</cf>. This switch also implies that associated
1006 routing tables are selected instead of default ones.
1008 <p>If BIRD is configured to keep filtered routes (see <cf/import keep
1009 filtered/ option), you can show them instead of routes by using
1010 <cf/filtered/ switch.
1012 <p>The <cf/stats/ switch requests showing of route statistics (the
1013 number of networks, number of routes before and after filtering). If
1014 you use <cf/count/ instead, only the statistics will be printed.
1016 <tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
1017 Reload configuration from a given file. BIRD will smoothly switch itself
1018 to the new configuration, protocols are reconfigured if possible,
1019 restarted otherwise. Changes in filters usually lead to restart of
1022 If <cf/soft/ option is used, changes in filters does not cause BIRD to
1023 restart affected protocols, therefore already accepted routes (according
1024 to old filters) would be still propagated, but new routes would be
1025 processed according to the new filters.
1027 If <cf/timeout/ option is used, config timer is activated. The new
1028 configuration could be either confirmed using <cf/configure confirm/
1029 command, or it will be reverted to the old one when the config timer
1030 expires. This is useful for cases when reconfiguration breaks current
1031 routing and a router becomes inaccessible for an administrator. The
1032 config timeout expiration is equivalent to <cf/configure undo/
1033 command. The timeout duration could be specified, default is 300 s.
1035 <tag><label id="cli-configure-confirm">configure confirm</tag>
1036 Deactivate the config undo timer and therefore confirm the current
1039 <tag><label id="cli-configure-undo">configure undo</tag>
1040 Undo the last configuration change and smoothly switch back to the
1041 previous (stored) configuration. If the last configuration change was
1042 soft, the undo change is also soft. There is only one level of undo, but
1043 in some specific cases when several reconfiguration requests are given
1044 immediately in a row and the intermediate ones are skipped then the undo
1045 also skips them back.
1047 <tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
1048 Read and parse given config file, but do not use it. useful for checking
1049 syntactic and some semantic validity of an config file.
1051 <tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
1052 Enable, disable or restart a given protocol instance, instances matching
1053 the <cf><m/pattern/</cf> or <cf/all/ instances.
1055 <tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
1056 Reload a given protocol instance, that means re-import routes from the
1057 protocol instance and re-export preferred routes to the instance. If
1058 <cf/in/ or <cf/out/ options are used, the command is restricted to one
1059 direction (re-import or re-export).
1061 This command is useful if appropriate filters have changed but the
1062 protocol instance was not restarted (or reloaded), therefore it still
1063 propagates the old set of routes. For example when <cf/configure soft/
1064 command was used to change filters.
1066 Re-export always succeeds, but re-import is protocol-dependent and might
1067 fail (for example, if BGP neighbor does not support route-refresh
1068 extension). In that case, re-export is also skipped. Note that for the
1069 pipe protocol, both directions are always reloaded together (<cf/in/ or
1070 <cf/out/ options are ignored in that case).
1072 <tag><label id="cli-down">down</tag>
1075 <tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
1076 Control protocol debugging.
1078 <tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
1079 Dump contents of internal data structures to the debugging output.
1081 <tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
1082 Control echoing of log messages to the command-line output.
1083 See <ref id="opt-log" name="log option"> for a list of log classes.
1085 <tag><label id="cli-eval">eval <m/expr/</tag>
1086 Evaluate given expression.
1091 <label id="filters">
1094 <label id="filters-intro">
1096 <p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
1097 There are two objects in this language: filters and functions. Filters are
1098 interpreted by BIRD core when a route is being passed between protocols and
1099 routing tables. The filter language contains control structures such as if's and
1100 switches, but it allows no loops. An example of a filter using many features can
1101 be found in <file>filter/test.conf</file>.
1103 <p>Filter gets the route, looks at its attributes and modifies some of them if
1104 it wishes. At the end, it decides whether to pass the changed route through
1105 (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
1112 if defined( rip_metric ) then
1118 if rip_metric > 10 then
1119 reject "RIP metric is too big";
1125 <p>As you can see, a filter has a header, a list of local variables, and a body.
1126 The header consists of the <cf/filter/ keyword followed by a (unique) name of
1127 filter. The list of local variables consists of <cf><M>type name</M>;</cf>
1128 pairs where each pair defines one local variable. The body consists of <cf>
1129 { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
1130 can group several statements to a single compound statement by using braces
1131 (<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
1132 block of code conditional.
1134 <p>BIRD supports functions, so that you don't have to repeat the same blocks of
1135 code over and over. Functions can have zero or more parameters and they can have
1136 local variables. Recursion is not allowed. Function definitions look like this:
1145 function with_parameters (int parameter)
1151 <p>Unlike in C, variables are declared after the <cf/function/ line, but before
1152 the first <cf/{/. You can't declare variables in nested blocks. Functions are
1153 called like in C: <cf>name(); with_parameters(5);</cf>. Function may return
1154 values using the <cf>return <m/[expr]/</cf> command. Returning a value exits
1155 from current function (this is similar to C).
1157 <p>Filters are declared in a way similar to functions except they can't have
1158 explicit parameters. They get a route table entry as an implicit parameter, it
1159 is also passed automatically to any functions called. The filter must terminate
1160 with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in
1161 filter, the route is rejected.
1163 <p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1164 from the command line client. An example session might look like:
1167 pavel@bug:~/bird$ ./birdc -s bird.ctl
1170 10.0.0.0/8 dev eth0 [direct1 23:21] (240)
1171 195.113.30.2/32 dev tunl1 [direct1 23:21] (240)
1172 127.0.0.0/8 dev lo [direct1 23:21] (240)
1174 show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1175 bird> show route filter { if 127.0.0.5 ˜ net then accept; }
1176 127.0.0.0/8 dev lo [direct1 23:21] (240)
1182 <label id="data-types">
1184 <p>Each variable and each value has certain type. Booleans, integers and enums
1185 are incompatible with each other (that is to prevent you from shooting in the
1189 <tag><label id="type-bool">bool</tag>
1190 This is a boolean type, it can have only two values, <cf/true/ and
1191 <cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1193 <tag><label id="type-int">int</tag>
1194 This is a general integer type. It is an unsigned 32bit type; i.e., you
1195 can expect it to store values from 0 to 4294967295. Overflows are not
1196 checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1198 <tag><label id="type-pair">pair</tag>
1199 This is a pair of two short integers. Each component can have values
1200 from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1201 The same syntax can also be used to construct a pair from two arbitrary
1202 integer expressions (for example <cf/(1+2,a)/).
1204 <tag><label id="type-quad">quad</tag>
1205 This is a dotted quad of numbers used to represent router IDs (and
1206 others). Each component can have a value from 0 to 255. Literals of
1207 this type are written like IPv4 addresses.
1209 <tag><label id="type-string">string</tag>
1210 This is a string of characters. There are no ways to modify strings in
1211 filters. You can pass them between functions, assign them to variables
1212 of type <cf/string/, print such variables, use standard string
1213 comparison operations (e.g. <cf/=, !=, <, >, <=, >=/), but
1214 you can't concatenate two strings. String literals are written as
1215 <cf/"This is a string constant"/. Additionally matching (<cf/˜,
1216 !˜/) operators could be used to match a string value against
1217 a shell pattern (represented also as a string).
1219 <tag><label id="type-ip">ip</tag>
1220 This type can hold a single IP address. The IPv4 addresses are stored as
1221 IPv4-Mapped IPv6 addresses so one data type for both of them is used.
1222 Whether the address is IPv4 or not may be checked by <cf>.is_ip4</cf>
1223 which returns <cf/bool/. IP addresses are written in the standard
1224 notation (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special
1225 operator <cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out
1226 all but first <cf><M>num</M></cf> bits from the IP address. So
1227 <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1229 <tag><label id="type-prefix">prefix</tag>
1230 This type can hold a network prefix consisting of IP address, prefix
1231 length and several other values. This is the key in route tables.
1233 Prefixes may be of several types, which can be determined by the special
1234 operator <cf/.type/. The type may be:
1236 <cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
1237 are written as <cf><m/ipaddress//<m/pxlen/</cf>. There are two special
1238 operators on these: <cf/.ip/ which extracts the IP address from the
1239 pair, and <cf/.len/, which separates prefix length from the pair.
1240 So <cf>1.2.0.0/16.len = 16</cf> is true.
1242 <cf/NET_VPN4/ and <cf/NET_VPN6/ prefixes hold an IP prefix with VPN
1243 Route Distinguisher (<rfc id="4364">). They support the same special
1244 operators as IP prefixes, and also <cf/.rd/ which extracts the Route
1245 Distinguisher. Their literals are written
1246 as <cf><m/vpnrd/ <m/ipprefix/</cf>
1248 <cf/NET_ROA4/ and <cf/NET_ROA6/ prefixes hold an IP prefix range
1249 together with an ASN. They support the same special operators as IP
1250 prefixes, and also <cf/.maxlen/ which extracts maximal prefix length,
1251 and <cf/.asn/ which extracts the ASN.
1253 <cf/NET_FLOW4/ and <cf/NET_FLOW6/ hold an IP prefix together with a
1254 flowspec rule. Filters currently don't support flowspec parsing.
1256 <cf/NET_MPLS/ holds a single MPLS label and its handling is currently
1259 <tag><label id="type-vpnrd">vpnrd</tag>
1260 This is a route distinguisher according to <rfc id="4364">. There are
1261 three kinds of RD's: <cf><m/asn/:<m/32bit int/</cf>, <cf><m/asn4/:<m/16bit int/</cf>
1262 and <cf><m/IPv4 address/:<m/32bit int/</cf>
1264 <tag><label id="type-ec">ec</tag>
1265 This is a specialized type used to represent BGP extended community
1266 values. It is essentially a 64bit value, literals of this type are
1267 usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1268 <cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1269 route target / route origin communities), the format and possible values
1270 of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1271 used kind. Similarly to pairs, ECs can be constructed using expressions
1272 for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1273 <cf/myas/ is an integer variable).
1275 <tag><label id="type-lc">lc</tag>
1276 This is a specialized type used to represent BGP large community
1277 values. It is essentially a triplet of 32bit values, where the first
1278 value is reserved for the AS number of the issuer, while meaning of
1279 remaining parts is defined by the issuer. Literals of this type are
1280 written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1281 pairs, LCs can be constructed using expressions for its parts, (e.g.
1282 <cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1284 <tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1285 Filters recognize four types of sets. Sets are similar to strings: you
1286 can pass them around but you can't modify them. Literals of type <cf>int
1287 set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1288 values and ranges are permitted in sets.
1290 For pair sets, expressions like <cf/(123,*)/ can be used to denote
1291 ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1292 <cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1293 <cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1294 such expressions are translated to a set of intervals, which may be
1295 memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1296 (1,4..20), (2,4..20), ... (65535, 4..20)/.
1298 EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1299 10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1300 (like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1303 Also LC sets use similar expressions like pair sets. You can use ranges
1304 and wildcards, but if one field uses that, more specific (later) fields
1305 must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1306 is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1309 You can also use expressions for int, pair, EC and LC set values.
1310 However, it must be possible to evaluate these expressions before daemon
1311 boots. So you can use only constants inside them. E.g.
1320 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1321 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1322 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1325 Sets of prefixes are special: their literals does not allow ranges, but
1326 allows prefix patterns that are written
1327 as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1328 Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1329 pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1330 first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1331 identical and <cf>len1 <= ip1 <= len2</cf>. A valid prefix pattern
1332 has to satisfy <cf>low <= high</cf>, but <cf/pxlen/ is not
1333 constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1334 prefix set literal if it matches any prefix pattern in the prefix set
1337 There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1338 is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1339 (where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1340 network prefix <cf><m/address//<m/len/</cf> and all its subnets.
1341 <cf><m/address//<m/len/-</cf> is a shorthand for
1342 <cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1343 <cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1346 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}
1347 ]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1348 <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1349 <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1350 matches all prefixes (regardless of IP address) whose prefix length is
1351 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1352 address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{15,17} ]</cf>
1353 is true, but <cf>1.0.0.0/16 ˜ [ 1.0.0.0/8- ]</cf> is false.
1355 Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1356 in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1357 <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1358 <cf>192.168.0.0/16{24,32}</cf>.
1360 It is possible to mix IPv4 and IPv6 prefixes/addresses in a prefix/ip set
1361 but its behavior may change between versions without any warning; don't do
1362 it unless you are more than sure what you are doing. (Really, don't do it.)
1364 <tag><label id="type-enum">enum</tag>
1365 Enumeration types are fixed sets of possibilities. You can't define your
1366 own variables of such type, but some route attributes are of enumeration
1367 type. Enumeration types are incompatible with each other.
1369 <tag><label id="type-bgppath">bgppath</tag>
1370 BGP path is a list of autonomous system numbers. You can't write
1371 literals of this type. There are several special operators on bgppaths:
1373 <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1375 <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1377 <cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1379 Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1380 ASN, for example if the path contains an AS set element as the first (or
1381 the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1382 may be used to get last ASN before any AS set.
1384 <cf><m/P/.len</cf> returns the length of path <m/P/.
1386 <cf><m/P/.empty</cf> makes the path <m/P/ empty.
1388 <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1391 <cf>delete(<m/P/,<m/A/)</cf> deletes all instances of ASN <m/A/ from
1392 from path <m/P/ and returns the result. <m/A/ may also be an integer
1393 set, in that case the operator deletes all ASNs from path <m/P/ that are
1394 also members of set <m/A/.
1396 <cf>filter(<m/P/,<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1397 not members of integer set <m/A/. I.e., <cf/filter/ do the same as
1398 <cf/delete/ with inverted set <m/A/.
1400 Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1401 <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1402 (for example <cf/bgp_path/). Similarly for <cf/delete/ and <cf/filter/.
1404 <tag><label id="type-bgpmask">bgpmask</tag>
1405 BGP masks are patterns used for BGP path matching (using <cf>path
1406 ˜ [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1407 as used by UNIX shells. Autonomous system numbers match themselves,
1408 <cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1409 <cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1410 is 4 3 2 1, then: <tt>bgp_path ˜ [= * 4 3 * =]</tt> is true,
1411 but <tt>bgp_path ˜ [= * 4 5 * =]</tt> is false. BGP mask
1412 expressions can also contain integer expressions enclosed in parenthesis
1413 and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>. You can
1414 also use ranges, for example <tt>[= * 3..5 2 100..200 * =]</tt>.
1416 <tag><label id="type-clist">clist</tag>
1417 Clist is similar to a set, except that unlike other sets, it can be
1418 modified. The type is used for community list (a set of pairs) and for
1419 cluster list (a set of quads). There exist no literals of this type.
1420 There are three special operators on clists:
1422 <cf><m/C/.len</cf> returns the length of clist <m/C/.
1424 <cf><m/C/.empty</cf> makes the list <m/C/ empty.
1426 <cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1427 returns the result. If item <m/P/ is already in clist <m/C/, it does
1428 nothing. <m/P/ may also be a clist, in that case all its members are
1429 added; i.e., it works as clist union.
1431 <cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1432 <m/C/ and returns the result. If clist <m/C/ does not contain item
1433 <m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1434 case the operator deletes all items from clist <m/C/ that are also
1435 members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1436 analogously; i.e., it works as clist difference.
1438 <cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist <m/C/ that are
1439 not members of pair (or quad) set <m/P/. I.e., <cf/filter/ do the same
1440 as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1441 works analogously; i.e., it works as clist intersection.
1443 Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1444 <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for
1445 example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.
1447 <tag><label id="type-eclist">eclist</tag>
1448 Eclist is a data type used for BGP extended community lists. Eclists
1449 are very similar to clists, but they are sets of ECs instead of pairs.
1450 The same operations (like <cf/add/, <cf/delete/ or <cf/˜/ and
1451 <cf/!˜/ membership operators) can be used to modify or test
1452 eclists, with ECs instead of pairs as arguments.
1454 <tag><label id="type-lclist">lclist/</tag>
1455 Lclist is a data type used for BGP large community lists. Like eclists,
1456 lclists are very similar to clists, but they are sets of LCs instead of
1457 pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/˜/
1458 and <cf/!˜/ membership operators) can be used to modify or test
1459 lclists, with LCs instead of pairs as arguments.
1463 <label id="operators">
1465 <p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1466 parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a<b, a>=b)/.
1467 Logical operations include unary not (<cf/!/), and (<cf/&&/), and or
1468 (<cf/||/). Special operators include (<cf/˜/,
1469 <cf/!˜/) for "is (not) element of a set" operation - it can be used on
1470 element and set of elements of the same type (returning true if element is
1471 contained in the given set), or on two strings (returning true if first string
1472 matches a shell-like pattern stored in second string) or on IP and prefix
1473 (returning true if IP is within the range defined by that prefix), or on prefix
1474 and prefix (returning true if first prefix is more specific than second one) or
1475 on bgppath and bgpmask (returning true if the path matches the mask) or on
1476 number and bgppath (returning true if the number is in the path) or on bgppath
1477 and int (number) set (returning true if any ASN from the path is in the set) or
1478 on pair/quad and clist (returning true if the pair/quad is element of the
1479 clist) or on clist and pair/quad set (returning true if there is an element of
1480 the clist that is also a member of the pair/quad set).
1482 <p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1483 examines a ROA table and does <rfc id="6483"> route origin validation for a
1484 given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1485 checks current route (which should be from BGP to have AS_PATH argument) in the
1486 specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1487 ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1488 ROAs but none of them match. There is also an extended variant
1489 <cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1490 prefix and an ASN as arguments.
1493 <sect>Control structures
1494 <label id="control-structures">
1496 <p>Filters support two control structures: conditions and case switches.
1498 <p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/commandT/;
1499 else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/;
1500 <M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1501 omitted. If the <cf><m>boolean expression</m></cf> is true, <m/commandT/ is
1502 executed, otherwise <m/commandF/ is executed.
1504 <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1505 <m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1506 ... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1507 on the left side of the ˜ operator and anything that could be a member of
1508 a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1509 grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1510 between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1511 neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1513 <p>Here is example that uses <cf/if/ and <cf/case/ structures:
1517 2: print "two"; print "I can do more commands without {}";
1518 3 .. 5: print "three to five";
1519 else: print "something else";
1522 if 1234 = i then printn "."; else {
1524 print "You need {} around multiple commands";
1529 <sect>Route attributes
1530 <label id="route-attributes">
1532 <p>A filter is implicitly passed a route, and it can access its attributes just
1533 like it accesses variables. Attempts to access undefined attribute result in a
1534 runtime error; you can check if an attribute is defined by using the
1535 <cf>defined( <m>attribute</m> )</cf> operator. One notable exception to this
1536 rule are attributes of bgppath and *clist types, where undefined value is
1537 regarded as empty bgppath/*clist for most purposes.
1540 <tag><label id="rta-net"><m/prefix/ net</tag>
1541 The network prefix or anything else the route is talking about. The
1542 primary key of the routing table. Read-only. (See the <ref id="routes"
1543 name="chapter about routes">.)
1545 <tag><label id="rta-scope"><m/enum/ scope</tag>
1546 The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1547 local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1548 link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1549 <cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1550 interpreted by BIRD and can be used to mark routes in filters. The
1551 default value for new routes is <cf/SCOPE_UNIVERSE/.
1553 <tag><label id="rta-preference"><m/int/ preference</tag>
1554 Preference of the route. Valid values are 0-65535. (See the chapter
1555 about routing tables.)
1557 <tag><label id="rta-from"><m/ip/ from</tag>
1558 The router which the route has originated from.
1560 <tag><label id="rta-gw"><m/ip/ gw</tag>
1561 Next hop packets routed using this route should be forwarded to.
1563 <tag><label id="rta-proto"><m/string/ proto</tag>
1564 The name of the protocol which the route has been imported from.
1567 <tag><label id="rta-source"><m/enum/ source</tag>
1568 what protocol has told me about this route. Possible values:
1569 <cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
1570 <cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/,
1571 <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/,
1572 <cf/RTS_PIPE/, <cf/RTS_BABEL/.
1574 <tag><label id="rta-dest"><m/enum/ dest</tag>
1575 Type of destination the packets should be sent to
1576 (<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1577 <cf/RTD_DEVICE/ for routing to a directly-connected network,
1578 <cf/RTD_MULTIPATH/ for multipath destinations,
1579 <cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1580 <cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
1581 returned with ICMP host unreachable / ICMP administratively prohibited
1582 messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
1583 <cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
1585 <tag><label id="rta-ifname"><m/string/ ifname</tag>
1586 Name of the outgoing interface. Sink routes (like blackhole, unreachable
1587 or prohibit) and multipath routes have no interface associated with
1588 them, so <cf/ifname/ returns an empty string for such routes. Read-only.
1590 <tag><label id="rta-ifindex"><m/int/ ifindex</tag>
1591 Index of the outgoing interface. System wide index of the interface. May
1592 be used for interface matching, however indexes might change on interface
1593 creation/removal. Zero is returned for routes with undefined outgoing
1594 interfaces. Read-only.
1596 <tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
1597 The optional attribute that can be used to specify a distance to the
1598 network for routes that do not have a native protocol metric attribute
1599 (like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
1600 compare internal distances to boundary routers (see below). It is also
1601 used when the route is exported to OSPF as a default value for OSPF type
1605 <p>There also exist protocol-specific attributes which are described in the
1606 corresponding protocol sections.
1609 <sect>Other statements
1610 <label id="other-statements">
1612 <p>The following statements are available:
1615 <tag><label id="assignment"><m/variable/ = <m/expr/</tag>
1616 Set variable to a given value.
1618 <tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
1619 Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1621 <tag><label id="return">return <m/expr/</tag>
1622 Return <cf><m>expr</m></cf> from the current function, the function ends
1625 <tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
1626 Prints given expressions; useful mainly while debugging filters. The
1627 <cf/printn/ variant does not terminate the line.
1629 <tag><label id="quitbird">quitbird</tag>
1630 Terminates BIRD. Useful when debugging the filter interpreter.
1635 <label id="protocols">
1641 <label id="babel-intro">
1643 <p>The Babel protocol
1644 (<rfc id="6126">) is a loop-avoiding distance-vector routing protocol that is
1645 robust and efficient both in ordinary wired networks and in wireless mesh
1646 networks. Babel is conceptually very simple in its operation and "just works"
1647 in its default configuration, though some configuration is possible and in some
1650 <p>The Babel protocol is dual stack; i.e., it can carry both IPv4 and IPv6
1651 routes over the same IPv6 transport. For sending and receiving Babel packets,
1652 only a link-local IPv6 address is needed.
1654 <p>BIRD does not implement any Babel extensions, but will coexist with
1655 implementations using extensions (and will just ignore extension messages).
1657 <sect1>Configuration
1658 <label id="babel-config">
1660 <p>Babel supports no global configuration options apart from those common to all
1661 other protocols, but supports the following per-interface configuration options:
1664 protocol babel [<name>] {
1665 ipv4 { <channel config> };
1666 ipv6 { <channel config> };
1667 interface <interface pattern> {
1668 type <wired|wireless>;
1671 hello interval <time>;
1672 update interval <time>;
1674 tx class|dscp <number>;
1675 tx priority <number>;
1678 check link <switch>;
1679 next hop ipv4 <address>;
1680 next hop ipv6 <address>;
1686 <tag><label id="babel-channel">ipv4|ipv6 <m/channel config/</tag>
1687 The supported channels are IPv4 and IPv6.
1689 <tag><label id="babel-type">type wired|wireless </tag>
1690 This option specifies the interface type: Wired or wireless. On wired
1691 interfaces a neighbor is considered unreachable after a small number of
1692 Hello packets are lost, as described by <cf/limit/ option. On wireless
1693 interfaces the ETX link quality estimation technique is used to compute
1694 the metrics of routes discovered over this interface. This technique will
1695 gradually degrade the metric of routes when packets are lost rather than
1696 the more binary up/down mechanism of wired type links. Default:
1699 <tag><label id="babel-rxcost">rxcost <m/num/</tag>
1700 This option specifies the nominal RX cost of the interface. The effective
1701 neighbor costs for route metrics will be computed from this value with a
1702 mechanism determined by the interface <cf/type/. Note that in contrast to
1703 other routing protocols like RIP or OSPF, the <cf/rxcost/ specifies the
1704 cost of RX instead of TX, so it affects primarily neighbors' route
1705 selection and not local route selection. Default: 96 for wired interfaces,
1708 <tag><label id="babel-limit">limit <m/num/</tag>
1709 BIRD keeps track of received Hello messages from each neighbor to
1710 establish neighbor reachability. For wired type interfaces, this option
1711 specifies how many of last 16 hellos have to be correctly received in
1712 order to neighbor is assumed to be up. The option is ignored on wireless
1713 type interfaces, where gradual cost degradation is used instead of sharp
1716 <tag><label id="babel-hello">hello interval <m/time/ s|ms</tag>
1717 Interval at which periodic Hello messages are sent on this interface,
1718 with time units. Default: 4 seconds.
1720 <tag><label id="babel-update">update interval <m/time/ s|ms</tag>
1721 Interval at which periodic (full) updates are sent, with time
1722 units. Default: 4 times the hello interval.
1724 <tag><label id="babel-port">port <m/number/</tag>
1725 This option selects an UDP port to operate on. The default is to operate
1726 on port 6696 as specified in the Babel RFC.
1728 <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
1729 These options specify the ToS/DiffServ/Traffic class/Priority of the
1730 outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
1731 option for detailed description.
1733 <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
1734 This option specifies the size of buffers used for packet processing.
1735 The buffer size should be bigger than maximal size of received packets.
1736 The default value is the interface MTU, and the value will be clamped to a
1737 minimum of 512 bytes + IP packet overhead.
1739 <tag><label id="babel-tx-length">tx length <m/number/</tag>
1740 This option specifies the maximum length of generated Babel packets. To
1741 avoid IP fragmentation, it should not exceed the interface MTU value.
1742 The default value is the interface MTU value, and the value will be
1743 clamped to a minimum of 512 bytes + IP packet overhead.
1745 <tag><label id="babel-check-link">check link <m/switch/</tag>
1746 If set, the hardware link state (as reported by OS) is taken into
1747 consideration. When the link disappears (e.g. an ethernet cable is
1748 unplugged), neighbors are immediately considered unreachable and all
1749 routes received from them are withdrawn. It is possible that some
1750 hardware drivers or platforms do not implement this feature. Default:
1753 <tag><label id="babel-next-hop-ipv4">next hop ipv4 <m/address/</tag>
1754 Set the next hop address advertised for IPv4 routes advertised on this
1755 interface. Default: the preferred IPv4 address of the interface.
1757 <tag><label id="babel-next-hop-ipv6">next hop ipv6 <m/address/</tag>
1758 Set the next hop address advertised for IPv6 routes advertised on this
1759 interface. If not set, the same link-local address that is used as the
1760 source for Babel packets will be used. In normal operation, it should not
1761 be necessary to set this option.
1765 <label id="babel-attr">
1767 <p>Babel defines just one attribute: the internal babel metric of the route. It
1768 is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
1772 <label id="babel-exam">
1779 interface "wlan0", "wlan1" {
1786 # This matches the default of babeld: redistribute all addresses
1787 # configured on local interfaces, plus re-distribute all routes received
1788 # from other babel peers.
1791 export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1794 export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1800 <label id="babel-issues">
1802 <p>When retracting a route, Babel generates an unreachable route for a little
1803 while (according to RFC). The interaction of this behavior with other protocols
1804 is not well tested and strange things may happen.
1811 <label id="bfd-intro">
1813 <p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
1814 is an independent tool providing liveness and failure detection. Routing
1815 protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
1816 liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
1817 seconds by default in OSPF, could be set down to several seconds). BFD offers
1818 universal, fast and low-overhead mechanism for failure detection, which could be
1819 attached to any routing protocol in an advisory role.
1821 <p>BFD consists of mostly independent BFD sessions. Each session monitors an
1822 unicast bidirectional path between two BFD-enabled routers. This is done by
1823 periodically sending control packets in both directions. BFD does not handle
1824 neighbor discovery, BFD sessions are created on demand by request of other
1825 protocols (like OSPF or BGP), which supply appropriate information like IP
1826 addresses and associated interfaces. When a session changes its state, these
1827 protocols are notified and act accordingly (e.g. break an OSPF adjacency when
1828 the BFD session went down).
1830 <p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
1831 advanced features like the echo mode or authentication are not implemented), IP
1832 transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
1833 interaction with client protocols as defined in <rfc id="5882">.
1834 We currently support at most one protocol instance.
1836 <p>BFD packets are sent with a dynamic source port number. Linux systems use by
1837 default a bit different dynamic port range than the IANA approved one
1838 (49152-65535). If you experience problems with compatibility, please adjust
1839 <cf>/proc/sys/net/ipv4/ip_local_port_range</cf>
1841 <sect1>Configuration
1842 <label id="bfd-config">
1844 <p>BFD configuration consists mainly of multiple definitions of interfaces.
1845 Most BFD config options are session specific. When a new session is requested
1846 and dynamically created, it is configured from one of these definitions. For
1847 sessions to directly connected neighbors, <cf/interface/ definitions are chosen
1848 based on the interface associated with the session, while <cf/multihop/
1849 definition is used for multihop sessions. If no definition is relevant, the
1850 session is just created with the default configuration. Therefore, an empty BFD
1851 configuration is often sufficient.
1853 <p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
1854 also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
1856 <p>Some of BFD session options require <m/time/ value, which has to be specified
1857 with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
1858 are allowed as units, practical minimum values are usually in order of tens of
1862 protocol bfd [<name>] {
1863 interface <interface pattern> {
1864 interval <time>;
1865 min rx interval <time>;
1866 min tx interval <time>;
1867 idle tx interval <time>;
1868 multiplier <num>;
1869 passive <switch>;
1870 authentication none;
1871 authentication simple;
1872 authentication [meticulous] keyed md5|sha1;
1873 password "<text>";
1874 password "<text>" {
1876 generate from "<date>";
1877 generate to "<date>";
1878 accept from "<date>";
1879 accept to "<date>";
1880 from "<date>";
1885 interval <time>;
1886 min rx interval <time>;
1887 min tx interval <time>;
1888 idle tx interval <time>;
1889 multiplier <num>;
1890 passive <switch>;
1892 neighbor <ip> [dev "<interface>"] [local <ip>] [multihop <switch>];
1897 <tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
1898 Interface definitions allow to specify options for sessions associated
1899 with such interfaces and also may contain interface specific options.
1900 See <ref id="proto-iface" name="interface"> common option for a detailed
1901 description of interface patterns. Note that contrary to the behavior of
1902 <cf/interface/ definitions of other protocols, BFD protocol would accept
1903 sessions (in default configuration) even on interfaces not covered by
1906 <tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
1907 Multihop definitions allow to specify options for multihop BFD sessions,
1908 in the same manner as <cf/interface/ definitions are used for directly
1909 connected sessions. Currently only one such definition (for all multihop
1910 sessions) could be used.
1912 <tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
1913 BFD sessions are usually created on demand as requested by other
1914 protocols (like OSPF or BGP). This option allows to explicitly add
1915 a BFD session to the specified neighbor regardless of such requests.
1917 The session is identified by the IP address of the neighbor, with
1918 optional specification of used interface and local IP. By default
1919 the neighbor must be directly connected, unless the session is
1920 configured as multihop. Note that local IP must be specified for
1924 <p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
1927 <tag><label id="bfd-interval">interval <m/time/</tag>
1928 BFD ensures availability of the forwarding path associated with the
1929 session by periodically sending BFD control packets in both
1930 directions. The rate of such packets is controlled by two options,
1931 <cf/min rx interval/ and <cf/min tx interval/ (see below). This option
1932 is just a shorthand to set both of these options together.
1934 <tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
1935 This option specifies the minimum RX interval, which is announced to the
1936 neighbor and used there to limit the neighbor's rate of generated BFD
1937 control packets. Default: 10 ms.
1939 <tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
1940 This option specifies the desired TX interval, which controls the rate
1941 of generated BFD control packets (together with <cf/min rx interval/
1942 announced by the neighbor). Note that this value is used only if the BFD
1943 session is up, otherwise the value of <cf/idle tx interval/ is used
1944 instead. Default: 100 ms.
1946 <tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
1947 In order to limit unnecessary traffic in cases where a neighbor is not
1948 available or not running BFD, the rate of generated BFD control packets
1949 is lower when the BFD session is not up. This option specifies the
1950 desired TX interval in such cases instead of <cf/min tx interval/.
1953 <tag><label id="bfd-multiplier">multiplier <m/num/</tag>
1954 Failure detection time for BFD sessions is based on established rate of
1955 BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
1956 multiplier, which is essentially (ignoring jitter) a number of missed
1957 packets after which the session is declared down. Note that rates and
1958 multipliers could be different in each direction of a BFD session.
1961 <tag><label id="bfd-passive">passive <m/switch/</tag>
1962 Generally, both BFD session endpoints try to establish the session by
1963 sending control packets to the other side. This option allows to enable
1964 passive mode, which means that the router does not send BFD packets
1965 until it has received one from the other side. Default: disabled.
1967 <tag>authentication none</tag>
1968 No passwords are sent in BFD packets. This is the default value.
1970 <tag>authentication simple</tag>
1971 Every packet carries 16 bytes of password. Received packets lacking this
1972 password are ignored. This authentication mechanism is very weak.
1974 <tag>authentication [meticulous] keyed md5|sha1</tag>
1975 An authentication code is appended to each packet. The cryptographic
1976 algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
1977 for all keys (on one interface), in contrast to OSPF or RIP, where it
1978 is a per-key option. Passwords (keys) are not sent open via network.
1980 The <cf/meticulous/ variant means that cryptographic sequence numbers
1981 are increased for each sent packet, while in the basic variant they are
1982 increased about once per second. Generally, the <cf/meticulous/ variant
1983 offers better resistance to replay attacks but may require more
1986 <tag>password "<M>text</M>"</tag>
1987 Specifies a password used for authentication. See <ref id="proto-pass"
1988 name="password"> common option for detailed description. Note that
1989 password option <cf/algorithm/ is not available in BFD protocol. The
1990 algorithm is selected by <cf/authentication/ option for all passwords.
1995 <label id="bfd-exam">
2000 min rx interval 20 ms;
2001 min tx interval 50 ms;
2002 idle tx interval 300 ms;
2014 neighbor 192.168.1.10;
2015 neighbor 192.168.2.2 dev "eth2";
2016 neighbor 192.168.10.1 local 192.168.1.1 multihop;
2024 <p>The Border Gateway Protocol is the routing protocol used for backbone level
2025 routing in the today's Internet. Contrary to other protocols, its convergence
2026 does not rely on all routers following the same rules for route selection,
2027 making it possible to implement any routing policy at any router in the network,
2028 the only restriction being that if a router advertises a route, it must accept
2029 and forward packets according to it.
2031 <p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
2032 is a part of the network with common management and common routing policy. It is
2033 identified by a unique 16-bit number (ASN). Routers within each AS usually
2034 exchange AS-internal routing information with each other using an interior
2035 gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
2036 the AS communicate global (inter-AS) network reachability information with their
2037 neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
2038 received information to other routers in the AS via interior BGP (iBGP).
2040 <p>Each BGP router sends to its neighbors updates of the parts of its routing
2041 table it wishes to export along with complete path information (a list of AS'es
2042 the packet will travel through if it uses the particular route) in order to
2043 avoid routing loops.
2045 <sect1>Supported standards
2046 <label id="bgp-standards">
2050 <item> <rfc id="4271"> - Border Gateway Protocol 4 (BGP)
2051 <item> <rfc id="1997"> - BGP Communities Attribute
2052 <item> <rfc id="2385"> - Protection of BGP Sessions via TCP MD5 Signature
2053 <item> <rfc id="2545"> - Use of BGP Multiprotocol Extensions for IPv6
2054 <item> <rfc id="2918"> - Route Refresh Capability
2055 <item> <rfc id="3107"> - Carrying Label Information in BGP
2056 <item> <rfc id="4360"> - BGP Extended Communities Attribute
2057 <item> <rfc id="4364"> - BGP/MPLS IPv4 Virtual Private Networks
2058 <item> <rfc id="4456"> - BGP Route Reflection
2059 <item> <rfc id="4486"> - Subcodes for BGP Cease Notification Message
2060 <item> <rfc id="4659"> - BGP/MPLS IPv6 Virtual Private Networks
2061 <item> <rfc id="4724"> - Graceful Restart Mechanism for BGP
2062 <item> <rfc id="4760"> - Multiprotocol extensions for BGP
2063 <item> <rfc id="4798"> - Connecting IPv6 Islands over IPv4 MPLS
2064 <item> <rfc id="5065"> - AS confederations for BGP
2065 <item> <rfc id="5082"> - Generalized TTL Security Mechanism
2066 <item> <rfc id="5492"> - Capabilities Advertisement with BGP
2067 <item> <rfc id="5549"> - Advertising IPv4 NLRI with an IPv6 Next Hop
2068 <item> <rfc id="5575"> - Dissemination of Flow Specification Rules
2069 <item> <rfc id="5668"> - 4-Octet AS Specific BGP Extended Community
2070 <item> <rfc id="6286"> - AS-Wide Unique BGP Identifier
2071 <item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error
2072 <item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers
2073 <item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP
2074 <item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages
2075 <item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP
2076 <item> <rfc id="7947"> - Internet Exchange BGP Route Server
2077 <item> <rfc id="8092"> - BGP Large Communities Attribute
2078 <item> <rfc id="8203"> - BGP Administrative Shutdown Communication
2079 <item> <rfc id="8212"> - Default EBGP Route Propagation Behavior without Policies
2082 <sect1>Route selection rules
2083 <label id="bgp-route-select-rules">
2085 <p>BGP doesn't have any simple metric, so the rules for selection of an optimal
2086 route among multiple BGP routes with the same preference are a bit more complex
2087 and they are implemented according to the following algorithm. It starts the
2088 first rule, if there are more "best" routes, then it uses the second rule to
2089 choose among them and so on.
2092 <item>Prefer route with the highest Local Preference attribute.
2093 <item>Prefer route with the shortest AS path.
2094 <item>Prefer IGP origin over EGP and EGP origin over incomplete.
2095 <item>Prefer the lowest value of the Multiple Exit Discriminator.
2096 <item>Prefer routes received via eBGP over ones received via iBGP.
2097 <item>Prefer routes with lower internal distance to a boundary router.
2098 <item>Prefer the route with the lowest value of router ID of the
2102 <sect1>IGP routing table
2103 <label id="bgp-igp-routing-table">
2105 <p>BGP is mainly concerned with global network reachability and with routes to
2106 other autonomous systems. When such routes are redistributed to routers in the
2107 AS via BGP, they contain IP addresses of a boundary routers (in route attribute
2108 NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
2109 determine immediate next hops for routes and to know their internal distances to
2110 boundary routers for the purpose of BGP route selection. In BIRD, there is
2111 usually one routing table used for both IGP routes and BGP routes.
2113 <sect1>Protocol configuration
2114 <label id="bgp-proto-config">
2116 <p>Each instance of the BGP corresponds to one neighboring router. This allows
2117 to set routing policy and all the other parameters differently for each neighbor
2118 using the following configuration parameters:
2121 <tag><label id="bgp-local">local [<m/ip/] as <m/number/</tag>
2122 Define which AS we are part of. (Note that contrary to other IP routers,
2123 BIRD is able to act as a router located in multiple AS'es simultaneously,
2124 but in such cases you need to tweak the BGP paths manually in the filters
2125 to get consistent behavior.) Optional <cf/ip/ argument specifies a source
2126 address, equivalent to the <cf/source address/ option (see below). This
2127 parameter is mandatory.
2129 <tag><label id="bgp-neighbor">neighbor [<m/ip/] [port <m/number/] [as <m/number/]</tag>
2130 Define neighboring router this instance will be talking to and what AS
2131 it is located in. In case the neighbor is in the same AS as we are, we
2132 automatically switch to iBGP. Optionally, the remote port may also be
2133 specified. The parameter may be used multiple times with different
2134 sub-options (e.g., both <cf/neighbor 10.0.0.1 as 65000;/ and
2135 <cf/neighbor 10.0.0.1; neighbor as 65000;/ are valid). This parameter is
2138 <tag><label id="bgp-iface">interface <m/string/</tag>
2139 Define interface we should use for link-local BGP IPv6 sessions.
2140 Interface can also be specified as a part of <cf/neighbor address/
2141 (e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). The option may also be
2142 used for non link-local sessions when it is necessary to explicitly
2143 specify an interface, but only for direct (not multihop) sessions.
2145 <tag><label id="bgp-direct">direct</tag>
2146 Specify that the neighbor is directly connected. The IP address of the
2147 neighbor must be from a directly reachable IP range (i.e. associated
2148 with one of your router's interfaces), otherwise the BGP session
2149 wouldn't start but it would wait for such interface to appear. The
2150 alternative is the <cf/multihop/ option. Default: enabled for eBGP.
2152 <tag><label id="bgp-multihop">multihop [<m/number/]</tag>
2153 Configure multihop BGP session to a neighbor that isn't directly
2154 connected. Accurately, this option should be used if the configured
2155 neighbor IP address does not match with any local network subnets. Such
2156 IP address have to be reachable through system routing table. The
2157 alternative is the <cf/direct/ option. For multihop BGP it is
2158 recommended to explicitly configure the source address to have it
2159 stable. Optional <cf/number/ argument can be used to specify the number
2160 of hops (used for TTL). Note that the number of networks (edges) in a
2161 path is counted; i.e., if two BGP speakers are separated by one router,
2162 the number of hops is 2. Default: enabled for iBGP.
2164 <tag><label id="bgp-source-address">source address <m/ip/</tag>
2165 Define local address we should use for next hop calculation and as a
2166 source address for the BGP session. Default: the address of the local
2167 end of the interface our neighbor is connected to.
2169 <tag><label id="bgp-strict-bind">strict bind <m/switch/</tag>
2170 Specify whether BGP listening socket should be bound to a specific local
2171 address (the same as the <cf/source address/) and associated interface,
2172 or to all addresses. Binding to a specific address could be useful in
2173 cases like running multiple BIRD instances on a machine, each using its
2174 IP address. Note that listening sockets bound to a specific address and
2175 to all addresses collide, therefore either all BGP protocols (of the
2176 same address family and using the same local port) should have set
2177 <cf/strict bind/, or none of them. Default: disabled.
2179 <tag><label id="bgp-check-link">check link <M>switch</M></tag>
2180 BGP could use hardware link state into consideration. If enabled,
2181 BIRD tracks the link state of the associated interface and when link
2182 disappears (e.g. an ethernet cable is unplugged), the BGP session is
2183 immediately shut down. Note that this option cannot be used with
2184 multihop BGP. Default: enabled for direct BGP, disabled otherwise.
2186 <tag><label id="bgp-bfd">bfd <M>switch</M></tag>
2187 BGP could use BFD protocol as an advisory mechanism for neighbor
2188 liveness and failure detection. If enabled, BIRD setups a BFD session
2189 for the BGP neighbor and tracks its liveness by it. This has an
2190 advantage of an order of magnitude lower detection times in case of
2191 failure. Note that BFD protocol also has to be configured, see
2192 <ref id="bfd" name="BFD"> section for details. Default: disabled.
2194 <tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
2195 Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
2196 protects against spoofed packets by ignoring received packets with a
2197 smaller than expected TTL. To work properly, GTSM have to be enabled on
2198 both sides of a BGP session. If both <cf/ttl security/ and
2199 <cf/multihop/ options are enabled, <cf/multihop/ option should specify
2200 proper hop value to compute expected TTL. Kernel support required:
2201 Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
2202 Note that full (ICMP protection, for example) <rfc id="5082"> support is
2203 provided by Linux only. Default: disabled.
2205 <tag><label id="bgp-password">password <m/string/</tag>
2206 Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
2207 used on BSD systems, see also <cf/setkey/ option below. Default: no
2210 <tag><label id="bgp-setkey">setkey <m/switch/</tag>
2211 On BSD systems, keys for TCP MD5 authentication are stored in the global
2212 SA/SP database, which can be accessed by external utilities (e.g.
2213 setkey(8)). BIRD configures security associations in the SA/SP database
2214 automatically based on <cf/password/ options (see above), this option
2215 allows to disable automatic updates by BIRD when manual configuration by
2216 external utilities is preferred. Note that automatic SA/SP database
2217 updates are currently implemented only for FreeBSD. Passwords have to be
2218 set manually by an external utility on NetBSD and OpenBSD. Default:
2219 enabled (ignored on non-FreeBSD).
2221 <tag><label id="bgp-passive">passive <m/switch/</tag>
2222 Standard BGP behavior is both initiating outgoing connections and
2223 accepting incoming connections. In passive mode, outgoing connections
2224 are not initiated. Default: off.
2226 <tag><label id="bgp-confederation">confederation <m/number/</tag>
2227 BGP confederations (<rfc id="5065">) are collections of autonomous
2228 systems that act as one entity to external systems, represented by one
2229 confederation identifier (instead of AS numbers). This option allows to
2230 enable BGP confederation behavior and to specify the local confederation
2231 identifier. When BGP confederations are used, all BGP speakers that are
2232 members of the BGP confederation should have the same confederation
2233 identifier configured. Default: 0 (no confederation).
2235 <tag><label id="bgp-confederation-member">confederation member <m/switch/</tag>
2236 When BGP confederations are used, this option allows to specify whether
2237 the BGP neighbor is a member of the same confederation as the local BGP
2238 speaker. The option is unnecessary (and ignored) for IBGP sessions, as
2239 the same AS number implies the same confederation. Default: no.
2241 <tag><label id="bgp-rr-client">rr client</tag>
2242 Be a route reflector and treat the neighbor as a route reflection
2243 client. Default: disabled.
2245 <tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2246 Route reflectors use cluster id to avoid route reflection loops. When
2247 there is one route reflector in a cluster it usually uses its router id
2248 as a cluster id, but when there are more route reflectors in a cluster,
2249 these need to be configured (using this option) to use a common cluster
2250 id. Clients in a cluster need not know their cluster id and this option
2251 is not allowed for them. Default: the same as router id.
2253 <tag><label id="bgp-rs-client">rs client</tag>
2254 Be a route server and treat the neighbor as a route server client.
2255 A route server is used as a replacement for full mesh EBGP routing in
2256 Internet exchange points in a similar way to route reflectors used in
2257 IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2258 uses ad-hoc implementation, which behaves like plain EBGP but reduces
2259 modifications to advertised route attributes to be transparent (for
2260 example does not prepend its AS number to AS PATH attribute and
2261 keeps MED attribute). Default: disabled.
2263 <tag><label id="bgp-allow-local-pref">allow bgp_local_pref <m/switch/</tag>
2264 A standard BGP implementation do not send the Local Preference attribute
2265 to eBGP neighbors and ignore this attribute if received from eBGP
2266 neighbors, as per <rfc id="4271">. When this option is enabled on an
2267 eBGP session, this attribute will be sent to and accepted from the peer,
2268 which is useful for example if you have a setup like in <rfc id="7938">.
2269 The option does not affect iBGP sessions. Default: off.
2271 <tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2272 BGP prevents routing loops by rejecting received routes with the local
2273 AS number in the AS path. This option allows to loose or disable the
2274 check. Optional <cf/number/ argument can be used to specify the maximum
2275 number of local ASNs in the AS path that is allowed for received
2276 routes. When the option is used without the argument, the check is
2277 completely disabled and you should ensure loop-free behavior by some
2278 other means. Default: 0 (no local AS number allowed).
2280 <tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
2281 After the initial route exchange, BGP protocol uses incremental updates
2282 to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
2283 changes its import filter, or if there is suspicion of inconsistency) it
2284 is necessary to do a new complete route exchange. BGP protocol extension
2285 Route Refresh (<rfc id="2918">) allows BGP speaker to request
2286 re-advertisement of all routes from its neighbor. BGP protocol
2287 extension Enhanced Route Refresh (<rfc id="7313">) specifies explicit
2288 begin and end for such exchanges, therefore the receiver can remove
2289 stale routes that were not advertised during the exchange. This option
2290 specifies whether BIRD advertises these capabilities and supports
2291 related procedures. Note that even when disabled, BIRD can send route
2292 refresh requests. Default: on.
2294 <tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
2295 When a BGP speaker restarts or crashes, neighbors will discard all
2296 received paths from the speaker, which disrupts packet forwarding even
2297 when the forwarding plane of the speaker remains intact. <rfc id="4724">
2298 specifies an optional graceful restart mechanism to alleviate this
2299 issue. This option controls the mechanism. It has three states:
2300 Disabled, when no support is provided. Aware, when the graceful restart
2301 support is announced and the support for restarting neighbors is
2302 provided, but no local graceful restart is allowed (i.e. receiving-only
2303 role). Enabled, when the full graceful restart support is provided
2304 (i.e. both restarting and receiving role). Restarting role could be also
2305 configured per-channel. Note that proper support for local graceful
2306 restart requires also configuration of other protocols. Default: aware.
2308 <tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
2309 The restart time is announced in the BGP graceful restart capability
2310 and specifies how long the neighbor would wait for the BGP session to
2311 re-establish after a restart before deleting stale routes. Default:
2314 <tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
2315 <rfc id="1997"> demands that BGP speaker should process well-known
2316 communities like no-export (65535, 65281) or no-advertise (65535,
2317 65282). For example, received route carrying a no-adverise community
2318 should not be advertised to any of its neighbors. If this option is
2319 enabled (which is by default), BIRD has such behavior automatically (it
2320 is evaluated when a route is exported to the BGP protocol just before
2321 the export filter). Otherwise, this integrated processing of
2322 well-known communities is disabled. In that case, similar behavior can
2323 be implemented in the export filter. Default: on.
2325 <tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
2326 BGP protocol was designed to use 2B AS numbers and was extended later to
2327 allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
2328 option it can be persuaded not to advertise it and to maintain old-style
2329 sessions with its neighbors. This might be useful for circumventing bugs
2330 in neighbor's implementation of 4B AS extension. Even when disabled
2331 (off), BIRD behaves internally as AS4-aware BGP router. Default: on.
2333 <tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
2334 The BGP protocol uses maximum message length of 4096 bytes. This option
2335 provides an extension to allow extended messages with length up
2336 to 65535 bytes. Default: off.
2338 <tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
2339 Use capability advertisement to advertise optional capabilities. This is
2340 standard behavior for newer BGP implementations, but there might be some
2341 older BGP implementations that reject such connection attempts. When
2342 disabled (off), features that request it (4B AS support) are also
2343 disabled. Default: on, with automatic fallback to off when received
2344 capability-related error.
2346 <tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag>
2347 Advertise IPv4 multiprotocol capability. This is not a correct behavior
2348 according to the strict interpretation of <rfc id="4760">, but it is
2349 widespread and required by some BGP implementations (Cisco and Quagga).
2350 This option is relevant to IPv4 mode with enabled capability
2351 advertisement only. Default: on.
2353 <tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
2354 When an error is encountered (either locally or by the other side),
2355 disable the instance automatically and wait for an administrator to fix
2356 the problem manually. Default: off.
2358 <tag><label id="bgp-hold-time">hold time <m/number/</tag>
2359 Time in seconds to wait for a Keepalive message from the other side
2360 before considering the connection stale. Default: depends on agreement
2361 with the neighboring router, we prefer 240 seconds if the other side is
2362 willing to accept it.
2364 <tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
2365 Value of the hold timer used before the routers have a chance to exchange
2366 open messages and agree on the real value. Default: 240 seconds.
2368 <tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
2369 Delay in seconds between sending of two consecutive Keepalive messages.
2370 Default: One third of the hold time.
2372 <tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
2373 Delay in seconds between protocol startup and the first attempt to
2374 connect. Default: 5 seconds.
2376 <tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
2377 Time in seconds to wait before retrying a failed attempt to connect.
2378 Default: 120 seconds.
2380 <tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
2381 Minimum and maximum delay in seconds between a protocol failure (either
2382 local or reported by the peer) and automatic restart. Doesn't apply
2383 when <cf/disable after error/ is configured. If consecutive errors
2384 happen, the delay is increased exponentially until it reaches the
2385 maximum. Default: 60, 300.
2387 <tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
2388 Maximum time in seconds between two protocol failures to treat them as a
2389 error sequence which makes <cf/error wait time/ increase exponentially.
2390 Default: 300 seconds.
2392 <tag><label id="bgp-path-metric">path metric <m/switch/</tag>
2393 Enable comparison of path lengths when deciding which BGP route is the
2394 best one. Default: on.
2396 <tag><label id="bgp-med-metric">med metric <m/switch/</tag>
2397 Enable comparison of MED attributes (during best route selection) even
2398 between routes received from different ASes. This may be useful if all
2399 MED attributes contain some consistent metric, perhaps enforced in
2400 import filters of AS boundary routers. If this option is disabled, MED
2401 attributes are compared only if routes are received from the same AS
2402 (which is the standard behavior). Default: off.
2404 <tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
2405 BGP route selection algorithm is often viewed as a comparison between
2406 individual routes (e.g. if a new route appears and is better than the
2407 current best one, it is chosen as the new best one). But the proper
2408 route selection, as specified by <rfc id="4271">, cannot be fully
2409 implemented in that way. The problem is mainly in handling the MED
2410 attribute. BIRD, by default, uses an simplification based on individual
2411 route comparison, which in some cases may lead to temporally dependent
2412 behavior (i.e. the selection is dependent on the order in which routes
2413 appeared). This option enables a different (and slower) algorithm
2414 implementing proper <rfc id="4271"> route selection, which is
2415 deterministic. Alternative way how to get deterministic behavior is to
2416 use <cf/med metric/ option. This option is incompatible with <ref
2417 id="dsc-table-sorted" name="sorted tables">. Default: off.
2419 <tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
2420 Enable comparison of internal distances to boundary routers during best
2421 route selection. Default: on.
2423 <tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
2424 Standard route selection algorithm breaks ties by comparing router IDs.
2425 This changes the behavior to prefer older routes (when both are external
2426 and from different peer). For details, see <rfc id="5004">. Default: off.
2428 <tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
2429 Value of the Multiple Exit Discriminator to be used during route
2430 selection when the MED attribute is missing. Default: 0.
2432 <tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
2433 A default value for the Local Preference attribute. It is used when
2434 a new Local Preference attribute is attached to a route by the BGP
2435 protocol itself (for example, if a route is received through eBGP and
2436 therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
2440 <sect1>Channel configuration
2441 <label id="bgp-channel-config">
2443 <p>BGP supports several AFIs and SAFIs over one connection. Every AFI/SAFI
2444 announced to the peer corresponds to one channel. The table of supported AFI/SAFIs
2445 together with their appropriate channels follows.
2448 <tabular ca="l|l|l|r|r">
2449 <bf/Channel name/ | <bf/Table nettype/ | <bf/IGP table allowed/ | <bf/AFI/ | <bf/SAFI/
2451 <cf/ipv4/ | <cf/ipv4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 1
2452 @ <cf/ipv6/ | <cf/ipv6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 1
2453 @ <cf/ipv4 multicast/ | <cf/ipv4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 2
2454 @ <cf/ipv6 multicast/ | <cf/ipv6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 2
2455 @ <cf/ipv4 mpls/ | <cf/ipv4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 4
2456 @ <cf/ipv6 mpls/ | <cf/ipv6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 4
2457 @ <cf/vpn4 mpls/ | <cf/vpn4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 128
2458 @ <cf/vpn6 mpls/ | <cf/vpn6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 128
2459 @ <cf/vpn4 multicast/ | <cf/vpn4/ | <cf/ipv4/ and <cf/ipv6/ | 1 | 129
2460 @ <cf/vpn6 multicast/ | <cf/vpn6/ | <cf/ipv4/ and <cf/ipv6/ | 2 | 129
2461 @ <cf/flow4/ | <cf/flow4/ | --- | 1 | 133
2462 @ <cf/flow6/ | <cf/flow6/ | --- | 2 | 133
2466 <p>Due to <rfc id="8212">, external BGP protocol requires explicit configuration
2467 of import and export policies (in contrast to other protocols, where default
2468 policies of <cf/import all/ and <cf/export none/ are used in absence of explicit
2469 configuration). Note that blanket policies like <cf/all/ or <cf/none/ can still
2470 be used in explicit configuration.
2472 <p>BGP channels have additional config options (together with the common ones):
2475 <tag><label id="bgp-next-hop-keep">next hop keep</tag>
2476 Forward the received Next Hop attribute even in situations where the
2477 local address should be used instead, like when the route is sent to an
2478 interface with a different subnet. Default: disabled.
2480 <tag><label id="bgp-next-hop-self">next hop self</tag>
2481 Avoid calculation of the Next Hop attribute and always advertise our own
2482 source address as a next hop. This needs to be used only occasionally to
2483 circumvent misconfigurations of other routers. Default: disabled.
2485 <tag><label id="bgp-next-hop-address">next hop address <m/ip/</tag>
2486 Avoid calculation of the Next Hop attribute and always advertise this address
2489 <tag><label id="bgp-missing-lladdr">missing lladdr self|drop|ignore</tag>
2490 Next Hop attribute in BGP-IPv6 sometimes contains just the global IPv6
2491 address, but sometimes it has to contain both global and link-local IPv6
2492 addresses. This option specifies what to do if BIRD have to send both
2493 addresses but does not know link-local address. This situation might
2494 happen when routes from other protocols are exported to BGP, or when
2495 improper updates are received from BGP peers. <cf/self/ means that BIRD
2496 advertises its own local address instead. <cf/drop/ means that BIRD
2497 skips that prefixes and logs error. <cf/ignore/ means that BIRD ignores
2498 the problem and sends just the global address (and therefore forms
2499 improper BGP update). Default: <cf/self/, unless BIRD is configured as a
2500 route server (option <cf/rs client/), in that case default is <cf/ignore/,
2501 because route servers usually do not forward packets themselves.
2503 <tag><label id="bgp-gateway">gateway direct|recursive</tag>
2504 For received routes, their <cf/gw/ (immediate next hop) attribute is
2505 computed from received <cf/bgp_next_hop/ attribute. This option
2506 specifies how it is computed. Direct mode means that the IP address from
2507 <cf/bgp_next_hop/ is used if it is directly reachable, otherwise the
2508 neighbor IP address is used. Recursive mode means that the gateway is
2509 computed by an IGP routing table lookup for the IP address from
2510 <cf/bgp_next_hop/. Note that there is just one level of indirection in
2511 recursive mode - the route obtained by the lookup must not be recursive
2512 itself, to prevent mutually recursive routes.
2514 Recursive mode is the behavior specified by the BGP
2515 standard. Direct mode is simpler, does not require any routes in a
2516 routing table, and was used in older versions of BIRD, but does not
2517 handle well nontrivial iBGP setups and multihop. Recursive mode is
2518 incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
2519 <cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
2521 <tag><label id="bgp-igp-table">igp table <m/name/</tag>
2522 Specifies a table that is used as an IGP routing table. The type of this
2523 table must be as allowed in the table above. This option is allowed once
2524 for every allowed table type. Default: the same as the main table
2525 the channel is connected to (if eligible).
2527 <tag><label id="bgp-secondary">secondary <m/switch/</tag>
2528 Usually, if an export filter rejects a selected route, no other route is
2529 propagated for that network. This option allows to try the next route in
2530 order until one that is accepted is found or all routes for that network
2531 are rejected. This can be used for route servers that need to propagate
2532 different tables to each client but do not want to have these tables
2533 explicitly (to conserve memory). This option requires that the connected
2534 routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
2536 <tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
2537 Standard BGP can propagate only one path (route) per destination network
2538 (usually the selected one). This option controls the add-path protocol
2539 extension, which allows to advertise any number of paths to a
2540 destination. Note that to be active, add-path has to be enabled on both
2541 sides of the BGP session, but it could be enabled separately for RX and
2542 TX direction. When active, all available routes accepted by the export
2543 filter are advertised to the neighbor. Default: off.
2545 <tag><label id="bgp-graceful-restart-c">graceful restart <m/switch/</tag>
2546 Although BGP graceful restart is configured mainly by protocol-wide
2547 <ref id="bgp-graceful-restart" name="options">, it is possible to
2548 configure restarting role per AFI/SAFI pair by this channel option.
2549 The option is ignored if graceful restart is disabled by protocol-wide
2550 option. Default: off in aware mode, on in full mode.
2554 <label id="bgp-attr">
2556 <p>BGP defines several route attributes. Some of them (those marked with
2557 `<tt/I/' in the table below) are available on internal BGP connections only,
2558 some of them (marked with `<tt/O/') are optional.
2561 <tag><label id="rta-bgp-path">bgppath bgp_path/</tag>
2562 Sequence of AS numbers describing the AS path the packet will travel
2563 through when forwarded according to the particular route. In case of
2564 internal BGP it doesn't contain the number of the local AS.
2566 <tag><label id="rta-bgp-local-pref">int bgp_local_pref/ [I]</tag>
2567 Local preference value used for selection among multiple BGP routes (see
2568 the selection rules above). It's used as an additional metric which is
2569 propagated through the whole local AS.
2571 <tag><label id="rta-bgp-med">int bgp_med/ [O]</tag>
2572 The Multiple Exit Discriminator of the route is an optional attribute
2573 which is used on external (inter-AS) links to convey to an adjacent AS
2574 the optimal entry point into the local AS. The received attribute is
2575 also propagated over internal BGP links. The attribute value is zeroed
2576 when a route is exported to an external BGP instance to ensure that the
2577 attribute received from a neighboring AS is not propagated to other
2578 neighboring ASes. A new value might be set in the export filter of an
2579 external BGP instance. See <rfc id="4451"> for further discussion of
2582 <tag><label id="rta-bgp-origin">enum bgp_origin/</tag>
2583 Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
2584 in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
2585 from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
2586 <cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
2588 <tag><label id="rta-bgp-next-hop">ip bgp_next_hop/</tag>
2589 Next hop to be used for forwarding of packets to this destination. On
2590 internal BGP connections, it's an address of the originating router if
2591 it's inside the local AS or a boundary router the packet will leave the
2592 AS through if it's an exterior route, so each BGP speaker within the AS
2593 has a chance to use the shortest interior path possible to this point.
2595 <tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr/ [O]</tag>
2596 This is an optional attribute which carries no value, but the sole
2597 presence of which indicates that the route has been aggregated from
2598 multiple routes by some router on the path from the originator.
2600 <!-- we don't handle aggregators right since they are of a very obscure type
2601 <tag>bgp_aggregator</tag>
2603 <tag><label id="rta-bgp-community">clist bgp_community/ [O]</tag>
2604 List of community values associated with the route. Each such value is a
2605 pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
2606 integers, the first of them containing the number of the AS which
2607 defines the community and the second one being a per-AS identifier.
2608 There are lots of uses of the community mechanism, but generally they
2609 are used to carry policy information like "don't export to USA peers".
2610 As each AS can define its own routing policy, it also has a complete
2611 freedom about which community attributes it defines and what will their
2614 <tag><label id="rta-bgp-ext-community">eclist bgp_ext_community/ [O]</tag>
2615 List of extended community values associated with the route. Extended
2616 communities have similar usage as plain communities, but they have an
2617 extended range (to allow 4B ASNs) and a nontrivial structure with a type
2618 field. Individual community values are represented using an <cf/ec/ data
2619 type inside the filters.
2621 <tag><label id="rta-bgp-large-community">lclist <cf/bgp_large_community/ [O]</tag>
2622 List of large community values associated with the route. Large BGP
2623 communities is another variant of communities, but contrary to extended
2624 communities they behave very much the same way as regular communities,
2625 just larger -- they are uniform untyped triplets of 32bit numbers.
2626 Individual community values are represented using an <cf/lc/ data type
2629 <tag><label id="rta-bgp-originator-id">quad bgp_originator_id/ [I, O]</tag>
2630 This attribute is created by the route reflector when reflecting the
2631 route and contains the router ID of the originator of the route in the
2634 <tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list/ [I, O]</tag>
2635 This attribute contains a list of cluster IDs of route reflectors. Each
2636 route reflector prepends its cluster ID when reflecting the route.
2640 <label id="bgp-exam">
2644 local 198.51.100.14 as 65000; # Use a private AS number
2645 neighbor 198.51.100.130 as 64496; # Our neighbor ...
2646 multihop; # ... which is connected indirectly
2648 export filter { # We use non-trivial export rules
2649 if source = RTS_STATIC then { # Export only static routes
2650 # Assign our community
2651 bgp_community.add((65000,64501));
2652 # Artificially increase path length
2653 # by advertising local AS number twice
2654 if bgp_path ~ [= 65000 =] then
2655 bgp_path.prepend(65000);
2661 next hop self; # advertise this router as next hop
2662 igp table myigptable4; # IGP table for routes with IPv4 nexthops
2663 igp table myigptable6; # IGP table for routes with IPv6 nexthops
2666 export filter mylargefilter; # We use a named filter
2668 missing lladdr self;
2669 igp table myigptable4; # IGP table for routes with IPv4 nexthops
2670 igp table myigptable6; # IGP table for routes with IPv6 nexthops
2674 export filter someotherfilter;
2675 table mymulticasttable4; # Another IPv4 table, dedicated for multicast
2676 igp table myigptable4;
2685 <p>The Device protocol is not a real routing protocol. It doesn't generate any
2686 routes and it only serves as a module for getting information about network
2687 interfaces from the kernel. This protocol supports no channel.
2689 <p>Except for very unusual circumstances, you probably should include this
2690 protocol in the configuration since almost all other protocols require network
2691 interfaces to be defined for them to work with.
2693 <sect1>Configuration
2694 <label id="device-config">
2697 <tag><label id="device-scan-time">scan time <m/number/</tag>
2698 Time in seconds between two scans of the network interface list. On
2699 systems where we are notified about interface status changes
2700 asynchronously (such as newer versions of Linux), we need to scan the
2701 list only in order to avoid confusion by lost notification messages,
2702 so the default time is set to a large value.
2704 <tag><label id="device-iface">interface <m/pattern/ [, <m/.../]</tag>
2706 By default, the Device protocol handles all interfaces without any
2707 configuration. Interface definitions allow to specify optional
2708 parameters for specific interfaces. See <ref id="proto-iface"
2709 name="interface"> common option for detailed description. Currently only
2710 one interface option is available:
2712 <tag><label id="device-preferred">preferred <m/ip/</tag>
2713 If a network interface has more than one IP address, BIRD chooses one of
2714 them as a preferred one. Preferred IP address is used as source address
2715 for packets or announced next hop by routing protocols. Precisely, BIRD
2716 chooses one preferred IPv4 address, one preferred IPv6 address and one
2717 preferred link-local IPv6 address. By default, BIRD chooses the first
2718 found IP address as the preferred one.
2720 This option allows to specify which IP address should be preferred. May
2721 be used multiple times for different address classes (IPv4, IPv6, IPv6
2722 link-local). In all cases, an address marked by operating system as
2723 secondary cannot be chosen as the primary one.
2726 <p>As the Device protocol doesn't generate any routes, it cannot have
2727 any attributes. Example configuration looks like this:
2731 scan time 10; # Scan the interfaces often
2733 preferred 192.168.1.1;
2734 preferred 2001:db8:1:10::1;
2743 <p>The Direct protocol is a simple generator of device routes for all the
2744 directly connected networks according to the list of interfaces provided by the
2745 kernel via the Device protocol. The Direct protocol supports both IPv4 and IPv6
2748 <p>The question is whether it is a good idea to have such device routes in BIRD
2749 routing table. OS kernel usually handles device routes for directly connected
2750 networks by itself so we don't need (and don't want) to export these routes to
2751 the kernel protocol. OSPF protocol creates device routes for its interfaces
2752 itself and BGP protocol is usually used for exporting aggregate routes. Although
2753 there are some use cases that use the direct protocol (like abusing eBGP as an
2754 IGP routing protocol), in most cases it is not needed to have these device
2755 routes in BIRD routing table and to use the direct protocol.
2757 <p>There is one notable case when you definitely want to use the direct protocol
2758 -- running BIRD on BSD systems. Having high priority device routes for directly
2759 connected networks from the direct protocol protects kernel device routes from
2760 being overwritten or removed by IGP routes during some transient network
2761 conditions, because a lower priority IGP route for the same network is not
2762 exported to the kernel routing table. This is an issue on BSD systems only, as
2763 on Linux systems BIRD cannot change non-BIRD route in the kernel routing table.
2765 <p>There are just few configuration options for the Direct protocol:
2768 <tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
2769 By default, the Direct protocol will generate device routes for all the
2770 interfaces available. If you want to restrict it to some subset of
2771 interfaces or addresses (e.g. if you're using multiple routing tables
2772 for policy routing and some of the policy domains don't contain all
2773 interfaces), just use this clause. See <ref id="proto-iface" name="interface">
2774 common option for detailed description. The Direct protocol uses
2775 extended interface clauses.
2777 <tag><label id="direct-check-link">check link <m/switch/</tag>
2778 If enabled, a hardware link state (reported by OS) is taken into
2779 consideration. Routes for directly connected networks are generated only
2780 if link up is reported and they are withdrawn when link disappears
2781 (e.g., an ethernet cable is unplugged). Default value is no.
2784 <p>Direct device routes don't contain any specific attributes.
2786 <p>Example config might look like this:
2792 interface "-arc*", "*"; # Exclude the ARCnets
2800 <p>The Kernel protocol is not a real routing protocol. Instead of communicating
2801 with other routers in the network, it performs synchronization of BIRD's routing
2802 tables with the OS kernel. Basically, it sends all routing table updates to the
2803 kernel and from time to time it scans the kernel tables to see whether some
2804 routes have disappeared (for example due to unnoticed up/down transition of an
2805 interface) or whether an `alien' route has been added by someone else (depending
2806 on the <cf/learn/ switch, such routes are either ignored or accepted to our
2809 <p>Unfortunately, there is one thing that makes the routing table synchronization
2810 a bit more complicated. In the kernel routing table there are also device routes
2811 for directly connected networks. These routes are usually managed by OS itself
2812 (as a part of IP address configuration) and we don't want to touch that. They
2813 are completely ignored during the scan of the kernel tables and also the export
2814 of device routes from BIRD tables to kernel routing tables is restricted to
2815 prevent accidental interference. This restriction can be disabled using
2816 <cf/device routes/ switch.
2818 <p>If your OS supports only a single routing table, you can configure only one
2819 instance of the Kernel protocol. If it supports multiple tables (in order to
2820 allow policy routing; such an OS is for example Linux), you can run as many
2821 instances as you want, but each of them must be connected to a different BIRD
2822 routing table and to a different kernel table.
2824 <p>Because the kernel protocol is partially integrated with the connected
2825 routing table, there are two limitations - it is not possible to connect more
2826 kernel protocols to the same routing table and changing route destination
2827 (gateway) in an export filter of a kernel protocol does not work. Both
2828 limitations can be overcome using another routing table and the pipe protocol.
2830 <p>The Kernel protocol supports both IPv4 and IPv6 channels; only one of them
2831 can be configured in each protocol instance.
2833 <sect1>Configuration
2834 <label id="krt-config">
2837 <tag><label id="krt-persist">persist <m/switch/</tag>
2838 Tell BIRD to leave all its routes in the routing tables when it exits
2839 (instead of cleaning them up).
2841 <tag><label id="krt-scan-time">scan time <m/number/</tag>
2842 Time in seconds between two consecutive scans of the kernel routing
2845 <tag><label id="krt-learn">learn <m/switch/</tag>
2846 Enable learning of routes added to the kernel routing tables by other
2847 routing daemons or by the system administrator. This is possible only on
2848 systems which support identification of route authorship.
2850 <tag><label id="krt-kernel-table">kernel table <m/number/</tag>
2851 Select which kernel table should this particular instance of the Kernel
2852 protocol work with. Available only on systems supporting multiple
2855 <tag><label id="krt-metric">metric <m/number/</tag> (Linux)
2856 Use specified value as a kernel metric (priority) for all routes sent to
2857 the kernel. When multiple routes for the same network are in the kernel
2858 routing table, the Linux kernel chooses one with lower metric. Also,
2859 routes with different metrics do not clash with each other, therefore
2860 using dedicated metric value is a reliable way to avoid overwriting
2861 routes from other sources (e.g. kernel device routes). Metric 0 has a
2862 special meaning of undefined metric, in which either OS default is used,
2863 or per-route metric can be set using <cf/krt_metric/ attribute. Default:
2866 <tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
2867 Participate in graceful restart recovery. If this option is enabled and
2868 a graceful restart recovery is active, the Kernel protocol will defer
2869 synchronization of routing tables until the end of the recovery. Note
2870 that import of kernel routes to BIRD is not affected.
2872 <tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
2873 Usually, only best routes are exported to the kernel protocol. With path
2874 merging enabled, both best routes and equivalent non-best routes are
2875 merged during export to generate one ECMP (equal-cost multipath) route
2876 for each network. This is useful e.g. for BGP multipath. Note that best
2877 routes are still pivotal for route export (responsible for most
2878 properties of resulting ECMP routes), while exported non-best routes are
2879 responsible just for additional multipath next hops. This option also
2880 allows to specify a limit on maximal number of nexthops in one route. By
2881 default, multipath merging is disabled. If enabled, default value of the
2886 <label id="krt-attr">
2888 <p>The Kernel protocol defines several attributes. These attributes are
2889 translated to appropriate system (and OS-specific) route attributes. We support
2893 <tag><label id="rta-krt-source">int krt_source/</tag>
2894 The original source of the imported kernel route. The value is
2895 system-dependent. On Linux, it is a value of the protocol field of the
2896 route. See /etc/iproute2/rt_protos for common values. On BSD, it is
2897 based on STATIC and PROTOx flags. The attribute is read-only.
2899 <tag><label id="rta-krt-metric">int krt_metric/</tag> (Linux)
2900 The kernel metric of the route. When multiple same routes are in a
2901 kernel routing table, the Linux kernel chooses one with lower metric.
2902 Note that preferred way to set kernel metric is to use protocol option
2903 <cf/metric/, unless per-route metric values are needed.
2905 <tag><label id="rta-krt-prefsrc">ip krt_prefsrc/</tag> (Linux)
2906 The preferred source address. Used in source address selection for
2907 outgoing packets. Has to be one of the IP addresses of the router.
2909 <tag><label id="rta-krt-realm">int krt_realm/</tag> (Linux)
2910 The realm of the route. Can be used for traffic classification.
2912 <tag><label id="rta-krt-scope">int krt_scope/</tag> (Linux IPv4)
2913 The scope of the route. Valid values are 0-254, although Linux kernel
2914 may reject some values depending on route type and nexthop. It is
2915 supposed to represent `indirectness' of the route, where nexthops of
2916 routes are resolved through routes with a higher scope, but in current
2917 kernels anything below <it/link/ (253) is treated as <it/global/ (0).
2918 When not present, global scope is implied for all routes except device
2919 routes, where link scope is used by default.
2922 <p>In Linux, there is also a plenty of obscure route attributes mostly focused
2923 on tuning TCP performance of local connections. BIRD supports most of these
2924 attributes, see Linux or iproute2 documentation for their meaning. Attributes
2925 <cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, others have type int.
2926 Supported attributes are:
2928 <cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
2929 <cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
2930 <cf/krt_sstresh/, <cf/krt_lock_sstresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
2931 <cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
2932 <cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
2933 <cf/krt_initcwnd/, <cf/krt_initrwnd/, <cf/krt_quickack/,
2934 <cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
2937 <label id="krt-exam">
2939 <p>A simple configuration can look this way:
2947 <p>Or for a system with two routing tables:
2950 protocol kernel { # Primary routing table
2951 learn; # Learn alien routes from the kernel
2952 persist; # Don't remove routes on bird shutdown
2953 scan time 10; # Scan kernel routing table every 10 seconds
2960 protocol kernel { # Secondary routing table
2974 <label id="ospf-intro">
2976 <p>Open Shortest Path First (OSPF) is a quite complex interior gateway
2977 protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
2978 the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
2979 state (a.k.a. shortest path first) protocol -- each router maintains a database
2980 describing the autonomous system's topology. Each participating router has an
2981 identical copy of the database and all routers run the same algorithm
2982 calculating a shortest path tree with themselves as a root. OSPF chooses the
2983 least cost path as the best path.
2985 <p>In OSPF, the autonomous system can be split to several areas in order to
2986 reduce the amount of resources consumed for exchanging the routing information
2987 and to protect the other areas from incorrect routing data. Topology of the area
2988 is hidden to the rest of the autonomous system.
2990 <p>Another very important feature of OSPF is that it can keep routing information
2991 from other protocols (like Static or BGP) in its link state database as external
2992 routes. Each external route can be tagged by the advertising router, making it
2993 possible to pass additional information between routers on the boundary of the
2996 <p>OSPF quickly detects topological changes in the autonomous system (such as
2997 router interface failures) and calculates new loop-free routes after a short
2998 period of convergence. Only a minimal amount of routing traffic is involved.
3000 <p>Each router participating in OSPF routing periodically sends Hello messages
3001 to all its interfaces. This allows neighbors to be discovered dynamically. Then
3002 the neighbors exchange theirs parts of the link state database and keep it
3003 identical by flooding updates. The flooding process is reliable and ensures that
3004 each router detects all changes.
3006 <sect1>Configuration
3007 <label id="ospf-config">
3009 <p>First, the desired OSPF version can be specified by using <cf/ospf v2/ or
3010 <cf/ospf v3/ as a protocol type. By default, OSPFv2 is used. In the main part of
3011 configuration, there can be multiple definitions of OSPF areas, each with a
3012 different id. These definitions includes many other switches and multiple
3013 definitions of interfaces. Definition of interface may contain many switches and
3014 constant definitions and list of neighbors on nonbroadcast networks.
3016 <p>OSPFv2 needs one IPv4 channel. OSPFv3 needs either one IPv6 channel, or one
3017 IPv4 channel (<rfc id="5838">). Therefore, it is possible to use OSPFv3 for both
3018 IPv4 and Pv6 routing, but it is necessary to have two protocol instances anyway.
3019 If no channel is configured, appropriate channel is defined with default
3023 protocol ospf [v2|v3] <name> {
3024 rfc1583compat <switch>;
3025 rfc5838 <switch>;
3026 instance id <num>;
3027 stub router <switch>;
3029 ecmp <switch> [limit <num>];
3030 merge external <switch>;
3034 summary <switch>;
3035 default nssa <switch>;
3036 default cost <num>;
3037 default cost2 <num>;
3038 translator <switch>;
3039 translator stability <num>;
3043 <prefix> hidden;
3047 <prefix> hidden;
3048 <prefix> tag <num>;
3050 stubnet <prefix>;
3051 stubnet <prefix> {
3052 hidden <switch>;
3053 summary <switch>;
3056 interface <interface pattern> [instance <num>] {
3058 stub <switch>;
3061 retransmit <num>;
3062 priority <num>;
3064 dead count <num>;
3066 secondary <switch>;
3067 rx buffer [normal|large|<num>];
3068 tx length <num>;
3069 type [broadcast|bcast|pointopoint|ptp|
3070 nonbroadcast|nbma|pointomultipoint|ptmp];
3071 link lsa suppression <switch>;
3072 strict nonbroadcast <switch>;
3073 real broadcast <switch>;
3074 ptp netmask <switch>;
3075 check link <switch>;
3077 ecmp weight <num>;
3078 ttl security [<switch>; | tx only]
3079 tx class|dscp <num>;
3080 tx priority <num>;
3081 authentication none|simple|cryptographic;
3082 password "<text>";
3083 password "<text>" {
3085 generate from "<date>";
3086 generate to "<date>";
3087 accept from "<date>";
3088 accept to "<date>";
3089 from "<date>";
3091 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3095 <ip> eligible;
3098 virtual link <id> [instance <num>] {
3100 retransmit <num>;
3102 dead count <num>;
3104 authentication none|simple|cryptographic;
3105 password "<text>";
3106 password "<text>" {
3108 generate from "<date>";
3109 generate to "<date>";
3110 accept from "<date>";
3111 accept to "<date>";
3112 from "<date>";
3114 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3122 <tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
3123 This option controls compatibility of routing table calculation with
3124 <rfc id="1583">. Default value is no.
3126 <tag><label id="ospf-rfc5838">rfc5838 <m/switch/</tag>
3127 Basic OSPFv3 is limited to IPv6 unicast routing. The <rfc id="5838">
3128 extension defines support for more address families (IPv4, IPv6, both
3129 unicast and multicast). The extension is enabled by default, but can be
3130 disabled if necessary, as it restricts the range of available instance
3131 IDs. Default value is yes.
3133 <tag><label id="ospf-instance-id">instance id <m/num/</tag>
3134 When multiple OSPF protocol instances are active on the same links, they
3135 should use different instance IDs to distinguish their packets. Although
3136 it could be done on per-interface basis, it is often preferred to set
3137 one instance ID to whole OSPF domain/topology (e.g., when multiple
3138 instances are used to represent separate logical topologies on the same
3139 physical network). This option specifies the instance ID for all
3140 interfaces of the OSPF instance, but can be overridden by
3141 <cf/interface/ option. Default value is 0 unless OSPFv3-AF extended
3142 address families are used, see <rfc id="5838"> for that case.
3144 <tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
3145 This option configures the router to be a stub router, i.e., a router
3146 that participates in the OSPF topology but does not allow transit
3147 traffic. In OSPFv2, this is implemented by advertising maximum metric
3148 for outgoing links. In OSPFv3, the stub router behavior is announced by
3149 clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
3150 Default value is no.
3152 <tag><label id="ospf-tick">tick <M>num</M></tag>
3153 The routing table calculation and clean-up of areas' databases is not
3154 performed when a single link state change arrives. To lower the CPU
3155 utilization, it's processed later at periodical intervals of <m/num/
3156 seconds. The default value is 1.
3158 <tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
3159 This option specifies whether OSPF is allowed to generate ECMP
3160 (equal-cost multipath) routes. Such routes are used when there are
3161 several directions to the destination, each with the same (computed)
3162 cost. This option also allows to specify a limit on maximum number of
3163 nexthops in one route. By default, ECMP is enabled if supported by
3164 Kernel. Default value of the limit is 16.
3166 <tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
3167 This option specifies whether OSPF should merge external routes from
3168 different routers/LSAs for the same destination. When enabled together
3169 with <cf/ecmp/, equal-cost external routes will be combined to multipath
3170 routes in the same way as regular routes. When disabled, external routes
3171 from different LSAs are treated as separate even if they represents the
3172 same destination. Default value is no.
3174 <tag><label id="ospf-area">area <M>id</M></tag>
3175 This defines an OSPF area with given area ID (an integer or an IPv4
3176 address, similarly to a router ID). The most important area is the
3177 backbone (ID 0) to which every other area must be connected.
3179 <tag><label id="ospf-stub">stub</tag>
3180 This option configures the area to be a stub area. External routes are
3181 not flooded into stub areas. Also summary LSAs can be limited in stub
3182 areas (see option <cf/summary/). By default, the area is not a stub
3185 <tag><label id="ospf-nssa">nssa</tag>
3186 This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
3187 is a variant of a stub area which allows a limited way of external route
3188 propagation. Global external routes are not propagated into a NSSA, but
3189 an external route can be imported into NSSA as a (area-wide) NSSA-LSA
3190 (and possibly translated and/or aggregated on area boundary). By
3191 default, the area is not NSSA.
3193 <tag><label id="ospf-summary">summary <M>switch</M></tag>
3194 This option controls propagation of summary LSAs into stub or NSSA
3195 areas. If enabled, summary LSAs are propagated as usual, otherwise just
3196 the default summary route (0.0.0.0/0) is propagated (this is sometimes
3197 called totally stubby area). If a stub area has more area boundary
3198 routers, propagating summary LSAs could lead to more efficient routing
3199 at the cost of larger link state database. Default value is no.
3201 <tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
3202 When <cf/summary/ option is enabled, default summary route is no longer
3203 propagated to the NSSA. In that case, this option allows to originate
3204 default route as NSSA-LSA to the NSSA. Default value is no.
3206 <tag><label id="ospf-default-cost">default cost <M>num</M></tag>
3207 This option controls the cost of a default route propagated to stub and
3208 NSSA areas. Default value is 1000.
3210 <tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
3211 When a default route is originated as NSSA-LSA, its cost can use either
3212 type 1 or type 2 metric. This option allows to specify the cost of a
3213 default route in type 2 metric. By default, type 1 metric (option
3214 <cf/default cost/) is used.
3216 <tag><label id="ospf-translator">translator <M>switch</M></tag>
3217 This option controls translation of NSSA-LSAs into external LSAs. By
3218 default, one translator per NSSA is automatically elected from area
3219 boundary routers. If enabled, this area boundary router would
3220 unconditionally translate all NSSA-LSAs regardless of translator
3221 election. Default value is no.
3223 <tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
3224 This option controls the translator stability interval (in seconds).
3225 When the new translator is elected, the old one keeps translating until
3226 the interval is over. Default value is 40.
3228 <tag><label id="ospf-networks">networks { <m/set/ }</tag>
3229 Definition of area IP ranges. This is used in summary LSA origination.
3230 Hidden networks are not propagated into other areas.
3232 <tag><label id="ospf-external">external { <m/set/ }</tag>
3233 Definition of external area IP ranges for NSSAs. This is used for
3234 NSSA-LSA translation. Hidden networks are not translated into external
3235 LSAs. Networks can have configured route tag.
3237 <tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
3238 Stub networks are networks that are not transit networks between OSPF
3239 routers. They are also propagated through an OSPF area as a part of a
3240 link state database. By default, BIRD generates a stub network record
3241 for each primary network address on each OSPF interface that does not
3242 have any OSPF neighbors, and also for each non-primary network address
3243 on each OSPF interface. This option allows to alter a set of stub
3244 networks propagated by this router.
3246 Each instance of this option adds a stub network with given network
3247 prefix to the set of propagated stub network, unless option <cf/hidden/
3248 is used. It also suppresses default stub networks for given network
3249 prefix. When option <cf/summary/ is used, also default stub networks
3250 that are subnetworks of given stub network are suppressed. This might be
3251 used, for example, to aggregate generated stub networks.
3253 <tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
3254 Defines that the specified interfaces belong to the area being defined.
3255 See <ref id="proto-iface" name="interface"> common option for detailed
3256 description. In OSPFv2, extended interface clauses are used, because
3257 each network prefix is handled as a separate virtual interface.
3259 You can specify alternative instance ID for the interface definition,
3260 therefore it is possible to have several instances of that interface
3261 with different options or even in different areas. For OSPFv2, instance
3262 ID support is an extension (<rfc id="6549">) and is supposed to be set
3263 per-protocol. For OSPFv3, it is an integral feature.
3265 <tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
3266 Virtual link to router with the router id. Virtual link acts as a
3267 point-to-point interface belonging to backbone. The actual area is used
3268 as a transport area. This item cannot be in the backbone. Like with
3269 <cf/interface/ option, you could also use several virtual links to one
3270 destination with different instance IDs.
3272 <tag><label id="ospf-cost">cost <M>num</M></tag>
3273 Specifies output cost (metric) of an interface. Default value is 10.
3275 <tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
3276 If set to interface it does not listen to any packet and does not send
3277 any hello. Default value is no.
3279 <tag><label id="ospf-hello">hello <M>num</M></tag>
3280 Specifies interval in seconds between sending of Hello messages. Beware,
3281 all routers on the same network need to have the same hello interval.
3282 Default value is 10.
3284 <tag><label id="ospf-poll">poll <M>num</M></tag>
3285 Specifies interval in seconds between sending of Hello messages for some
3286 neighbors on NBMA network. Default value is 20.
3288 <tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
3289 Specifies interval in seconds between retransmissions of unacknowledged
3290 updates. Default value is 5.
3292 <tag><label id="ospf-priority">priority <M>num</M></tag>
3293 On every multiple access network (e.g., the Ethernet) Designated Router
3294 and Backup Designated router are elected. These routers have some special
3295 functions in the flooding process. Higher priority increases preferences
3296 in this election. Routers with priority 0 are not eligible. Default
3299 <tag><label id="ospf-wait">wait <M>num</M></tag>
3300 After start, router waits for the specified number of seconds between
3301 starting election and building adjacency. Default value is 4*<m/hello/.
3303 <tag><label id="ospf-dead-count">dead count <M>num</M></tag>
3304 When the router does not receive any messages from a neighbor in
3305 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
3307 <tag><label id="ospf-dead">dead <M>num</M></tag>
3308 When the router does not receive any messages from a neighbor in
3309 <m/dead/ seconds, it will consider the neighbor down. If both directives
3310 <cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
3312 <tag><label id="ospf-secondary">secondary <M>switch</M></tag>
3313 On BSD systems, older versions of BIRD supported OSPFv2 only for the
3314 primary IP address of an interface, other IP ranges on the interface
3315 were handled as stub networks. Since v1.4.1, regular operation on
3316 secondary IP addresses is supported, but disabled by default for
3317 compatibility. This option allows to enable it. The option is a
3318 transitional measure, will be removed in the next major release as the
3319 behavior will be changed. On Linux systems, the option is irrelevant, as
3320 operation on non-primary addresses is already the regular behavior.
3322 <tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
3323 This option allows to specify the size of buffers used for packet
3324 processing. The buffer size should be bigger than maximal size of any
3325 packets. By default, buffers are dynamically resized as needed, but a
3326 fixed value could be specified. Value <cf/large/ means maximal allowed
3327 packet size - 65535.
3329 <tag><label id="ospf-tx-length">tx length <M>num</M></tag>
3330 Transmitted OSPF messages that contain large amount of information are
3331 segmented to separate OSPF packets to avoid IP fragmentation. This
3332 option specifies the soft ceiling for the length of generated OSPF
3333 packets. Default value is the MTU of the network interface. Note that
3334 larger OSPF packets may still be generated if underlying OSPF messages
3335 cannot be splitted (e.g. when one large LSA is propagated).
3337 <tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
3338 BIRD detects a type of a connected network automatically, but sometimes
3339 it's convenient to force use of a different type manually. On broadcast
3340 networks (like ethernet), flooding and Hello messages are sent using
3341 multicasts (a single packet for all the neighbors). A designated router
3342 is elected and it is responsible for synchronizing the link-state
3343 databases and originating network LSAs. This network type cannot be used
3344 on physically NBMA networks and on unnumbered networks (networks without
3347 <tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
3348 Point-to-point networks connect just 2 routers together. No election is
3349 performed and no network LSA is originated, which makes it simpler and
3350 faster to establish. This network type is useful not only for physically
3351 PtP ifaces (like PPP or tunnels), but also for broadcast networks used
3352 as PtP links. This network type cannot be used on physically NBMA
3355 <tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
3356 On NBMA networks, the packets are sent to each neighbor separately
3357 because of lack of multicast capabilities. Like on broadcast networks,
3358 a designated router is elected, which plays a central role in propagation
3359 of LSAs. This network type cannot be used on unnumbered networks.
3361 <tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
3362 This is another network type designed to handle NBMA networks. In this
3363 case the NBMA network is treated as a collection of PtP links. This is
3364 useful if not every pair of routers on the NBMA network has direct
3365 communication, or if the NBMA network is used as an (possibly
3366 unnumbered) PtP link.
3368 <tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
3369 In OSPFv3, link LSAs are generated for each link, announcing link-local
3370 IPv6 address of the router to its local neighbors. These are useless on
3371 PtP or PtMP networks and this option allows to suppress the link LSA
3372 origination for such interfaces. The option is ignored on other than PtP
3373 or PtMP interfaces. Default value is no.
3375 <tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
3376 If set, don't send hello to any undefined neighbor. This switch is
3377 ignored on other than NBMA or PtMP interfaces. Default value is no.
3379 <tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
3380 In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
3381 packets are sent as IP multicast packets. This option changes the
3382 behavior to using old-fashioned IP broadcast packets. This may be useful
3383 as a workaround if IP multicast for some reason does not work or does
3384 not work reliably. This is a non-standard option and probably is not
3385 interoperable with other OSPF implementations. Default value is no.
3387 <tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
3388 In <cf/type ptp/ network configurations, OSPFv2 implementations should
3389 ignore received netmask field in hello packets and should send hello
3390 packets with zero netmask field on unnumbered PtP links. But some OSPFv2
3391 implementations perform netmask checking even for PtP links. This option
3392 specifies whether real netmask will be used in hello packets on <cf/type
3393 ptp/ interfaces. You should ignore this option unless you meet some
3394 compatibility problems related to this issue. Default value is no for
3395 unnumbered PtP links, yes otherwise.
3397 <tag><label id="ospf-check-link">check link <M>switch</M></tag>
3398 If set, a hardware link state (reported by OS) is taken into consideration.
3399 When a link disappears (e.g. an ethernet cable is unplugged), neighbors
3400 are immediately considered unreachable and only the address of the iface
3401 (instead of whole network prefix) is propagated. It is possible that
3402 some hardware drivers or platforms do not implement this feature.
3403 Default value is yes.
3405 <tag><label id="ospf-bfd">bfd <M>switch</M></tag>
3406 OSPF could use BFD protocol as an advisory mechanism for neighbor
3407 liveness and failure detection. If enabled, BIRD setups a BFD session
3408 for each OSPF neighbor and tracks its liveness by it. This has an
3409 advantage of an order of magnitude lower detection times in case of
3410 failure. Note that BFD protocol also has to be configured, see
3411 <ref id="bfd" name="BFD"> section for details. Default value is no.
3413 <tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3414 TTL security is a feature that protects routing protocols from remote
3415 spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3416 destined to neighbors. Because TTL is decremented when packets are
3417 forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3418 locations. Note that this option would interfere with OSPF virtual
3421 If this option is enabled, the router will send OSPF packets with TTL
3422 255 and drop received packets with TTL less than 255. If this option si
3423 set to <cf/tx only/, TTL 255 is used for sent packets, but is not
3424 checked for received packets. Default value is no.
3426 <tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
3427 These options specify the ToS/DiffServ/Traffic class/Priority of the
3428 outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
3429 option for detailed description.
3431 <tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
3432 When ECMP (multipath) routes are allowed, this value specifies a
3433 relative weight used for nexthops going through the iface. Allowed
3434 values are 1-256. Default value is 1.
3436 <tag><label id="ospf-auth-none">authentication none</tag>
3437 No passwords are sent in OSPF packets. This is the default value.
3439 <tag><label id="ospf-auth-simple">authentication simple</tag>
3440 Every packet carries 8 bytes of password. Received packets lacking this
3441 password are ignored. This authentication mechanism is very weak.
3442 This option is not available in OSPFv3.
3444 <tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
3445 An authentication code is appended to every packet. The specific
3446 cryptographic algorithm is selected by option <cf/algorithm/ for each
3447 key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
3448 and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
3449 network, so this mechanism is quite secure. Packets can still be read by
3452 <tag><label id="ospf-pass">password "<M>text</M>"</tag>
3453 Specifies a password used for authentication. See
3454 <ref id="proto-pass" name="password"> common option for detailed
3457 <tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
3458 A set of neighbors to which Hello messages on NBMA or PtMP networks are
3459 to be sent. For NBMA networks, some of them could be marked as eligible.
3460 In OSPFv3, link-local addresses should be used, using global ones is
3461 possible, but it is nonstandard and might be problematic. And definitely,
3462 link-local and global addresses should not be mixed.
3466 <label id="ospf-attr">
3468 <p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
3470 <p>Metric is ranging from 1 to infinity (65535). External routes use
3471 <cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
3472 with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
3473 <cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
3474 <cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
3475 2/ is stored in attribute <cf/ospf_metric2/. If you specify both metrics only
3478 <p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
3479 integer which is used when exporting routes to other protocols; otherwise, it
3480 doesn't affect routing inside the OSPF domain at all. The fourth attribute
3481 <cf/ospf_router_id/ is a router ID of the router advertising that route /
3482 network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
3486 <label id="ospf-exam">
3489 protocol ospf MyOSPF {
3492 if source = RTS_BGP then {
3505 authentication simple;
3510 authentication cryptographic;
3513 generate to "22-04-2003 11:00:06";
3514 accept from "17-01-2001 12:01:05";
3515 algorithm hmac sha384;
3519 generate to "22-07-2005 17:03:21";
3520 accept from "22-02-2001 11:34:06";
3521 algorithm hmac sha512;
3534 172.16.2.0/24 hidden;
3536 interface "-arc0" , "arc*" {
3538 authentication none;
3539 strict nonbroadcast yes;
3544 192.168.120.1 eligible;
3558 <label id="pipe-intro">
3560 <p>The Pipe protocol serves as a link between two routing tables, allowing
3561 routes to be passed from a table declared as primary (i.e., the one the pipe is
3562 connected to using the <cf/table/ configuration keyword) to the secondary one
3563 (declared using <cf/peer table/) and vice versa, depending on what's allowed by
3564 the filters. Export filters control export of routes from the primary table to
3565 the secondary one, import filters control the opposite direction. Both tables
3566 must be of the same nettype.
3568 <p>The Pipe protocol may work in the transparent mode mode or in the opaque
3569 mode. In the transparent mode, the Pipe protocol retransmits all routes from
3570 one table to the other table, retaining their original source and attributes.
3571 If import and export filters are set to accept, then both tables would have
3572 the same content. The transparent mode is the default mode.
3574 <p>In the opaque mode, the Pipe protocol retransmits optimal route from one
3575 table to the other table in a similar way like other protocols send and receive
3576 routes. Retransmitted route will have the source set to the Pipe protocol, which
3577 may limit access to protocol specific route attributes. This mode is mainly for
3578 compatibility, it is not suggested for new configs. The mode can be changed by
3581 <p>The primary use of multiple routing tables and the Pipe protocol is for
3582 policy routing, where handling of a single packet doesn't depend only on its
3583 destination address, but also on its source address, source interface, protocol
3584 type and other similar parameters. In many systems (Linux being a good example),
3585 the kernel allows to enforce routing policies by defining routing rules which
3586 choose one of several routing tables to be used for a packet according to its
3587 parameters. Setting of these rules is outside the scope of BIRD's work (on
3588 Linux, you can use the <tt/ip/ command), but you can create several routing
3589 tables in BIRD, connect them to the kernel ones, use filters to control which
3590 routes appear in which tables and also you can employ the Pipe protocol for
3591 exporting a selected subset of one table to another one.
3593 <sect1>Configuration
3594 <label id="pipe-config">
3596 <p>Essentially, the Pipe protocol is just a channel connected to a table on both
3597 sides. Therefore, the configuration block for <cf/protocol pipe/ shall directly
3598 include standard channel config options; see the example below.
3601 <tag><label id="pipe-peer-table">peer table <m/table/</tag>
3602 Defines secondary routing table to connect to. The primary one is
3603 selected by the <cf/table/ keyword.
3607 <label id="pipe-attr">
3609 <p>The Pipe protocol doesn't define any route attributes.
3612 <label id="pipe-exam">
3614 <p>Let's consider a router which serves as a boundary router of two different
3615 autonomous systems, each of them connected to a subset of interfaces of the
3616 router, having its own exterior connectivity and wishing to use the other AS as
3617 a backup connectivity in case of outage of its own exterior line.
3619 <p>Probably the simplest solution to this situation is to use two routing tables
3620 (we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
3621 packets having arrived from interfaces belonging to the first AS will be routed
3622 according to <cf/as1/ and similarly for the second AS. Thus we have split our
3623 router to two logical routers, each one acting on its own routing table, having
3624 its own routing protocols on its own interfaces. In order to use the other AS's
3625 routes for backup purposes, we can pass the routes between the tables through a
3626 Pipe protocol while decreasing their preferences and correcting their BGP paths
3627 to reflect the AS boundary crossing.
3630 ipv4 table as1; # Define the tables
3633 protocol kernel kern1 { # Synchronize them with the kernel
3634 ipv4 { table as1; export all; };
3638 protocol kernel kern2 {
3639 ipv4 { table as2; export all; };
3643 protocol bgp bgp1 { # The outside connections
3644 ipv4 { table as1; import all; export all; };
3646 neighbor 192.168.0.1 as 1001;
3650 ipv4 { table as2; import all; export all; };
3652 neighbor 10.0.0.1 as 1002;
3655 protocol pipe { # The Pipe
3659 if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks
3660 if preference>10 then preference = preference-10;
3661 if source=RTS_BGP then bgp_path.prepend(1);
3667 if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks
3668 if preference>10 then preference = preference-10;
3669 if source=RTS_BGP then bgp_path.prepend(2);
3682 <label id="radv-intro">
3684 <p>The RAdv protocol is an implementation of Router Advertisements, which are
3685 used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
3686 time intervals or as an answer to a request) advertisement packets to connected
3687 networks. These packets contain basic information about a local network (e.g. a
3688 list of network prefixes), which allows network hosts to autoconfigure network
3689 addresses and choose a default route. BIRD implements router behavior as defined
3690 in <rfc id="4861">, router preferences and specific routes (<rfc id="4191">),
3691 and DNS extensions (<rfc id="6106">).
3693 <p>The RAdv protocols supports just IPv6 channel.
3695 <sect1>Configuration
3696 <label id="radv-config">
3698 <p>There are several classes of definitions in RAdv configuration -- interface
3699 definitions, prefix definitions and DNS definitions:
3702 <tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3703 Interface definitions specify a set of interfaces on which the
3704 protocol is activated and contain interface specific options.
3705 See <ref id="proto-iface" name="interface"> common options for
3706 detailed description.
3708 <tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
3709 Prefix definitions allow to modify a list of advertised prefixes. By
3710 default, the advertised prefixes are the same as the network prefixes
3711 assigned to the interface. For each network prefix, the matching prefix
3712 definition is found and its options are used. If no matching prefix
3713 definition is found, the prefix is used with default options.
3715 Prefix definitions can be either global or interface-specific. The
3716 second ones are part of interface options. The prefix definition
3717 matching is done in the first-match style, when interface-specific
3718 definitions are processed before global definitions. As expected, the
3719 prefix definition is matching if the network prefix is a subnet of the
3720 prefix in prefix definition.
3722 <tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
3723 RDNSS definitions allow to specify a list of advertised recursive DNS
3724 servers together with their options. As options are seldom necessary,
3725 there is also a short variant <cf>rdnss <m/address/</cf> that just
3726 specifies one DNS server. Multiple definitions are cumulative. RDNSS
3727 definitions may also be interface-specific when used inside interface
3728 options. By default, interface uses both global and interface-specific
3729 options, but that can be changed by <cf/rdnss local/ option.
3731 <tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
3732 DNSSL definitions allow to specify a list of advertised DNS search
3733 domains together with their options. Like <cf/rdnss/ above, multiple
3734 definitions are cumulative, they can be used also as interface-specific
3735 options and there is a short variant <cf>dnssl <m/domain/</cf> that just
3736 specifies one DNS search domain.
3738 <tag><label id="radv-trigger">trigger <m/prefix/</tag>
3739 RAdv protocol could be configured to change its behavior based on
3740 availability of routes. When this option is used, the protocol waits in
3741 suppressed state until a <it/trigger route/ (for the specified network)
3742 is exported to the protocol, the protocol also returnsd to suppressed
3743 state if the <it/trigger route/ disappears. Note that route export
3744 depends on specified export filter, as usual. This option could be used,
3745 e.g., for handling failover in multihoming scenarios.
3747 During suppressed state, router advertisements are generated, but with
3748 some fields zeroed. Exact behavior depends on which fields are zeroed,
3749 this can be configured by <cf/sensitive/ option for appropriate
3750 fields. By default, just <cf/default lifetime/ (also called <cf/router
3751 lifetime/) is zeroed, which means hosts cannot use the router as a
3752 default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
3753 also be configured as <cf/sensitive/ for a prefix, which would cause
3754 autoconfigured IPs to be deprecated or even removed.
3756 <tag><label id="radv-propagate-routes">propagate routes <m/switch/</tag>
3757 This option controls propagation of more specific routes, as defined in
3758 <rfc id="4191">. If enabled, all routes exported to the RAdv protocol,
3759 with the exception of the trigger prefix, are added to advertisments as
3760 additional options. The lifetime and preference of advertised routes can
3761 be set individually by <cf/ra_lifetime/ and <cf/ra_preference/ route
3762 attributes, or per interface by <cf/route lifetime/ and
3763 <cf/route preference/ options. Default: disabled.
3765 Note that the RFC discourages from sending more than 17 routes and
3766 recommends the routes to be configured manually.
3769 <p>Interface specific options:
3772 <tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
3773 Unsolicited router advertisements are sent in irregular time intervals.
3774 This option specifies the maximum length of these intervals, in seconds.
3775 Valid values are 4-1800. Default: 600
3777 <tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
3778 This option specifies the minimum length of that intervals, in seconds.
3779 Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
3780 about 1/3 * <cf/max ra interval/.
3782 <tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
3783 The minimum delay between two consecutive router advertisements, in
3786 <tag><label id="radv-iface-managed">managed <m/switch/</tag>
3787 This option specifies whether hosts should use DHCPv6 for IP address
3788 configuration. Default: no
3790 <tag><label id="radv-iface-other-config">other config <m/switch/</tag>
3791 This option specifies whether hosts should use DHCPv6 to receive other
3792 configuration information. Default: no
3794 <tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
3795 This option specifies which value of MTU should be used by hosts. 0
3796 means unspecified. Default: 0
3798 <tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
3799 This option specifies the time (in milliseconds) how long hosts should
3800 assume a neighbor is reachable (from the last confirmation). Maximum is
3801 3600000, 0 means unspecified. Default 0.
3803 <tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
3804 This option specifies the time (in milliseconds) how long hosts should
3805 wait before retransmitting Neighbor Solicitation messages. 0 means
3806 unspecified. Default 0.
3808 <tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
3809 This option specifies which value of Hop Limit should be used by
3810 hosts. Valid values are 0-255, 0 means unspecified. Default: 64
3812 <tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
3813 This option specifies the time (in seconds) how long (since the receipt
3814 of RA) hosts may use the router as a default router. 0 means do not use
3815 as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3816 Default: 3 * <cf/max ra interval/, <cf/sensitive/ yes.
3818 <tag><label id="radv-iface-default-preference">default preference low|medium|high</tag>
3819 This option specifies the Default Router Preference value to advertise
3820 to hosts. Default: medium.
3822 <tag><label id="radv-iface-route-lifetime">route lifetime <m/expr/ [sensitive <m/switch/]</tag>
3823 This option specifies the default value of advertised lifetime for
3824 specific routes; i.e., the time (in seconds) for how long (since the
3825 receipt of RA) hosts should consider these routes valid. A special value
3826 0xffffffff represents infinity. The lifetime can be overriden on a per
3827 route basis by the <ref id="rta-ra-lifetime" name="ra_lifetime"> route
3828 attribute. Default: 3 * <cf/max ra interval/, <cf/sensitive/ no.
3830 For the <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3831 If <cf/sensitive/ is enabled, even the routes with the <cf/ra_lifetime/
3832 attribute become sensitive to the trigger.
3834 <tag><label id="radv-iface-route-preference">route preference low|medium|high</tag>
3835 This option specifies the default value of advertised route preference
3836 for specific routes. The value can be overriden on a per route basis by
3837 the <ref id="rta-ra-preference" name="ra_preference"> route attribute.
3840 <tag><label id="radv-prefix-linger-time">prefix linger time <m/expr/</tag>
3841 When a prefix or a route disappears, it is advertised for some time with
3842 zero lifetime, to inform clients it is no longer valid. This option
3843 specifies the time (in seconds) for how long prefixes are advertised
3844 that way. Default: 3 * <cf/max ra interval/.
3846 <tag><label id="radv-route-linger-time">route linger time <m/expr/</tag>
3847 When a prefix or a route disappears, it is advertised for some time with
3848 zero lifetime, to inform clients it is no longer valid. This option
3849 specifies the time (in seconds) for how long routes are advertised
3850 that way. Default: 3 * <cf/max ra interval/.
3852 <tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
3853 Use only local (interface-specific) RDNSS definitions for this
3854 interface. Otherwise, both global and local definitions are used. Could
3855 also be used to disable RDNSS for given interface if no local definitons
3856 are specified. Default: no.
3858 <tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
3859 Use only local DNSSL definitions for this interface. See <cf/rdnss local/
3860 option above. Default: no.
3863 <p>Prefix specific options
3866 <tag><label id="radv-prefix-skip">skip <m/switch/</tag>
3867 This option allows to specify that given prefix should not be
3868 advertised. This is useful for making exceptions from a default policy
3869 of advertising all prefixes. Note that for withdrawing an already
3870 advertised prefix it is more useful to advertise it with zero valid
3871 lifetime. Default: no
3873 <tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
3874 This option specifies whether hosts may use the advertised prefix for
3875 onlink determination. Default: yes
3877 <tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
3878 This option specifies whether hosts may use the advertised prefix for
3879 stateless autoconfiguration. Default: yes
3881 <tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
3882 This option specifies the time (in seconds) how long (after the
3883 receipt of RA) the prefix information is valid, i.e., autoconfigured
3884 IP addresses can be assigned and hosts with that IP addresses are
3885 considered directly reachable. 0 means the prefix is no longer
3886 valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3887 Default: 86400 (1 day), <cf/sensitive/ no.
3889 <tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
3890 This option specifies the time (in seconds) how long (after the
3891 receipt of RA) IP addresses generated from the prefix using stateless
3892 autoconfiguration remain preferred. For <cf/sensitive/ option,
3893 see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
3897 <p>RDNSS specific options:
3900 <tag><label id="radv-rdnss-ns">ns <m/address/</tag>
3901 This option specifies one recursive DNS server. Can be used multiple
3902 times for multiple servers. It is mandatory to have at least one
3903 <cf/ns/ option in <cf/rdnss/ definition.
3905 <tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
3906 This option specifies the time how long the RDNSS information may be
3907 used by clients after the receipt of RA. It is expressed either in
3908 seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
3909 interval/. Note that RDNSS information is also invalidated when
3910 <cf/default lifetime/ expires. 0 means these addresses are no longer
3911 valid DNS servers. Default: 3 * <cf/max ra interval/.
3914 <p>DNSSL specific options:
3917 <tag><label id="radv-dnssl-domain">domain <m/address/</tag>
3918 This option specifies one DNS search domain. Can be used multiple times
3919 for multiple domains. It is mandatory to have at least one <cf/domain/
3920 option in <cf/dnssl/ definition.
3922 <tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
3923 This option specifies the time how long the DNSSL information may be
3924 used by clients after the receipt of RA. Details are the same as for
3925 RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
3929 <label id="radv-attr">
3931 <p>RAdv defines two route attributes:
3934 <tag><label id="rta-ra-preference">enum ra_preference/</tag>
3935 The preference of the route. The value can be <it/RA_PREF_LOW/,
3936 <it/RA_PREF_MEDIUM/ or <it/RA_PREF_HIGH/. If the attribute is not set,
3937 the <ref id="radv-iface-route-preference" name="route preference">
3940 <tag><label id="rta-ra-lifetime">int ra_lifetime/</tag>
3941 The advertised lifetime of the route, in seconds. The special value of
3942 0xffffffff represents infinity. If the attribute is not set, the
3943 <ref id="radv-iface-route-lifetime" name="route lifetime">
3948 <label id="radv-exam">
3951 ipv6 table radv_routes; # Manually configured routes go here
3954 ipv6 { table radv_routes; };
3956 route 2001:0DB8:4000::/48 unreachable;
3957 route 2001:0DB8:4010::/48 unreachable;
3959 route 2001:0DB8:4020::/48 unreachable {
3960 ra_preference = RA_PREF_HIGH;
3966 propagate routes yes; # Propagate the routes from the radv_routes table
3967 ipv6 { table radv_routes; export all; };
3970 max ra interval 5; # Fast failover with more routers
3971 managed yes; # Using DHCPv6 on eth2
3973 autonomous off; # So do not autoconfigure any IP
3977 interface "eth*"; # No need for any other options
3979 prefix 2001:0DB8:1234::/48 {
3980 preferred lifetime 0; # Deprecated address range
3983 prefix 2001:0DB8:2000::/48 {
3984 autonomous off; # Do not autoconfigure
3987 rdnss 2001:0DB8:1234::10; # Short form of RDNSS
3991 ns 2001:0DB8:1234::11;
3992 ns 2001:0DB8:1234::12;
4008 <label id="rip-intro">
4010 <p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
4011 where each router broadcasts (to all its neighbors) distances to all networks it
4012 can reach. When a router hears distance to another network, it increments it and
4013 broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
4014 network goes unreachable, routers keep telling each other that its distance is
4015 the original distance plus 1 (actually, plus interface metric, which is usually
4016 one). After some time, the distance reaches infinity (that's 15 in RIP) and all
4017 routers know that network is unreachable. RIP tries to minimize situations where
4018 counting to infinity is necessary, because it is slow. Due to infinity being 16,
4019 you can't use RIP on networks where maximal distance is higher than 15
4022 <p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
4023 id="2080">), and RIP cryptographic authentication (<rfc id="4822">).
4025 <p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
4026 convergence, big network load and inability to handle larger networks makes it
4027 pretty much obsolete. It is still usable on very small networks.
4029 <sect1>Configuration
4030 <label id="rip-config">
4032 <p>RIP configuration consists mainly of common protocol options and interface
4033 definitions, most RIP options are interface specific. RIPng (RIP for IPv6)
4034 protocol instance can be configured by using <cf/rip ng/ instead of just
4035 <cf/rip/ as a protocol type.
4037 <p>RIP needs one IPv4 channel. RIPng needs one IPv6 channel. If no channel is
4038 configured, appropriate channel is defined with default parameters.
4041 protocol rip [ng] [<name>] {
4042 infinity <number>;
4043 ecmp <switch> [limit <number>];
4044 interface <interface pattern> {
4045 metric <number>;
4046 mode multicast|broadcast;
4047 passive <switch>;
4049 port <number>;
4051 split horizon <switch>;
4052 poison reverse <switch>;
4053 check zero <switch>;
4054 update time <number>;
4055 timeout time <number>;
4056 garbage time <number>;
4057 ecmp weight <number>;
4058 ttl security <switch>; | tx only;
4059 tx class|dscp <number>;
4060 tx priority <number>;
4061 rx buffer <number>;
4062 tx length <number>;
4063 check link <switch>;
4064 authentication none|plaintext|cryptographic;
4065 password "<text>";
4066 password "<text>" {
4068 generate from "<date>";
4069 generate to "<date>";
4070 accept from "<date>";
4071 accept to "<date>";
4072 from "<date>";
4074 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
4081 <tag><label id="rip-infinity">infinity <M>number</M></tag>
4082 Selects the distance of infinity. Bigger values will make
4083 protocol convergence even slower. The default value is 16.
4085 <tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
4086 This option specifies whether RIP is allowed to generate ECMP
4087 (equal-cost multipath) routes. Such routes are used when there are
4088 several directions to the destination, each with the same (computed)
4089 cost. This option also allows to specify a limit on maximum number of
4090 nexthops in one route. By default, ECMP is enabled if supported by
4091 Kernel. Default value of the limit is 16.
4093 <tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
4094 Interface definitions specify a set of interfaces on which the
4095 protocol is activated and contain interface specific options.
4096 See <ref id="proto-iface" name="interface"> common options for
4097 detailed description.
4100 <p>Interface specific options:
4103 <tag><label id="rip-iface-metric">metric <m/num/</tag>
4104 This option specifies the metric of the interface. When a route is
4105 received from the interface, its metric is increased by this value
4106 before further processing. Valid values are 1-255, but values higher
4107 than infinity has no further meaning. Default: 1.
4109 <tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
4110 This option selects the mode for RIP to use on the interface. The
4111 default is multicast mode for RIPv2 and broadcast mode for RIPv1.
4112 RIPng always uses the multicast mode.
4114 <tag><label id="rip-iface-passive">passive <m/switch/</tag>
4115 Passive interfaces receive routing updates but do not transmit any
4116 messages. Default: no.
4118 <tag><label id="rip-iface-address">address <m/ip/</tag>
4119 This option specifies a destination address used for multicast or
4120 broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
4121 (ff02::9) multicast address, or an appropriate broadcast address in the
4124 <tag><label id="rip-iface-port">port <m/number/</tag>
4125 This option selects an UDP port to operate on, the default is the
4126 official RIP (520) or RIPng (521) port.
4128 <tag><label id="rip-iface-version">version 1|2</tag>
4129 This option selects the version of RIP used on the interface. For RIPv1,
4130 automatic subnet aggregation is not implemented, only classful network
4131 routes and host routes are propagated. Note that BIRD allows RIPv1 to be
4132 configured with features that are defined for RIPv2 only, like
4133 authentication or using multicast sockets. The default is RIPv2 for IPv4
4134 RIP, the option is not supported for RIPng, as no further versions are
4137 <tag><label id="rip-iface-version-only">version only <m/switch/</tag>
4138 Regardless of RIP version configured for the interface, BIRD accepts
4139 incoming packets of any RIP version. This option restrict accepted
4140 packets to the configured version. Default: no.
4142 <tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
4143 Split horizon is a scheme for preventing routing loops. When split
4144 horizon is active, routes are not regularly propagated back to the
4145 interface from which they were received. They are either not propagated
4146 back at all (plain split horizon) or propagated back with an infinity
4147 metric (split horizon with poisoned reverse). Therefore, other routers
4148 on the interface will not consider the router as a part of an
4149 independent path to the destination of the route. Default: yes.
4151 <tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
4152 When split horizon is active, this option specifies whether the poisoned
4153 reverse variant (propagating routes back with an infinity metric) is
4154 used. The poisoned reverse has some advantages in faster convergence,
4155 but uses more network traffic. Default: yes.
4157 <tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
4158 Received RIPv1 packets with non-zero values in reserved fields should
4159 be discarded. This option specifies whether the check is performed or
4160 such packets are just processed as usual. Default: yes.
4162 <tag><label id="rip-iface-update-time">update time <m/number/</tag>
4163 Specifies the number of seconds between periodic updates. A lower number
4164 will mean faster convergence but bigger network load. Default: 30.
4166 <tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
4167 Specifies the time interval (in seconds) between the last received route
4168 announcement and the route expiration. After that, the network is
4169 considered unreachable, but still is propagated with infinity distance.
4172 <tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
4173 Specifies the time interval (in seconds) between the route expiration
4174 and the removal of the unreachable network entry. The garbage interval,
4175 when a route with infinity metric is propagated, is used for both
4176 internal (after expiration) and external (after withdrawal) routes.
4179 <tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
4180 When ECMP (multipath) routes are allowed, this value specifies a
4181 relative weight used for nexthops going through the iface. Valid
4182 values are 1-256. Default value is 1.
4184 <tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
4185 Selects authentication method to be used. <cf/none/ means that packets
4186 are not authenticated at all, <cf/plaintext/ means that a plaintext
4187 password is embedded into each packet, and <cf/cryptographic/ means that
4188 packets are authenticated using some cryptographic hash function
4189 selected by option <cf/algorithm/ for each key. The default
4190 cryptographic algorithm for RIP keys is Keyed-MD5. If you set
4191 authentication to not-none, it is a good idea to add <cf>password</cf>
4192 section. Default: none.
4194 <tag><label id="rip-iface-pass">password "<m/text/"</tag>
4195 Specifies a password used for authentication. See <ref id="proto-pass"
4196 name="password"> common option for detailed description.
4198 <tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
4199 TTL security is a feature that protects routing protocols from remote
4200 spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
4201 destined to neighbors. Because TTL is decremented when packets are
4202 forwarded, it is non-trivial to spoof packets with TTL 255 from remote
4205 If this option is enabled, the router will send RIP packets with TTL 255
4206 and drop received packets with TTL less than 255. If this option si set
4207 to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
4208 for received packets. Such setting does not offer protection, but offers
4209 compatibility with neighbors regardless of whether they use ttl
4212 For RIPng, TTL security is a standard behavior (required by <rfc
4213 id="2080">) and therefore default value is yes. For IPv4 RIP, default
4216 <tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
4217 These options specify the ToS/DiffServ/Traffic class/Priority of the
4218 outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
4219 option for detailed description.
4221 <tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
4222 This option specifies the size of buffers used for packet processing.
4223 The buffer size should be bigger than maximal size of received packets.
4224 The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
4226 <tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
4227 This option specifies the maximum length of generated RIP packets. To
4228 avoid IP fragmentation, it should not exceed the interface MTU value.
4229 The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
4231 <tag><label id="rip-iface-check-link">check link <m/switch/</tag>
4232 If set, the hardware link state (as reported by OS) is taken into
4233 consideration. When the link disappears (e.g. an ethernet cable is
4234 unplugged), neighbors are immediately considered unreachable and all
4235 routes received from them are withdrawn. It is possible that some
4236 hardware drivers or platforms do not implement this feature.
4241 <label id="rip-attr">
4243 <p>RIP defines two route attributes:
4246 <tag>int <cf/rip_metric/</tag>
4247 RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
4248 from different RIP instances are available and all of them have the same
4249 preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
4250 non-RIP route is exported to RIP, the default metric is 1.
4252 <tag><label id="rta-rip-tag">int rip_tag/</tag>
4253 RIP route tag: a 16-bit number which can be used to carry additional
4254 information with the route (for example, an originating AS number in
4255 case of external routes). When a non-RIP route is exported to RIP, the
4260 <label id="rip-exam">
4274 authentication cryptographic;
4275 password "secret" { algorithm hmac sha256; };
4285 <p>The Resource Public Key Infrastructure (RPKI) is mechanism for origin
4286 validation of BGP routes (RFC 6480). BIRD supports only so-called RPKI-based
4287 origin validation. There is implemented RPKI to Router (RPKI-RTR) protocol (RFC
4288 6810). It uses some of the RPKI data to allow a router to verify that the
4289 autonomous system announcing an IP address prefix is in fact authorized to do
4290 so. This is not crypto checked so can be violated. But it should prevent the
4291 vast majority of accidental hijackings on the Internet today, e.g. the famous
4292 Pakastani accidental announcement of YouTube's address space.
4294 <p>The RPKI-RTR protocol receives and maintains a set of ROAs from a cache
4295 server (also called validator). You can validate routes (RFC 6483) using
4296 function <cf/roa_check()/ in filter and set it as import filter at the BGP
4297 protocol. BIRD should re-validate all of affected routes after RPKI update by
4298 RFC 6811, but we don't support it yet! You can use a BIRD's client command
4299 <cf>reload in <m/bgp_protocol_name/</cf> for manual call of revalidation of all
4302 <sect1>Supported transports
4305 <item>Unprotected transport over TCP uses a port 323. The cache server
4306 and BIRD router should be on the same trusted and controlled network
4307 for security reasons.
4308 <item>SSHv2 encrypted transport connection uses the normal SSH port
4312 <sect1>Configuration
4314 <p>We currently support just one cache server per protocol. However you can
4315 define more RPKI protocols generally.
4318 protocol rpki [<name>] {
4319 roa4 { table <tab>; };
4320 roa6 { table <tab>; };
4321 remote <ip> | "<domain>" [port <num>];
4323 refresh [keep] <num>;
4324 retry [keep] <num>;
4325 expire [keep] <num>;
4328 bird private key "</path/to/id_rsa>";
4329 remote public key "</path/to/known_host>";
4330 user "<name>";
4335 <p>Alse note that you have to specify the ROA channel. If you want to import
4336 only IPv4 prefixes you have to specify only roa4 channel. Similarly with IPv6
4337 prefixes only. If you want to fetch both IPv4 and even IPv6 ROAs you have to
4338 specify both channels.
4340 <sect2>RPKI protocol options
4343 <tag>remote <m/ip/ | "<m/hostname/" [port <m/num/]</tag> Specifies
4344 a destination address of the cache server. Can be specified by an IP
4345 address or by full domain name string. Only one cache can be specified
4346 per protocol. This option is required.
4348 <tag>port <m/num/</tag> Specifies the port number. The default port
4349 number is 323 for transport without any encryption and 22 for transport
4350 with SSH encryption.
4352 <tag>refresh [keep] <m/num/</tag> Time period in seconds. Tells how
4353 long to wait before next attempting to poll the cache using a Serial
4354 Query or a Reset Query packet. Must be lower than 86400 seconds (one
4355 day). Too low value can caused a false positive detection of
4356 network connection problems. A keyword <cf/keep/ suppresses updating
4357 this value by a cache server.
4358 Default: 3600 seconds
4360 <tag>retry [keep] <m/num/</tag> Time period in seconds between a failed
4361 Serial/Reset Query and a next attempt. Maximum allowed value is 7200
4362 seconds (two hours). Too low value can caused a false positive
4363 detection of network connection problems. A keyword <cf/keep/
4364 suppresses updating this value by a cache server.
4365 Default: 600 seconds
4367 <tag>expire [keep] <m/num/</tag> Time period in seconds. Received
4368 records are deleted if the client was unable to successfully refresh
4369 data for this time period. Must be in range from 600 seconds (ten
4370 minutes) to 172800 seconds (two days). A keyword <cf/keep/
4371 suppresses updating this value by a cache server.
4372 Default: 7200 seconds
4374 <tag>transport tcp</tag> Unprotected transport over TCP. It's a default
4375 transport. Should be used only on secure private networks.
4378 <tag>transport ssh { <m/SSH transport options.../ }</tag> It enables a
4379 SSHv2 transport encryption. Cannot be combined with a TCP transport.
4383 <sect3>SSH transport options
4386 <tag>bird private key "<m>/path/to/id_rsa</m>"</tag>
4387 A path to the BIRD's private SSH key for authentication.
4388 It can be a <cf><m>id_rsa</m></cf> file.
4390 <tag>remote public key "<m>/path/to/known_host</m>"</tag>
4391 A path to the cache's public SSH key for verification identity
4392 of the cache server. It could be a path to <cf><m>known_host</m></cf> file.
4394 <tag>user "<m/name/"</tag>
4395 A SSH user name for authentication. This option is a required.
4399 <sect2>BGP origin validation
4400 <p>Policy: Don't import <cf/ROA_INVALID/ routes.
4411 # Please, do not use rpki-validator.realmv6.org in production
4412 remote "rpki-validator.realmv6.org" port 8282;
4420 if (roa_check(r4, net, bgp_path.last) = ROA_INVALID) then
4422 print "Ignore invalid ROA ", net, " for ASN ", bgp_path.last;
4431 neighbor 192.168.2.1 as 65001;
4433 import filter peer_in_v4;
4439 <sect2>SSHv2 transport encryption
4451 remote 127.0.0.1 port 2345;
4453 bird private key "/home/birdgeek/.ssh/id_rsa";
4454 remote public key "/home/birdgeek/.ssh/known_hosts";
4458 # Default interval values
4466 <p>The Static protocol doesn't communicate with other routers in the network,
4467 but instead it allows you to define routes manually. This is often used for
4468 specifying how to forward packets to parts of the network which don't use
4469 dynamic routing at all and also for defining sink routes (i.e., those telling to
4470 return packets as undeliverable if they are in your IP block, you don't have any
4471 specific destination for them and you don't want to send them out through the
4472 default route to prevent routing loops).
4474 <p>There are three classes of definitions in Static protocol configuration --
4475 global options, static route definitions, and per-route options. Usually, the
4476 definition of the protocol contains mainly a list of static routes.
4477 Static routes have no specific attributes.
4482 <tag><label id="static-check-link">check link <m/switch/</tag>
4483 If set, hardware link states of network interfaces are taken into
4484 consideration. When link disappears (e.g. ethernet cable is unplugged),
4485 static routes directing to that interface are removed. It is possible
4486 that some hardware drivers or platforms do not implement this feature.
4489 <tag><label id="static-igp-table">igp table <m/name/</tag>
4490 Specifies a table that is used for route table lookups of recursive
4491 routes. Default: the same table as the protocol is connected to.
4494 <p>Route definitions (each may also contain a block of per-route options):
4496 <sect1>Regular routes; MPLS switching rules
4498 <p>There exist several types of routes; keep in mind that <m/prefix/ syntax is
4499 <ref id="type-prefix" name="dependent on network type">.
4502 <tag>route <m/prefix/ via <m/ip/|<m/"interface"/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4503 Next hop routes may bear one or more <ref id="route-next-hop" name="next hops">.
4504 Every next hop is preceded by <cf/via/ and configured as shown.
4506 <tag>route <m/prefix/ recursive <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4507 Recursive nexthop resolves the given IP in the configured IGP table and
4508 uses that route's next hop. The MPLS stacks are concatenated; on top is
4509 the IGP's nexthop stack and on bottom is this route's stack.
4511 <tag>route <m/prefix/ blackhole|unreachable|prohibit</tag>
4512 Special routes specifying to silently drop the packet, return it as
4513 unreachable or return it as administratively prohibited. First two
4514 targets are also known as <cf/drop/ and <cf/reject/.
4517 <p>When the particular destination is not available (the interface is down or
4518 the next hop of the route is not a neighbor at the moment), Static just
4519 uninstalls the route from the table it is connected to and adds it again as soon
4520 as the destination becomes adjacent again.
4522 <sect1>Route Origin Authorization
4524 <p>The ROA config is just <cf>route <m/prefix/ max <m/int/ as <m/int/</cf> with no nexthop.
4527 <label id="flowspec-network-type">
4529 <p>The flow specification are rules for routers and firewalls for filtering
4530 purpose. It is described by <rfc id="5575">. There are 3 types of arguments:
4531 <m/inet4/ or <m/inet6/ prefixes, bitmasks matching expressions and numbers
4532 matching expressions.
4534 Bitmasks matching is written using <m/value/<cf>/</cf><m/mask/ or
4535 <cf/!/<m/value/<cf>/</cf><m/mask/ pairs. It means that <cf/(/<m/data/ <cf/&/
4536 <m/mask/<cf/)/ is or is not equal to <m/value/.
4538 Numbers matching is a matching sequence of numbers and ranges separeted by a
4539 commas (<cf/,/) (e.g. <cf/10,20,30/). Ranges can be written using double dots
4540 <cf/../ notation (e.g. <cf/80..90,120..124/). An alternative notation are
4541 sequence of one or more pairs of relational operators and values separated by
4542 logical operators <cf/&&/ or <cf/||/. Allowed relational operators are <cf/=/,
4543 <cf/!=/, <cf/</, <cf/<=/, <cf/>/, <cf/>=/, <cf/true/ and <cf/false/.
4545 <sect2>IPv4 Flowspec
4548 <tag><label id="flow-dst">dst <m/inet4/</tag>
4549 Set a matching destination prefix (e.g. <cf>dst 192.168.0.0/16</cf>).
4550 Only this option is mandatory in IPv4 Flowspec.
4552 <tag><label id="flow-src">src <m/inet4/</tag>
4553 Set a matching source prefix (e.g. <cf>src 10.0.0.0/8</cf>).
4555 <tag><label id="flow-proto">proto <m/numbers-match/</tag>
4556 Set a matching IP protocol numbers (e.g. <cf/proto 6/).
4558 <tag><label id="flow-port">port <m/numbers-match/</tag>
4559 Set a matching source or destination TCP/UDP port numbers (e.g.
4560 <cf>port 1..1023,1194,3306</cf>).
4562 <tag><label id="flow-dport">dport <m/numbers-match/</tag>
4563 Set a mating destination port numbers (e.g. <cf>dport 49151</cf>).
4565 <tag><label id="flow-sport">sport <m/numbers-match/</tag>
4566 Set a matching source port numbers (e.g. <cf>sport = 0</cf>).
4568 <tag><label id="flow-icmp-type">icmp type <m/numbers-match/</tag>
4569 Set a matching type field number of an ICMP packet (e.g. <cf>icmp type
4572 <tag><label id="flow-icmp-code">icmp code <m/numbers-match/</tag>
4573 Set a matching code field number of an ICMP packet (e.g. <cf>icmp code
4576 <tag><label id="flow-tcp-flags">tcp flags <m/bitmask-match/</tag>
4577 Set a matching bitmask for TCP header flags (aka control bits) (e.g.
4578 <cf>tcp flags 0x03/0x0f;</cf>). The maximum length of mask is 12 bits
4581 <tag><label id="flow-length">length <m/numbers-match/</tag>
4582 Set a matching packet length (e.g. <cf>length > 1500;</cf>)
4584 <tag><label id="flow-dscp">dscp <m/numbers-match/</tag>
4585 Set a matching DiffServ Code Point number (e.g. <cf>length > 1500;</cf>).
4587 <tag><label id="flow-fragment">fragment <m/fragmentation-type/</tag>
4588 Set a matching type of packet fragmentation. Allowed fragmentation
4589 types are <cf/dont_fragment/, <cf/is_fragment/, <cf/first_fragment/,
4590 <cf/last_fragment/ (e.g. <cf>fragment is_fragment &&
4591 !dont_fragment</cf>).
4600 port > 24 && < 30 || 40..50,60..70,80 && >= 90;
4601 tcp flags 0x03/0x0f;
4604 fragment dont_fragment, is_fragment || !first_fragment;
4609 <sect2>Differences for IPv6 Flowspec
4611 <p>Flowspec IPv6 are same as Flowspec IPv4 with a few exceptions.
4613 <item>Prefixes <m/inet6/ can be specified not only with prefix length,
4614 but with prefix <cf/offset/ <m/num/ too (e.g.
4615 <cf>::1234:5678:9800:0000/101 offset 64</cf>). Offset means to don't
4616 care of <m/num/ first bits.
4617 <item>IPv6 Flowspec hasn't mandatory any flowspec component.
4618 <item>In IPv6 packets, there is a matching the last next header value
4619 for a matching IP protocol number (e.g. <cf>next header 6</cf>).
4620 <item>It is not possible to set <cf>dont_fragment</cf> as a type of
4621 packet fragmentation.
4625 <tag><label id="flow6-dst">dst <m/inet6/ [offset <m/num/]</tag>
4626 Set a matching destination IPv6 prefix (e.g. <cf>dst
4627 ::1c77:3769:27ad:a11a/128 offset 64</cf>).
4629 <tag><label id="flow6-src">src <m/inet6/ [offset <m/num/]</tag>
4630 Set a matching source IPv6 prefix (e.g. <cf>src fe80::/64</cf>).
4632 <tag><label id="flow6-next-header">next header <m/numbers-match/</tag>
4633 Set a matching IP protocol numbers (e.g. <cf>next header != 6</cf>).
4635 <tag><label id="flow6-label">label <m/bitmask-match/</tag>
4636 Set a 20-bit bitmask for matching Flow Label field in IPv6 packets
4637 (e.g. <cf>label 0x8e5/0x8e5</cf>).
4642 flow6 { table myflow6; };
4645 dst fec0:1122:3344:5566:7788:99aa:bbcc:ddee/128;
4646 src 0000:0000:0000:0001:1234:5678:9800:0000/101 offset 63;
4648 sport > 24 && < 30 || = 40 || 50,60,70..80;
4650 tcp flags 0x03/0x0f, !0/0xff || 0x33/0x33;
4651 fragment !is_fragment || !first_fragment;
4652 label 0xaaaa/0xaaaa && 0x33/0x33;
4657 <sect1>Per-route options
4660 <tag><label id="static-route-bfd">bfd <m/switch/</tag>
4661 The Static protocol could use BFD protocol for next hop liveness
4662 detection. If enabled, a BFD session to the route next hop is created
4663 and the static route is BFD-controlled -- the static route is announced
4664 only if the next hop liveness is confirmed by BFD. If the BFD session
4665 fails, the static route is removed. Note that this is a bit different
4666 compared to other protocols, which may use BFD as an advisory mechanism
4667 for fast failure detection but ignores it if a BFD session is not even
4670 This option can be used for static routes with a direct next hop, or
4671 also for for individual next hops in a static multipath route (see
4672 above). Note that BFD protocol also has to be configured, see
4673 <ref id="bfd" name="BFD"> section for details. Default value is no.
4675 <tag><label id="static-route-filter"><m/filter expression/</tag>
4676 This is a special option that allows filter expressions to be configured
4677 on per-route basis. Can be used multiple times. These expressions are
4678 evaluated when the route is originated, similarly to the import filter
4679 of the static protocol. This is especially useful for configuring route
4680 attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
4681 exported to the OSPF protocol.
4684 <sect1>Example static config
4688 ipv4 { table testable; }; # Connect to a non-default routing table
4689 check link; # Advertise routes only if link is up
4690 route 0.0.0.0/0 via 198.51.100.130; # Default route
4691 route 10.0.0.0/8 # Multipath route
4692 via 198.51.100.10 weight 2
4693 via 198.51.100.20 bfd # BFD-controlled next hop
4695 route 203.0.113.0/24 unreachable; # Sink route
4696 route 10.2.0.0/24 via "arc0"; # Secondary network
4697 route 192.168.10.0/24 via 198.51.100.100 {
4698 ospf_metric1 = 20; # Set extended attribute
4700 route 192.168.10.0/24 via 198.51.100.100 {
4701 ospf_metric2 = 100; # Set extended attribute
4702 ospf_tag = 2; # Set extended attribute
4703 bfd; # BFD-controlled route
4710 <label id="conclusion">
4713 <label id="future-work">
4715 <p>Although BIRD supports all the commonly used routing protocols, there are
4716 still some features which would surely deserve to be implemented in future
4721 <item>Route aggregation and flap dampening
4722 <item>Multicast routing protocols
4723 <item>Ports to other systems
4727 <sect>Getting more help
4730 <p>If you use BIRD, you're welcome to join the bird-users mailing list
4731 (<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
4732 where you can share your experiences with the other users and consult
4733 your problems with the authors. To subscribe to the list, visit
4734 <HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
4735 The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
4737 <p>BIRD is a relatively young system and it probably contains some bugs. You can
4738 report any problems to the bird-users list and the authors will be glad to solve
4739 them, but before you do so, please make sure you have read the available
4740 documentation and that you are running the latest version (available at
4741 <HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
4742 (Of course, a patch which fixes the bug is always welcome as an attachment.)
4744 <p>If you want to understand what is going inside, Internet standards are a good
4745 and interesting reading. You can get them from
4746 <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
4747 nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
4748 name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
4755 LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel
4756 LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
4757 LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
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4759 LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek
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