1 <!doctype birddoc system>
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11 considered definition of configuration primitives, <cf> is fragment of
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17 Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
23 <title>BIRD 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 Ondrej Zajicek <it/<santiago@crfreenet.org>/
32 This document contains user documentation for the BIRD Internet Routing Daemon project.
35 <!-- Table of contents -->
38 <!-- Begin the document -->
45 <label id="what-is-bird">
47 <p>The name `BIRD' is actually an acronym standing for `BIRD Internet Routing
48 Daemon'. Let's take a closer look at the meaning of the name:
50 <p><em/BIRD/: Well, we think we have already explained that. It's an acronym
51 standing for `BIRD Internet Routing Daemon', you remember, don't you? :-)
53 <p><em/Internet Routing/: It's a program (well, a daemon, as you are going to
54 discover in a moment) which works as a dynamic router in an Internet type
55 network (that is, in a network running either the IPv4 or the IPv6 protocol).
56 Routers are devices which forward packets between interconnected networks in
57 order to allow hosts not connected directly to the same local area network to
58 communicate with each other. They also communicate with the other routers in the
59 Internet to discover the topology of the network which allows them to find
60 optimal (in terms of some metric) rules for forwarding of packets (which are
61 called routing tables) and to adapt themselves to the changing conditions such
62 as outages of network links, building of new connections and so on. Most of
63 these routers are costly dedicated devices running obscure firmware which is
64 hard to configure and not open to any changes (on the other hand, their special
65 hardware design allows them to keep up with lots of high-speed network
66 interfaces, better than general-purpose computer does). Fortunately, most
67 operating systems of the UNIX family allow an ordinary computer to act as a
68 router and forward packets belonging to the other hosts, but only according to a
69 statically configured table.
71 <p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program
72 running on background which does the dynamic part of Internet routing, that is
73 it communicates with the other routers, calculates routing tables and sends them
74 to the OS kernel which does the actual packet forwarding. There already exist
75 other such routing daemons: routed (RIP only), GateD (non-free),
76 <HTMLURL URL="http://www.zebra.org" name="Zebra"> and
77 <HTMLURL URL="http://sourceforge.net/projects/mrt" name="MRTD">,
78 but their capabilities are limited and they are relatively hard to configure
81 <p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
82 to support all the routing technology used in the today's Internet or planned to
83 be used in near future and to have a clean extensible architecture allowing new
84 routing protocols to be incorporated easily. Among other features, BIRD
88 <item>both IPv4 and IPv6 protocols
89 <item>multiple routing tables
90 <item>the Border Gateway Protocol (BGPv4)
91 <item>the Routing Information Protocol (RIPv2)
92 <item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
93 <item>the Router Advertisements for IPv6 hosts
94 <item>a virtual protocol for exchange of routes between different
95 routing tables on a single host
96 <item>a command-line interface allowing on-line control and inspection
97 of status of the daemon
98 <item>soft reconfiguration (no need to use complex online commands to
99 change the configuration, just edit the configuration file and
100 notify BIRD to re-read it and it will smoothly switch itself to
101 the new configuration, not disturbing routing protocols unless
102 they are affected by the configuration changes)
103 <item>a powerful language for route filtering
106 <p>BIRD has been developed at the Faculty of Math and Physics, Charles
107 University, Prague, Czech Republic as a student project. It can be freely
108 distributed under the terms of the GNU General Public License.
110 <p>BIRD has been designed to work on all UNIX-like systems. It has been
111 developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD
112 and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively
113 easy due to its highly modular architecture.
115 <p>BIRD supports either IPv4 or IPv6 protocol, but have to be compiled separately
116 for each one. Therefore, a dualstack router would run two instances of BIRD (one
117 for IPv4 and one for IPv6), with completely separate setups (configuration
121 <sect>Installing BIRD
124 <p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make)
125 and Perl, installing BIRD should be as easy as:
131 vi /usr/local/etc/bird.conf
135 <p>You can use <tt>./configure --help</tt> to get a list of configure
136 options. The most important ones are: <tt/--enable-ipv6/ which enables building
137 of an IPv6 version of BIRD, <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.
220 <chapt>About routing tables
221 <label id="routing-tables">
223 <p>BIRD has one or more routing tables which may or may not be synchronized with
224 OS kernel and which may or may not be synchronized with each other (see the Pipe
225 protocol). Each routing table contains a list of known routes. Each route
229 <item>network prefix this route is for (network address and prefix
230 length -- the number of bits forming the network part of the
231 address; also known as a netmask)
232 <item>preference of this route
233 <item>IP address of router which told us about this route
234 <item>IP address of router we should forward the packets to using this
236 <item>other attributes common to all routes
237 <item>dynamic attributes defined by protocols which may or may not be
238 present (typically protocol metrics)
241 Routing table maintains multiple entries for a network, but at most one entry
242 for one network and one protocol. The entry with the highest preference is used
243 for routing (we will call such an entry the <it/selected route/). If there are
244 more entries with the same preference and they are from the same protocol, the
245 protocol decides (typically according to metrics). If they aren't, an internal
246 ordering is used to break the tie. You can get the list of route attributes in
247 the Route attributes section.
249 <p>Each protocol is connected to a routing table through two filters which can
250 accept, reject and modify the routes. An <it/export/ filter checks routes passed
251 from the routing table to the protocol, an <it/import/ filter checks routes in
252 the opposite direction. When the routing table gets a route from a protocol, it
253 recalculates the selected route and broadcasts it to all protocols connected to
254 the table. The protocols typically send the update to other routers in the
255 network. Note that although most protocols are interested in receiving just
256 selected routes, some protocols (e.g. the <cf/Pipe/ protocol) receive and
257 process all entries in routing tables (accepted by filters).
259 <p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected route
260 from a list of entries for one network. But if the <cf/sorted/ option is
261 activated, these lists of entries are kept completely sorted (according to
262 preference or some protocol-dependent metric). This is needed for some features
263 of some protocols (e.g. <cf/secondary/ option of BGP protocol, which allows to
264 accept not just a selected route, but the first route (in the sorted list) that
265 is accepted by filters), but it is incompatible with some other features (e.g.
266 <cf/deterministic med/ option of BGP protocol, which activates a way of choosing
267 selected route that cannot be described using comparison and ordering). Minor
268 advantage is that routes are shown sorted in <cf/show route/, minor disadvantage
269 is that it is slightly more computationally expensive.
272 <sect>Graceful restart
273 <label id="graceful-restart">
275 <p>When BIRD is started after restart or crash, it repopulates routing tables in
276 an uncoordinated manner, like after clean start. This may be impractical in some
277 cases, because if the forwarding plane (i.e. kernel routing tables) remains
278 intact, then its synchronization with BIRD would temporarily disrupt packet
279 forwarding until protocols converge. Graceful restart is a mechanism that could
280 help with this issue. Generally, it works by starting protocols and letting them
281 repopulate routing tables while deferring route propagation until protocols
282 acknowledge their convergence. Note that graceful restart behavior have to be
283 configured for all relevant protocols and requires protocol-specific support
284 (currently implemented for Kernel and BGP protocols), it is activated for
285 particular boot by option <cf/-R/.
292 <label id="config-intro">
294 <p>BIRD is configured using a text configuration file. Upon startup, BIRD reads
295 <it/prefix/<file>/etc/bird.conf</file> (unless the <tt/-c/ command line option
296 is given). Configuration may be changed at user's request: if you modify the
297 config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
298 config. Then there's the client which allows you to talk with BIRD in an
301 <p>In the config, everything on a line after <cf/#/ or inside <cf>/* */</cf> is
302 a comment, whitespace characters are treated as a single space. If there's a
303 variable number of options, they are grouped using the <cf/{ }/ brackets. Each
304 option is terminated by a <cf/;/. Configuration is case sensitive. There are two
305 ways how to name symbols (like protocol names, filter names, constants etc.). You
306 can either use a simple string starting with a letter followed by any
307 combination of letters and numbers (e.g. "R123", "myfilter", "bgp5") or you can
308 enclose the name into apostrophes (<cf/'/) and than you can use any combination
309 of numbers, letters. hyphens, dots and colons (e.g. "'1:strange-name'",
310 "'-NAME-'", "'cool::name'").
312 <p>Here is an example of a simple config file. It enables synchronization of
313 routing tables with OS kernel, scans for new network interfaces every 10 seconds
314 and runs RIP on all network interfaces found.
318 persist; # Don't remove routes on BIRD shutdown
319 scan time 20; # Scan kernel routing table every 20 seconds
320 export all; # Default is export none
324 scan time 10; # Scan interfaces every 10 seconds
336 <label id="global-opts">
339 <tag><label id="opt-include">include "<m/filename/"</tag>
340 This statement causes inclusion of a new file. <m/Filename/ could also
341 be a wildcard, in that case matching files are included in alphabetic
342 order. The maximal depth is 8. Note that this statement could be used
343 anywhere in the config file, not just as a top-level option.
345 <tag><label id="opt-log">log "<m/filename/"|syslog [name <m/name/]|stderr all|{ <m/list of classes/ }</tag>
346 Set logging of messages having the given class (either <cf/all/ or
347 <cf/{ error|trace [, <m/.../] }/ etc.) into selected destination (a file specified
348 as a filename string, syslog with optional name argument, or the stderr
349 output). Classes are:
350 <cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
351 <cf/debug/ for debugging messages,
352 <cf/trace/ when you want to know what happens in the network,
353 <cf/remote/ for messages about misbehavior of remote machines,
354 <cf/auth/ about authentication failures,
355 <cf/bug/ for internal BIRD bugs.
356 You may specify more than one <cf/log/ line to establish logging to
357 multiple destinations. Default: log everything to the system log.
359 <tag><label id="opt-debug-protocols">debug protocols all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
360 Set global defaults of protocol debugging options. See <cf/debug/ in the
361 following section. Default: off.
363 <tag><label id="opt-debug-commands">debug commands <m/number/</tag>
364 Control logging of client connections (0 for no logging, 1 for logging
365 of connects and disconnects, 2 and higher for logging of all client
366 commands). Default: 0.
368 <tag><label id="opt-debug-latency">debug latency <m/switch/</tag>
369 Activate tracking of elapsed time for internal events. Recent events
370 could be examined using <cf/dump events/ command. Default: off.
372 <tag><label id="opt-debug-latency-limit">debug latency limit <m/time/</tag>
373 If <cf/debug latency/ is enabled, this option allows to specify a limit
374 for elapsed time. Events exceeding the limit are logged. Default: 1 s.
376 <tag><label id="opt-watchdog-warn">watchdog warning <m/time/</tag>
377 Set time limit for I/O loop cycle. If one iteration took more time to
378 complete, a warning is logged. Default: 5 s.
380 <tag><label id="opt-watchdog-timeout">watchdog timeout <m/time/</tag>
381 Set time limit for I/O loop cycle. If the limit is breached, BIRD is
382 killed by abort signal. The timeout has effective granularity of
383 seconds, zero means disabled. Default: disabled (0).
385 <tag><label id="opt-mrtdump">mrtdump "<m/filename/"</tag>
386 Set MRTdump file name. This option must be specified to allow MRTdump
387 feature. Default: no dump file.
389 <tag><label id="opt-mrtdump-protocols">mrtdump protocols all|off|{ states|messages [, <m/.../] }</tag>
390 Set global defaults of MRTdump options. See <cf/mrtdump/ in the
391 following section. Default: off.
393 <tag><label id="opt-filter">filter <m/name local variables/{ <m/commands/ }</tag>
394 Define a filter. You can learn more about filters in the following
397 <tag><label id="opt-function">function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag>
398 Define a function. You can learn more about functions in the following chapter.
400 <tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
401 Define a protocol instance called <cf><m/name/</cf> (or with a name like
402 "rip5" generated automatically if you don't specify any
403 <cf><m/name/</cf>). You can learn more about configuring protocols in
404 their own chapters. When <cf>from <m/name2/</cf> expression is used,
405 initial protocol options are taken from protocol or template
406 <cf><m/name2/</cf> You can run more than one instance of most protocols
407 (like RIP or BGP). By default, no instances are configured.
409 <tag><label id="opt-template">template rip|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
410 Define a protocol template instance called <m/name/ (or with a name like
411 "bgp1" generated automatically if you don't specify any <m/name/).
412 Protocol templates can be used to group common options when many
413 similarly configured protocol instances are to be defined. Protocol
414 instances (and other templates) can use templates by using <cf/from/
415 expression and the name of the template. At the moment templates (and
416 <cf/from/ expression) are not implemented for OSPF protocol.
418 <tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
419 Define a constant. You can use it later in every place you could use a
420 value of the same type. Besides, there are some predefined numeric
421 constants based on /etc/iproute2/rt_* files. A list of defined constants
422 can be seen (together with other symbols) using 'show symbols' command.
424 <tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
425 Set BIRD's router ID. It's a world-wide unique identification of your
426 router, usually one of router's IPv4 addresses. Default: in IPv4
427 version, the lowest IP address of a non-loopback interface. In IPv6
428 version, this option is mandatory.
430 <tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
431 Set BIRD's router ID based on an IP address of an interface specified by
432 an interface pattern. The option is applicable for IPv4 version only.
433 See <ref id="proto-iface" name="interface"> section for detailed
434 description of interface patterns with extended clauses.
436 <tag><label id="opt-listen-bgp">listen bgp [address <m/address/] [port <m/port/] [dual]</tag>
437 This option allows to specify address and port where BGP protocol should
438 listen. It is global option as listening socket is common to all BGP
439 instances. Default is to listen on all addresses (0.0.0.0) and port 179.
440 In IPv6 mode, option <cf/dual/ can be used to specify that BGP socket
441 should accept both IPv4 and IPv6 connections (but even in that case,
442 BIRD would accept IPv6 routes only). Such behavior was default in older
445 <tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
446 During graceful restart recovery, BIRD waits for convergence of routing
447 protocols. This option allows to specify a timeout for the recovery to
448 prevent waiting indefinitely if some protocols cannot converge. Default:
451 <tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
452 This option allows to specify a format of date/time used by BIRD. The
453 first argument specifies for which purpose such format is used.
454 <cf/route/ is a format used in 'show route' command output,
455 <cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
456 used for other commands and <cf/log/ is used in a log file.
458 "<m/format1/" is a format string using <it/strftime(3)/ notation (see
459 <it/man strftime/ for details). <m/limit> and "<m/format2/" allow to
460 specify the second format string for times in past deeper than <m/limit/
461 seconds. There are few shorthands: <cf/iso long/ is a ISO 8601 date/time
462 format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F %T"/.
463 <cf/iso short/ is a variant of ISO 8601 that uses just the time format
464 (hh:mm:ss) for near times (up to 20 hours in the past) and the date
465 format (YYYY-MM-DD) for far times. This is a shorthand for
466 <cf/"%T" 72000 "%F"/.
468 By default, BIRD uses the <cf/iso short/ format for <cf/route/ and
469 <cf/protocol/ times, and the <cf/iso long/ format for <cf/base/ and
472 In pre-1.4.0 versions, BIRD used an short, ad-hoc format for <cf/route/
473 and <cf/protocol/ times, and a <cf/iso long/ similar format (DD-MM-YYYY
474 hh:mm:ss) for <cf/base/ and <cf/log/. These timeformats could be set by
475 <cf/old short/ and <cf/old long/ compatibility shorthands.
477 <tag><label id="opt-table">table <m/name/ [sorted]</tag>
478 Create a new routing table. The default routing table is created
479 implicitly, other routing tables have to be added by this command.
480 Option <cf/sorted/ can be used to enable sorting of routes, see
481 <ref id="dsc-table-sorted" name="sorted table"> description for details.
483 <tag><label id="opt-roa-table">roa table <m/name/ [ { <m/roa table options .../ } ]</tag>
484 Create a new ROA (Route Origin Authorization) table. ROA tables can be
485 used to validate route origination of BGP routes. A ROA table contains
486 ROA entries, each consist of a network prefix, a max prefix length and
487 an AS number. A ROA entry specifies prefixes which could be originated
488 by that AS number. ROA tables could be filled with data from RPKI (<rfc
489 id="6480">) or from public databases like Whois. ROA tables are
490 examined by <cf/roa_check()/ operator in filters.
492 Currently, there is just one option, <cf>roa <m/prefix/ max <m/num/ as
493 <m/num/</cf>, which can be used to populate the ROA table with static
494 ROA entries. The option may be used multiple times. Other entries can be
495 added dynamically by <cf/add roa/ command.
497 <tag><label id="opt-eval">eval <m/expr/</tag>
498 Evaluates given filter expression. It is used by us for testing of filters.
502 <sect>Protocol options
503 <label id="protocol-opts">
505 <p>For each protocol instance, you can configure a bunch of options. Some of
506 them (those described in this section) are generic, some are specific to the
507 protocol (see sections talking about the protocols).
509 <p>Several options use a <m/switch/ argument. It can be either <cf/on/,
510 <cf/yes/ or a numeric expression with a non-zero value for the option to be
511 enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
512 disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
516 <tag><label id="proto-preference">preference <m/expr/</tag>
517 Sets the preference of routes generated by this protocol. Default:
520 <tag><label id="proto-disabled">disabled <m/switch/</tag>
521 Disables the protocol. You can change the disable/enable status from the
522 command line interface without needing to touch the configuration.
523 Disabled protocols are not activated. Default: protocol is enabled.
525 <tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
526 Set protocol debugging options. If asked, each protocol is capable of
527 writing trace messages about its work to the log (with category
528 <cf/trace/). You can either request printing of <cf/all/ trace messages
529 or only of the types selected: <cf/states/ for protocol state changes
530 (protocol going up, down, starting, stopping etc.), <cf/routes/ for
531 routes exchanged with the routing table, <cf/filters/ for details on
532 route filtering, <cf/interfaces/ for interface change events sent to the
533 protocol, <cf/events/ for events internal to the protocol and <cf/packets/
534 for packets sent and received by the protocol. Default: off.
536 <tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
537 Set protocol MRTdump flags. MRTdump is a standard binary format for
538 logging information from routing protocols and daemons. These flags
539 control what kind of information is logged from the protocol to the
540 MRTdump file (which must be specified by global <cf/mrtdump/ option, see
541 the previous section). Although these flags are similar to flags of
542 <cf/debug/ option, their meaning is different and protocol-specific. For
543 BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
544 received BGP messages. Other protocols does not support MRTdump yet.
546 <tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
547 This option can be used to override global router id for a given
548 protocol. Default: uses global router id.
550 <tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/filter expression/</tag>
551 Specify a filter to be used for filtering routes coming from the
552 protocol to the routing table. <cf/all/ is shorthand for <cf/where true/
553 and <cf/none/ is shorthand for <cf/where false/. Default: <cf/all/.
555 <tag><label id="proto-export">export <m/filter/</tag>
556 This is similar to the <cf>import</cf> keyword, except that it works in
557 the direction from the routing table to the protocol. Default: <cf/none/.
559 <tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
560 Usually, if an import filter rejects a route, the route is forgotten.
561 When this option is active, these routes are kept in the routing table,
562 but they are hidden and not propagated to other protocols. But it is
563 possible to show them using <cf/show route filtered/. Note that this
564 option does not work for the pipe protocol. Default: off.
566 <tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
567 Specify an import route limit (a maximum number of routes imported from
568 the protocol) and optionally the action to be taken when the limit is
569 hit. Warn action just prints warning log message. Block action discards
570 new routes coming from the protocol. Restart and disable actions shut
571 the protocol down like appropriate commands. Disable is the default
572 action if an action is not explicitly specified. Note that limits are
573 reset during protocol reconfigure, reload or restart. Default: <cf/off/.
575 <tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
576 Specify an receive route limit (a maximum number of routes received from
577 the protocol and remembered). It works almost identically to <cf>import
578 limit</cf> option, the only difference is that if <cf/import keep
579 filtered/ option is active, filtered routes are counted towards the
580 limit and blocked routes are forgotten, as the main purpose of the
581 receive limit is to protect routing tables from overflow. Import limit,
582 on the contrary, counts accepted routes only and routes blocked by the
583 limit are handled like filtered routes. Default: <cf/off/.
585 <tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
586 Specify an export route limit, works similarly to the <cf>import
587 limit</cf> option, but for the routes exported to the protocol. This
588 option is experimental, there are some problems in details of its
589 behavior -- the number of exported routes can temporarily exceed the
590 limit without triggering it during protocol reload, exported routes
591 counter ignores route blocking and block action also blocks route
592 updates of already accepted routes -- and these details will probably
593 change in the future. Default: <cf/off/.
595 <tag><label id="proto-description">description "<m/text/"</tag>
596 This is an optional description of the protocol. It is displayed as a
597 part of the output of 'show route all' command.
599 <tag><label id="proto-table">table <m/name/</tag>
600 Connect this protocol to a non-default routing table.
603 <p>There are several options that give sense only with certain protocols:
606 <tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
607 Specifies a set of interfaces on which the protocol is activated with
608 given interface-specific options. A set of interfaces specified by one
609 interface option is described using an interface pattern. The interface
610 pattern consists of a sequence of clauses (separated by commas), each
611 clause is a mask specified as a shell-like pattern. Interfaces are
612 matched by their name.
614 An interface matches the pattern if it matches any of its clauses. If
615 the clause begins with <cf/-/, matching interfaces are excluded. Patterns
616 are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
617 means eth0 and all non-ethernets.
619 Some protocols (namely OSPFv2 and Direct) support extended clauses that
620 may contain a mask, a prefix, or both of them. An interface matches such
621 clause if its name matches the mask (if specified) and its address
622 matches the prefix (if specified). Extended clauses are used when the
623 protocol handles multiple addresses on an interface independently.
625 An interface option can be used more times with different interface-specific
626 options, in that case for given interface the first matching interface
629 This option is allowed in Babel, BFD, Direct, OSPF, RAdv and RIP
630 protocols, but in OSPF protocol it is used in the <cf/area/ subsection.
636 <cf>interface "*" { type broadcast; };</cf> - start the protocol on all
637 interfaces with <cf>type broadcast</cf> option.
639 <cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
640 protocol on enumerated interfaces with <cf>type ptp</cf> option.
642 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
643 on all interfaces that have address from 192.168.0.0/16, but not from
646 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
647 on all interfaces that have address from 192.168.0.0/16, but not from
650 <cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
651 ethernet interfaces that have address from 192.168.1.0/24.
653 <tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
654 This option specifies the value of ToS/DS/Class field in IP headers of
655 the outgoing protocol packets. This may affect how the protocol packets
656 are processed by the network relative to the other network traffic. With
657 <cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
658 octet (but two bits reserved for ECN are ignored). With <cf/dscp/
659 keyword, the value (0-63) is used just for the DS field in the octet.
660 Default value is 0xc0 (DSCP 0x30 - CS6).
662 <tag><label id="proto-tx-priority">tx priority <m/num/</tag>
663 This option specifies the local packet priority. This may affect how the
664 protocol packets are processed in the local TX queues. This option is
665 Linux specific. Default value is 7 (highest priority, privileged traffic).
667 <tag><label id="proto-pass">password "<m/password/" [ { <m>password options</m> } ]</tag>
668 Specifies a password that can be used by the protocol as a shared secret
669 key. Password option can be used more times to specify more passwords.
670 If more passwords are specified, it is a protocol-dependent decision
671 which one is really used. Specifying passwords does not mean that
672 authentication is enabled, authentication can be enabled by separate,
673 protocol-dependent <cf/authentication/ option.
675 This option is allowed in BFD, OSPF and RIP protocols. BGP has also
676 <cf/password/ option, but it is slightly different and described
681 <p>Password option can contain section with some (not necessary all) password sub-options:
684 <tag><label id="proto-pass-id">id <M>num</M></tag>
685 ID of the password, (1-255). If it is not used, BIRD will choose ID based
686 on an order of the password item in the interface. For example, second
687 password item in one interface will have default ID 2. ID is used by
688 some routing protocols to identify which password was used to
689 authenticate protocol packets.
691 <tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
692 The start time of the usage of the password for packet signing.
693 The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
695 <tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
696 The last time of the usage of the password for packet signing.
698 <tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
699 The start time of the usage of the password for packet verification.
701 <tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
702 The last time of the usage of the password for packet verification.
704 <tag><label id="proto-pass-from">from "<m/time/"</tag>
705 Shorthand for setting both <cf/generate from/ and <cf/accept from/.
707 <tag><label id="proto-pass-to">to "<m/time/"</tag>
708 Shorthand for setting both <cf/generate to/ and <cf/accept to/.
710 <tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 )</tag>
711 The message authentication algorithm for the password when cryptographic
712 authentication is enabled. The default value depends on the protocol.
713 For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3
714 protocol it is HMAC-SHA-256.
719 <sect>Flowspec network type
720 <label id="flowspec-network-type">
722 <p>The flow specification are rules for routers and firewalls for filtering
723 purpose. It is described by <rfc id="5575">. There are 3 types of arguments:
724 <m/inet4/ or <m/inet6/ prefixes, bitmasks matching expressions and numbers
725 matching expressions.
727 Bitmasks matching is written using <m/value/<cf>/</cf><m/mask/ or
728 <cf/!/<m/value/<cf>/</cf><m/mask/ pairs. It means that <cf/(/<m/data/ <cf/&/
729 <m/mask/<cf/)/ is or is not equal to <m/value/.
731 Numbers matching is a matching sequence of numbers and ranges separeted by a
732 commas (<cf/,/) (e.g. <cf/10,20,30/). Ranges can be written using double dots
733 <cf/../ notation (e.g. <cf/80..90,120..124/). An alternative notation are
734 sequence of one or more pairs of relational operators and values separated by
735 logical operators <cf/&&/ or <cf/||/. Allowed relational operators are <cf/=/,
736 <cf/!=/, <cf/</, <cf/<=/, <cf/>/, <cf/>=/, <cf/true/ and <cf/false/.
741 <tag><label id="flow-dst">dst <m/inet4/</tag>
742 Set a matching destination prefix (e.g. <cf>dst 192.168.0.0/16</cf>).
743 Only this option is mandatory in IPv4 Flowspec.
745 <tag><label id="flow-src">src <m/inet4/</tag>
746 Set a matching source prefix (e.g. <cf>src 10.0.0.0/8</cf>).
748 <tag><label id="flow-proto">proto <m/numbers-match/</tag>
749 Set a matching IP protocol numbers (e.g. <cf/proto 6/).
751 <tag><label id="flow-port">port <m/numbers-match/</tag>
752 Set a matching source or destination TCP/UDP port numbers (e.g.
753 <cf>port 1..1023,1194,3306</cf>).
755 <tag><label id="flow-dport">dport <m/numbers-match/</tag>
756 Set a mating destination port numbers (e.g. <cf>dport 49151</cf>).
758 <tag><label id="flow-sport">sport <m/numbers-match/</tag>
759 Set a matching source port numbers (e.g. <cf>sport = 0</cf>).
761 <tag><label id="flow-icmp-type">icmp type <m/numbers-match/</tag>
762 Set a matching type field number of an ICMP packet (e.g. <cf>icmp type
765 <tag><label id="flow-icmp-code">icmp code <m/numbers-match/</tag>
766 Set a matching code field number of an ICMP packet (e.g. <cf>icmp code
769 <tag><label id="flow-tcp-flags">tcp flags <m/bitmask-match/</tag>
770 Set a matching bitmask for TCP header flags (aka control bits) (e.g.
771 <cf>tcp flags 0x03/0x0f;</cf>). The maximum length of mask is 12 bits
774 <tag><label id="flow-length">length <m/numbers-match/</tag>
775 Set a matching packet length (e.g. <cf>length > 1500;</cf>)
777 <tag><label id="flow-dscp">dscp <m/numbers-match/</tag>
778 Set a matching DiffServ Code Point number (e.g. <cf>length > 1500;</cf>).
780 <tag><label id="flow-fragment">fragment <m/fragmentation-type/</tag>
781 Set a matching type of packet fragmentation. Allowed fragmentation
782 types are <cf/dont_fragment/, <cf/is_fragment/, <cf/first_fragment/,
783 <cf/last_fragment/ (e.g. <cf>fragment is_fragment &&
784 !dont_fragment</cf>).
793 port > 24 && < 30 || 40..50,60..70,80 && >= 90;
797 fragment dont_fragment, is_fragment || !first_fragment;
802 <sect1>Differences for IPv6 Flowspec
804 <p>Flowspec IPv6 are same as Flowspec IPv4 with a few exceptions.
806 <item>Prefixes <m/inet6/ can be specified not only with prefix length,
807 but with prefix <cf/offset/ <m/num/ too (e.g.
808 <cf>::1234:5678:9800:0000/101 offset 64</cf>). Offset means to don't
809 care of <m/num/ first bits.
810 <item>IPv6 Flowspec hasn't mandatory any flowspec component.
811 <item>In IPv6 packets, there is a matching the last next header value
812 for a matching IP protocol number (e.g. <cf>next header 6</cf>).
813 <item>It is not possible to set <cf>dont_fragment</cf> as a type of
814 packet fragmentation.
818 <tag><label id="flow6-dst">dst <m/inet6/ [offset <m/num/]</tag>
819 Set a matching destination IPv6 prefix (e.g. <cf>dst
820 ::1c77:3769:27ad:a11a/128 offset 64</cf>).
822 <tag><label id="flow6-src">src <m/inet6/ [offset <m/num/]</tag>
823 Set a matching source IPv6 prefix (e.g. <cf>src fe80::/64</cf>).
825 <tag><label id="flow6-next-header">next header <m/numbers-match/</tag>
826 Set a matching IP protocol numbers (e.g. <cf>next header != 6</cf>).
828 <tag><label id="flow6-label">label <m/bitmask-match/</tag>
829 Set a 20-bit bitmask for matching Flow Label field in IPv6 packets
830 (e.g. <cf>label 0x8e5/0x8e5</cf>).
838 dst fec0:1122:3344:5566:7788:99aa:bbcc:ddee/128;
839 src 0000:0000:0000:0001:1234:5678:9800:0000/101 offset 63;
841 sport > 24 && < 30 || = 40 || 50,60,70..80;
843 tcp flags 0x03/0x0f, !0/0xff || 0x33/0x33;
844 fragment !is_fragment || !first_fragment;
845 label 0xaaaa/0xaaaa && 0x33/0x33;
850 <chapt>Remote control
851 <label id="remote-control">
853 <p>You can use the command-line client <file>birdc</file> to talk with a running
854 BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
855 changed with the <tt/-s/ option given to both the server and the client). The
856 commands can perform simple actions such as enabling/disabling of protocols,
857 telling BIRD to show various information, telling it to show routing table
858 filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
859 get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
860 client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
861 be passed to the client, to make it dump numeric return codes along with the
862 messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
863 own applications could do that, too -- the format of communication between BIRD
864 and <file/birdc/ is stable (see the programmer's documentation).
866 <p>There is also lightweight variant of BIRD client called <file/birdcl/, which
867 does not support command line editing and history and has minimal dependencies.
868 This is useful for running BIRD in resource constrained environments, where
869 Readline library (required for regular BIRD client) is not available.
871 <p>Many commands have the <m/name/ of the protocol instance as an argument.
872 This argument can be omitted if there exists only a single instance.
874 <p>Here is a brief list of supported functions:
877 <tag><label id="cli-show-status">show status</tag>
878 Show router status, that is BIRD version, uptime and time from last
881 <tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
882 Show the list of interfaces. For each interface, print its type, state,
883 MTU and addresses assigned.
885 <tag><label id="cli-show-protocols">show protocols [all]</tag>
886 Show list of protocol instances along with tables they are connected to
887 and protocol status, possibly giving verbose information, if <cf/all/ is
890 <tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
891 Show detailed information about OSPF interfaces.
893 <tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
894 Show a list of OSPF neighbors and a state of adjacency to them.
896 <tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
897 Show detailed information about OSPF areas based on a content of the
898 link-state database. It shows network topology, stub networks,
899 aggregated networks and routers from other areas and external routes.
900 The command shows information about reachable network nodes, use option
901 <cf/all/ to show information about all network nodes in the link-state
904 <tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
905 Show a topology of OSPF areas based on a content of the link-state
906 database. It is just a stripped-down version of 'show ospf state'.
908 <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>
909 Show contents of an OSPF LSA database. Options could be used to filter
912 <tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
913 Show detailed information about RIP interfaces.
915 <tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
916 Show a list of RIP neighbors and associated state.
918 <tag><label id="cli-show-static">show static [<m/name/]</tag>
919 Show detailed information about static routes.
921 <tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/]</tag>
922 Show information about BFD sessions.
924 <tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
925 Show the list of symbols defined in the configuration (names of
926 protocols, routing tables etc.).
928 <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>
929 Show contents of specified routing tables, that is routes, their metrics
930 and (in case the <cf/all/ switch is given) all their attributes.
932 <p>You can specify a <m/prefix/ if you want to print routes for a
933 specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
934 the entry which will be used for forwarding of packets to the given
935 destination. By default, all routes for each network are printed with
936 the selected one at the top, unless <cf/primary/ is given in which case
937 only the selected route is shown.
939 <p>The <cf/show route/ command can process one or multiple routing
940 tables. The set of selected tables is determined on three levels: First,
941 tables can be explicitly selected by <cf/table/ switch, which could be
942 used multiple times, all tables are specified by <cf/table all/. Second,
943 tables can be implicitly selected by channels or protocols that are
944 arguments of several other switches (e.g., <cf/export/, <cf/protocol/).
945 Last, the set of default tables is used: <cf/master4/, <cf/master6/ and
946 each first table of any other network type.
948 <p>You can also ask for printing only routes processed and accepted by
949 a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
950 </cf> or matching a given condition (<cf>where <m/condition/</cf>).
952 The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
953 printing of routes that are exported to the specified protocol or
954 channel. With <cf/preexport/, the export filter of the channel is
955 skipped. With <cf/noexport/, routes rejected by the export filter are
956 printed instead. Note that routes not exported for other reasons
957 (e.g. secondary routes or routes imported from that protocol) are not
958 printed even with <cf/noexport/. These switches also imply that
959 associated routing tables are selected instead of default ones.
961 <p>You can also select just routes added by a specific protocol.
962 <cf>protocol <m/p/</cf>. This switch also implies that associated
963 routing tables are selected instead of default ones.
965 <p>If BIRD is configured to keep filtered routes (see <cf/import keep
966 filtered/ option), you can show them instead of routes by using
967 <cf/filtered/ switch.
969 <p>The <cf/stats/ switch requests showing of route statistics (the
970 number of networks, number of routes before and after filtering). If
971 you use <cf/count/ instead, only the statistics will be printed.
973 <tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
974 Reload configuration from a given file. BIRD will smoothly switch itself
975 to the new configuration, protocols are reconfigured if possible,
976 restarted otherwise. Changes in filters usually lead to restart of
979 If <cf/soft/ option is used, changes in filters does not cause BIRD to
980 restart affected protocols, therefore already accepted routes (according
981 to old filters) would be still propagated, but new routes would be
982 processed according to the new filters.
984 If <cf/timeout/ option is used, config timer is activated. The new
985 configuration could be either confirmed using <cf/configure confirm/
986 command, or it will be reverted to the old one when the config timer
987 expires. This is useful for cases when reconfiguration breaks current
988 routing and a router becomes inaccessible for an administrator. The
989 config timeout expiration is equivalent to <cf/configure undo/
990 command. The timeout duration could be specified, default is 300 s.
992 <tag><label id="cli-configure-confirm">configure confirm</tag>
993 Deactivate the config undo timer and therefore confirm the current
996 <tag><label id="cli-configure-undo">configure undo</tag>
997 Undo the last configuration change and smoothly switch back to the
998 previous (stored) configuration. If the last configuration change was
999 soft, the undo change is also soft. There is only one level of undo, but
1000 in some specific cases when several reconfiguration requests are given
1001 immediately in a row and the intermediate ones are skipped then the undo
1002 also skips them back.
1004 <tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
1005 Read and parse given config file, but do not use it. useful for checking
1006 syntactic and some semantic validity of an config file.
1008 <tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
1009 Enable, disable or restart a given protocol instance, instances matching
1010 the <cf><m/pattern/</cf> or <cf/all/ instances.
1012 <tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
1013 Reload a given protocol instance, that means re-import routes from the
1014 protocol instance and re-export preferred routes to the instance. If
1015 <cf/in/ or <cf/out/ options are used, the command is restricted to one
1016 direction (re-import or re-export).
1018 This command is useful if appropriate filters have changed but the
1019 protocol instance was not restarted (or reloaded), therefore it still
1020 propagates the old set of routes. For example when <cf/configure soft/
1021 command was used to change filters.
1023 Re-export always succeeds, but re-import is protocol-dependent and might
1024 fail (for example, if BGP neighbor does not support route-refresh
1025 extension). In that case, re-export is also skipped. Note that for the
1026 pipe protocol, both directions are always reloaded together (<cf/in/ or
1027 <cf/out/ options are ignored in that case).
1029 <tag><label id="cli-down">down</tag>
1032 <tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
1033 Control protocol debugging.
1035 <tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
1036 Dump contents of internal data structures to the debugging output.
1038 <tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
1039 Control echoing of log messages to the command-line output.
1040 See <ref id="opt-log" name="log option"> for a list of log classes.
1042 <tag><label id="cli-eval">eval <m/expr/</tag>
1043 Evaluate given expression.
1048 <label id="filters">
1051 <label id="filters-intro">
1053 <p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
1054 There are two objects in this language: filters and functions. Filters are
1055 interpreted by BIRD core when a route is being passed between protocols and
1056 routing tables. The filter language contains control structures such as if's and
1057 switches, but it allows no loops. An example of a filter using many features can
1058 be found in <file>filter/test.conf</file>.
1060 <p>Filter gets the route, looks at its attributes and modifies some of them if
1061 it wishes. At the end, it decides whether to pass the changed route through
1062 (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
1069 if defined( rip_metric ) then
1075 if rip_metric > 10 then
1076 reject "RIP metric is too big";
1082 <p>As you can see, a filter has a header, a list of local variables, and a body.
1083 The header consists of the <cf/filter/ keyword followed by a (unique) name of
1084 filter. The list of local variables consists of <cf><M>type name</M>;</cf>
1085 pairs where each pair defines one local variable. The body consists of <cf>
1086 { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
1087 can group several statements to a single compound statement by using braces
1088 (<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
1089 block of code conditional.
1091 <p>BIRD supports functions, so that you don't have to repeat the same blocks of
1092 code over and over. Functions can have zero or more parameters and they can have
1093 local variables. Recursion is not allowed. Function definitions look like this:
1102 function with_parameters (int parameter)
1108 <p>Unlike in C, variables are declared after the <cf/function/ line, but before
1109 the first <cf/{/. You can't declare variables in nested blocks. Functions are
1110 called like in C: <cf>name(); with_parameters(5);</cf>. Function may return
1111 values using the <cf>return <m/[expr]/</cf> command. Returning a value exits
1112 from current function (this is similar to C).
1114 <p>Filters are declared in a way similar to functions except they can't have
1115 explicit parameters. They get a route table entry as an implicit parameter, it
1116 is also passed automatically to any functions called. The filter must terminate
1117 with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in
1118 filter, the route is rejected.
1120 <p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1121 from the command line client. An example session might look like:
1124 pavel@bug:~/bird$ ./birdc -s bird.ctl
1127 10.0.0.0/8 dev eth0 [direct1 23:21] (240)
1128 195.113.30.2/32 dev tunl1 [direct1 23:21] (240)
1129 127.0.0.0/8 dev lo [direct1 23:21] (240)
1131 show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1132 bird> show route filter { if 127.0.0.5 ˜ net then accept; }
1133 127.0.0.0/8 dev lo [direct1 23:21] (240)
1139 <label id="data-types">
1141 <p>Each variable and each value has certain type. Booleans, integers and enums
1142 are incompatible with each other (that is to prevent you from shooting in the
1146 <tag><label id="type-bool">bool</tag>
1147 This is a boolean type, it can have only two values, <cf/true/ and
1148 <cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1150 <tag><label id="type-int">int</tag>
1151 This is a general integer type. It is an unsigned 32bit type; i.e., you
1152 can expect it to store values from 0 to 4294967295. Overflows are not
1153 checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1155 <tag><label id="type-pair">pair</tag>
1156 This is a pair of two short integers. Each component can have values
1157 from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1158 The same syntax can also be used to construct a pair from two arbitrary
1159 integer expressions (for example <cf/(1+2,a)/).
1161 <tag><label id="type-quad">quad</tag>
1162 This is a dotted quad of numbers used to represent router IDs (and
1163 others). Each component can have a value from 0 to 255. Literals of
1164 this type are written like IPv4 addresses.
1166 <tag><label id="type-string">string</tag>
1167 This is a string of characters. There are no ways to modify strings in
1168 filters. You can pass them between functions, assign them to variables
1169 of type <cf/string/, print such variables, use standard string
1170 comparison operations (e.g. <cf/=, !=, <, >, <=, >=/), but
1171 you can't concatenate two strings. String literals are written as
1172 <cf/"This is a string constant"/. Additionally matching (<cf/˜,
1173 !˜/) operators could be used to match a string value against
1174 a shell pattern (represented also as a string).
1176 <tag><label id="type-ip">ip</tag>
1177 This type can hold a single IP address. Depending on the compile-time
1178 configuration of BIRD you are using, it is either an IPv4 or IPv6
1179 address; this may be checked by <cf>.is_ip4</cf> which returns <cf/bool/.
1180 IP addresses are written in the standard notation
1181 (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special operator
1182 <cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out all but
1183 first <cf><M>num</M></cf> bits from the IP address. So
1184 <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1186 <tag><label id="type-prefix">prefix</tag>
1187 This type can hold a network prefix consisting of IP address, prefix
1188 length and several other values. This is the key in route tables.
1190 Prefixes may be of several types, which can be determined by the special
1191 operator <cf/.type/. The type may be:
1193 <cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
1194 are written as <cf><m/ipaddress//<m/pxlen/</cf>,
1195 or <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
1196 operators on IP prefixes: <cf/.ip/ which extracts the IP address from
1197 the pair, and <cf/.len/, which separates prefix length from the pair.
1198 So <cf>1.2.0.0/16.len = 16</cf> is true.
1200 <cf/NET_VPN4/ and <cf/NET_VPN6/ prefixes hold an IP prefix with VPN
1201 Route Distinguisher (<rfc id="4364">). They support the same special
1202 operators as IP prefixes, and also <cf/.rd/ which extracts the Route
1203 Distinguisher. Their literals are written
1204 as <cf><m/vpnrd/ <m/ipprefix/</cf>
1206 <cf/NET_ROA4/ and <cf/NET_ROA6/ prefixes hold an IP prefix range
1207 together with an ASN. They support the same special operators as IP
1208 prefixes, and also <cf/.maxlen/ which extracts maximal prefix length,
1209 and <cf/.asn/ which extracts the ASN.
1211 <cf/NET_FLOW4/ and <cf/NET_FLOW6/ hold an IP prefix together with a
1212 flowspec rule. Filters currently don't support flowspec parsing.
1214 <tag><label id="type-ec">ec</tag>
1215 This is a specialized type used to represent BGP extended community
1216 values. It is essentially a 64bit value, literals of this type are
1217 usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1218 <cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1219 route target / route origin communities), the format and possible values
1220 of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1221 used kind. Similarly to pairs, ECs can be constructed using expressions
1222 for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1223 <cf/myas/ is an integer variable).
1225 <tag><label id="type-lc">lc</tag>
1226 This is a specialized type used to represent BGP large community
1227 values. It is essentially a triplet of 32bit values, where the first
1228 value is reserved for the AS number of the issuer, while meaning of
1229 remaining parts is defined by the issuer. Literals of this type are
1230 written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1231 pairs, LCs can be constructed using expressions for its parts, (e.g.
1232 <cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1234 <tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1235 Filters recognize four types of sets. Sets are similar to strings: you
1236 can pass them around but you can't modify them. Literals of type <cf>int
1237 set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1238 values and ranges are permitted in sets.
1240 For pair sets, expressions like <cf/(123,*)/ can be used to denote
1241 ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1242 <cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1243 <cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1244 such expressions are translated to a set of intervals, which may be
1245 memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1246 (1,4..20), (2,4..20), ... (65535, 4..20)/.
1248 EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1249 10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1250 (like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1253 Also LC sets use similar expressions like pair sets. You can use ranges
1254 and wildcards, but if one field uses that, more specific (later) fields
1255 must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1256 is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1259 You can also use expressions for int, pair, EC and LC set values.
1260 However, it must be possible to evaluate these expressions before daemon
1261 boots. So you can use only constants inside them. E.g.
1270 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1271 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1272 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1275 Sets of prefixes are special: their literals does not allow ranges, but
1276 allows prefix patterns that are written
1277 as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1278 Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1279 pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1280 first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1281 identical and <cf>len1 <= ip1 <= len2</cf>. A valid prefix pattern
1282 has to satisfy <cf>low <= high</cf>, but <cf/pxlen/ is not
1283 constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1284 prefix set literal if it matches any prefix pattern in the prefix set
1287 There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1288 is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1289 (where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1290 network prefix <cf><m/address//<m/len/</cf> and all its subnets.
1291 <cf><m/address//<m/len/-</cf> is a shorthand for
1292 <cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1293 <cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1296 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}
1297 ]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1298 <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1299 <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1300 matches all prefixes (regardless of IP address) whose prefix length is
1301 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1302 address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{15,17} ]</cf>
1303 is true, but <cf>1.0.0.0/16 ˜ [ 1.0.0.0/8- ]</cf> is false.
1305 Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1306 in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1307 <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1308 <cf>192.168.0.0/16{24,32}</cf>.
1310 <tag><label id="type-enum">enum</tag>
1311 Enumeration types are fixed sets of possibilities. You can't define your
1312 own variables of such type, but some route attributes are of enumeration
1313 type. Enumeration types are incompatible with each other.
1315 <tag><label id="type-bgppath">bgppath</tag>
1316 BGP path is a list of autonomous system numbers. You can't write
1317 literals of this type. There are several special operators on bgppaths:
1319 <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1321 <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1323 <cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1325 Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1326 ASN, for example if the path contains an AS set element as the first (or
1327 the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1328 may be used to get last ASN before any AS set.
1330 <cf><m/P/.len</cf> returns the length of path <m/P/.
1332 <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1335 <cf>delete(<m/P/,<m/A/)</cf> deletes all instances of ASN <m/A/ from
1336 from path <m/P/ and returns the result. <m/A/ may also be an integer
1337 set, in that case the operator deletes all ASNs from path <m/P/ that are
1338 also members of set <m/A/.
1340 <cf>filter(<m/P/,<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1341 not members of integer set <m/A/. I.e., <cf/filter/ do the same as
1342 <cf/delete/ with inverted set <m/A/.
1344 Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1345 <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1346 (for example <cf/bgp_path/). Similarly for <cf/delete/ and <cf/filter/.
1348 <tag><label id="type-bgpmask">bgpmask</tag>
1349 BGP masks are patterns used for BGP path matching (using <cf>path
1350 ˜ [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1351 as used by UNIX shells. Autonomous system numbers match themselves,
1352 <cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1353 <cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1354 is 4 3 2 1, then: <tt>bgp_path ˜ [= * 4 3 * =]</tt> is true,
1355 but <tt>bgp_path ˜ [= * 4 5 * =]</tt> is false. BGP mask
1356 expressions can also contain integer expressions enclosed in parenthesis
1357 and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>. You can
1358 also use ranges, for example <tt>[= * 3..5 2 100..200 * =]</tt>.
1359 There is also old (deprecated) syntax that uses / .. / instead of [= .. =]
1362 <tag><label id="type-clist">clist</tag>
1363 Clist is similar to a set, except that unlike other sets, it can be
1364 modified. The type is used for community list (a set of pairs) and for
1365 cluster list (a set of quads). There exist no literals of this type.
1366 There are three special operators on clists:
1368 <cf><m/C/.len</cf> returns the length of clist <m/C/.
1370 <cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1371 returns the result. If item <m/P/ is already in clist <m/C/, it does
1372 nothing. <m/P/ may also be a clist, in that case all its members are
1373 added; i.e., it works as clist union.
1375 <cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1376 <m/C/ and returns the result. If clist <m/C/ does not contain item
1377 <m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1378 case the operator deletes all items from clist <m/C/ that are also
1379 members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1380 analogously; i.e., it works as clist difference.
1382 <cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist <m/C/ that are
1383 not members of pair (or quad) set <m/P/. I.e., <cf/filter/ do the same
1384 as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1385 works analogously; i.e., it works as clist intersection.
1387 Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1388 <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for
1389 example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.
1391 <tag><label id="type-eclist">eclist</tag>
1392 Eclist is a data type used for BGP extended community lists. Eclists
1393 are very similar to clists, but they are sets of ECs instead of pairs.
1394 The same operations (like <cf/add/, <cf/delete/ or <cf/˜/ and
1395 <cf/!˜/ membership operators) can be used to modify or test
1396 eclists, with ECs instead of pairs as arguments.
1398 <tag><label id="type-lclist">lclist/</tag>
1399 Lclist is a data type used for BGP large community lists. Like eclists,
1400 lclists are very similar to clists, but they are sets of LCs instead of
1401 pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/˜/
1402 and <cf/!˜/ membership operators) can be used to modify or test
1403 lclists, with LCs instead of pairs as arguments.
1408 <label id="operators">
1410 <p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1411 parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a<b, a>=b)/.
1412 Logical operations include unary not (<cf/!/), and (<cf/&&/) and or
1413 (<cf/||/). Special operators include (<cf/˜/,
1414 <cf/!˜/) for "is (not) element of a set" operation - it can be used on
1415 element and set of elements of the same type (returning true if element is
1416 contained in the given set), or on two strings (returning true if first string
1417 matches a shell-like pattern stored in second string) or on IP and prefix
1418 (returning true if IP is within the range defined by that prefix), or on prefix
1419 and prefix (returning true if first prefix is more specific than second one) or
1420 on bgppath and bgpmask (returning true if the path matches the mask) or on
1421 number and bgppath (returning true if the number is in the path) or on bgppath
1422 and int (number) set (returning true if any ASN from the path is in the set) or
1423 on pair/quad and clist (returning true if the pair/quad is element of the
1424 clist) or on clist and pair/quad set (returning true if there is an element of
1425 the clist that is also a member of the pair/quad set).
1427 <p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1428 examines a ROA table and does <rfc id="6483"> route origin validation for a
1429 given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1430 checks current route (which should be from BGP to have AS_PATH argument) in the
1431 specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1432 ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1433 ROAs but none of them match. There is also an extended variant
1434 <cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1435 prefix and an ASN as arguments.
1438 <sect>Control structures
1439 <label id="control-structures">
1441 <p>Filters support two control structures: conditions and case switches.
1443 <p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/command1/;
1444 else <m/command2/;</cf> and you can use <cf>{ <m/command_1/; <m/command_2/;
1445 <M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1446 omitted. If the <cf><m>boolean expression</m></cf> is true, <m/command1/ is
1447 executed, otherwise <m/command2/ is executed.
1449 <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1450 <m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1451 ... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1452 on the left side of the ˜ operator and anything that could be a member of
1453 a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1454 grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1455 between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1456 neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1458 <p>Here is example that uses <cf/if/ and <cf/case/ structures:
1462 2: print "two"; print "I can do more commands without {}";
1463 3 .. 5: print "three to five";
1464 else: print "something else";
1467 if 1234 = i then printn "."; else {
1469 print "You need {} around multiple commands";
1474 <sect>Route attributes
1475 <label id="route-attributes">
1477 <p>A filter is implicitly passed a route, and it can access its attributes just
1478 like it accesses variables. Attempts to access undefined attribute result in a
1479 runtime error; you can check if an attribute is defined by using the
1480 <cf>defined( <m>attribute</m> )</cf> operator. One notable exception to this
1481 rule are attributes of clist type, where undefined value is regarded as empty
1482 clist for most purposes.
1485 <tag><label id="rta-net"><m/prefix/ net</tag>
1486 Network the route is talking about. Read-only. (See the chapter about
1489 <tag><label id="rta-scope"><m/enum/ scope</tag>
1490 The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1491 local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1492 link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1493 <cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1494 interpreted by BIRD and can be used to mark routes in filters. The
1495 default value for new routes is <cf/SCOPE_UNIVERSE/.
1497 <tag><label id="rta-preference"><m/int/ preference</tag>
1498 Preference of the route. Valid values are 0-65535. (See the chapter
1499 about routing tables.)
1501 <tag><label id="rta-from"><m/ip/ from</tag>
1502 The router which the route has originated from.
1504 <tag><label id="rta-gw"><m/ip/ gw</tag>
1505 Next hop packets routed using this route should be forwarded to.
1507 <tag><label id="rta-proto"><m/string/ proto</tag>
1508 The name of the protocol which the route has been imported from.
1511 <tag><label id="rta-source"><m/enum/ source</tag>
1512 what protocol has told me about this route. Possible values:
1513 <cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
1514 <cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/,
1515 <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/,
1516 <cf/RTS_PIPE/, <cf/RTS_BABEL/.
1518 <tag><label id="rta-cast"><m/enum/ cast</tag>
1519 Route type (Currently <cf/RTC_UNICAST/ for normal routes,
1520 <cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will be used in
1521 the future for broadcast, multicast and anycast routes). Read-only.
1523 <tag><label id="rta-dest"><m/enum/ dest</tag>
1524 Type of destination the packets should be sent to
1525 (<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1526 <cf/RTD_DEVICE/ for routing to a directly-connected network,
1527 <cf/RTD_MULTIPATH/ for multipath destinations,
1528 <cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1529 <cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
1530 returned with ICMP host unreachable / ICMP administratively prohibited
1531 messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
1532 <cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
1534 <tag><label id="rta-ifname"><m/string/ ifname</tag>
1535 Name of the outgoing interface. Sink routes (like blackhole, unreachable
1536 or prohibit) and multipath routes have no interface associated with
1537 them, so <cf/ifname/ returns an empty string for such routes. Read-only.
1539 <tag><label id="rta-ifindex"><m/int/ ifindex</tag>
1540 Index of the outgoing interface. System wide index of the interface. May
1541 be used for interface matching, however indexes might change on interface
1542 creation/removal. Zero is returned for routes with undefined outgoing
1543 interfaces. Read-only.
1545 <tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
1546 The optional attribute that can be used to specify a distance to the
1547 network for routes that do not have a native protocol metric attribute
1548 (like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
1549 compare internal distances to boundary routers (see below). It is also
1550 used when the route is exported to OSPF as a default value for OSPF type
1554 <p>There also exist some protocol-specific attributes which are described in the
1555 corresponding protocol sections.
1558 <sect>Other statements
1559 <label id="other-statements">
1561 <p>The following statements are available:
1564 <tag><label id="assignment"><m/variable/ = <m/expr/</tag>
1565 Set variable to a given value.
1567 <tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
1568 Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1570 <tag><label id="return">return <m/expr/</tag>
1571 Return <cf><m>expr</m></cf> from the current function, the function ends
1574 <tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
1575 Prints given expressions; useful mainly while debugging filters. The
1576 <cf/printn/ variant does not terminate the line.
1578 <tag><label id="quitbird">quitbird</tag>
1579 Terminates BIRD. Useful when debugging the filter interpreter.
1584 <label id="protocols">
1590 <label id="babel-intro">
1592 <p>The Babel protocol
1593 (<rfc id="6126">) is a loop-avoiding distance-vector routing protocol that is
1594 robust and efficient both in ordinary wired networks and in wireless mesh
1595 networks. Babel is conceptually very simple in its operation and "just works"
1596 in its default configuration, though some configuration is possible and in some
1599 <p>While the Babel protocol is dual stack (i.e., can carry both IPv4 and IPv6
1600 routes over the same IPv6 transport), BIRD presently implements only the IPv6
1601 subset of the protocol. No Babel extensions are implemented, but the BIRD
1602 implementation can coexist with implementations using the extensions (and will
1603 just ignore extension messages).
1605 <p>The Babel protocol implementation in BIRD is currently in alpha stage.
1607 <sect1>Configuration
1608 <label id="babel-config">
1610 <p>Babel supports no global configuration options apart from those common to all
1611 other protocols, but supports the following per-interface configuration options:
1614 protocol babel [<name>] {
1615 interface <interface pattern> {
1616 type <wired|wireless>;
1618 hello interval <number>;
1619 update interval <number>;
1621 tx class|dscp <number>;
1622 tx priority <number>;
1625 check link <switch>;
1631 <tag><label id="babel-type">type wired|wireless </tag>
1632 This option specifies the interface type: Wired or wireless. Wired
1633 interfaces are considered more reliable, and so the default hello
1634 interval is higher, and a neighbour is considered unreachable after only
1635 a small number of "hello" packets are lost. On wireless interfaces,
1636 hello packets are sent more often, and the ETX link quality estimation
1637 technique is used to compute the metrics of routes discovered over this
1638 interface. This technique will gradually degrade the metric of routes
1639 when packets are lost rather than the more binary up/down mechanism of
1640 wired type links. Default: <cf/wired/.
1642 <tag><label id="babel-rxcost">rxcost <m/num/</tag>
1643 This specifies the RX cost of the interface. The route metrics will be
1644 computed from this value with a mechanism determined by the interface
1645 <cf/type/. Default: 96 for wired interfaces, 256 for wireless.
1647 <tag><label id="babel-hello">hello interval <m/num/</tag>
1648 Interval at which periodic "hello" messages are sent on this interface,
1649 in seconds. Default: 4 seconds.
1651 <tag><label id="babel-update">update interval <m/num/</tag>
1652 Interval at which periodic (full) updates are sent. Default: 4 times the
1655 <tag><label id="babel-port">port <m/number/</tag>
1656 This option selects an UDP port to operate on. The default is to operate
1657 on port 6696 as specified in the Babel RFC.
1659 <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
1660 These options specify the ToS/DiffServ/Traffic class/Priority of the
1661 outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
1662 option for detailed description.
1664 <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
1665 This option specifies the size of buffers used for packet processing.
1666 The buffer size should be bigger than maximal size of received packets.
1667 The default value is the interface MTU, and the value will be clamped to a
1668 minimum of 512 bytes + IP packet overhead.
1670 <tag><label id="babel-tx-length">tx length <m/number/</tag>
1671 This option specifies the maximum length of generated Babel packets. To
1672 avoid IP fragmentation, it should not exceed the interface MTU value.
1673 The default value is the interface MTU value, and the value will be
1674 clamped to a minimum of 512 bytes + IP packet overhead.
1676 <tag><label id="babel-check-link">check link <m/switch/</tag>
1677 If set, the hardware link state (as reported by OS) is taken into
1678 consideration. When the link disappears (e.g. an ethernet cable is
1679 unplugged), neighbors are immediately considered unreachable and all
1680 routes received from them are withdrawn. It is possible that some
1681 hardware drivers or platforms do not implement this feature. Default:
1686 <label id="babel-attr">
1688 <p>Babel defines just one attribute: the internal babel metric of the route. It
1689 is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
1693 <label id="babel-exam">
1700 interface "wlan0", "wlan1" {
1707 # This matches the default of babeld: redistribute all addresses
1708 # configured on local interfaces, plus re-distribute all routes received
1709 # from other babel peers.
1711 export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1720 <label id="bfd-intro">
1722 <p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
1723 is an independent tool providing liveness and failure detection. Routing
1724 protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
1725 liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
1726 seconds by default in OSPF, could be set down to several seconds). BFD offers
1727 universal, fast and low-overhead mechanism for failure detection, which could be
1728 attached to any routing protocol in an advisory role.
1730 <p>BFD consists of mostly independent BFD sessions. Each session monitors an
1731 unicast bidirectional path between two BFD-enabled routers. This is done by
1732 periodically sending control packets in both directions. BFD does not handle
1733 neighbor discovery, BFD sessions are created on demand by request of other
1734 protocols (like OSPF or BGP), which supply appropriate information like IP
1735 addresses and associated interfaces. When a session changes its state, these
1736 protocols are notified and act accordingly (e.g. break an OSPF adjacency when
1737 the BFD session went down).
1739 <p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
1740 advanced features like the echo mode or authentication are not implemented), IP
1741 transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
1742 interaction with client protocols as defined in <rfc id="5882">.
1744 <p>Note that BFD implementation in BIRD is currently a new feature in
1745 development, expect some rough edges and possible UI and configuration changes
1746 in the future. Also note that we currently support at most one protocol instance.
1748 <p>BFD packets are sent with a dynamic source port number. Linux systems use by
1749 default a bit different dynamic port range than the IANA approved one
1750 (49152-65535). If you experience problems with compatibility, please adjust
1751 <cf>/proc/sys/net/ipv4/ip_local_port_range</cf>
1753 <sect1>Configuration
1754 <label id="bfd-config">
1756 <p>BFD configuration consists mainly of multiple definitions of interfaces.
1757 Most BFD config options are session specific. When a new session is requested
1758 and dynamically created, it is configured from one of these definitions. For
1759 sessions to directly connected neighbors, <cf/interface/ definitions are chosen
1760 based on the interface associated with the session, while <cf/multihop/
1761 definition is used for multihop sessions. If no definition is relevant, the
1762 session is just created with the default configuration. Therefore, an empty BFD
1763 configuration is often sufficient.
1765 <p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
1766 also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
1768 <p>Some of BFD session options require <m/time/ value, which has to be specified
1769 with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
1770 are allowed as units, practical minimum values are usually in order of tens of
1774 protocol bfd [<name>] {
1775 interface <interface pattern> {
1776 interval <time>;
1777 min rx interval <time>;
1778 min tx interval <time>;
1779 idle tx interval <time>;
1780 multiplier <num>;
1781 passive <switch>;
1782 authentication none;
1783 authentication simple;
1784 authentication [meticulous] keyed md5|sha1;
1785 password "<text>";
1786 password "<text>" {
1788 generate from "<date>";
1789 generate to "<date>";
1790 accept from "<date>";
1791 accept to "<date>";
1792 from "<date>";
1797 interval <time>;
1798 min rx interval <time>;
1799 min tx interval <time>;
1800 idle tx interval <time>;
1801 multiplier <num>;
1802 passive <switch>;
1804 neighbor <ip> [dev "<interface>"] [local <ip>] [multihop <switch>];
1809 <tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
1810 Interface definitions allow to specify options for sessions associated
1811 with such interfaces and also may contain interface specific options.
1812 See <ref id="proto-iface" name="interface"> common option for a detailed
1813 description of interface patterns. Note that contrary to the behavior of
1814 <cf/interface/ definitions of other protocols, BFD protocol would accept
1815 sessions (in default configuration) even on interfaces not covered by
1818 <tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
1819 Multihop definitions allow to specify options for multihop BFD sessions,
1820 in the same manner as <cf/interface/ definitions are used for directly
1821 connected sessions. Currently only one such definition (for all multihop
1822 sessions) could be used.
1824 <tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
1825 BFD sessions are usually created on demand as requested by other
1826 protocols (like OSPF or BGP). This option allows to explicitly add
1827 a BFD session to the specified neighbor regardless of such requests.
1829 The session is identified by the IP address of the neighbor, with
1830 optional specification of used interface and local IP. By default
1831 the neighbor must be directly connected, unless the session is
1832 configured as multihop. Note that local IP must be specified for
1836 <p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
1839 <tag><label id="bfd-interval">interval <m/time/</tag>
1840 BFD ensures availability of the forwarding path associated with the
1841 session by periodically sending BFD control packets in both
1842 directions. The rate of such packets is controlled by two options,
1843 <cf/min rx interval/ and <cf/min tx interval/ (see below). This option
1844 is just a shorthand to set both of these options together.
1846 <tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
1847 This option specifies the minimum RX interval, which is announced to the
1848 neighbor and used there to limit the neighbor's rate of generated BFD
1849 control packets. Default: 10 ms.
1851 <tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
1852 This option specifies the desired TX interval, which controls the rate
1853 of generated BFD control packets (together with <cf/min rx interval/
1854 announced by the neighbor). Note that this value is used only if the BFD
1855 session is up, otherwise the value of <cf/idle tx interval/ is used
1856 instead. Default: 100 ms.
1858 <tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
1859 In order to limit unnecessary traffic in cases where a neighbor is not
1860 available or not running BFD, the rate of generated BFD control packets
1861 is lower when the BFD session is not up. This option specifies the
1862 desired TX interval in such cases instead of <cf/min tx interval/.
1865 <tag><label id="bfd-multiplier">multiplier <m/num/</tag>
1866 Failure detection time for BFD sessions is based on established rate of
1867 BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
1868 multiplier, which is essentially (ignoring jitter) a number of missed
1869 packets after which the session is declared down. Note that rates and
1870 multipliers could be different in each direction of a BFD session.
1873 <tag><label id="bfd-passive">passive <m/switch/</tag>
1874 Generally, both BFD session endpoints try to establish the session by
1875 sending control packets to the other side. This option allows to enable
1876 passive mode, which means that the router does not send BFD packets
1877 until it has received one from the other side. Default: disabled.
1879 <tag>authentication none</tag>
1880 No passwords are sent in BFD packets. This is the default value.
1882 <tag>authentication simple</tag>
1883 Every packet carries 16 bytes of password. Received packets lacking this
1884 password are ignored. This authentication mechanism is very weak.
1886 <tag>authentication [meticulous] keyed md5|sha1</tag>
1887 An authentication code is appended to each packet. The cryptographic
1888 algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
1889 for all keys (on one interface), in contrast to OSPF or RIP, where it
1890 is a per-key option. Passwords (keys) are not sent open via network.
1892 The <cf/meticulous/ variant means that cryptographic sequence numbers
1893 are increased for each sent packet, while in the basic variant they are
1894 increased about once per second. Generally, the <cf/meticulous/ variant
1895 offers better resistance to replay attacks but may require more
1898 <tag>password "<M>text</M>"</tag>
1899 Specifies a password used for authentication. See <ref id="dsc-pass"
1900 name="password"> common option for detailed description. Note that
1901 password option <cf/algorithm/ is not available in BFD protocol. The
1902 algorithm is selected by <cf/authentication/ option for all passwords.
1907 <label id="bfd-exam">
1912 min rx interval 20 ms;
1913 min tx interval 50 ms;
1914 idle tx interval 300 ms;
1926 neighbor 192.168.1.10;
1927 neighbor 192.168.2.2 dev "eth2";
1928 neighbor 192.168.10.1 local 192.168.1.1 multihop;
1936 <p>The Border Gateway Protocol is the routing protocol used for backbone level
1937 routing in the today's Internet. Contrary to other protocols, its convergence
1938 does not rely on all routers following the same rules for route selection,
1939 making it possible to implement any routing policy at any router in the network,
1940 the only restriction being that if a router advertises a route, it must accept
1941 and forward packets according to it.
1943 <p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
1944 is a part of the network with common management and common routing policy. It is
1945 identified by a unique 16-bit number (ASN). Routers within each AS usually
1946 exchange AS-internal routing information with each other using an interior
1947 gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
1948 the AS communicate global (inter-AS) network reachability information with their
1949 neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
1950 received information to other routers in the AS via interior BGP (iBGP).
1952 <p>Each BGP router sends to its neighbors updates of the parts of its routing
1953 table it wishes to export along with complete path information (a list of AS'es
1954 the packet will travel through if it uses the particular route) in order to
1955 avoid routing loops.
1957 <sect1>Supported standards:
1958 <label id="bgp-standards">
1961 <item> <rfc id="4271"> - Border Gateway Protocol 4 (BGP)
1962 <item> <rfc id="1997"> - BGP Communities Attribute
1963 <item> <rfc id="2385"> - Protection of BGP Sessions via TCP MD5 Signature
1964 <item> <rfc id="2545"> - Use of BGP Multiprotocol Extensions for IPv6
1965 <item> <rfc id="2918"> - Route Refresh Capability
1966 <item> <rfc id="3107"> - Carrying Label Information in BGP
1967 <item> <rfc id="4360"> - BGP Extended Communities Attribute
1968 <item> <rfc id="4364"> - BGP/MPLS IPv4 Virtual Private Networks
1969 <item> <rfc id="4456"> - BGP Route Reflection
1970 <item> <rfc id="4486"> - Subcodes for BGP Cease Notification Message
1971 <item> <rfc id="4659"> - BGP/MPLS IPv6 Virtual Private Networks
1972 <item> <rfc id="4724"> - Graceful Restart Mechanism for BGP
1973 <item> <rfc id="4760"> - Multiprotocol extensions for BGP
1974 <item> <rfc id="4798"> - Connecting IPv6 Islands over IPv4 MPLS
1975 <item> <rfc id="5065"> - AS confederations for BGP
1976 <item> <rfc id="5082"> - Generalized TTL Security Mechanism
1977 <item> <rfc id="5492"> - Capabilities Advertisement with BGP
1978 <item> <rfc id="5549"> - Advertising IPv4 NLRI with an IPv6 Next Hop
1979 <item> <rfc id="5575"> - Dissemination of Flow Specification Rules
1980 <item> <rfc id="5668"> - 4-Octet AS Specific BGP Extended Community
1981 <item> <rfc id="6286"> - AS-Wide Unique BGP Identifier
1982 <item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error
1983 <item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers
1984 <item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP
1985 <item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages
1986 <item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP
1987 <item> <rfc id="7947"> - Internet Exchange BGP Route Server
1988 <item> <rfc id="8092"> - BGP Large Communities Attribute
1991 <sect1>Route selection rules
1992 <label id="bgp-route-select-rules">
1994 <p>BGP doesn't have any simple metric, so the rules for selection of an optimal
1995 route among multiple BGP routes with the same preference are a bit more complex
1996 and they are implemented according to the following algorithm. It starts the
1997 first rule, if there are more "best" routes, then it uses the second rule to
1998 choose among them and so on.
2001 <item>Prefer route with the highest Local Preference attribute.
2002 <item>Prefer route with the shortest AS path.
2003 <item>Prefer IGP origin over EGP and EGP origin over incomplete.
2004 <item>Prefer the lowest value of the Multiple Exit Discriminator.
2005 <item>Prefer routes received via eBGP over ones received via iBGP.
2006 <item>Prefer routes with lower internal distance to a boundary router.
2007 <item>Prefer the route with the lowest value of router ID of the
2011 <sect1>IGP routing table
2012 <label id="bgp-igp-routing-table">
2014 <p>BGP is mainly concerned with global network reachability and with routes to
2015 other autonomous systems. When such routes are redistributed to routers in the
2016 AS via BGP, they contain IP addresses of a boundary routers (in route attribute
2017 NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
2018 determine immediate next hops for routes and to know their internal distances to
2019 boundary routers for the purpose of BGP route selection. In BIRD, there is
2020 usually one routing table used for both IGP routes and BGP routes.
2022 <sect1>Configuration
2023 <label id="bgp-config">
2025 <p>Each instance of the BGP corresponds to one neighboring router. This allows
2026 to set routing policy and all the other parameters differently for each neighbor
2027 using the following configuration parameters:
2030 <tag><label id="bgp-local">local [<m/ip/] as <m/number/</tag>
2031 Define which AS we are part of. (Note that contrary to other IP routers,
2032 BIRD is able to act as a router located in multiple AS'es simultaneously,
2033 but in such cases you need to tweak the BGP paths manually in the filters
2034 to get consistent behavior.) Optional <cf/ip/ argument specifies a source
2035 address, equivalent to the <cf/source address/ option (see below). This
2036 parameter is mandatory.
2038 <tag><label id="bgp-neighbor">neighbor [<m/ip/] [port <m/number/] [as <m/number/]</tag>
2039 Define neighboring router this instance will be talking to and what AS
2040 it is located in. In case the neighbor is in the same AS as we are, we
2041 automatically switch to iBGP. Optionally, the remote port may also be
2042 specified. The parameter may be used multiple times with different
2043 sub-options (e.g., both <cf/neighbor 10.0.0.1 as 65000;/ and
2044 <cf/neighbor 10.0.0.1; neighbor as 65000;/ are valid). This parameter is
2047 <tag><label id="bgp-iface">interface <m/string/</tag>
2048 Define interface we should use for link-local BGP IPv6 sessions.
2049 Interface can also be specified as a part of <cf/neighbor address/
2050 (e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). The option may also be
2051 used for non link-local sessions when it is necessary to explicitly
2052 specify an interface, but only for direct (not multihop) sessions.
2054 <tag><label id="bgp-direct">direct</tag>
2055 Specify that the neighbor is directly connected. The IP address of the
2056 neighbor must be from a directly reachable IP range (i.e. associated
2057 with one of your router's interfaces), otherwise the BGP session
2058 wouldn't start but it would wait for such interface to appear. The
2059 alternative is the <cf/multihop/ option. Default: enabled for eBGP.
2061 <tag><label id="bgp-multihop">multihop [<m/number/]</tag>
2062 Configure multihop BGP session to a neighbor that isn't directly
2063 connected. Accurately, this option should be used if the configured
2064 neighbor IP address does not match with any local network subnets. Such
2065 IP address have to be reachable through system routing table. The
2066 alternative is the <cf/direct/ option. For multihop BGP it is
2067 recommended to explicitly configure the source address to have it
2068 stable. Optional <cf/number/ argument can be used to specify the number
2069 of hops (used for TTL). Note that the number of networks (edges) in a
2070 path is counted; i.e., if two BGP speakers are separated by one router,
2071 the number of hops is 2. Default: enabled for iBGP.
2073 <tag><label id="bgp-source-address">source address <m/ip/</tag>
2074 Define local address we should use for next hop calculation and as a
2075 source address for the BGP session. Default: the address of the local
2076 end of the interface our neighbor is connected to.
2078 <tag><label id="bgp-strict-bind">strict bind <m/switch/</tag>
2079 Specify whether BGP listening socket should be bound to a specific local
2080 address (the same as the <cf/source address/) and associated interface,
2081 or to all addresses. Binding to a specific address could be useful in
2082 cases like running multiple BIRD instances on a machine, each using its
2083 IP address. Note that listening sockets bound to a specific address and
2084 to all addresses collide, therefore either all BGP protocols (of the
2085 same address family and using the same local port) should have set
2086 <cf/strict bind/, or none of them. Default: disabled.
2088 <tag><label id="bgp-next-hop-self">next hop self</tag>
2089 Avoid calculation of the Next Hop attribute and always advertise our own
2090 source address as a next hop. This needs to be used only occasionally to
2091 circumvent misconfigurations of other routers. Default: disabled.
2093 <tag><label id="bgp-next-hop-keep">next hop keep</tag>
2094 Forward the received Next Hop attribute even in situations where the
2095 local address should be used instead, like when the route is sent to an
2096 interface with a different subnet. Default: disabled.
2098 <tag><label id="bgp-missing-lladdr">missing lladdr self|drop|ignore</tag>
2099 Next Hop attribute in BGP-IPv6 sometimes contains just the global IPv6
2100 address, but sometimes it has to contain both global and link-local IPv6
2101 addresses. This option specifies what to do if BIRD have to send both
2102 addresses but does not know link-local address. This situation might
2103 happen when routes from other protocols are exported to BGP, or when
2104 improper updates are received from BGP peers. <cf/self/ means that BIRD
2105 advertises its own local address instead. <cf/drop/ means that BIRD
2106 skips that prefixes and logs error. <cf/ignore/ means that BIRD ignores
2107 the problem and sends just the global address (and therefore forms
2108 improper BGP update). Default: <cf/self/, unless BIRD is configured as a
2109 route server (option <cf/rs client/), in that case default is <cf/ignore/,
2110 because route servers usually do not forward packets themselves.
2112 <tag><label id="bgp-gateway">gateway direct|recursive</tag>
2113 For received routes, their <cf/gw/ (immediate next hop) attribute is
2114 computed from received <cf/bgp_next_hop/ attribute. This option
2115 specifies how it is computed. Direct mode means that the IP address from
2116 <cf/bgp_next_hop/ is used if it is directly reachable, otherwise the
2117 neighbor IP address is used. Recursive mode means that the gateway is
2118 computed by an IGP routing table lookup for the IP address from
2119 <cf/bgp_next_hop/. Note that there is just one level of indirection in
2120 recursive mode - the route obtained by the lookup must not be recursive
2121 itself, to prevent mutually recursive routes.
2123 Recursive mode is the behavior specified by the BGP
2124 standard. Direct mode is simpler, does not require any routes in a
2125 routing table, and was used in older versions of BIRD, but does not
2126 handle well nontrivial iBGP setups and multihop. Recursive mode is
2127 incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
2128 <cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
2130 <tag><label id="bgp-igp-table">igp table <m/name/</tag>
2131 Specifies a table that is used as an IGP routing table. Default: the
2132 same as the table BGP is connected to.
2134 <tag><label id="bgp-check-link">check link <M>switch</M></tag>
2135 BGP could use hardware link state into consideration. If enabled,
2136 BIRD tracks the link state of the associated interface and when link
2137 disappears (e.g. an ethernet cable is unplugged), the BGP session is
2138 immediately shut down. Note that this option cannot be used with
2139 multihop BGP. Default: disabled.
2141 <tag><label id="bgp-bfd">bfd <M>switch</M></tag>
2142 BGP could use BFD protocol as an advisory mechanism for neighbor
2143 liveness and failure detection. If enabled, BIRD setups a BFD session
2144 for the BGP neighbor and tracks its liveness by it. This has an
2145 advantage of an order of magnitude lower detection times in case of
2146 failure. Note that BFD protocol also has to be configured, see
2147 <ref id="bfd" name="BFD"> section for details. Default: disabled.
2149 <tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
2150 Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
2151 protects against spoofed packets by ignoring received packets with a
2152 smaller than expected TTL. To work properly, GTSM have to be enabled on
2153 both sides of a BGP session. If both <cf/ttl security/ and
2154 <cf/multihop/ options are enabled, <cf/multihop/ option should specify
2155 proper hop value to compute expected TTL. Kernel support required:
2156 Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
2157 Note that full (ICMP protection, for example) <rfc id="5082"> support is
2158 provided by Linux only. Default: disabled.
2160 <tag><label id="bgp-password">password <m/string/</tag>
2161 Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
2162 used on BSD systems, see also <cf/setkey/ option below. Default: no
2165 <tag><label id="bgp-setkey">setkey <m/switch/</tag>
2166 On BSD systems, keys for TCP MD5 authentication are stored in the global
2167 SA/SP database, which can be accessed by external utilities (e.g.
2168 setkey(8)). BIRD configures security associations in the SA/SP database
2169 automatically based on <cf/password/ options (see above), this option
2170 allows to disable automatic updates by BIRD when manual configuration by
2171 external utilities is preferred. Note that automatic SA/SP database
2172 updates are currently implemented only for FreeBSD. Passwords have to be
2173 set manually by an external utility on NetBSD and OpenBSD. Default:
2174 enabled (ignored on non-FreeBSD).
2176 <tag><label id="bgp-passive">passive <m/switch/</tag>
2177 Standard BGP behavior is both initiating outgoing connections and
2178 accepting incoming connections. In passive mode, outgoing connections
2179 are not initiated. Default: off.
2181 <tag><label id="bgp-confederation">confederation <m/number/</tag>
2182 BGP confederations (<rfc id="5065">) are collections of autonomous
2183 systems that act as one entity to external systems, represented by one
2184 confederation identifier (instead of AS numbers). This option allows to
2185 enable BGP confederation behavior and to specify the local confederation
2186 identifier. When BGP confederations are used, all BGP speakers that are
2187 members of the BGP confederation should have the same confederation
2188 identifier configured. Default: 0 (no confederation).
2190 <tag><label id="bgp-confederation-member">confederation member <m/switch/</tag>
2191 When BGP confederations are used, this option allows to specify whether
2192 the BGP neighbor is a member of the same confederation as the local BGP
2193 speaker. The option is unnecessary (and ignored) for IBGP sessions, as
2194 the same AS number implies the same confederation. Default: no.
2196 <tag><label id="bgp-rr-client">rr client</tag>
2197 Be a route reflector and treat the neighbor as a route reflection
2198 client. Default: disabled.
2200 <tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2201 Route reflectors use cluster id to avoid route reflection loops. When
2202 there is one route reflector in a cluster it usually uses its router id
2203 as a cluster id, but when there are more route reflectors in a cluster,
2204 these need to be configured (using this option) to use a common cluster
2205 id. Clients in a cluster need not know their cluster id and this option
2206 is not allowed for them. Default: the same as router id.
2208 <tag><label id="bgp-rs-client">rs client</tag>
2209 Be a route server and treat the neighbor as a route server client.
2210 A route server is used as a replacement for full mesh EBGP routing in
2211 Internet exchange points in a similar way to route reflectors used in
2212 IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2213 uses ad-hoc implementation, which behaves like plain EBGP but reduces
2214 modifications to advertised route attributes to be transparent (for
2215 example does not prepend its AS number to AS PATH attribute and
2216 keeps MED attribute). Default: disabled.
2218 <tag><label id="bgp-secondary">secondary <m/switch/</tag>
2219 Usually, if an export filter rejects a selected route, no other route is
2220 propagated for that network. This option allows to try the next route in
2221 order until one that is accepted is found or all routes for that network
2222 are rejected. This can be used for route servers that need to propagate
2223 different tables to each client but do not want to have these tables
2224 explicitly (to conserve memory). This option requires that the connected
2225 routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
2227 <tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
2228 Standard BGP can propagate only one path (route) per destination network
2229 (usually the selected one). This option controls the add-path protocol
2230 extension, which allows to advertise any number of paths to a
2231 destination. Note that to be active, add-path has to be enabled on both
2232 sides of the BGP session, but it could be enabled separately for RX and
2233 TX direction. When active, all available routes accepted by the export
2234 filter are advertised to the neighbor. Default: off.
2236 <tag><label id="bgp-allow-local-pref">allow bgp_local_pref <m/switch/</tag>
2237 A standard BGP implementation do not send the Local Preference attribute
2238 to eBGP neighbors and ignore this attribute if received from eBGP
2239 neighbors, as per <rfc id="4271">. When this option is enabled on an
2240 eBGP session, this attribute will be sent to and accepted from the peer,
2241 which is useful for example if you have a setup like in <rfc id="7938">.
2242 The option does not affect iBGP sessions. Default: off.
2244 <tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2245 BGP prevents routing loops by rejecting received routes with the local
2246 AS number in the AS path. This option allows to loose or disable the
2247 check. Optional <cf/number/ argument can be used to specify the maximum
2248 number of local ASNs in the AS path that is allowed for received
2249 routes. When the option is used without the argument, the check is
2250 completely disabled and you should ensure loop-free behavior by some
2251 other means. Default: 0 (no local AS number allowed).
2253 <tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
2254 After the initial route exchange, BGP protocol uses incremental updates
2255 to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
2256 changes its import filter, or if there is suspicion of inconsistency) it
2257 is necessary to do a new complete route exchange. BGP protocol extension
2258 Route Refresh (<rfc id="2918">) allows BGP speaker to request
2259 re-advertisement of all routes from its neighbor. BGP protocol
2260 extension Enhanced Route Refresh (<rfc id="7313">) specifies explicit
2261 begin and end for such exchanges, therefore the receiver can remove
2262 stale routes that were not advertised during the exchange. This option
2263 specifies whether BIRD advertises these capabilities and supports
2264 related procedures. Note that even when disabled, BIRD can send route
2265 refresh requests. Default: on.
2267 <tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
2268 When a BGP speaker restarts or crashes, neighbors will discard all
2269 received paths from the speaker, which disrupts packet forwarding even
2270 when the forwarding plane of the speaker remains intact. <rfc
2271 id="4724"> specifies an optional graceful restart mechanism to
2272 alleviate this issue. This option controls the mechanism. It has three
2273 states: Disabled, when no support is provided. Aware, when the graceful
2274 restart support is announced and the support for restarting neighbors
2275 is provided, but no local graceful restart is allowed (i.e.
2276 receiving-only role). Enabled, when the full graceful restart
2277 support is provided (i.e. both restarting and receiving role). Note
2278 that proper support for local graceful restart requires also
2279 configuration of other protocols. Default: aware.
2281 <tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
2282 The restart time is announced in the BGP graceful restart capability
2283 and specifies how long the neighbor would wait for the BGP session to
2284 re-establish after a restart before deleting stale routes. Default:
2287 <tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
2288 <rfc id="1997"> demands that BGP speaker should process well-known
2289 communities like no-export (65535, 65281) or no-advertise (65535,
2290 65282). For example, received route carrying a no-adverise community
2291 should not be advertised to any of its neighbors. If this option is
2292 enabled (which is by default), BIRD has such behavior automatically (it
2293 is evaluated when a route is exported to the BGP protocol just before
2294 the export filter). Otherwise, this integrated processing of
2295 well-known communities is disabled. In that case, similar behavior can
2296 be implemented in the export filter. Default: on.
2298 <tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
2299 BGP protocol was designed to use 2B AS numbers and was extended later to
2300 allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
2301 option it can be persuaded not to advertise it and to maintain old-style
2302 sessions with its neighbors. This might be useful for circumventing bugs
2303 in neighbor's implementation of 4B AS extension. Even when disabled
2304 (off), BIRD behaves internally as AS4-aware BGP router. Default: on.
2306 <tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
2307 The BGP protocol uses maximum message length of 4096 bytes. This option
2308 provides an extension to allow extended messages with length up
2309 to 65535 bytes. Default: off.
2311 <tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
2312 Use capability advertisement to advertise optional capabilities. This is
2313 standard behavior for newer BGP implementations, but there might be some
2314 older BGP implementations that reject such connection attempts. When
2315 disabled (off), features that request it (4B AS support) are also
2316 disabled. Default: on, with automatic fallback to off when received
2317 capability-related error.
2319 <tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag>
2320 Advertise IPv4 multiprotocol capability. This is not a correct behavior
2321 according to the strict interpretation of <rfc id="4760">, but it is
2322 widespread and required by some BGP implementations (Cisco and Quagga).
2323 This option is relevant to IPv4 mode with enabled capability
2324 advertisement only. Default: on.
2326 <tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
2327 When an error is encountered (either locally or by the other side),
2328 disable the instance automatically and wait for an administrator to fix
2329 the problem manually. Default: off.
2331 <tag><label id="bgp-hold-time">hold time <m/number/</tag>
2332 Time in seconds to wait for a Keepalive message from the other side
2333 before considering the connection stale. Default: depends on agreement
2334 with the neighboring router, we prefer 240 seconds if the other side is
2335 willing to accept it.
2337 <tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
2338 Value of the hold timer used before the routers have a chance to exchange
2339 open messages and agree on the real value. Default: 240 seconds.
2341 <tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
2342 Delay in seconds between sending of two consecutive Keepalive messages.
2343 Default: One third of the hold time.
2345 <tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
2346 Delay in seconds between protocol startup and the first attempt to
2347 connect. Default: 5 seconds.
2349 <tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
2350 Time in seconds to wait before retrying a failed attempt to connect.
2351 Default: 120 seconds.
2353 <tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
2354 Minimum and maximum delay in seconds between a protocol failure (either
2355 local or reported by the peer) and automatic restart. Doesn't apply
2356 when <cf/disable after error/ is configured. If consecutive errors
2357 happen, the delay is increased exponentially until it reaches the
2358 maximum. Default: 60, 300.
2360 <tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
2361 Maximum time in seconds between two protocol failures to treat them as a
2362 error sequence which makes <cf/error wait time/ increase exponentially.
2363 Default: 300 seconds.
2365 <tag><label id="bgp-path-metric">path metric <m/switch/</tag>
2366 Enable comparison of path lengths when deciding which BGP route is the
2367 best one. Default: on.
2369 <tag><label id="bgp-med-metric">med metric <m/switch/</tag>
2370 Enable comparison of MED attributes (during best route selection) even
2371 between routes received from different ASes. This may be useful if all
2372 MED attributes contain some consistent metric, perhaps enforced in
2373 import filters of AS boundary routers. If this option is disabled, MED
2374 attributes are compared only if routes are received from the same AS
2375 (which is the standard behavior). Default: off.
2377 <tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
2378 BGP route selection algorithm is often viewed as a comparison between
2379 individual routes (e.g. if a new route appears and is better than the
2380 current best one, it is chosen as the new best one). But the proper
2381 route selection, as specified by <rfc id="4271">, cannot be fully
2382 implemented in that way. The problem is mainly in handling the MED
2383 attribute. BIRD, by default, uses an simplification based on individual
2384 route comparison, which in some cases may lead to temporally dependent
2385 behavior (i.e. the selection is dependent on the order in which routes
2386 appeared). This option enables a different (and slower) algorithm
2387 implementing proper <rfc id="4271"> route selection, which is
2388 deterministic. Alternative way how to get deterministic behavior is to
2389 use <cf/med metric/ option. This option is incompatible with <ref
2390 id="dsc-table-sorted" name="sorted tables">. Default: off.
2392 <tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
2393 Enable comparison of internal distances to boundary routers during best
2394 route selection. Default: on.
2396 <tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
2397 Standard route selection algorithm breaks ties by comparing router IDs.
2398 This changes the behavior to prefer older routes (when both are external
2399 and from different peer). For details, see <rfc id="5004">. Default: off.
2401 <tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
2402 Value of the Multiple Exit Discriminator to be used during route
2403 selection when the MED attribute is missing. Default: 0.
2405 <tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
2406 A default value for the Local Preference attribute. It is used when
2407 a new Local Preference attribute is attached to a route by the BGP
2408 protocol itself (for example, if a route is received through eBGP and
2409 therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
2414 <label id="bgp-attr">
2416 <p>BGP defines several route attributes. Some of them (those marked with
2417 `<tt/I/' in the table below) are available on internal BGP connections only,
2418 some of them (marked with `<tt/O/') are optional.
2421 <tag><label id="rta-bgp-path">bgppath bgp_path/</tag>
2422 Sequence of AS numbers describing the AS path the packet will travel
2423 through when forwarded according to the particular route. In case of
2424 internal BGP it doesn't contain the number of the local AS.
2426 <tag><label id="rta-bgp-local-pref">int bgp_local_pref/ [I]</tag>
2427 Local preference value used for selection among multiple BGP routes (see
2428 the selection rules above). It's used as an additional metric which is
2429 propagated through the whole local AS.
2431 <tag><label id="rta-bgp-med">int bgp_med/ [O]</tag>
2432 The Multiple Exit Discriminator of the route is an optional attribute
2433 which is used on external (inter-AS) links to convey to an adjacent AS
2434 the optimal entry point into the local AS. The received attribute is
2435 also propagated over internal BGP links. The attribute value is zeroed
2436 when a route is exported to an external BGP instance to ensure that the
2437 attribute received from a neighboring AS is not propagated to other
2438 neighboring ASes. A new value might be set in the export filter of an
2439 external BGP instance. See <rfc id="4451"> for further discussion of
2442 <tag><label id="rta-bgp-origin">enum bgp_origin/</tag>
2443 Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
2444 in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
2445 from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
2446 <cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
2448 <tag><label id="rta-bgp-next-hop">ip bgp_next_hop/</tag>
2449 Next hop to be used for forwarding of packets to this destination. On
2450 internal BGP connections, it's an address of the originating router if
2451 it's inside the local AS or a boundary router the packet will leave the
2452 AS through if it's an exterior route, so each BGP speaker within the AS
2453 has a chance to use the shortest interior path possible to this point.
2455 <tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr/ [O]</tag>
2456 This is an optional attribute which carries no value, but the sole
2457 presence of which indicates that the route has been aggregated from
2458 multiple routes by some router on the path from the originator.
2460 <!-- we don't handle aggregators right since they are of a very obscure type
2461 <tag>bgp_aggregator</tag>
2463 <tag><label id="rta-bgp-community">clist bgp_community/ [O]</tag>
2464 List of community values associated with the route. Each such value is a
2465 pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
2466 integers, the first of them containing the number of the AS which
2467 defines the community and the second one being a per-AS identifier.
2468 There are lots of uses of the community mechanism, but generally they
2469 are used to carry policy information like "don't export to USA peers".
2470 As each AS can define its own routing policy, it also has a complete
2471 freedom about which community attributes it defines and what will their
2474 <tag><label id="rta-bgp-ext-community">eclist bgp_ext_community/ [O]</tag>
2475 List of extended community values associated with the route. Extended
2476 communities have similar usage as plain communities, but they have an
2477 extended range (to allow 4B ASNs) and a nontrivial structure with a type
2478 field. Individual community values are represented using an <cf/ec/ data
2479 type inside the filters.
2481 <tag><label id="rta-bgp-large-community">lclist <cf/bgp_large_community/ [O]</tag>
2482 List of large community values associated with the route. Large BGP
2483 communities is another variant of communities, but contrary to extended
2484 communities they behave very much the same way as regular communities,
2485 just larger -- they are uniform untyped triplets of 32bit numbers.
2486 Individual community values are represented using an <cf/lc/ data type
2489 <tag><label id="rta-bgp-originator-id">quad bgp_originator_id/ [I, O]</tag>
2490 This attribute is created by the route reflector when reflecting the
2491 route and contains the router ID of the originator of the route in the
2494 <tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list/ [I, O]</tag>
2495 This attribute contains a list of cluster IDs of route reflectors. Each
2496 route reflector prepends its cluster ID when reflecting the route.
2500 <label id="bgp-exam">
2504 local as 65000; # Use a private AS number
2505 neighbor 198.51.100.130 as 64496; # Our neighbor ...
2506 multihop; # ... which is connected indirectly
2507 export filter { # We use non-trivial export rules
2508 if source = RTS_STATIC then { # Export only static routes
2509 # Assign our community
2510 bgp_community.add((65000,64501));
2511 # Artificially increase path length
2512 # by advertising local AS number twice
2513 if bgp_path ~ [= 65000 =] then
2514 bgp_path.prepend(65000);
2520 source address 198.51.100.14; # Use a non-standard source address
2528 <p>The Device protocol is not a real routing protocol. It doesn't generate any
2529 routes and it only serves as a module for getting information about network
2530 interfaces from the kernel.
2532 <p>Except for very unusual circumstances, you probably should include this
2533 protocol in the configuration since almost all other protocols require network
2534 interfaces to be defined for them to work with.
2536 <sect1>Configuration
2537 <label id="device-config">
2541 <tag><label id="device-scan-time">scan time <m/number/</tag>
2542 Time in seconds between two scans of the network interface list. On
2543 systems where we are notified about interface status changes
2544 asynchronously (such as newer versions of Linux), we need to scan the
2545 list only in order to avoid confusion by lost notification messages,
2546 so the default time is set to a large value.
2548 <tag><label id="device-primary">primary [ "<m/mask/" ] <m/prefix/</tag>
2549 If a network interface has more than one network address, BIRD has to
2550 choose one of them as a primary one. By default, BIRD chooses the
2551 lexicographically smallest address as the primary one.
2553 This option allows to specify which network address should be chosen as
2554 a primary one. Network addresses that match <m/prefix/ are preferred to
2555 non-matching addresses. If more <cf/primary/ options are used, the first
2556 one has the highest preference. If "<m/mask/" is specified, then such
2557 <cf/primary/ option is relevant only to matching network interfaces.
2559 In all cases, an address marked by operating system as secondary cannot
2560 be chosen as the primary one.
2563 <p>As the Device protocol doesn't generate any routes, it cannot have
2564 any attributes. Example configuration looks like this:
2568 scan time 10; # Scan the interfaces often
2569 primary "eth0" 192.168.1.1;
2570 primary 192.168.0.0/16;
2578 <p>The Direct protocol is a simple generator of device routes for all the
2579 directly connected networks according to the list of interfaces provided by the
2580 kernel via the Device protocol.
2582 <p>The question is whether it is a good idea to have such device routes in BIRD
2583 routing table. OS kernel usually handles device routes for directly connected
2584 networks by itself so we don't need (and don't want) to export these routes to
2585 the kernel protocol. OSPF protocol creates device routes for its interfaces
2586 itself and BGP protocol is usually used for exporting aggregate routes. Although
2587 there are some use cases that use the direct protocol (like abusing eBGP as an
2588 IGP routing protocol), in most cases it is not needed to have these device
2589 routes in BIRD routing table and to use the direct protocol.
2591 <p>There is one notable case when you definitely want to use the direct protocol
2592 -- running BIRD on BSD systems. Having high priority device routes for directly
2593 connected networks from the direct protocol protects kernel device routes from
2594 being overwritten or removed by IGP routes during some transient network
2595 conditions, because a lower priority IGP route for the same network is not
2596 exported to the kernel routing table. This is an issue on BSD systems only, as
2597 on Linux systems BIRD cannot change non-BIRD route in the kernel routing table.
2599 <p>There are just few configuration options for the Direct protocol:
2602 <tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
2603 By default, the Direct protocol will generate device routes for all the
2604 interfaces available. If you want to restrict it to some subset of
2605 interfaces or addresses (e.g. if you're using multiple routing tables
2606 for policy routing and some of the policy domains don't contain all
2607 interfaces), just use this clause. See <ref id="proto-iface" name="interface">
2608 common option for detailed description. The Direct protocol uses
2609 extended interface clauses.
2611 <tag><label id="direct-check-link">check link <m/switch/</tag>
2612 If enabled, a hardware link state (reported by OS) is taken into
2613 consideration. Routes for directly connected networks are generated only
2614 if link up is reported and they are withdrawn when link disappears
2615 (e.g., an ethernet cable is unplugged). Default value is no.
2618 <p>Direct device routes don't contain any specific attributes.
2620 <p>Example config might look like this:
2624 interface "-arc*", "*"; # Exclude the ARCnets
2632 <p>The Kernel protocol is not a real routing protocol. Instead of communicating
2633 with other routers in the network, it performs synchronization of BIRD's routing
2634 tables with the OS kernel. Basically, it sends all routing table updates to the
2635 kernel and from time to time it scans the kernel tables to see whether some
2636 routes have disappeared (for example due to unnoticed up/down transition of an
2637 interface) or whether an `alien' route has been added by someone else (depending
2638 on the <cf/learn/ switch, such routes are either ignored or accepted to our
2641 <p>Unfortunately, there is one thing that makes the routing table synchronization
2642 a bit more complicated. In the kernel routing table there are also device routes
2643 for directly connected networks. These routes are usually managed by OS itself
2644 (as a part of IP address configuration) and we don't want to touch that. They
2645 are completely ignored during the scan of the kernel tables and also the export
2646 of device routes from BIRD tables to kernel routing tables is restricted to
2647 prevent accidental interference. This restriction can be disabled using
2648 <cf/device routes/ switch.
2650 <p>If your OS supports only a single routing table, you can configure only one
2651 instance of the Kernel protocol. If it supports multiple tables (in order to
2652 allow policy routing; such an OS is for example Linux), you can run as many
2653 instances as you want, but each of them must be connected to a different BIRD
2654 routing table and to a different kernel table.
2656 <p>Because the kernel protocol is partially integrated with the connected
2657 routing table, there are two limitations - it is not possible to connect more
2658 kernel protocols to the same routing table and changing route destination
2659 (gateway) in an export filter of a kernel protocol does not work. Both
2660 limitations can be overcome using another routing table and the pipe protocol.
2662 <sect1>Configuration
2663 <label id="krt-config">
2666 <tag><label id="krt-persist">persist <m/switch/</tag>
2667 Tell BIRD to leave all its routes in the routing tables when it exits
2668 (instead of cleaning them up).
2670 <tag><label id="krt-scan-time">scan time <m/number/</tag>
2671 Time in seconds between two consecutive scans of the kernel routing
2674 <tag><label id="krt-learn">learn <m/switch/</tag>
2675 Enable learning of routes added to the kernel routing tables by other
2676 routing daemons or by the system administrator. This is possible only on
2677 systems which support identification of route authorship.
2679 <tag><label id="krt-device-routes">device routes <m/switch/</tag>
2680 Enable export of device routes to the kernel routing table. By default,
2681 such routes are rejected (with the exception of explicitly configured
2682 device routes from the static protocol) regardless of the export filter
2683 to protect device routes in kernel routing table (managed by OS itself)
2684 from accidental overwriting or erasing.
2686 <tag><label id="krt-kernel-table">kernel table <m/number/</tag>
2687 Select which kernel table should this particular instance of the Kernel
2688 protocol work with. Available only on systems supporting multiple
2691 <tag><label id="krt-metric">metric <m/number/</tag> (Linux)
2692 Use specified value as a kernel metric (priority) for all routes sent to
2693 the kernel. When multiple routes for the same network are in the kernel
2694 routing table, the Linux kernel chooses one with lower metric. Also,
2695 routes with different metrics do not clash with each other, therefore
2696 using dedicated metric value is a reliable way to avoid overwriting
2697 routes from other sources (e.g. kernel device routes). Metric 0 has a
2698 special meaning of undefined metric, in which either OS default is used,
2699 or per-route metric can be set using <cf/krt_metric/ attribute. Default:
2702 <tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
2703 Participate in graceful restart recovery. If this option is enabled and
2704 a graceful restart recovery is active, the Kernel protocol will defer
2705 synchronization of routing tables until the end of the recovery. Note
2706 that import of kernel routes to BIRD is not affected.
2708 <tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
2709 Usually, only best routes are exported to the kernel protocol. With path
2710 merging enabled, both best routes and equivalent non-best routes are
2711 merged during export to generate one ECMP (equal-cost multipath) route
2712 for each network. This is useful e.g. for BGP multipath. Note that best
2713 routes are still pivotal for route export (responsible for most
2714 properties of resulting ECMP routes), while exported non-best routes are
2715 responsible just for additional multipath next hops. This option also
2716 allows to specify a limit on maximal number of nexthops in one route. By
2717 default, multipath merging is disabled. If enabled, default value of the
2722 <label id="krt-attr">
2724 <p>The Kernel protocol defines several attributes. These attributes are
2725 translated to appropriate system (and OS-specific) route attributes. We support
2729 <tag><label id="rta-krt-source">int krt_source/</tag>
2730 The original source of the imported kernel route. The value is
2731 system-dependent. On Linux, it is a value of the protocol field of the
2732 route. See /etc/iproute2/rt_protos for common values. On BSD, it is
2733 based on STATIC and PROTOx flags. The attribute is read-only.
2735 <tag><label id="rta-krt-metric">int krt_metric/</tag> (Linux)
2736 The kernel metric of the route. When multiple same routes are in a
2737 kernel routing table, the Linux kernel chooses one with lower metric.
2738 Note that preferred way to set kernel metric is to use protocol option
2739 <cf/metric/, unless per-route metric values are needed.
2741 <tag><label id="rta-krt-prefsrc">ip krt_prefsrc/</tag> (Linux)
2742 The preferred source address. Used in source address selection for
2743 outgoing packets. Has to be one of the IP addresses of the router.
2745 <tag><label id="rta-krt-realm">int krt_realm/</tag> (Linux)
2746 The realm of the route. Can be used for traffic classification.
2748 <tag><label id="rta-krt-scope">int krt_scope/</tag> (Linux IPv4)
2749 The scope of the route. Valid values are 0-254, although Linux kernel
2750 may reject some values depending on route type and nexthop. It is
2751 supposed to represent `indirectness' of the route, where nexthops of
2752 routes are resolved through routes with a higher scope, but in current
2753 kernels anything below <it/link/ (253) is treated as <it/global/ (0).
2754 When not present, global scope is implied for all routes except device
2755 routes, where link scope is used by default.
2758 <p>In Linux, there is also a plenty of obscure route attributes mostly focused
2759 on tuning TCP performance of local connections. BIRD supports most of these
2760 attributes, see Linux or iproute2 documentation for their meaning. Attributes
2761 <cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, others have type int.
2762 Supported attributes are:
2764 <cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
2765 <cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
2766 <cf/krt_sstresh/, <cf/krt_lock_sstresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
2767 <cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
2768 <cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
2769 <cf/krt_initcwnd/, <cf/krt_initrwnd/, <cf/krt_quickack/,
2770 <cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
2773 <label id="krt-exam">
2775 <p>A simple configuration can look this way:
2783 <p>Or for a system with two routing tables:
2786 protocol kernel { # Primary routing table
2787 learn; # Learn alien routes from the kernel
2788 persist; # Don't remove routes on bird shutdown
2789 scan time 10; # Scan kernel routing table every 10 seconds
2794 protocol kernel { # Secondary routing table
2806 <label id="ospf-intro">
2808 <p>Open Shortest Path First (OSPF) is a quite complex interior gateway
2809 protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
2810 the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
2811 state (a.k.a. shortest path first) protocol -- each router maintains a database
2812 describing the autonomous system's topology. Each participating router has an
2813 identical copy of the database and all routers run the same algorithm
2814 calculating a shortest path tree with themselves as a root. OSPF chooses the
2815 least cost path as the best path.
2817 <p>In OSPF, the autonomous system can be split to several areas in order to
2818 reduce the amount of resources consumed for exchanging the routing information
2819 and to protect the other areas from incorrect routing data. Topology of the area
2820 is hidden to the rest of the autonomous system.
2822 <p>Another very important feature of OSPF is that it can keep routing information
2823 from other protocols (like Static or BGP) in its link state database as external
2824 routes. Each external route can be tagged by the advertising router, making it
2825 possible to pass additional information between routers on the boundary of the
2828 <p>OSPF quickly detects topological changes in the autonomous system (such as
2829 router interface failures) and calculates new loop-free routes after a short
2830 period of convergence. Only a minimal amount of routing traffic is involved.
2832 <p>Each router participating in OSPF routing periodically sends Hello messages
2833 to all its interfaces. This allows neighbors to be discovered dynamically. Then
2834 the neighbors exchange theirs parts of the link state database and keep it
2835 identical by flooding updates. The flooding process is reliable and ensures that
2836 each router detects all changes.
2838 <sect1>Configuration
2839 <label id="ospf-config">
2841 <p>First, the desired OSPF version can be specified by using <cf/ospf v2/ or
2842 <cf/ospf v3/ as a protocol type. By default, OSPFv2 is used. In the main part of
2843 configuration, there can be multiple definitions of OSPF areas, each with a
2844 different id. These definitions includes many other switches and multiple
2845 definitions of interfaces. Definition of interface may contain many switches and
2846 constant definitions and list of neighbors on nonbroadcast networks.
2849 protocol ospf [v2|v3] <name> {
2850 rfc1583compat <switch>;
2851 instance id <num>;
2852 stub router <switch>;
2854 ecmp <switch> [limit <num>];
2855 merge external <switch>;
2859 summary <switch>;
2860 default nssa <switch>;
2861 default cost <num>;
2862 default cost2 <num>;
2863 translator <switch>;
2864 translator stability <num>;
2868 <prefix> hidden;
2872 <prefix> hidden;
2873 <prefix> tag <num>;
2875 stubnet <prefix>;
2876 stubnet <prefix> {
2877 hidden <switch>;
2878 summary <switch>;
2881 interface <interface pattern> [instance <num>] {
2883 stub <switch>;
2886 retransmit <num>;
2887 priority <num>;
2889 dead count <num>;
2891 secondary <switch>;
2892 rx buffer [normal|large|<num>];
2893 tx length <num>;
2894 type [broadcast|bcast|pointopoint|ptp|
2895 nonbroadcast|nbma|pointomultipoint|ptmp];
2896 link lsa suppression <switch>;
2897 strict nonbroadcast <switch>;
2898 real broadcast <switch>;
2899 ptp netmask <switch>;
2900 check link <switch>;
2902 ecmp weight <num>;
2903 ttl security [<switch>; | tx only]
2904 tx class|dscp <num>;
2905 tx priority <num>;
2906 authentication none|simple|cryptographic;
2907 password "<text>";
2908 password "<text>" {
2910 generate from "<date>";
2911 generate to "<date>";
2912 accept from "<date>";
2913 accept to "<date>";
2914 from "<date>";
2916 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2920 <ip> eligible;
2923 virtual link <id> [instance <num>] {
2925 retransmit <num>;
2927 dead count <num>;
2929 authentication none|simple|cryptographic;
2930 password "<text>";
2931 password "<text>" {
2933 generate from "<date>";
2934 generate to "<date>";
2935 accept from "<date>";
2936 accept to "<date>";
2937 from "<date>";
2939 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2947 <tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
2948 This option controls compatibility of routing table calculation with
2949 <rfc id="1583">. Default value is no.
2951 <tag><label id="ospf-instance-id">instance id <m/num/</tag>
2952 When multiple OSPF protocol instances are active on the same links, they
2953 should use different instance IDs to distinguish their packets. Although
2954 it could be done on per-interface basis, it is often preferred to set
2955 one instance ID to whole OSPF domain/topology (e.g., when multiple
2956 instances are used to represent separate logical topologies on the same
2957 physical network). This option specifies the default instance ID for all
2958 interfaces of the OSPF instance. Note that this option, if used, must
2959 precede interface definitions. Default value is 0.
2961 <tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
2962 This option configures the router to be a stub router, i.e., a router
2963 that participates in the OSPF topology but does not allow transit
2964 traffic. In OSPFv2, this is implemented by advertising maximum metric
2965 for outgoing links. In OSPFv3, the stub router behavior is announced by
2966 clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
2967 Default value is no.
2969 <tag><label id="ospf-tick">tick <M>num</M></tag>
2970 The routing table calculation and clean-up of areas' databases is not
2971 performed when a single link state change arrives. To lower the CPU
2972 utilization, it's processed later at periodical intervals of <m/num/
2973 seconds. The default value is 1.
2975 <tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
2976 This option specifies whether OSPF is allowed to generate ECMP
2977 (equal-cost multipath) routes. Such routes are used when there are
2978 several directions to the destination, each with the same (computed)
2979 cost. This option also allows to specify a limit on maximum number of
2980 nexthops in one route. By default, ECMP is disabled. If enabled,
2981 default value of the limit is 16.
2983 <tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
2984 This option specifies whether OSPF should merge external routes from
2985 different routers/LSAs for the same destination. When enabled together
2986 with <cf/ecmp/, equal-cost external routes will be combined to multipath
2987 routes in the same way as regular routes. When disabled, external routes
2988 from different LSAs are treated as separate even if they represents the
2989 same destination. Default value is no.
2991 <tag><label id="ospf-area">area <M>id</M></tag>
2992 This defines an OSPF area with given area ID (an integer or an IPv4
2993 address, similarly to a router ID). The most important area is the
2994 backbone (ID 0) to which every other area must be connected.
2996 <tag><label id="ospf-stub">stub</tag>
2997 This option configures the area to be a stub area. External routes are
2998 not flooded into stub areas. Also summary LSAs can be limited in stub
2999 areas (see option <cf/summary/). By default, the area is not a stub
3002 <tag><label id="ospf-nssa">nssa</tag>
3003 This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
3004 is a variant of a stub area which allows a limited way of external route
3005 propagation. Global external routes are not propagated into a NSSA, but
3006 an external route can be imported into NSSA as a (area-wide) NSSA-LSA
3007 (and possibly translated and/or aggregated on area boundary). By
3008 default, the area is not NSSA.
3010 <tag><label id="ospf-summary">summary <M>switch</M></tag>
3011 This option controls propagation of summary LSAs into stub or NSSA
3012 areas. If enabled, summary LSAs are propagated as usual, otherwise just
3013 the default summary route (0.0.0.0/0) is propagated (this is sometimes
3014 called totally stubby area). If a stub area has more area boundary
3015 routers, propagating summary LSAs could lead to more efficient routing
3016 at the cost of larger link state database. Default value is no.
3018 <tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
3019 When <cf/summary/ option is enabled, default summary route is no longer
3020 propagated to the NSSA. In that case, this option allows to originate
3021 default route as NSSA-LSA to the NSSA. Default value is no.
3023 <tag><label id="ospf-default-cost">default cost <M>num</M></tag>
3024 This option controls the cost of a default route propagated to stub and
3025 NSSA areas. Default value is 1000.
3027 <tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
3028 When a default route is originated as NSSA-LSA, its cost can use either
3029 type 1 or type 2 metric. This option allows to specify the cost of a
3030 default route in type 2 metric. By default, type 1 metric (option
3031 <cf/default cost/) is used.
3033 <tag><label id="ospf-translator">translator <M>switch</M></tag>
3034 This option controls translation of NSSA-LSAs into external LSAs. By
3035 default, one translator per NSSA is automatically elected from area
3036 boundary routers. If enabled, this area boundary router would
3037 unconditionally translate all NSSA-LSAs regardless of translator
3038 election. Default value is no.
3040 <tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
3041 This option controls the translator stability interval (in seconds).
3042 When the new translator is elected, the old one keeps translating until
3043 the interval is over. Default value is 40.
3045 <tag><label id="ospf-networks">networks { <m/set/ }</tag>
3046 Definition of area IP ranges. This is used in summary LSA origination.
3047 Hidden networks are not propagated into other areas.
3049 <tag><label id="ospf-external">external { <m/set/ }</tag>
3050 Definition of external area IP ranges for NSSAs. This is used for
3051 NSSA-LSA translation. Hidden networks are not translated into external
3052 LSAs. Networks can have configured route tag.
3054 <tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
3055 Stub networks are networks that are not transit networks between OSPF
3056 routers. They are also propagated through an OSPF area as a part of a
3057 link state database. By default, BIRD generates a stub network record
3058 for each primary network address on each OSPF interface that does not
3059 have any OSPF neighbors, and also for each non-primary network address
3060 on each OSPF interface. This option allows to alter a set of stub
3061 networks propagated by this router.
3063 Each instance of this option adds a stub network with given network
3064 prefix to the set of propagated stub network, unless option <cf/hidden/
3065 is used. It also suppresses default stub networks for given network
3066 prefix. When option <cf/summary/ is used, also default stub networks
3067 that are subnetworks of given stub network are suppressed. This might be
3068 used, for example, to aggregate generated stub networks.
3070 <tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
3071 Defines that the specified interfaces belong to the area being defined.
3072 See <ref id="proto-iface" name="interface"> common option for detailed
3073 description. In OSPFv2, extended interface clauses are used, because
3074 each network prefix is handled as a separate virtual interface.
3076 You can specify alternative instance ID for the interface definition,
3077 therefore it is possible to have several instances of that interface
3078 with different options or even in different areas. For OSPFv2, instance
3079 ID support is an extension (<rfc id="6549">) and is supposed to be set
3080 per-protocol. For OSPFv3, it is an integral feature.
3082 <tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
3083 Virtual link to router with the router id. Virtual link acts as a
3084 point-to-point interface belonging to backbone. The actual area is used
3085 as a transport area. This item cannot be in the backbone. Like with
3086 <cf/interface/ option, you could also use several virtual links to one
3087 destination with different instance IDs.
3089 <tag><label id="ospf-cost">cost <M>num</M></tag>
3090 Specifies output cost (metric) of an interface. Default value is 10.
3092 <tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
3093 If set to interface it does not listen to any packet and does not send
3094 any hello. Default value is no.
3096 <tag><label id="ospf-hello">hello <M>num</M></tag>
3097 Specifies interval in seconds between sending of Hello messages. Beware,
3098 all routers on the same network need to have the same hello interval.
3099 Default value is 10.
3101 <tag><label id="ospf-poll">poll <M>num</M></tag>
3102 Specifies interval in seconds between sending of Hello messages for some
3103 neighbors on NBMA network. Default value is 20.
3105 <tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
3106 Specifies interval in seconds between retransmissions of unacknowledged
3107 updates. Default value is 5.
3109 <tag><label id="ospf-priority">priority <M>num</M></tag>
3110 On every multiple access network (e.g., the Ethernet) Designated Router
3111 and Backup Designated router are elected. These routers have some special
3112 functions in the flooding process. Higher priority increases preferences
3113 in this election. Routers with priority 0 are not eligible. Default
3116 <tag><label id="ospf-wait">wait <M>num</M></tag>
3117 After start, router waits for the specified number of seconds between
3118 starting election and building adjacency. Default value is 4*<m/hello/.
3120 <tag><label id="ospf-dead-count">dead count <M>num</M></tag>
3121 When the router does not receive any messages from a neighbor in
3122 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
3124 <tag><label id="ospf-dead">dead <M>num</M></tag>
3125 When the router does not receive any messages from a neighbor in
3126 <m/dead/ seconds, it will consider the neighbor down. If both directives
3127 <cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
3129 <tag><label id="ospf-secondary">secondary <M>switch</M></tag>
3130 On BSD systems, older versions of BIRD supported OSPFv2 only for the
3131 primary IP address of an interface, other IP ranges on the interface
3132 were handled as stub networks. Since v1.4.1, regular operation on
3133 secondary IP addresses is supported, but disabled by default for
3134 compatibility. This option allows to enable it. The option is a
3135 transitional measure, will be removed in the next major release as the
3136 behavior will be changed. On Linux systems, the option is irrelevant, as
3137 operation on non-primary addresses is already the regular behavior.
3139 <tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
3140 This option allows to specify the size of buffers used for packet
3141 processing. The buffer size should be bigger than maximal size of any
3142 packets. By default, buffers are dynamically resized as needed, but a
3143 fixed value could be specified. Value <cf/large/ means maximal allowed
3144 packet size - 65535.
3146 <tag><label id="ospf-tx-length">tx length <M>num</M></tag>
3147 Transmitted OSPF messages that contain large amount of information are
3148 segmented to separate OSPF packets to avoid IP fragmentation. This
3149 option specifies the soft ceiling for the length of generated OSPF
3150 packets. Default value is the MTU of the network interface. Note that
3151 larger OSPF packets may still be generated if underlying OSPF messages
3152 cannot be splitted (e.g. when one large LSA is propagated).
3154 <tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
3155 BIRD detects a type of a connected network automatically, but sometimes
3156 it's convenient to force use of a different type manually. On broadcast
3157 networks (like ethernet), flooding and Hello messages are sent using
3158 multicasts (a single packet for all the neighbors). A designated router
3159 is elected and it is responsible for synchronizing the link-state
3160 databases and originating network LSAs. This network type cannot be used
3161 on physically NBMA networks and on unnumbered networks (networks without
3164 <tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
3165 Point-to-point networks connect just 2 routers together. No election is
3166 performed and no network LSA is originated, which makes it simpler and
3167 faster to establish. This network type is useful not only for physically
3168 PtP ifaces (like PPP or tunnels), but also for broadcast networks used
3169 as PtP links. This network type cannot be used on physically NBMA
3172 <tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
3173 On NBMA networks, the packets are sent to each neighbor separately
3174 because of lack of multicast capabilities. Like on broadcast networks,
3175 a designated router is elected, which plays a central role in propagation
3176 of LSAs. This network type cannot be used on unnumbered networks.
3178 <tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
3179 This is another network type designed to handle NBMA networks. In this
3180 case the NBMA network is treated as a collection of PtP links. This is
3181 useful if not every pair of routers on the NBMA network has direct
3182 communication, or if the NBMA network is used as an (possibly
3183 unnumbered) PtP link.
3185 <tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
3186 In OSPFv3, link LSAs are generated for each link, announcing link-local
3187 IPv6 address of the router to its local neighbors. These are useless on
3188 PtP or PtMP networks and this option allows to suppress the link LSA
3189 origination for such interfaces. The option is ignored on other than PtP
3190 or PtMP interfaces. Default value is no.
3192 <tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
3193 If set, don't send hello to any undefined neighbor. This switch is
3194 ignored on other than NBMA or PtMP interfaces. Default value is no.
3196 <tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
3197 In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
3198 packets are sent as IP multicast packets. This option changes the
3199 behavior to using old-fashioned IP broadcast packets. This may be useful
3200 as a workaround if IP multicast for some reason does not work or does
3201 not work reliably. This is a non-standard option and probably is not
3202 interoperable with other OSPF implementations. Default value is no.
3204 <tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
3205 In <cf/type ptp/ network configurations, OSPFv2 implementations should
3206 ignore received netmask field in hello packets and should send hello
3207 packets with zero netmask field on unnumbered PtP links. But some OSPFv2
3208 implementations perform netmask checking even for PtP links. This option
3209 specifies whether real netmask will be used in hello packets on <cf/type
3210 ptp/ interfaces. You should ignore this option unless you meet some
3211 compatibility problems related to this issue. Default value is no for
3212 unnumbered PtP links, yes otherwise.
3214 <tag><label id="ospf-check-link">check link <M>switch</M></tag>
3215 If set, a hardware link state (reported by OS) is taken into consideration.
3216 When a link disappears (e.g. an ethernet cable is unplugged), neighbors
3217 are immediately considered unreachable and only the address of the iface
3218 (instead of whole network prefix) is propagated. It is possible that
3219 some hardware drivers or platforms do not implement this feature.
3220 Default value is no.
3222 <tag><label id="ospf-bfd">bfd <M>switch</M></tag>
3223 OSPF could use BFD protocol as an advisory mechanism for neighbor
3224 liveness and failure detection. If enabled, BIRD setups a BFD session
3225 for each OSPF neighbor and tracks its liveness by it. This has an
3226 advantage of an order of magnitude lower detection times in case of
3227 failure. Note that BFD protocol also has to be configured, see
3228 <ref id="bfd" name="BFD"> section for details. Default value is no.
3230 <tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3231 TTL security is a feature that protects routing protocols from remote
3232 spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3233 destined to neighbors. Because TTL is decremented when packets are
3234 forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3235 locations. Note that this option would interfere with OSPF virtual
3238 If this option is enabled, the router will send OSPF packets with TTL
3239 255 and drop received packets with TTL less than 255. If this option si
3240 set to <cf/tx only/, TTL 255 is used for sent packets, but is not
3241 checked for received packets. Default value is no.
3243 <tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
3244 These options specify the ToS/DiffServ/Traffic class/Priority of the
3245 outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
3246 option for detailed description.
3248 <tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
3249 When ECMP (multipath) routes are allowed, this value specifies a
3250 relative weight used for nexthops going through the iface. Allowed
3251 values are 1-256. Default value is 1.
3253 <tag><label id="ospf-auth-none">authentication none</tag>
3254 No passwords are sent in OSPF packets. This is the default value.
3256 <tag><label id="ospf-auth-simple">authentication simple</tag>
3257 Every packet carries 8 bytes of password. Received packets lacking this
3258 password are ignored. This authentication mechanism is very weak.
3259 This option is not available in OSPFv3.
3261 <tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
3262 An authentication code is appended to every packet. The specific
3263 cryptographic algorithm is selected by option <cf/algorithm/ for each
3264 key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
3265 and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
3266 network, so this mechanism is quite secure. Packets can still be read by
3269 <tag><label id="ospf-pass">password "<M>text</M>"</tag>
3270 Specifies a password used for authentication. See
3271 <ref id="proto-pass" name="password"> common option for detailed
3274 <tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
3275 A set of neighbors to which Hello messages on NBMA or PtMP networks are
3276 to be sent. For NBMA networks, some of them could be marked as eligible.
3277 In OSPFv3, link-local addresses should be used, using global ones is
3278 possible, but it is nonstandard and might be problematic. And definitely,
3279 link-local and global addresses should not be mixed.
3283 <label id="ospf-attr">
3285 <p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
3287 <p>Metric is ranging from 1 to infinity (65535). External routes use
3288 <cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
3289 with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
3290 <cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
3291 <cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
3292 2/ is stored in attribute <cf/ospf_metric2/. If you specify both metrics only
3295 <p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
3296 integer which is used when exporting routes to other protocols; otherwise, it
3297 doesn't affect routing inside the OSPF domain at all. The fourth attribute
3298 <cf/ospf_router_id/ is a router ID of the router advertising that route /
3299 network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
3303 <label id="ospf-exam">
3306 protocol ospf MyOSPF {
3310 if source = RTS_BGP then {
3322 authentication simple;
3327 authentication cryptographic;
3330 generate to "22-04-2003 11:00:06";
3331 accept from "17-01-2001 12:01:05";
3332 algorithm hmac sha384;
3336 generate to "22-07-2005 17:03:21";
3337 accept from "22-02-2001 11:34:06";
3338 algorithm hmac sha512;
3351 172.16.2.0/24 hidden;
3353 interface "-arc0" , "arc*" {
3355 authentication none;
3356 strict nonbroadcast yes;
3361 192.168.120.1 eligible;
3375 <label id="pipe-intro">
3377 <p>The Pipe protocol serves as a link between two routing tables, allowing
3378 routes to be passed from a table declared as primary (i.e., the one the pipe is
3379 connected to using the <cf/table/ configuration keyword) to the secondary one
3380 (declared using <cf/peer table/) and vice versa, depending on what's allowed by
3381 the filters. Export filters control export of routes from the primary table to
3382 the secondary one, import filters control the opposite direction.
3384 <p>The Pipe protocol may work in the transparent mode mode or in the opaque
3385 mode. In the transparent mode, the Pipe protocol retransmits all routes from
3386 one table to the other table, retaining their original source and attributes.
3387 If import and export filters are set to accept, then both tables would have
3388 the same content. The transparent mode is the default mode.
3390 <p>In the opaque mode, the Pipe protocol retransmits optimal route from one
3391 table to the other table in a similar way like other protocols send and receive
3392 routes. Retransmitted route will have the source set to the Pipe protocol, which
3393 may limit access to protocol specific route attributes. This mode is mainly for
3394 compatibility, it is not suggested for new configs. The mode can be changed by
3397 <p>The primary use of multiple routing tables and the Pipe protocol is for
3398 policy routing, where handling of a single packet doesn't depend only on its
3399 destination address, but also on its source address, source interface, protocol
3400 type and other similar parameters. In many systems (Linux being a good example),
3401 the kernel allows to enforce routing policies by defining routing rules which
3402 choose one of several routing tables to be used for a packet according to its
3403 parameters. Setting of these rules is outside the scope of BIRD's work (on
3404 Linux, you can use the <tt/ip/ command), but you can create several routing
3405 tables in BIRD, connect them to the kernel ones, use filters to control which
3406 routes appear in which tables and also you can employ the Pipe protocol for
3407 exporting a selected subset of one table to another one.
3409 <sect1>Configuration
3410 <label id="pipe-config">
3413 <tag><label id="pipe-peer-table">peer table <m/table/</tag>
3414 Defines secondary routing table to connect to. The primary one is
3415 selected by the <cf/table/ keyword.
3417 <tag><label id="pipe-mode">mode opaque|transparent</tag>
3418 Specifies the mode for the pipe to work in. Default is transparent.
3422 <label id="pipe-attr">
3424 <p>The Pipe protocol doesn't define any route attributes.
3427 <label id="pipe-exam">
3429 <p>Let's consider a router which serves as a boundary router of two different
3430 autonomous systems, each of them connected to a subset of interfaces of the
3431 router, having its own exterior connectivity and wishing to use the other AS as
3432 a backup connectivity in case of outage of its own exterior line.
3434 <p>Probably the simplest solution to this situation is to use two routing tables
3435 (we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
3436 packets having arrived from interfaces belonging to the first AS will be routed
3437 according to <cf/as1/ and similarly for the second AS. Thus we have split our
3438 router to two logical routers, each one acting on its own routing table, having
3439 its own routing protocols on its own interfaces. In order to use the other AS's
3440 routes for backup purposes, we can pass the routes between the tables through a
3441 Pipe protocol while decreasing their preferences and correcting their BGP paths
3442 to reflect the AS boundary crossing.
3445 table as1; # Define the tables
3448 protocol kernel kern1 { # Synchronize them with the kernel
3453 protocol kernel kern2 {
3458 protocol bgp bgp1 { # The outside connections
3461 neighbor 192.168.0.1 as 1001;
3469 neighbor 10.0.0.1 as 1002;
3474 protocol pipe { # The Pipe
3478 if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks
3479 if preference>10 then preference = preference-10;
3480 if source=RTS_BGP then bgp_path.prepend(1);
3486 if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks
3487 if preference>10 then preference = preference-10;
3488 if source=RTS_BGP then bgp_path.prepend(2);
3501 <label id="radv-intro">
3503 <p>The RAdv protocol is an implementation of Router Advertisements, which are
3504 used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
3505 time intervals or as an answer to a request) advertisement packets to connected
3506 networks. These packets contain basic information about a local network (e.g. a
3507 list of network prefixes), which allows network hosts to autoconfigure network
3508 addresses and choose a default route. BIRD implements router behavior as defined
3509 in <rfc id="4861"> and also the DNS extensions from <rfc id="6106">.
3511 <sect1>Configuration
3512 <label id="radv-config">
3514 <p>There are several classes of definitions in RAdv configuration -- interface
3515 definitions, prefix definitions and DNS definitions:
3518 <tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3519 Interface definitions specify a set of interfaces on which the
3520 protocol is activated and contain interface specific options.
3521 See <ref id="proto-iface" name="interface"> common options for
3522 detailed description.
3524 <tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
3525 Prefix definitions allow to modify a list of advertised prefixes. By
3526 default, the advertised prefixes are the same as the network prefixes
3527 assigned to the interface. For each network prefix, the matching prefix
3528 definition is found and its options are used. If no matching prefix
3529 definition is found, the prefix is used with default options.
3531 Prefix definitions can be either global or interface-specific. The
3532 second ones are part of interface options. The prefix definition
3533 matching is done in the first-match style, when interface-specific
3534 definitions are processed before global definitions. As expected, the
3535 prefix definition is matching if the network prefix is a subnet of the
3536 prefix in prefix definition.
3538 <tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
3539 RDNSS definitions allow to specify a list of advertised recursive DNS
3540 servers together with their options. As options are seldom necessary,
3541 there is also a short variant <cf>rdnss <m/address/</cf> that just
3542 specifies one DNS server. Multiple definitions are cumulative. RDNSS
3543 definitions may also be interface-specific when used inside interface
3544 options. By default, interface uses both global and interface-specific
3545 options, but that can be changed by <cf/rdnss local/ option.
3547 <tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
3548 DNSSL definitions allow to specify a list of advertised DNS search
3549 domains together with their options. Like <cf/rdnss/ above, multiple
3550 definitions are cumulative, they can be used also as interface-specific
3551 options and there is a short variant <cf>dnssl <m/domain/</cf> that just
3552 specifies one DNS search domain.
3554 <tag><label id="radv-trigger">trigger <m/prefix/</tag>
3555 RAdv protocol could be configured to change its behavior based on
3556 availability of routes. When this option is used, the protocol waits in
3557 suppressed state until a <it/trigger route/ (for the specified network)
3558 is exported to the protocol, the protocol also returnsd to suppressed
3559 state if the <it/trigger route/ disappears. Note that route export
3560 depends on specified export filter, as usual. This option could be used,
3561 e.g., for handling failover in multihoming scenarios.
3563 During suppressed state, router advertisements are generated, but with
3564 some fields zeroed. Exact behavior depends on which fields are zeroed,
3565 this can be configured by <cf/sensitive/ option for appropriate
3566 fields. By default, just <cf/default lifetime/ (also called <cf/router
3567 lifetime/) is zeroed, which means hosts cannot use the router as a
3568 default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
3569 also be configured as <cf/sensitive/ for a prefix, which would cause
3570 autoconfigured IPs to be deprecated or even removed.
3573 <p>Interface specific options:
3576 <tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
3577 Unsolicited router advertisements are sent in irregular time intervals.
3578 This option specifies the maximum length of these intervals, in seconds.
3579 Valid values are 4-1800. Default: 600
3581 <tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
3582 This option specifies the minimum length of that intervals, in seconds.
3583 Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
3584 about 1/3 * <cf/max ra interval/.
3586 <tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
3587 The minimum delay between two consecutive router advertisements, in
3590 <tag><label id="radv-iface-managed">managed <m/switch/</tag>
3591 This option specifies whether hosts should use DHCPv6 for IP address
3592 configuration. Default: no
3594 <tag><label id="radv-iface-other-config">other config <m/switch/</tag>
3595 This option specifies whether hosts should use DHCPv6 to receive other
3596 configuration information. Default: no
3598 <tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
3599 This option specifies which value of MTU should be used by hosts. 0
3600 means unspecified. Default: 0
3602 <tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
3603 This option specifies the time (in milliseconds) how long hosts should
3604 assume a neighbor is reachable (from the last confirmation). Maximum is
3605 3600000, 0 means unspecified. Default 0.
3607 <tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
3608 This option specifies the time (in milliseconds) how long hosts should
3609 wait before retransmitting Neighbor Solicitation messages. 0 means
3610 unspecified. Default 0.
3612 <tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
3613 This option specifies which value of Hop Limit should be used by
3614 hosts. Valid values are 0-255, 0 means unspecified. Default: 64
3616 <tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
3617 This option specifies the time (in seconds) how long (after the receipt
3618 of RA) hosts may use the router as a default router. 0 means do not use
3619 as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3620 Default: 3 * <cf/max ra interval/, <cf/sensitive/ yes.
3622 <tag><label id="radv-iface-default-preference-low">default preference low|medium|high</tag>
3623 This option specifies the Default Router Preference value to advertise
3624 to hosts. Default: medium.
3626 <tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
3627 Use only local (interface-specific) RDNSS definitions for this
3628 interface. Otherwise, both global and local definitions are used. Could
3629 also be used to disable RDNSS for given interface if no local definitons
3630 are specified. Default: no.
3632 <tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
3633 Use only local DNSSL definitions for this interface. See <cf/rdnss local/
3634 option above. Default: no.
3638 <p>Prefix specific options
3641 <tag><label id="radv-prefix-skip">skip <m/switch/</tag>
3642 This option allows to specify that given prefix should not be
3643 advertised. This is useful for making exceptions from a default policy
3644 of advertising all prefixes. Note that for withdrawing an already
3645 advertised prefix it is more useful to advertise it with zero valid
3646 lifetime. Default: no
3648 <tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
3649 This option specifies whether hosts may use the advertised prefix for
3650 onlink determination. Default: yes
3652 <tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
3653 This option specifies whether hosts may use the advertised prefix for
3654 stateless autoconfiguration. Default: yes
3656 <tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
3657 This option specifies the time (in seconds) how long (after the
3658 receipt of RA) the prefix information is valid, i.e., autoconfigured
3659 IP addresses can be assigned and hosts with that IP addresses are
3660 considered directly reachable. 0 means the prefix is no longer
3661 valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3662 Default: 86400 (1 day), <cf/sensitive/ no.
3664 <tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
3665 This option specifies the time (in seconds) how long (after the
3666 receipt of RA) IP addresses generated from the prefix using stateless
3667 autoconfiguration remain preferred. For <cf/sensitive/ option,
3668 see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
3673 <p>RDNSS specific options:
3676 <tag><label id="radv-rdnss-ns">ns <m/address/</tag>
3677 This option specifies one recursive DNS server. Can be used multiple
3678 times for multiple servers. It is mandatory to have at least one
3679 <cf/ns/ option in <cf/rdnss/ definition.
3681 <tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
3682 This option specifies the time how long the RDNSS information may be
3683 used by clients after the receipt of RA. It is expressed either in
3684 seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
3685 interval/. Note that RDNSS information is also invalidated when
3686 <cf/default lifetime/ expires. 0 means these addresses are no longer
3687 valid DNS servers. Default: 3 * <cf/max ra interval/.
3691 <p>DNSSL specific options:
3694 <tag><label id="radv-dnssl-domain">domain <m/address/</tag>
3695 This option specifies one DNS search domain. Can be used multiple times
3696 for multiple domains. It is mandatory to have at least one <cf/domain/
3697 option in <cf/dnssl/ definition.
3699 <tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
3700 This option specifies the time how long the DNSSL information may be
3701 used by clients after the receipt of RA. Details are the same as for
3702 RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
3707 <label id="radv-exam">
3712 max ra interval 5; # Fast failover with more routers
3713 managed yes; # Using DHCPv6 on eth2
3715 autonomous off; # So do not autoconfigure any IP
3719 interface "eth*"; # No need for any other options
3721 prefix 2001:0DB8:1234::/48 {
3722 preferred lifetime 0; # Deprecated address range
3725 prefix 2001:0DB8:2000::/48 {
3726 autonomous off; # Do not autoconfigure
3729 rdnss 2001:0DB8:1234::10; # Short form of RDNSS
3733 ns 2001:0DB8:1234::11;
3734 ns 2001:0DB8:1234::12;
3750 <label id="rip-intro">
3752 <p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
3753 where each router broadcasts (to all its neighbors) distances to all networks it
3754 can reach. When a router hears distance to another network, it increments it and
3755 broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
3756 network goes unreachable, routers keep telling each other that its distance is
3757 the original distance plus 1 (actually, plus interface metric, which is usually
3758 one). After some time, the distance reaches infinity (that's 15 in RIP) and all
3759 routers know that network is unreachable. RIP tries to minimize situations where
3760 counting to infinity is necessary, because it is slow. Due to infinity being 16,
3761 you can't use RIP on networks where maximal distance is higher than 15
3764 <p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
3765 id="2080">), and RIP cryptographic authentication (<rfc id="4822">).
3767 <p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
3768 convergence, big network load and inability to handle larger networks makes it
3769 pretty much obsolete. It is still usable on very small networks.
3771 <sect1>Configuration
3772 <label id="rip-config">
3774 <p>RIP configuration consists mainly of common protocol options and interface
3775 definitions, most RIP options are interface specific. RIPng (RIP for IPv6)
3776 protocol instance can be configured by using <cf/rip ng/ instead of just
3777 <cf/rip/ as a protocol type.
3780 protocol rip [ng] [<name>] {
3781 infinity <number>;
3782 ecmp <switch> [limit <number>];
3783 interface <interface pattern> {
3784 metric <number>;
3785 mode multicast|broadcast;
3786 passive <switch>;
3788 port <number>;
3790 split horizon <switch>;
3791 poison reverse <switch>;
3792 check zero <switch>;
3793 update time <number>;
3794 timeout time <number>;
3795 garbage time <number>;
3796 ecmp weight <number>;
3797 ttl security <switch>; | tx only;
3798 tx class|dscp <number>;
3799 tx priority <number>;
3800 rx buffer <number>;
3801 tx length <number>;
3802 check link <switch>;
3803 authentication none|plaintext|cryptographic;
3804 password "<text>";
3805 password "<text>" {
3807 generate from "<date>";
3808 generate to "<date>";
3809 accept from "<date>";
3810 accept to "<date>";
3811 from "<date>";
3813 algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3820 <tag><label id="rip-infinity">infinity <M>number</M></tag>
3821 Selects the distance of infinity. Bigger values will make
3822 protocol convergence even slower. The default value is 16.
3824 <tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
3825 This option specifies whether RIP is allowed to generate ECMP
3826 (equal-cost multipath) routes. Such routes are used when there are
3827 several directions to the destination, each with the same (computed)
3828 cost. This option also allows to specify a limit on maximum number of
3829 nexthops in one route. By default, ECMP is disabled. If enabled,
3830 default value of the limit is 16.
3832 <tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3833 Interface definitions specify a set of interfaces on which the
3834 protocol is activated and contain interface specific options.
3835 See <ref id="proto-iface" name="interface"> common options for
3836 detailed description.
3839 <p>Interface specific options:
3842 <tag><label id="rip-iface-metric">metric <m/num/</tag>
3843 This option specifies the metric of the interface. When a route is
3844 received from the interface, its metric is increased by this value
3845 before further processing. Valid values are 1-255, but values higher
3846 than infinity has no further meaning. Default: 1.
3848 <tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
3849 This option selects the mode for RIP to use on the interface. The
3850 default is multicast mode for RIPv2 and broadcast mode for RIPv1.
3851 RIPng always uses the multicast mode.
3853 <tag><label id="rip-iface-passive">passive <m/switch/</tag>
3854 Passive interfaces receive routing updates but do not transmit any
3855 messages. Default: no.
3857 <tag><label id="rip-iface-address">address <m/ip/</tag>
3858 This option specifies a destination address used for multicast or
3859 broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
3860 (ff02::9) multicast address, or an appropriate broadcast address in the
3863 <tag><label id="rip-iface-port">port <m/number/</tag>
3864 This option selects an UDP port to operate on, the default is the
3865 official RIP (520) or RIPng (521) port.
3867 <tag><label id="rip-iface-version">version 1|2</tag>
3868 This option selects the version of RIP used on the interface. For RIPv1,
3869 automatic subnet aggregation is not implemented, only classful network
3870 routes and host routes are propagated. Note that BIRD allows RIPv1 to be
3871 configured with features that are defined for RIPv2 only, like
3872 authentication or using multicast sockets. The default is RIPv2 for IPv4
3873 RIP, the option is not supported for RIPng, as no further versions are
3876 <tag><label id="rip-iface-version-only">version only <m/switch/</tag>
3877 Regardless of RIP version configured for the interface, BIRD accepts
3878 incoming packets of any RIP version. This option restrict accepted
3879 packets to the configured version. Default: no.
3881 <tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
3882 Split horizon is a scheme for preventing routing loops. When split
3883 horizon is active, routes are not regularly propagated back to the
3884 interface from which they were received. They are either not propagated
3885 back at all (plain split horizon) or propagated back with an infinity
3886 metric (split horizon with poisoned reverse). Therefore, other routers
3887 on the interface will not consider the router as a part of an
3888 independent path to the destination of the route. Default: yes.
3890 <tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
3891 When split horizon is active, this option specifies whether the poisoned
3892 reverse variant (propagating routes back with an infinity metric) is
3893 used. The poisoned reverse has some advantages in faster convergence,
3894 but uses more network traffic. Default: yes.
3896 <tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
3897 Received RIPv1 packets with non-zero values in reserved fields should
3898 be discarded. This option specifies whether the check is performed or
3899 such packets are just processed as usual. Default: yes.
3901 <tag><label id="rip-iface-update-time">update time <m/number/</tag>
3902 Specifies the number of seconds between periodic updates. A lower number
3903 will mean faster convergence but bigger network load. Default: 30.
3905 <tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
3906 Specifies the time interval (in seconds) between the last received route
3907 announcement and the route expiration. After that, the network is
3908 considered unreachable, but still is propagated with infinity distance.
3911 <tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
3912 Specifies the time interval (in seconds) between the route expiration
3913 and the removal of the unreachable network entry. The garbage interval,
3914 when a route with infinity metric is propagated, is used for both
3915 internal (after expiration) and external (after withdrawal) routes.
3918 <tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
3919 When ECMP (multipath) routes are allowed, this value specifies a
3920 relative weight used for nexthops going through the iface. Valid
3921 values are 1-256. Default value is 1.
3923 <tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
3924 Selects authentication method to be used. <cf/none/ means that packets
3925 are not authenticated at all, <cf/plaintext/ means that a plaintext
3926 password is embedded into each packet, and <cf/cryptographic/ means that
3927 packets are authenticated using some cryptographic hash function
3928 selected by option <cf/algorithm/ for each key. The default
3929 cryptographic algorithm for RIP keys is Keyed-MD5. If you set
3930 authentication to not-none, it is a good idea to add <cf>password</cf>
3931 section. Default: none.
3933 <tag><label id="rip-iface-pass">password "<m/text/"</tag>
3934 Specifies a password used for authentication. See <ref id="proto-pass"
3935 name="password"> common option for detailed description.
3937 <tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3938 TTL security is a feature that protects routing protocols from remote
3939 spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3940 destined to neighbors. Because TTL is decremented when packets are
3941 forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3944 If this option is enabled, the router will send RIP packets with TTL 255
3945 and drop received packets with TTL less than 255. If this option si set
3946 to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
3947 for received packets. Such setting does not offer protection, but offers
3948 compatibility with neighbors regardless of whether they use ttl
3951 For RIPng, TTL security is a standard behavior (required by <rfc
3952 id="2080">) and therefore default value is yes. For IPv4 RIP, default
3955 <tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
3956 These options specify the ToS/DiffServ/Traffic class/Priority of the
3957 outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
3958 option for detailed description.
3960 <tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
3961 This option specifies the size of buffers used for packet processing.
3962 The buffer size should be bigger than maximal size of received packets.
3963 The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
3965 <tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
3966 This option specifies the maximum length of generated RIP packets. To
3967 avoid IP fragmentation, it should not exceed the interface MTU value.
3968 The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
3970 <tag><label id="rip-iface-check-link">check link <m/switch/</tag>
3971 If set, the hardware link state (as reported by OS) is taken into
3972 consideration. When the link disappears (e.g. an ethernet cable is
3973 unplugged), neighbors are immediately considered unreachable and all
3974 routes received from them are withdrawn. It is possible that some
3975 hardware drivers or platforms do not implement this feature.
3980 <label id="rip-attr">
3982 <p>RIP defines two route attributes:
3985 <tag>int <cf/rip_metric/</tag>
3986 RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
3987 from different RIP instances are available and all of them have the same
3988 preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
3989 non-RIP route is exported to RIP, the default metric is 1.
3991 <tag><label id="rta-rip-tag">int rip_tag/</tag>
3992 RIP route tag: a 16-bit number which can be used to carry additional
3993 information with the route (for example, an originating AS number in
3994 case of external routes). When a non-RIP route is exported to RIP, the
3999 <label id="rip-exam">
4011 authentication cryptographic;
4012 password "secret" { algorithm hmac sha256; };
4021 <p>The Resource Public Key Infrastructure (RPKI) is mechanism for origin
4022 validation of BGP routes (RFC 6480). BIRD supports only so-called RPKI-based
4023 origin validation. There is implemented RPKI to Router (RPKI-RTR) protocol (RFC
4024 6810). It uses some of the RPKI data to allow a router to verify that the
4025 autonomous system announcing an IP address prefix is in fact authorized to do
4026 so. This is not crypto checked so can be violated. But it should prevent the
4027 vast majority of accidental hijackings on the Internet today, e.g. the famous
4028 Pakastani accidental announcement of YouTube's address space.
4030 <p>The RPKI-RTR protocol receives and maintains a set of ROAs from a cache
4031 server (also called validator). You can validate routes (RFC 6483) using
4032 function <cf/roa_check()/ in filter and set it as import filter at the BGP
4033 protocol. BIRD should re-validate all of affected routes after RPKI update by
4034 RFC 6811, but we don't support it yet! You can use a BIRD's client command
4035 <cf>reload in <m/bgp_protocol_name/</cf> for manual call of revalidation of all
4038 <sect1>Supported transports
4040 <item>Unprotected transport over TCP uses a port 323. The cache server
4041 and BIRD router should be on the same trusted and controlled network
4042 for security reasons.
4043 <item>SSHv2 encrypted transport connection uses the normal SSH port
4047 <sect1>Configuration
4049 <p>We currently support just one cache server per protocol. However you can
4050 define more RPKI protocols generally.
4053 protocol rpki [<name>] {
4054 roa4 { table <tab>; };
4055 roa6 { table <tab>; };
4056 remote <ip> | "<domain>" [port <num>];
4058 refresh [keep] <num>;
4059 retry [keep] <num>;
4060 expire [keep] <num>;
4063 bird private key "</path/to/id_rsa>";
4064 remote public key "</path/to/known_host>";
4065 user "<name>";
4070 <p>Alse note that you have to specify ROA table into which will be imported
4071 routes from a cache server. If you want to import only IPv4 prefixes you have
4072 to specify only roa4 table. Similarly with IPv6 prefixes only. If you want to
4073 fetch both IPv4 and even IPv6 ROAs you have to specify both types of ROA
4076 <sect2>RPKI protocol options
4079 <tag>remote <m/ip/ | "<m/hostname/" [port <m/num/]</tag> Specifies
4080 a destination address of the cache server. Can be specified by an IP
4081 address or by full domain name string. Only one cache can be specified
4082 per protocol. This option is required.
4084 <tag>port <m/num/</tag> Specifies the port number. The default port
4085 number is 323 for transport without any encryption and 22 for transport
4086 with SSH encryption.
4088 <tag>refresh [keep] <m/num/</tag> Time period in seconds. Tells how
4089 long to wait before next attempting to poll the cache using a Serial
4090 Query or a Reset Query packet. Must be lower than 86400 seconds (one
4091 day). Too low value can caused a false positive detection of
4092 network connection problems. A keyword <cf/keep/ suppresses updating
4093 this value by a cache server.
4094 Default: 3600 seconds
4096 <tag>retry [keep] <m/num/</tag> Time period in seconds between a failed
4097 Serial/Reset Query and a next attempt. Maximum allowed value is 7200
4098 seconds (two hours). Too low value can caused a false positive
4099 detection of network connection problems. A keyword <cf/keep/
4100 suppresses updating this value by a cache server.
4101 Default: 600 seconds
4103 <tag>expire [keep] <m/num/</tag> Time period in seconds. Received
4104 records are deleted if the client was unable to successfully refresh
4105 data for this time period. Must be in range from 600 seconds (ten
4106 minutes) to 172800 seconds (two days). A keyword <cf/keep/
4107 suppresses updating this value by a cache server.
4108 Default: 7200 seconds
4110 <tag>transport tcp</tag> Unprotected transport over TCP. It's a default
4111 transport. Should be used only on secure private networks.
4114 <tag>transport ssh { <m/SSH transport options.../ }</tag> It enables a
4115 SSHv2 transport encryption. Cannot be combined with a TCP transport.
4119 <sect3>SSH transport options
4121 <tag>bird private key "<m>/path/to/id_rsa</m>"</tag>
4122 A path to the BIRD's private SSH key for authentication.
4123 It can be a <cf><m>id_rsa</m></cf> file.
4125 <tag>remote public key "<m>/path/to/known_host</m>"</tag>
4126 A path to the cache's public SSH key for verification identity
4127 of the cache server. It could be a path to <cf><m>known_host</m></cf> file.
4129 <tag>user "<m/name/"</tag>
4130 A SSH user name for authentication. This option is a required.
4134 <sect2>BGP origin validation
4135 <p>Policy: Don't import <cf/ROA_INVALID/ routes.
4146 # Please, do not use rpki-validator.realmv6.org in production
4147 remote "rpki-validator.realmv6.org" port 8282;
4155 if (roa_check(r4, net, bgp_path.last) = ROA_INVALID ||
4156 roa_check(r6, net, bgp_path.last) = ROA_INVALID) then
4158 print "Ignore invalid ROA ", net, " for ASN ", bgp_path.last;
4167 neighbor 192.168.2.1 as 65001;
4168 import filter peer_in;
4172 <sect2>SSHv2 transport encryption
4183 remote 127.0.0.1 port 2345;
4185 bird private key "/home/birdgeek/.ssh/id_rsa";
4186 remote public key "/home/birdgeek/.ssh/known_hosts";
4190 # Default interval values
4199 <p>The Static protocol doesn't communicate with other routers in the network,
4200 but instead it allows you to define routes manually. This is often used for
4201 specifying how to forward packets to parts of the network which don't use
4202 dynamic routing at all and also for defining sink routes (i.e., those telling to
4203 return packets as undeliverable if they are in your IP block, you don't have any
4204 specific destination for them and you don't want to send them out through the
4205 default route to prevent routing loops).
4207 <p>There are four types of static routes: `classical' routes telling to forward
4208 packets to a neighboring router (single path or multipath, possibly weighted),
4209 device routes specifying forwarding to hosts on a directly connected network,
4210 recursive routes computing their nexthops by doing route table lookups for a
4211 given IP, and special routes (sink, blackhole etc.) which specify a special
4212 action to be done instead of forwarding the packet.
4214 <p>When the particular destination is not available (the interface is down or
4215 the next hop of the route is not a neighbor at the moment), Static just
4216 uninstalls the route from the table it is connected to and adds it again as soon
4217 as the destination becomes adjacent again.
4219 <p>There are three classes of definitions in Static protocol configuration --
4220 global options, static route definitions, and per-route options. Usually, the
4221 definition of the protocol contains mainly a list of static routes.
4226 <tag><label id="static-check-link">check link <m/switch/</tag>
4227 If set, hardware link states of network interfaces are taken into
4228 consideration. When link disappears (e.g. ethernet cable is unplugged),
4229 static routes directing to that interface are removed. It is possible
4230 that some hardware drivers or platforms do not implement this feature.
4233 <tag><label id="static-igp-table">igp table <m/name/</tag>
4234 Specifies a table that is used for route table lookups of recursive
4235 routes. Default: the same table as the protocol is connected to.
4238 <p>Route definitions (each may also contain a block of per-route options):
4241 <tag><label id="static-route-via-ip">route <m/prefix/ via <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4242 Static single path route through a neighboring router. For link-local next hops,
4243 interface can be specified as a part of the address (e.g.,
4244 <cf/via fe80::1234%eth0/). MPLS labels should be specified in outer-first order.
4246 <tag><label id="static-route-via-mpath">route <m/prefix/ via <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]] [weight <m/num/] [bfd <m/switch/] [via ...]</tag>
4247 Static multipath route. Contains several nexthops (gateways), possibly
4248 with their weights and MPLS labels.
4250 <tag><label id="static-route-via-iface">route <m/prefix/ via <m/"interface"/</tag>
4251 Static device route through an interface to hosts on a directly
4254 <tag><label id="static-route-recursive">route <m/prefix/ recursive <m/ip/</tag>
4255 Static recursive route, its nexthop depends on a route table lookup for
4258 <tag><label id="static-route-drop">route <m/prefix/ blackhole|unreachable|prohibit</tag>
4259 Special routes specifying to silently drop the packet, return it as
4260 unreachable or return it as administratively prohibited. First two
4261 targets are also known as <cf/drop/ and <cf/reject/.
4264 <p>Per-route options:
4267 <tag><label id="static-route-bfd">bfd <m/switch/</tag>
4268 The Static protocol could use BFD protocol for next hop liveness
4269 detection. If enabled, a BFD session to the route next hop is created
4270 and the static route is BFD-controlled -- the static route is announced
4271 only if the next hop liveness is confirmed by BFD. If the BFD session
4272 fails, the static route is removed. Note that this is a bit different
4273 compared to other protocols, which may use BFD as an advisory mechanism
4274 for fast failure detection but ignores it if a BFD session is not even
4277 This option can be used for static routes with a direct next hop, or
4278 also for for individual next hops in a static multipath route (see
4279 above). Note that BFD protocol also has to be configured, see
4280 <ref id="bfd" name="BFD"> section for details. Default value is no.
4282 <tag><label id="static-route-filter"><m/filter expression/</tag>
4283 This is a special option that allows filter expressions to be configured
4284 on per-route basis. Can be used multiple times. These expressions are
4285 evaluated when the route is originated, similarly to the import filter
4286 of the static protocol. This is especially useful for configuring route
4287 attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
4288 exported to the OSPF protocol.
4291 <p>Static routes have no specific attributes.
4293 <p>Example static config might look like this:
4297 table testable; # Connect to a non-default routing table
4298 check link; # Advertise routes only if link is up
4299 route 0.0.0.0/0 via 198.51.100.130; # Default route
4300 route 10.0.0.0/8 multipath # Multipath route
4301 via 198.51.100.10 weight 2
4302 via 198.51.100.20 bfd # BFD-controlled next hop
4304 route 203.0.113.0/24 unreachable; # Sink route
4305 route 10.2.0.0/24 via "arc0"; # Secondary network
4306 route 192.168.10.0/24 via 198.51.100.100 {
4307 ospf_metric1 = 20; # Set extended attribute
4309 route 192.168.10.0/24 via 198.51.100.100 {
4310 ospf_metric2 = 100; # Set extended attribute
4311 ospf_tag = 2; # Set extended attribute
4312 bfd; # BFD-controlled route
4319 <label id="conclusion">
4322 <label id="future-work">
4324 <p>Although BIRD supports all the commonly used routing protocols, there are
4325 still some features which would surely deserve to be implemented in future
4330 <item>Route aggregation and flap dampening
4331 <item>Multipath routes
4332 <item>Multicast routing protocols
4333 <item>Ports to other systems
4337 <sect>Getting more help
4340 <p>If you use BIRD, you're welcome to join the bird-users mailing list
4341 (<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
4342 where you can share your experiences with the other users and consult
4343 your problems with the authors. To subscribe to the list, visit
4344 <HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
4345 The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
4347 <p>BIRD is a relatively young system and it probably contains some bugs. You can
4348 report any problems to the bird-users list and the authors will be glad to solve
4349 them, but before you do so, please make sure you have read the available
4350 documentation and that you are running the latest version (available at
4351 <HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
4352 (Of course, a patch which fixes the bug is always welcome as an attachment.)
4354 <p>If you want to understand what is going inside, Internet standards are a good
4355 and interesting reading. You can get them from
4356 <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
4357 nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
4358 name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
4365 LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel
4366 LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
4367 LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
4368 LocalWords: len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth
4369 LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek
4370 LocalWords: EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC
4371 LocalWords: OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU
4372 LocalWords: uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc
4373 LocalWords: compat multicasts nonbroadcast pointopoint loopback sym stats
4374 LocalWords: Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt
4375 LocalWords: proto wildcard Ondrej Filip