1 <!doctype birddoc system>
6 This documentation can have 4 forms: sgml (this is master copy), html,
7 ASCII text and dvi/postscript (generated from sgml using
8 sgmltools). You should always edit master copy.
10 This is a slightly modified linuxdoc dtd. Anything in <descrip> tags is considered definition of
11 configuration primitives, <cf> is fragment of configuration within normal text, <m> is
12 "meta" information within fragment of configuration - something in config which is not keyword.
16 Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
22 <title>BIRD User's Guide
24 Ondrej Filip <it/<feela@network.cz>/,
25 Pavel Machek <it/<pavel@ucw.cz>/,
26 Martin Mares <it/<mj@ucw.cz>/,
27 Ondrej Zajicek <it/<santiago@crfreenet.org>/
31 This document contains user documentation for the BIRD Internet Routing Daemon project.
34 <!-- Table of contents -->
37 <!-- Begin the document -->
44 The name `BIRD' is actually an acronym standing for `BIRD Internet Routing Daemon'.
45 Let's take a closer look at the meaning of the name:
47 <p><em/BIRD/: Well, we think we have already explained that. It's an acronym standing
48 for `BIRD Internet Routing Daemon', you remember, don't you? :-)
50 <p><em/Internet Routing/: It's a program (well, a daemon, as you are going to discover in a moment)
51 which works as a dynamic router in an Internet type network (that is, in a network running either
52 the IPv4 or the IPv6 protocol). Routers are devices which forward packets between interconnected
53 networks in order to allow hosts not connected directly to the same local area network to
54 communicate with each other. They also communicate with the other routers in the Internet to discover
55 the topology of the network which allows them to find optimal (in terms of some metric) rules for
56 forwarding of packets (which are called routing tables) and to adapt themselves to the
57 changing conditions such as outages of network links, building of new connections and so on. Most of
58 these routers are costly dedicated devices running obscure firmware which is hard to configure and
59 not open to any changes (on the other hand, their special hardware design allows them to keep up with lots of high-speed network interfaces, better than general-purpose computer does). Fortunately, most operating systems of the UNIX family allow an ordinary
60 computer to act as a router and forward packets belonging to the other hosts, but only according to
61 a statically configured table.
63 <p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program running on
64 background which does the dynamic part of Internet routing, that is it communicates
65 with the other routers, calculates routing tables and sends them to the OS kernel
66 which does the actual packet forwarding. There already exist other such routing
67 daemons: routed (RIP only), GateD (non-free), Zebra<HTMLURL URL="http://www.zebra.org">
68 and MRTD<HTMLURL URL="http://sourceforge.net/projects/mrt">, but their capabilities are
69 limited and they are relatively hard to configure and maintain.
71 <p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
72 to support all the routing technology used in the today's Internet or planned to be
73 used in near future and to have a clean extensible architecture allowing new routing
74 protocols to be incorporated easily. Among other features, BIRD supports:
77 <item>both IPv4 and IPv6 protocols
78 <item>multiple routing tables
79 <item>the Border Gateway Protocol (BGPv4)
80 <item>the Routing Information Protocol (RIPv2)
81 <item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
82 <item>a virtual protocol for exchange of routes between different routing tables on a single host
83 <item>a command-line interface allowing on-line control and inspection
84 of status of the daemon
85 <item>soft reconfiguration (no need to use complex online commands
86 to change the configuration, just edit the configuration file
87 and notify BIRD to re-read it and it will smoothly switch itself
88 to the new configuration, not disturbing routing protocols
89 unless they are affected by the configuration changes)
90 <item>a powerful language for route filtering
93 <p>BIRD has been developed at the Faculty of Math and Physics, Charles University, Prague,
94 Czech Republic as a student project. It can be freely distributed under the terms of the GNU General
97 <p>BIRD has been designed to work on all UNIX-like systems. It has been developed and
98 tested under Linux 2.0 to 2.4, and then ported to FreeBSD and NetBSD, porting to other
99 systems (even non-UNIX ones) should be relatively easy due to its highly modular architecture.
101 <sect>Installing BIRD
103 <p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make) and Perl, installing BIRD should be as easy as:
109 vi /usr/local/etc/bird.conf
113 <p>You can use <tt>./configure --help</tt> to get a list of configure
114 options. The most important ones are:
115 <tt/--enable-ipv6/ which enables building of an IPv6 version of BIRD,
116 <tt/--with-protocols=/ to produce a slightly smaller BIRD executable by configuring out routing protocols you don't use, and
117 <tt/--prefix=/ to install BIRD to a place different from.
118 <file>/usr/local</file>.
122 <p>You can pass several command-line options to bird:
125 <tag>-c <m/config name/</tag>
126 use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>.
129 enable debug messages and run bird in foreground.
131 <tag>-D <m/filename of debug log/</tag>
132 log debugging information to given file instead of stderr.
135 just parse the config file and exit. Return value is zero if the config file is valid,
136 nonzero if there are some errors.
138 <tag>-s <m/name of communication socket/</tag>
139 use given filename for a socket for communications with the client, default is <it/prefix/<file>/var/run/bird.ctl</file>.
142 <p>BIRD writes messages about its work to log files or syslog (according to config).
144 <chapt>About routing tables
146 <p>BIRD has one or more routing tables which may or may not be
147 synchronized with OS kernel and which may or may not be synchronized with
148 each other (see the Pipe protocol). Each routing table contains a list of
149 known routes. Each route consists of:
152 <item>network prefix this route is for (network address and prefix length -- the number of bits forming the network part of the address; also known as a netmask)
153 <item>preference of this route
154 <item>IP address of router which told us about this route
155 <item>IP address of router we should forward the packets to
157 <item>other attributes common to all routes
158 <item>dynamic attributes defined by protocols which may or
159 may not be present (typically protocol metrics)
162 Routing table maintains multiple entries
163 for a network, but at most one entry for one network and one
164 protocol. The entry with the highest preference is used for routing (we
165 will call such an entry the <it/selected route/). If
166 there are more entries with the same preference and they are from the same
167 protocol, the protocol decides (typically according to metrics). If they aren't,
168 an internal ordering is used to break the tie. You can
169 get the list of route attributes in the Route attributes section.
171 <p>Each protocol is connected to a routing table through two filters
172 which can accept, reject and modify the routes. An <it/export/
173 filter checks routes passed from the routing table to the protocol,
174 an <it/import/ filter checks routes in the opposite direction.
175 When the routing table gets a route from a protocol, it recalculates
176 the selected route and broadcasts it to all protocols connected to
177 the table. The protocols typically send the update to other routers
184 <p>BIRD is configured using a text configuration file. Upon startup, BIRD reads <it/prefix/<file>/etc/bird.conf</file> (unless the
185 <tt/-c/ command line option is given). Configuration may be changed at user's request: if you modify
186 the config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
187 config. Then there's the client
188 which allows you to talk with BIRD in an extensive way.
190 <p>In the config, everything on a line after <cf/#/ or inside <cf>/*
191 */</cf> is a comment, whitespace characters are treated as a single space. If there's a variable number of options, they are grouped using
192 the <cf/{ }/ brackets. Each option is terminated by a <cf/;/. Configuration
195 <p>Here is an example of a simple config file. It enables
196 synchronization of routing tables with OS kernel, scans for
197 new network interfaces every 10 seconds and runs RIP on all network interfaces found.
202 persist; # Don't remove routes on BIRD shutdown
203 scan time 20; # Scan kernel routing table every 20 seconds
204 export all; # Default is export none
208 scan time 10; # Scan interfaces every 10 seconds
222 <tag>log "<m/filename/"|syslog|stderr all|{ <m/list of classes/ }</tag>
223 Set logging of messages having the given class (either <cf/all/ or <cf/{
224 error, trace }/ etc.) into selected destination. Classes are:
225 <cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
226 <cf/debug/ for debugging messages,
227 <cf/trace/ when you want to know what happens in the network,
228 <cf/remote/ for messages about misbehavior of remote machines,
229 <cf/auth/ about authentication failures,
230 <cf/bug/ for internal BIRD bugs. You may specify more than one <cf/log/ line to establish logging to multiple
231 destinations. Default: log everything to the system log.
233 <tag>debug protocols all|off|{ states, routes, filters, interfaces, events, packets }</tag>
234 Set global defaults of protocol debugging options. See <cf/debug/ in the following section. Default: off.
236 <tag>debug commands <m/number/</tag>
237 Control logging of client connections (0 for no logging, 1 for
238 logging of connects and disconnects, 2 and higher for logging of
239 all client commands). Default: 0.
241 <tag>mrtdump "<m/filename/"</tag>
242 Set MRTdump file name. This option must be specified to allow MRTdump feature.
243 Default: no dump file.
245 <tag>mrtdump protocols all|off|{ states, messages }</tag>
246 Set global defaults of MRTdump options. See <cf/mrtdump/ in the following section.
249 <tag>filter <m/name local variables/{ <m/commands/ }</tag> Define a filter. You can learn more about filters
250 in the following chapter.
252 <tag>function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag> Define a function. You can learn more
253 about functions in the following chapter.
255 <tag>protocol rip|ospf|bgp|... <m/[name]/ { <m>protocol options</m> }</tag> Define a protocol
256 instance called <cf><m/name/</cf> (or with a name like "rip5" generated automatically if you don't specify any <cf><m/name/</cf>). You can learn more
257 about configuring protocols in their own chapters. You can run more than one instance of
258 most protocols (like RIP or BGP). By default, no instances are configured.
260 <tag>define <m/constant/ = (<m/expression/)|<m/number/|<m/IP address/</tag> Define a constant. You can use it later in every place
261 you could use a simple integer or an IP address.
263 <tag>router id <m/IPv4 address/</tag> Set BIRD's router ID. It's a world-wide unique identification of your router, usually one of router's IPv4 addresses. Default: in IPv4 version, the lowest IP address of a non-loopback interface. In IPv6 version, this option is mandatory.
265 <tag>listen bgp [address <m/address/] [port <m/port/] [v6only]</tag>
266 This option allows to specify address and port where BGP
267 protocol should listen. It is global option as listening
268 socket is common to all BGP instances. Default is to listen on
269 all addresses (0.0.0.0) and port 179. In IPv6 mode, option
270 <cf/v6only/ can be used to specify that BGP socket should
271 listen to IPv6 connections only. This is needed if you want to
272 run both bird and bird6 on the same port.
274 <tag>timeformat route|protocol|base|log "<m/format1/" [<m/limit> "<m/format2/"]</tag>
275 This option allows to specify a format of date/time used by
276 BIRD. The first argument specifies for which purpose such
277 format is used. <cf/route/ is a format used in 'show route'
278 command output, <cf/protocol/ is used in 'show protocols'
279 command output, <cf/base/ is used for other commands and
280 <cf/log/ is used in a log file.
282 "<m/format1/" is a format string using <i/strftime(3)/
283 notation (see <i/man strftime/ for details). <m/limit> and
284 "<m/format2/" allow to specify the second format string for
285 times in past deeper than <m/limit/ seconds. There are two
286 shorthands: <cf/iso long/ is a ISO 8601 date/time format
287 (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F
288 %T"/. <cf/iso short/ is a variant of ISO 8601 that uses just
289 the time format (hh:mm:ss) for near times (up to 20 hours in
290 the past) and the date format (YYYY-MM-DD) for far times. This
291 is a shorthand for <cf/"%T" 72000 "%F"/.
293 By default, BIRD uses an short, ad-hoc format for <cf/route/
294 and <cf/protocol/ times, and a <cf/iso long/ similar format
295 (DD-MM-YYYY hh:mm:ss) for <cf/base/ and <cf/log/. These
296 defaults are here for a compatibility with older versions
297 and might change in the future.
299 <tag>table <m/name/</tag> Create a new routing table. The default
300 routing table is created implicitly, other routing tables have
301 to be added by this command.
303 <tag>eval <m/expr/</tag> Evaluates given filter expression. It
304 is used by us for testing of filters.
307 <sect>Protocol options
309 <p>For each protocol instance, you can configure a bunch of options.
310 Some of them (those described in this section) are generic, some are
311 specific to the protocol (see sections talking about the protocols).
313 <p>Several options use a <cf><m/switch/</cf> argument. It can be either
314 <cf/on/, <cf/yes/ or a numeric expression with a non-zero value for the
315 option to be enabled or <cf/off/, <cf/no/ or a numeric expression evaluating
316 to zero to disable it. An empty <cf><m/switch/</cf> is equivalent to <cf/on/
317 ("silence means agreement").
320 <tag>preference <m/expr/</tag> Sets the preference of routes generated by this protocol. Default: protocol dependent.
322 <tag>disabled <m/switch/</tag> Disables the protocol. You can change the disable/enable status from the command
323 line interface without needing to touch the configuration. Disabled protocols are not activated. Default: protocol is enabled.
325 <tag>debug all|off|{ states, routes, filters, interfaces, events, packets }</tag>
326 Set protocol debugging options. If asked, each protocol is capable of
327 writing trace messages about its work to the log (with category
328 <cf/trace/). You can either request printing of <cf/all/ trace messages
329 or only of the types selected: <cf/states/ for protocol state changes
330 (protocol going up, down, starting, stopping etc.),
331 <cf/routes/ for routes exchanged with the routing table,
332 <cf/filters/ for details on route filtering,
333 <cf/interfaces/ for interface change events sent to the protocol,
334 <cf/events/ for events internal to the protocol and
335 <cf/packets/ for packets sent and received by the protocol. Default: off.
337 <tag>mrtdump all|off|{ states, messages }</tag>
339 Set protocol MRTdump flags. MRTdump is a standard binary
340 format for logging information from routing protocols and
341 daemons. These flags control what kind of information is
342 logged from the protocol to the MRTdump file (which must be
343 specified by global <cf/mrtdump/ option, see the previous
344 section). Although these flags are similar to flags of
345 <cf/debug/ option, their meaning is different and
346 protocol-specific. For BGP protocol, <cf/states/ logs BGP
347 state changes and <cf/messages/ logs received BGP messages.
348 Other protocols does not support MRTdump yet.
350 <tag>router id <m/IPv4 address/</tag> This option can be used
351 to override global router id for a given protocol. Default:
352 uses global router id.
354 <tag>import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/filter expression/</tag>
355 Specify a filter to be used for filtering routes coming from the protocol to the routing table. <cf/all/ is shorthand for <cf/where true/ and <cf/none/ is shorthand for <cf/where false/. Default: <cf/all/.
357 <tag>export <m/filter/</tag> This is similar to the <cf>import</cf> keyword, except that it
358 works in the direction from the routing table to the protocol. Default: <cf/none/.
360 <tag>description "<m/text/"</tag> This is an optional
361 description of the protocol. It is displayed as a part of the
362 output of 'show route all' command.
364 <tag>table <m/name/</tag> Connect this protocol to a non-default routing table.
367 <p>There are several options that give sense only with certain protocols:
370 <tag><label id="dsc-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, ...] [ { <m/option/ ; [...] } ]</tag>
372 Specifies a set of interfaces on which the protocol is activated with
373 given interface-specific options. A set of interfaces specified by one
374 interface option is described using an interface pattern. The
375 interface pattern consists of a sequence of clauses (separated by
376 commas), each clause may contain a mask, a prefix, or both of them. An
377 interface matches the clause if its name matches the mask (if
378 specified) and its address matches the prefix (if specified). Mask is
379 specified as shell-like pattern.
381 An interface matches the pattern if it matches any of its
382 clauses. If the clause begins with <cf/-/, matching interfaces are
383 excluded. Patterns are parsed left-to-right, thus
384 <cf/interface "eth0", -"eth*", "*";/ means eth0 and all
387 An interface option can be used more times with different
388 interfaces-specific options, in that case for given interface
389 the first matching interface option is used.
391 This option is allowed in Direct, OSPF and RIP protocols,
392 but in OSPF protocol it is used in <cf/area/ subsection.
398 <cf>interface "*" { type broadcast; };</cf> - start the protocol on all interfaces with
399 <cf>type broadcast</cf> option.
401 <cf>interface "eth1", "eth4", "eth5" { type pointopoint; };</cf> - start the protocol
402 on enumerated interfaces with <cf>type pointopoint</cf> option.
404 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol on all
405 interfaces that have address from 192.168.0.0/16, but not
408 <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol on all
409 interfaces that have address from 192.168.0.0/16, but not
412 <cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
413 ethernet interfaces that have address from 192.168.1.0/24.
415 <tag><label id="dsc-pass">password "<m/password/" [ { id <m/num/; generate from <m/time/; generate to <m/time/; accept from <m/time/; accept to <m/time/; } ]</tag>
416 Specifies a password that can be used by the protocol. Password option can
417 be used more times to specify more passwords. If more passwords are
418 specified, it is a protocol-dependent decision which one is really
419 used. Specifying passwords does not mean that authentication is
420 enabled, authentication can be enabled by separate, protocol-dependent
421 <cf/authentication/ option.
423 This option is allowed in OSPF and RIP protocols. BGP has also
424 <cf/password/ option, but it is slightly different and described
430 <p>Password option can contain section with some (not necessary all) password sub-options:
433 <tag>id <M>num</M></tag>
434 ID of the password, (0-255). If it's not used, BIRD will choose
435 ID based on an order of the password item in the interface. For
436 example, second password item in one interface will have default
437 ID 2. ID is used by some routing protocols to identify which
438 password was used to authenticate protocol packets.
440 <tag>generate from "<m/time/"</tag>
441 The start time of the usage of the password for packet signing.
442 The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
444 <tag>generate to "<m/time/"</tag>
445 The last time of the usage of the password for packet signing.
447 <tag>accept from "<m/time/"</tag>
448 The start time of the usage of the password for packet verification.
450 <tag>accept to "<m/time/"</tag>
451 The last time of the usage of the password for packet verification.
454 <chapt>Remote control
456 <p>You can use the command-line client <file>birdc</file> to talk with
457 a running BIRD. Communication is done using a <file/bird.ctl/ UNIX domain
458 socket (unless changed with the <tt/-s/ option given to both the server and
459 the client). The commands can perform simple actions such as enabling/disabling
460 of protocols, telling BIRD to show various information, telling it to
461 show routing table filtered by filter, or asking BIRD to
462 reconfigure. Press <tt/?/ at any time to get online help. Option
463 <tt/-v/ can be passed to the client, to make it dump numeric return
464 codes along with the messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
465 own applications could do that, too -- the format of communication between
466 BIRD and <file/birdc/ is stable (see the programmer's documentation).
468 Many commands have the <m/name/ of the protocol instance as an argument.
469 This argument can be omitted if there exists only a single instance.
471 <p>Here is a brief list of supported functions:
474 <tag>dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
475 Dump contents of internal data structures to the debugging output.
477 <tag>show status</tag>
478 Show router status, that is BIRD version, uptime and time from last reconfiguration.
480 <tag>show protocols [all]</tag>
481 Show list of protocol instances along with tables they are connected to and protocol status, possibly giving verbose information, if <cf/all/ is specified.
483 <tag>show ospf interface [<m/name/] ["<m/interface/"]</tag>
484 Show detailed information about OSPF interfaces.
486 <tag>show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
487 Show a list of OSPF neighbors and a state of adjacency to them.
489 <tag>show ospf state [<m/name/]</tag>
490 Show detailed information about OSPF areas based on a content of link-state database.
491 It shows network topology, aggregated networks and routers from other areas and external routes.
493 <tag>show ospf topology [<m/name/]</tag>
494 Show a topology of OSPF areas based on a content of link-state database.
495 It is just a stripped-down version of 'show ospf state'.
497 <tag>show static [<m/name/]</tag>
498 Show detailed information about static routes.
500 <tag>show interfaces [summary]</tag>
501 Show the list of interfaces. For each interface, print its type, state, MTU and addresses assigned.
503 <tag>show symbols</tag>
504 Show the list of symbols defined in the configuration (names of protocols, routing tables etc.).
506 <tag>show route [[for] <m/prefix/|<m/IP/] [table <m/sym/] [filter <m/f/|where <m/c/] [(export|preexport) <m/p/] [protocol <m/p/] [<m/options/]</tag>
507 Show contents of a routing table (by default of the main one),
508 that is routes, their metrics and (in case the <cf/all/ switch is given)
509 all their attributes.
511 <p>You can specify a <m/prefix/ if you want to print routes for a
512 specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
513 the entry which will be used for forwarding of packets to the given
514 destination. By default, all routes for each network are printed with
515 the selected one at the top, unless <cf/primary/ is given in which case
516 only the selected route is shown.
518 <p>You can also ask for printing only routes processed and accepted by
519 a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
520 </cf> or matching a given condition (<cf>where <m/condition/</cf>).
521 The <cf/export/ and <cf/preexport/ switches ask for printing of entries
522 that are exported to the specified protocol. With <cf/preexport/, the
523 export filter of the protocol is skipped.
525 <p>You can also select just routes added by a specific protocol.
526 <cf>protocol <m/p/</cf>.
528 <p>The <cf/stats/ switch requests showing of route statistics (the
529 number of networks, number of routes before and after filtering). If
530 you use <cf/count/ instead, only the statistics will be printed.
532 <tag>configure [soft] ["<m/config file/"]</tag>
533 Reload configuration from a given file. BIRD will smoothly
534 switch itself to the new configuration, protocols are
535 reconfigured if possible, restarted otherwise. Changes in
536 filters usually lead to restart of affected protocols. If
537 <cf/soft/ option is used, changes in filters does not cause
538 BIRD to restart affected protocols, therefore already accepted
539 routes (according to old filters) would be still propagated,
540 but new routes would be processed according to the new
543 <tag>enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
544 Enable, disable or restart a given protocol instance, instances matching the <cf><m/pattern/</cf> or <cf/all/ instances.
546 <tag>reload [in|out] <m/name/|"<m/pattern/"|all</tag>
548 Reload a given protocol instance, that means re-import routes
549 from the protocol instance and re-export preferred routes to
550 the instance. If <cf/in/ or <cf/out/ options are used, the
551 command is restricted to one direction (re-import or
554 This command is useful if appropriate filters have changed but
555 the protocol instance was not restarted (or reloaded),
556 therefore it still propagates the old set of routes. For example
557 when <cf/configure soft/ command was used to change filters.
559 Re-export always succeeds, but re-import is protocol-dependent
560 and might fail (for example, if BGP neighbor does not support
561 route-refresh extension). In that case, re-export is also
562 skipped. Note that for the pipe protocol, both directions are
563 always reloaded together (<cf/in/ or <cf/out/ options are
564 ignored in that case).
569 <tag>debug <m/protocol/|<m/pattern/|all all|off|{ states | routes | filters | events | packets }</tag>
570 Control protocol debugging.
577 <p>BIRD contains a simple programming language. (No, it can't yet read mail :-). There are
578 two objects in this language: filters and functions. Filters are interpreted by BIRD core when a route is
579 being passed between protocols and routing tables. The filter language contains control structures such
580 as if's and switches, but it allows no loops. An example of a filter using many features can be found in <file>filter/test.conf</file>.
582 <p>Filter gets the route, looks at its attributes and
583 modifies some of them if it wishes. At the end, it decides whether to
584 pass the changed route through (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks
591 if defined( rip_metric ) then
597 if rip_metric > 10 then
598 reject "RIP metric is too big";
604 <p>As you can see, a filter has a header, a list of local variables, and a body. The header consists of
605 the <cf/filter/ keyword followed by a (unique) name of filter. The list of local variables consists of
606 <cf><M>type name</M>;</cf> pairs where each pair defines one local variable. The body consists of
607 <cf> { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You can group
608 several statements to a single compound statement by using braces (<cf>{ <M>statements</M> }</cf>) which is useful if
609 you want to make a bigger block of code conditional.
611 <p>BIRD supports functions, so that you don't have to repeat the same blocks of code over and
612 over. Functions can have zero or more parameters and they can have local variables. Recursion is not allowed. Function definitions
622 function with_parameters (int parameter)
628 <p>Unlike in C, variables are declared after the <cf/function/ line, but before the first <cf/{/. You can't declare
629 variables in nested blocks. Functions are called like in C: <cf>name();
630 with_parameters(5);</cf>. Function may return values using the <cf>return <m/[expr]/</cf>
631 command. Returning a value exits from current function (this is similar to C).
633 <p>Filters are declared in a way similar to functions except they can't have explicit
634 parameters. They get a route table entry as an implicit parameter, it is also passed automatically
635 to any functions called. The filter must terminate with either
636 <cf/accept/ or <cf/reject/ statement. If there's a runtime error in filter, the route
639 <p>A nice trick to debug filters is to use <cf>show route filter
640 <m/name/</cf> from the command line client. An example session might look
644 pavel@bug:~/bird$ ./birdc -s bird.ctl
647 10.0.0.0/8 dev eth0 [direct1 23:21] (240)
648 195.113.30.2/32 dev tunl1 [direct1 23:21] (240)
649 127.0.0.0/8 dev lo [direct1 23:21] (240)
651 show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
652 bird> show route filter { if 127.0.0.5 ˜ net then accept; }
653 127.0.0.0/8 dev lo [direct1 23:21] (240)
659 <p>Each variable and each value has certain type. Booleans, integers and enums are
660 incompatible with each other (that is to prevent you from shooting in the foot).
663 <tag/bool/ This is a boolean type, it can have only two values, <cf/true/ and
664 <cf/false/. Boolean is the only type you can use in <cf/if/
667 <tag/int/ This is a general integer type, you can expect it to store signed values from -2000000000
668 to +2000000000. Overflows are not checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
670 <tag/pair/ This is a pair of two short integers. Each component can have values from 0 to
671 65535. Literals of this type are written as <cf/(1234,5678)/. The same syntax can also be
672 used to construct a pair from two arbitrary integer expressions (for example <cf/(1+2,a)/).
674 <tag/string/ This is a string of characters. There are no ways to modify strings in
675 filters. You can pass them between functions, assign them to variables of type <cf/string/, print
676 such variables, but you can't concatenate two strings. String literals
677 are written as <cf/"This is a string constant"/.
679 <tag/ip/ This type can hold a single IP address. Depending on the compile-time configuration of BIRD you are using, it
680 is either an IPv4 or IPv6 address. IP addresses are written in the standard notation (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special operator <cf>.mask(<M>num</M>)</cf>
681 on values of type ip. It masks out all but first <cf><M>num</M></cf> bits from the IP
682 address. So <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
684 <tag/prefix/ This type can hold a network prefix consisting of IP address and prefix length. Prefix literals are written as
685 <cf><M>ipaddress</M>/<M>pxlen</M></cf>, or
686 <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
687 operators on prefixes:
688 <cf/.ip/ which extracts the IP address from the pair, and <cf/.len/, which separates prefix
689 length from the pair. So <cf>1.2.0.0/16.pxlen = 16</cf> is true.
691 <tag/int|ip|prefix|pair|enum set/
692 Filters recognize four types of sets. Sets are similar to strings: you can pass them around
693 but you can't modify them. Literals of type <cf>set int</cf> look like <cf>
694 [ 1, 2, 5..7 ]</cf>. As you can see, both simple values and ranges are permitted in
697 Sets of prefixes are special: their literals does not allow ranges, but allows
698 prefix patterns that are written as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
699 Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> iff
700 the first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are identical and <cf>len1 <= ip1 <= len2</cf>.
701 A valid prefix pattern has to satisfy <cf>low <= high</cf>, but <cf/pxlen/ is not constrained by <cf/low/
702 or <cf/high/. Obviously, a prefix matches a prefix set literal iff it matches any prefix pattern in the
705 There are also two shorthands for prefix patterns: <cf><m>address</m>/<m/len/+</cf> is a shorthand for
706 <cf><m>address</m>/<m/len/{<m/len/,<m/maxlen/}</cf> (where <cf><m>maxlen</m></cf> is 32 for IPv4 and 128 for IPv6),
707 that means network prefix <cf><m>address</m>/<m/len/</cf> and all its subnets. <cf><m>address</m>/<m/len/-</cf>
708 is a shorthand for <cf><m>address</m>/<m/len/{0,<m/len/}</cf>, that means network prefix <cf><m>address</m>/<m/len/</cf>
709 and all its supernets (network prefixes that contain it).
711 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} ]</cf> matches
712 prefix <cf>1.0.0.0/8</cf>, all subprefixes of <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
713 <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf> matches all prefixes (regardless of
714 IP address) whose prefix length is 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP address
715 <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{15,17} ]</cf> is true,
716 but <cf>1.0.0.0/16 ˜ [ 1.0.0.0/8- ]</cf> is false.
718 Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
719 in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
720 <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
721 <cf>192.168.0.0/16{24,32}</cf>.
724 Enumeration types are fixed sets of possibilities. You can't define your own
725 variables of such type, but some route attributes are of enumeration
726 type. Enumeration types are incompatible with each other.
729 BGP path is a list of autonomous system numbers. You can't write literals of this type.
730 There are several special operators on bgppaths:
732 <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
734 <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
736 Both <cf/first/ and <cf/last/ return zero if there is no appropriate ASN,
737 for example if the path contains an AS set element as the first (or the last) part.
739 <cf><m/P/.len</cf> returns the length of path <m/P/.
741 <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and returns the result.
742 Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
743 <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
744 (for example <cf/bgp_path/).
747 BGP masks are patterns used for BGP path matching
748 (using <cf>path ˜ [= 2 3 5 * =]</cf> syntax). The masks
749 resemble wildcard patterns as used by UNIX shells. Autonomous
750 system numbers match themselves, <cf/*/ matches any (even empty)
751 sequence of arbitrary AS numbers and <cf/?/ matches one arbitrary AS number.
752 For example, if <cf>bgp_path</cf> is 4 3 2 1, then:
753 <tt>bgp_path ˜ [= * 4 3 * =]</tt> is true, but
754 <tt>bgp_path ˜ [= * 4 5 * =]</tt> is false.
755 BGP mask expressions can also contain integer expressions enclosed in parenthesis
756 and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>.
757 There is also old syntax that uses / .. / instead of [= .. =] and ? instead of *.
760 Community list is similar to set of pairs,
761 except that unlike other sets, it can be modified.
762 There exist no literals of this type.
763 There are two special operators on clists:
765 <cf>add(<m/C/,<m/P/)</cf> adds pair <m/P/ to clist <m/C/ and returns the result.
767 <cf>delete(<m/C/,<m/P/)</cf> deletes pair <m/P/ from clist <m/C/ and returns the result.
769 Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
770 <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute
771 (for example <cf/bgp_community/). Similarly for <cf/delete/.
777 <p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>, parentheses <cf/(a*(b+c))/, comparison
778 <cf/(a=b, a!=b, a<b, a>=b)/. Logical operations include unary not (<cf/!/), and (<cf/&&/) and or (<cf/||/).
779 Special operators include <cf/˜/ for "is element of a set" operation - it can be
780 used on element and set of elements of the same type (returning true if element is contained in the given set), or
781 on two strings (returning true if first string matches a shell-like pattern stored in second string) or on IP and prefix (returning true if IP is within the range defined by that prefix), or on
782 prefix and prefix (returning true if first prefix is more specific than second one) or on bgppath and bgpmask (returning true if the path matches the mask) or on pair and clist (returning true if the community is element of the community list).
785 <sect>Control structures
787 <p>Filters support two control structures: conditions and case switches.
789 <p>Syntax of a condition is: <cf>if
790 <M>boolean expression</M> then <M>command1</M>; else <M>command2</M>;</cf> and you can use <cf>{
791 <M>command_1</M>; <M>command_2</M>; <M>...</M> }</cf> instead of either command. The <cf>else</cf>
792 clause may be omitted. If the <cf><m>boolean expression</m></cf> is true, <cf><m>command1</m></cf> is executed, otherwise <cf><m>command2</m></cf> is executed.
794 <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case <m/expr/ { else |
795 <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [ ... ] }</cf>. The expression after
796 <cf>case</cf> can be of any type which can be on the left side of the ˜ operator and anything that could
797 be a member of a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/ grouping.
798 If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
800 <p>Here is example that uses <cf/if/ and <cf/case/ structures:
804 2: print "two"; print "I can do more commands without {}";
805 3 .. 5: print "three to five";
806 else: print "something else";
809 if 1234 = i then printn "."; else {
811 print "You need {} around multiple commands";
815 <sect>Route attributes
817 <p>A filter is implicitly passed a route, and it can access its
818 attributes just like it accesses variables. Attempts to access undefined
819 attribute result in a runtime error; you can check if an attribute is
820 defined by using the <cf>defined( <m>attribute</m> )</cf> operator.
823 <tag><m/prefix/ net</tag>
824 Network the route is talking about. Read-only. (See the chapter about routing tables.)
826 <tag><m/enum/ scope</tag>
827 The scope of the route. Possible values: <cf/SCOPE_HOST/ for
828 routes local to this host, <cf/SCOPE_LINK/ for those specific
829 for a physical link, <cf/SCOPE_SITE/ and
830 <cf/SCOPE_ORGANIZATION/ for private routes and
831 <cf/SCOPE_UNIVERSE/ for globally visible routes. This
832 attribute is not interpreted by BIRD and can be used to mark
833 routes in filters. The default value for new routes is
836 <tag><m/int/ preference</tag>
837 Preference of the route. Valid values are 0-65535. (See the chapter about routing tables.)
839 <tag><m/ip/ from</tag>
840 The router which the route has originated from. Read-only.
843 Next hop packets routed using this route should be forwarded to.
845 <tag><m/string/ proto</tag>
846 The name of the protocol which the route has been imported from. Read-only.
848 <tag><m/enum/ source</tag>
849 what protocol has told me about this route. Possible values: <cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/, <cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/, <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT/, <cf/RTS_BGP/, <cf/RTS_PIPE/.
851 <tag><m/enum/ cast</tag>
853 Route type (Currently <cf/RTC_UNICAST/ for normal routes,
854 <cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will
855 be used in the future for broadcast, multicast and anycast
858 <tag><m/enum/ dest</tag>
859 Type of destination the packets should be sent to (<cf/RTD_ROUTER/ for forwarding to a neighboring router, <cf/RTD_NETWORK/ for routing to a directly-connected network, <cf/RTD_BLACKHOLE/ for packets to be silently discarded, <cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be returned with ICMP host unreachable / ICMP administratively prohibited messages). Read-only.
862 <p>There also exist some protocol-specific attributes which are described in the corresponding protocol sections.
864 <sect>Other statements
866 <p>The following statements are available:
869 <tag><m/variable/ = <m/expr/</tag> Set variable to a given value.
871 <tag>accept|reject [ <m/expr/ ]</tag> Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
873 <tag>return <m/expr/</tag> Return <cf><m>expr</m></cf> from the current function, the function ends at this point.
875 <tag>print|printn <m/expr/ [<m/, expr.../]</tag>
876 Prints given expressions; useful mainly while debugging
877 filters. The <cf/printn/ variant does not terminate the line.
880 Terminates BIRD. Useful when debugging the filter interpreter.
887 <p>The Border Gateway Protocol is the routing protocol used for backbone
888 level routing in the today's Internet. Contrary to the other protocols, its convergence
889 doesn't rely on all routers following the same rules for route selection,
890 making it possible to implement any routing policy at any router in the
891 network, the only restriction being that if a router advertises a route,
892 it must accept and forward packets according to it.
894 <p>BGP works in terms of autonomous systems (often abbreviated as AS). Each
895 AS is a part of the network with common management and common routing policy. It is identified by a unique 16-bit number.
896 Routers within each AS usually communicate with each other using either a interior routing
897 protocol (such as OSPF or RIP) or an interior variant of BGP (called iBGP).
898 Boundary routers at the border of the AS communicate with their peers
899 in the neighboring AS'es via exterior BGP (eBGP).
901 <p>Each BGP router sends to its neighbors updates of the parts of its
902 routing table it wishes to export along with complete path information
903 (a list of AS'es the packet will travel through if it uses the particular
904 route) in order to avoid routing loops.
906 <p>BIRD supports all requirements of the BGP4 standard as defined in
907 RFC 4271<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4271.txt">
908 It also supports the community attributes
909 (RFC 1997<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1997.txt">),
910 capability negotiation
911 (RFC 3392<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc3392.txt">),
912 MD5 password authentication
913 (RFC 2385<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2385.txt">),
915 (RFC 4456<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4456.txt">),
916 multiprotocol extensions
917 (RFC 4760<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4760.txt">),
919 (RFC 4893<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4893.txt">).
922 For IPv6, it uses the standard multiprotocol extensions defined in
923 RFC 2283<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2283.txt">
924 including changes described in the
925 latest draft<htmlurl url="ftp://ftp.rfc-editor.org/internet-drafts/draft-ietf-idr-bgp4-multiprotocol-v2-05.txt">
926 and applied to IPv6 according to
927 RFC 2545<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2545.txt">.
929 <sect1>Route selection rules
931 <p>BGP doesn't have any simple metric, so the rules for selection of an optimal
932 route among multiple BGP routes with the same preference are a bit more complex
933 and they are implemented according to the following algorithm. It starts the first
934 rule, if there are more "best" routes, then it uses the second rule to choose
935 among them and so on.
938 <item>Prefer route with the highest Local Preference attribute.
939 <item>Prefer route with the shortest AS path.
940 <item>Prefer IGP origin over EGP and EGP over incomplete.
941 <item>Prefer the lowest value of the Multiple Exit Discriminator.
942 <item>Prefer internal routes over external ones.
943 <item>Prefer the route with the lowest value of router ID of the
949 <p>Each instance of the BGP corresponds to one neighboring router.
950 This allows to set routing policy and all the other parameters differently
951 for each neighbor using the following configuration parameters:
954 <tag>local as <m/number/</tag> Define which AS we are part of. (Note that
955 contrary to other IP routers, BIRD is able to act as a router located
956 in multiple AS'es simultaneously, but in such cases you need to tweak
957 the BGP paths manually in the filters to get consistent behavior.)
958 This parameter is mandatory.
960 <tag>neighbor <m/ip/ as <m/number/</tag> Define neighboring router
961 this instance will be talking to and what AS it's located in. Unless
962 you use the <cf/multihop/ clause, it must be directly connected to one
963 of your router's interfaces. In case the neighbor is in the same AS
964 as we are, we automatically switch to iBGP. This parameter is mandatory.
966 <tag>multihop <m/number/ via <m/ip/</tag> Configure multihop BGP to a
967 neighbor which is connected at most <m/number/ hops far and to which
968 we should route via our direct neighbor with address <m/ip/.
969 Default: switched off.
971 <tag>next hop self</tag> Avoid calculation of the Next Hop
972 attribute and always advertise our own source address (see
973 below) as a next hop. This needs to be used only occasionally
974 to circumvent misconfigurations of other routers.
977 <tag>missing lladdr self|drop|ignore</tag>Next Hop attribute
978 in BGP-IPv6 sometimes contains just the global IPv6 address,
979 but sometimes it has to contain both global and link-local
980 IPv6 addresses. This option specifies what to do if BIRD have
981 to send both addresses but does not know link-local address.
982 This situation might happen when routes from other protocols
983 are exported to BGP, or when improper updates are received
984 from BGP peers. <cf/self/ means that BIRD advertises its own
985 local address instead. <cf/drop/ means that BIRD skips that
986 prefixes and logs error. <cf/ignore/ means that BIRD ignores
987 the problem and sends just the global address (and therefore
988 forms improper BGP update). Default: <cf/self/, unless BIRD
989 is configured as a route server (option <cf/rs client/), in
990 that case default is <cf/drop/, because route servers usually
991 does not forward packets ifselves.
993 <tag>source address <m/ip/</tag> Define local address we should use
994 for next hop calculation. Default: the address of the local end
995 of the interface our neighbor is connected to.
997 <tag>password <m/string/</tag> Use this password for MD5 authentication
998 of BGP sessions. Default: no authentication. Password has to be set by
999 external utility (e.g. setkey(8)) on BSD systems.
1001 <tag>passive <m/switch/</tag> Standard BGP behavior is both
1002 initiating outgoing connections and accepting incoming
1003 connections. In passive mode, outgoing connections are not
1004 initiated. Default: off.
1006 <tag>rr client</tag> Be a route reflector and treat the neighbor as
1007 a route reflection client. Default: disabled.
1009 <tag>rr cluster id <m/IPv4 address/</tag> Route reflectors use cluster id
1010 to avoid route reflection loops. When there is one route reflector in a cluster
1011 it usually uses its router id as a cluster id, but when there are more route
1012 reflectors in a cluster, these need to be configured (using this option) to
1013 use a common cluster id. Clients in a cluster need not know their cluster
1014 id and this option is not allowed for them. Default: the same as router id.
1016 <tag>rs client</tag> Be a route server and treat the neighbor
1017 as a route server client. A route server is used as a
1018 replacement for full mesh EBGP routing in Internet exchange
1019 points in a similar way to route reflectors used in IBGP routing.
1020 BIRD does not implement obsoleted RFC 1863, but uses ad-hoc implementation,
1021 which behaves like plain EBGP but reduces modifications to advertised route
1022 attributes to be transparent (for example does not prepend its AS number to
1023 AS PATH attribute and keep MED attribute). Default: disabled.
1025 <tag>enable route refresh <m/switch/</tag> When BGP speaker
1026 changes its import filter, it has to re-examine all routes
1027 received from its neighbor against the new filter. As these
1028 routes might not be available, there is a BGP protocol
1029 extension Route Refresh (specified in RFC 2918) that allows
1030 BGP speaker to request re-advertisement of all routes from its
1031 neighbor. This option specifies whether BIRD advertises this
1032 capability and accepts such requests. Even when disabled, BIRD
1033 can send route refresh requests. Default: on.
1035 <tag>interpret communities <m/switch/</tag> RFC 1997 demands
1036 that BGP speaker should process well-known communities like
1037 no-export (65535, 65281) or no-advertise (65535, 65282). For
1038 example, received route carrying a no-adverise community
1039 should not be advertised to any of its neighbors. If this
1040 option is enabled (which is by default), BIRD has such
1041 behavior automatically (it is evaluated when a route is
1042 exported to the BGP protocol just before the export filter).
1043 Otherwise, this integrated processing of well-known
1044 communities is disabled. In that case, similar behavior can be
1045 implemented in the export filter. Default: on.
1047 <tag>enable as4 <m/switch/</tag> BGP protocol was designed to use 2B AS numbers
1048 and was extended later to allow 4B AS number. BIRD supports 4B AS extension,
1049 but by disabling this option it can be persuaded not to advertise it and
1050 to maintain old-style sessions with its neighbors. This might be useful for
1051 circumventing bugs in neighbor's implementation of 4B AS extension.
1052 Even when disabled (off), BIRD behaves internally as AS4-aware BGP router.
1055 <tag>capabilities <m/switch/</tag> Use capability advertisement
1056 to advertise optional capabilities. This is standard behavior
1057 for newer BGP implementations, but there might be some older
1058 BGP implementations that reject such connection attempts.
1059 When disabled (off), features that request it (4B AS support)
1060 are also disabled. Default: on, with automatic fallback to
1061 off when received capability-related error.
1063 <tag>advertise ipv4 <m/switch/</tag> Advertise IPv4 multiprotocol capability.
1064 This is not a correct behavior according to the strict interpretation
1065 of RFC 4760, but it is widespread and required by some BGP
1066 implementations (Cisco and Quagga). This option is relevant
1067 to IPv4 mode with enabled capability advertisement only. Default: on.
1069 <tag>route limit <m/number/</tag> The maximal number of routes
1070 that may be imported from the protocol. If the route limit is
1071 exceeded, the connection is closed with error. Default: no limit.
1073 <tag>disable after error <m/switch/</tag> When an error is encountered (either
1074 locally or by the other side), disable the instance automatically
1075 and wait for an administrator to fix the problem manually. Default: off.
1077 <tag>hold time <m/number/</tag> Time in seconds to wait for a Keepalive
1078 message from the other side before considering the connection stale.
1079 Default: depends on agreement with the neighboring router, we prefer
1080 240 seconds if the other side is willing to accept it.
1082 <tag>startup hold time <m/number/</tag> Value of the hold timer used
1083 before the routers have a chance to exchange open messages and agree
1084 on the real value. Default: 240 seconds.
1086 <tag>keepalive time <m/number/</tag> Delay in seconds between sending
1087 of two consecutive Keepalive messages. Default: One third of the hold time.
1089 <tag>connect retry time <m/number/</tag> Time in seconds to wait before
1090 retrying a failed attempt to connect. Default: 120 seconds.
1092 <tag>start delay time <m/number/</tag> Delay in seconds between protocol
1093 startup and the first attempt to connect. Default: 5 seconds.
1095 <tag>error wait time <m/number/,<m/number/</tag> Minimum and maximum delay in seconds between a protocol
1096 failure (either local or reported by the peer) and automatic restart.
1097 Doesn't apply when <cf/disable after error/ is configured. If consecutive
1098 errors happen, the delay is increased exponentially until it reaches the maximum. Default: 60, 300.
1100 <tag>error forget time <m/number/</tag> Maximum time in seconds between two protocol
1101 failures to treat them as a error sequence which makes the <cf/error wait time/
1102 increase exponentially. Default: 300 seconds.
1104 <tag>path metric <m/switch/</tag> Enable comparison of path lengths
1105 when deciding which BGP route is the best one. Default: on.
1107 <tag>prefer older <m/switch/</tag> Standard route selection algorithm
1108 breaks ties by comparing router IDs. This changes the behavior
1109 to prefer older routes (when both are external and from different
1110 peer). For details, see RFC 5004. Default: off.
1112 <tag>default bgp_med <m/number/</tag> Value of the Multiple Exit
1113 Discriminator to be used during route selection when the MED attribute
1114 is missing. Default: 0.
1116 <tag>default bgp_local_pref <m/number/</tag> A default value
1117 for the Local Preference attribute. It is used when a new
1118 Local Preference attribute is attached to a route by the BGP
1119 protocol itself (for example, if a route is received through
1120 eBGP and therefore does not have such attribute). Default: 100
1121 (0 in pre-1.2.0 versions of BIRD).
1126 <p>BGP defines several route attributes. Some of them (those marked with `<tt/I/' in the
1127 table below) are available on internal BGP connections only, some of them (marked
1128 with `<tt/O/') are optional.
1131 <tag>bgppath <cf/bgp_path/</tag> Sequence of AS numbers describing the AS path
1132 the packet will travel through when forwarded according to the particular route. In case of
1133 internal BGP it doesn't contain the number of the local AS.
1135 <tag>int <cf/bgp_local_pref/ [I]</tag> Local preference value used for
1136 selection among multiple BGP routes (see the selection rules above). It's
1137 used as an additional metric which is propagated through the whole local AS.
1139 <tag>int <cf/bgp_med/ [O]</tag> The Multiple Exit Discriminator of the route
1140 is an optional attribute which is used on on external (inter-AS) links to
1141 convey to an adjacent AS the optimal entry point into the local AS.
1142 The received attribute may be also propagated over internal BGP links
1143 (and this is default behavior). The attribute value is zeroed when a route
1144 is exported from a routing table to a BGP instance to ensure that the attribute
1145 received from a neighboring AS is not propagated to other neighboring ASes.
1146 A new value might be set in the export filter of a BGP instance.
1147 See RFC 4451<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4451.txt">
1148 for further discussion of BGP MED attribute.
1150 <tag>enum <cf/bgp_origin/</tag> Origin of the route: either <cf/ORIGIN_IGP/
1151 if the route has originated in an interior routing protocol or
1152 <cf/ORIGIN_EGP/ if it's been imported from the <tt>EGP</tt> protocol
1153 (nowadays it seems to be obsolete) or <cf/ORIGIN_INCOMPLETE/ if the origin
1156 <tag>ip <cf/bgp_next_hop/</tag> Next hop to be used for forwarding of packets
1157 to this destination. On internal BGP connections, it's an address of the
1158 originating router if it's inside the local AS or a boundary router the
1159 packet will leave the AS through if it's an exterior route, so each BGP
1160 speaker within the AS has a chance to use the shortest interior path
1161 possible to this point.
1163 <tag>void <cf/bgp_atomic_aggr/ [O]</tag> This is an optional attribute
1164 which carries no value, but the sole presence of which indicates that the route
1165 has been aggregated from multiple routes by some router on the path from
1168 <!-- we don't handle aggregators right since they are of a very obscure type
1169 <tag>bgp_aggregator</tag>
1171 <tag>clist <cf/bgp_community/ [O]</tag> List of community values associated
1172 with the route. Each such value is a pair (represented as a <cf/pair/ data
1173 type inside the filters) of 16-bit integers, the first of them containing the number of the AS which defines
1174 the community and the second one being a per-AS identifier. There are lots
1175 of uses of the community mechanism, but generally they are used to carry
1176 policy information like "don't export to USA peers". As each AS can define
1177 its own routing policy, it also has a complete freedom about which community
1178 attributes it defines and what will their semantics be.
1185 local as 65000; # Use a private AS number
1186 neighbor 62.168.0.130 as 5588; # Our neighbor ...
1187 multihop 20 via 62.168.0.13; # ... which is connected indirectly
1188 export filter { # We use non-trivial export rules
1189 if source = RTS_STATIC then { # Export only static routes
1190 # Assign our community
1191 bgp_community.add((65000,5678));
1192 # Artificially increase path length
1193 # by advertising local AS number twice
1194 if bgp_path ~ [= 65000 =] then
1195 bgp_path.prepend(65000);
1201 source address 62.168.0.1; # Use a non-standard source address
1207 <p>The Device protocol is not a real routing protocol. It doesn't generate
1208 any routes and it only serves as a module for getting information about network
1209 interfaces from the kernel.
1211 <p>Except for very unusual circumstances, you probably should include
1212 this protocol in the configuration since almost all other protocols
1213 require network interfaces to be defined for them to work with.
1215 <sect1>Configuration
1218 <tag>scan time <m/number/</tag> Time in seconds between two scans
1219 of the network interface list. On systems where we are notified about
1220 interface status changes asynchronously (such as newer versions of
1221 Linux), we need to scan the list only in order to avoid confusion by lost
1222 notification messages, so the default time is set to a large value.
1224 <tag>primary [ "<m/mask/" ] <m/prefix/</tag>
1225 If a network interface has more than one network address,
1226 BIRD has to choose one of them as a primary one, because some
1227 routing protocols (for example OSPFv2) suppose there is only
1228 one network address per interface. By default, BIRD chooses
1229 the lexicographically smallest address as the primary one.
1231 This option allows to specify which network address should be
1232 chosen as a primary one. Network addresses that match
1233 <m/prefix/ are preferred to non-matching addresses. If more
1234 <cf/primary/ options are used, the first one has the highest
1235 preference. If "<m/mask/" is specified, then such
1236 <cf/primary/ option is relevant only to matching network
1239 In all cases, an address marked by operating system as
1240 secondary cannot be chosen as the primary one.
1243 <p>As the Device protocol doesn't generate any routes, it cannot have
1244 any attributes. Example configuration looks like this:
1248 scan time 10; # Scan the interfaces often
1249 primary "eth0" 192.168.1.1;
1250 primary 192.168.0.0/16;
1256 <p>The Direct protocol is a simple generator of device routes for all the
1257 directly connected networks according to the list of interfaces provided
1258 by the kernel via the Device protocol.
1260 <p>It's highly recommended to include this protocol in your configuration
1261 unless you want to use BIRD as a route server or a route reflector, that is
1262 on a machine which doesn't forward packets itself and only participates in
1263 distribution of routing information.
1265 <p>The only configurable thing about direct is what interfaces it watches:
1268 <tag>interface <m/pattern [, ...]/</tag> By default, the Direct
1269 protocol will generate device routes for all the interfaces
1270 available. If you want to restrict it to some subset of interfaces
1271 (for example if you're using multiple routing tables for policy
1272 routing and some of the policy domains don't contain all interfaces),
1273 just use this clause.
1276 <p>Direct device routes don't contain any specific attributes.
1278 <p>Example config might look like this:
1282 interface "-arc*", "*"; # Exclude the ARCnets
1288 <p>The Kernel protocol is not a real routing protocol. Instead of communicating
1289 the with other routers in the network, it performs synchronization of BIRD's routing
1290 tables with the OS kernel. Basically, it sends all routing table updates to the kernel
1291 and from time to time it scans the kernel tables to see whether some routes have
1292 disappeared (for example due to unnoticed up/down transition of an interface)
1293 or whether an `alien' route has been added by someone else (depending on the
1294 <cf/learn/ switch, such routes are either deleted or accepted to our
1297 <p>If your OS supports only a single routing table, you can configure only one
1298 instance of the Kernel protocol. If it supports multiple tables (in order to
1299 allow policy routing; such an OS is for example Linux 2.2), you can run as many instances as you want, but each of
1300 them must be connected to a different BIRD routing table and to a different
1303 <sect1>Configuration
1306 <tag>persist <m/switch/</tag> Tell BIRD to leave all its routes in the
1307 routing tables when it exits (instead of cleaning them up).
1308 <tag>scan time <m/number/</tag> Time in seconds between two consecutive scans of the
1309 kernel routing table.
1310 <tag>learn <m/switch/</tag> Enable learning of routes added to the kernel
1311 routing tables by other routing daemons or by the system administrator.
1312 This is possible only on systems which support identification of route
1314 <tag>kernel table <m/number/</tag> Select which kernel table should
1315 this particular instance of the Kernel protocol work with. Available
1316 only on systems supporting multiple routing tables.
1319 <p>The Kernel protocol doesn't define any route attributes.
1320 <p>A simple configuration can look this way:
1329 <p>Or for a system with two routing tables:
1332 protocol kernel { # Primary routing table
1333 learn; # Learn alien routes from the kernel
1334 persist; # Don't remove routes on bird shutdown
1335 scan time 10; # Scan kernel routing table every 10 seconds
1340 protocol kernel { # Secondary routing table
1351 <p>Open Shortest Path First (OSPF) is a quite complex interior gateway
1352 protocol. The current IPv4 version (OSPFv2) is defined in RFC
1353 2328<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt"> and
1354 the current IPv6 version (OSPFv3) is defined in RFC 5340<htmlurl
1355 url="ftp://ftp.rfc-editor.org/in-notes/rfc5340.txt"> It's a link state
1356 (a.k.a. shortest path first) protocol -- each router maintains a
1357 database describing the autonomous system's topology. Each participating
1358 router has an identical copy of the database and all routers run the
1359 same algorithm calculating a shortest path tree with themselves as a
1360 root. OSPF chooses the least cost path as the best path.
1362 <p>In OSPF, the autonomous system can be split to several areas in order
1363 to reduce the amount of resources consumed for exchanging the routing
1364 information and to protect the other areas from incorrect routing data.
1365 Topology of the area is hidden to the rest of the autonomous system.
1367 <p>Another very important feature of OSPF is that
1368 it can keep routing information from other protocols (like Static or BGP)
1369 in its link state database as external routes. Each external route can
1370 be tagged by the advertising router, making it possible to pass additional
1371 information between routers on the boundary of the autonomous system.
1373 <p>OSPF quickly detects topological changes in the autonomous system (such
1374 as router interface failures) and calculates new loop-free routes after a short
1375 period of convergence. Only a minimal amount of
1376 routing traffic is involved.
1378 <p>Each router participating in OSPF routing periodically sends Hello messages
1379 to all its interfaces. This allows neighbors to be discovered dynamically.
1380 Then the neighbors exchange theirs parts of the link state database and keep it
1381 identical by flooding updates. The flooding process is reliable and ensures
1382 that each router detects all changes.
1384 <sect1>Configuration
1386 <p>In the main part of configuration, there can be multiple definitions of
1387 OSPF area witch different id included. These definitions includes many other
1388 switches and multiple definitions of interfaces. Definition of interface
1389 may contain many switches and constant definitions and list of neighbors
1390 on nonbroadcast networks.
1393 protocol ospf <name> {
1394 rfc1583compat <switch>;
1397 stub cost <num>;
1400 <prefix> hidden;
1402 stubnet <prefix>;
1403 stubnet <prefix> {
1404 hidden <switch>;
1405 summary <switch>;
1408 interface <interface pattern> {
1410 stub <switch>;
1413 retransmit <num>;
1414 priority <num>;
1416 dead count <num>;
1418 rx buffer [normal|large|<num>];
1419 type [broadcast|nonbroadcast|pointopoint];
1420 strict nonbroadcast <switch>;
1421 authentication [none|simple|cryptographic];
1422 password "<text>";
1423 password "<text>" {
1425 generate from "<date>";
1426 generate to "<date>";
1427 accept from "<date>";
1428 accept to "<date>";
1432 <ip> eligible;
1435 virtual link <id> {
1437 retransmit <num>;
1439 dead count <num>;
1441 authentication [none|simple|cryptographic];
1442 password "<text>";
1449 <tag>rfc1583compat <M>switch</M></tag>
1450 This option controls compatibility of routing table
1451 calculation with RFC 1583<htmlurl
1452 url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
1455 <tag>area <M>id</M></tag>
1456 This defines an OSPF area with given area ID (an integer or an IPv4
1457 address, similarly to a router ID).
1458 The most important area is
1459 the backbone (ID 0) to which every other area must be connected.
1461 <tag>stub cost <M>num</M></tag>
1462 No external (except default) routes are flooded into stub areas.
1463 Setting this value marks area stub with defined cost of default route.
1464 Default value is no. (Area is not stub.)
1466 <tag>tick <M>num</M></tag>
1467 The routing table calculation and clean-up of areas' databases
1468 is not performed when a single link state
1469 change arrives. To lower the CPU utilization, it's processed later
1470 at periodical intervals of <m/num/ seconds. The default value is 1.
1472 <tag>networks { <m/set/ }</tag>
1473 Definition of area IP ranges. This is used in summary LSA origination.
1474 Hidden networks are not propagated into other areas.
1476 <tag>stubnet <m/prefix/ { <m/options/ }</tag>
1477 Stub networks are networks that are not transit networks
1478 between OSPF routers. They are also propagated through an
1479 OSPF area as a part of a link state database. By default,
1480 BIRD generates a stub network record for each primary network
1481 address on each OSPF interface that does not have any OSPF
1482 neighbors, and also for each non-primary network address on
1483 each OSPF interface. This option allows to alter a set of
1484 stub networks propagated by this router.
1486 Each instance of this option adds a stub network with given
1487 network prefix to the set of propagated stub network, unless
1488 option <cf/hidden/ is used. It also suppresses default stub
1489 networks for given network prefix. When option
1490 <cf/summary/ is used, also default stub networks that are
1491 subnetworks of given stub network are suppressed. This might
1492 be used, for example, to aggregate generated stub networks.
1494 <tag>interface <M>pattern</M></tag>
1495 Defines that the specified interfaces belong to the area being defined.
1496 See <ref id="dsc-iface" name="interface"> common option for detailed description.
1498 <tag>virtual link <M>id</M></tag>
1499 Virtual link to router with the router id. Virtual link acts as a
1500 point-to-point interface belonging to backbone. The actual area is
1501 used as transport area. This item cannot be in the backbone.
1503 <tag>cost <M>num</M></tag>
1504 Specifies output cost (metric) of an interface. Default value is 10.
1506 <tag>stub <M>switch</M></tag>
1507 If set to interface it does not listen to any packet and does not send
1508 any hello. Default value is no.
1510 <tag>hello <M>num</M></tag>
1511 Specifies interval in seconds between sending of Hello messages. Beware, all
1512 routers on the same network need to have the same hello interval.
1513 Default value is 10.
1515 <tag>poll <M>num</M></tag>
1516 Specifies interval in seconds between sending of Hello messages for
1517 some neighbors on NBMA network. Default value is 20.
1519 <tag>retransmit <M>num</M></tag>
1520 Specifies interval in seconds between retransmissions of unacknowledged updates.
1523 <tag>priority <M>num</M></tag>
1524 On every multiple access network (e.g., the Ethernet) Designed Router
1525 and Backup Designed router are elected. These routers have some
1526 special functions in the flooding process. Higher priority increases
1527 preferences in this election. Routers with priority 0 are not
1528 eligible. Default value is 1.
1530 <tag>wait <M>num</M></tag>
1531 After start, router waits for the specified number of seconds between starting
1532 election and building adjacency. Default value is 40.
1534 <tag>dead count <M>num</M></tag>
1535 When the router does not receive any messages from a neighbor in
1536 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
1538 <tag>dead <M>num</M></tag>
1539 When the router does not receive any messages from a neighbor in
1540 <m/dead/ seconds, it will consider the neighbor down. If both directives
1541 <m/dead count/ and <m/dead/ are used, <m/dead/ has precendence.
1543 <tag>rx buffer <M>num</M></tag>
1544 This sets the size of buffer used for receiving packets. The buffer should
1545 be bigger than maximal size of any packets. Value NORMAL (default)
1546 means 2*MTU, value LARGE means maximal allowed packet - 65536.
1548 <tag>type broadcast</tag>
1549 BIRD detects a type of a connected network automatically, but sometimes it's
1550 convenient to force use of a different type manually.
1551 On broadcast networks, flooding and Hello messages are sent using multicasts
1552 (a single packet for all the neighbors).
1554 <tag>type pointopoint</tag>
1555 Point-to-point networks connect just 2 routers together. No election
1556 is performed there which reduces the number of messages sent.
1558 <tag>type nonbroadcast</tag>
1559 On nonbroadcast networks, the packets are sent to each neighbor
1560 separately because of lack of multicast capabilities.
1562 <tag>strict nonbroadcast <M>switch</M></tag>
1563 If set, don't send hello to any undefined neighbor. This switch
1564 is ignored on any non-NBMA network. Default is No.
1566 <tag>authentication none</tag>
1567 No passwords are sent in OSPF packets. This is the default value.
1569 <tag>authentication simple</tag>
1570 Every packet carries 8 bytes of password. Received packets
1571 lacking this password are ignored. This authentication mechanism is
1574 <tag>authentication cryptographic</tag>
1575 16-byte long MD5 digest is appended to every packet. For the digest
1576 generation 16-byte long passwords are used. Those passwords are
1577 not sent via network, so this mechanism is quite secure.
1578 Packets can still be read by an attacker.
1580 <tag>password "<M>text</M>"</tag>
1581 An 8-byte or 16-byte password used for authentication.
1582 See <ref id="dsc-pass" name="password"> common option for detailed description.
1584 <tag>neighbors { <m/set/ } </tag>
1585 A set of neighbors to which Hello messages on nonbroadcast networks
1586 are to be sent. Some of them could be marked as eligible.
1592 <p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
1593 Metric is ranging from 1 to infinity (65535).
1594 External routes use <cf/metric type 1/ or <cf/metric type 2/.
1595 A <cf/metric of type 1/ is comparable with internal <cf/metric/, a
1596 <cf/metric of type 2/ is always longer
1597 than any <cf/metric of type 1/ or any <cf/internal metric/.
1598 If you specify both metrics only metric1 is used.
1599 Each external route can also carry a <cf/tag/ which is a 32-bit
1600 integer which is used when exporting routes to other protocols;
1601 otherwise, it doesn't affect routing inside the OSPF domain at all.
1602 The fourth attribute is a <cf/router_id/ of the router advertising
1603 that route/network. This attribute is read-only.
1604 Default is <cf/metric of type 2 = 10000/ and <cf/tag = 0/.
1611 protocol ospf MyOSPF {
1615 if source = RTS_BGP then {
1627 authentication simple;
1632 authentication cryptographic;
1635 generate to "22-04-2003 11:00:06";
1636 accept from "17-01-2001 12:01:05";
1640 generate to "22-07-2005 17:03:21";
1641 accept from "22-02-2001 11:34:06";
1654 172.16.2.0/24 hidden;
1656 interface "-arc0" , "arc*" {
1658 authentication none;
1659 strict nonbroadcast yes;
1664 192.168.120.1 eligible;
1677 <p>The Pipe protocol serves as a link between two routing tables, allowing routes to be
1678 passed from a table declared as primary (i.e., the one the pipe is connected to using the
1679 <cf/table/ configuration keyword) to the secondary one (declared using <cf/peer table/)
1680 and vice versa, depending on what's allowed by the filters. Export filters control export
1681 of routes from the primary table to the secondary one, import filters control the opposite
1684 <p>The Pipe protocol may work in the opaque mode or in the transparent
1685 mode. In the opaque mode, the Pipe protocol retransmits optimal route
1686 from one table to the other table in a similar way like other
1687 protocols send and receive routes. Retransmitted route will have the
1688 source set to the Pipe protocol, which may limit access to protocol
1689 specific route attributes. The opaque mode is a default mode.
1691 <p>In transparent mode, the Pipe protocol retransmits all routes from
1692 one table to the other table, retaining their original source and
1693 attributes. If import and export filters are set to accept, then both
1694 tables would have the same content. The mode can be set by
1697 <p>The primary use of multiple routing tables and the Pipe protocol is for policy routing,
1698 where handling of a single packet doesn't depend only on its destination address, but also
1699 on its source address, source interface, protocol type and other similar parameters.
1700 In many systems (Linux being a good example), the kernel allows to enforce routing policies
1701 by defining routing rules which choose one of several routing tables to be used for a packet
1702 according to its parameters. Setting of these rules is outside the scope of BIRD's work
1703 (on Linux, you can use the <tt/ip/ command), but you can create several routing tables in BIRD,
1704 connect them to the kernel ones, use filters to control which routes appear in which tables
1705 and also you can employ the Pipe protocol for exporting a selected subset of one table to
1708 <sect1>Configuration
1711 <tag>peer table <m/table/</tag> Defines secondary routing table to connect to. The
1712 primary one is selected by the <cf/table/ keyword.
1714 <tag>mode opaque|transparent</tag> Specifies the mode for the pipe to work in. Default is opaque.
1719 <p>The Pipe protocol doesn't define any route attributes.
1723 <p>Let's consider a router which serves as a boundary router of two different autonomous
1724 systems, each of them connected to a subset of interfaces of the router, having its own
1725 exterior connectivity and wishing to use the other AS as a backup connectivity in case
1726 of outage of its own exterior line.
1728 <p>Probably the simplest solution to this situation is to use two routing tables (we'll
1729 call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that packets having
1730 arrived from interfaces belonging to the first AS will be routed according to <cf/as1/
1731 and similarly for the second AS. Thus we have split our router to two logical routers,
1732 each one acting on its own routing table, having its own routing protocols on its own
1733 interfaces. In order to use the other AS's routes for backup purposes, we can pass
1734 the routes between the tables through a Pipe protocol while decreasing their preferences
1735 and correcting their BGP paths to reflect the AS boundary crossing.
1738 table as1; # Define the tables
1741 protocol kernel kern1 { # Synchronize them with the kernel
1746 protocol kernel kern2 {
1751 protocol bgp bgp1 { # The outside connections
1754 neighbor 192.168.0.1 as 1001;
1762 neighbor 10.0.0.1 as 1002;
1767 protocol pipe { # The Pipe
1771 if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks
1772 if preference>10 then preference = preference-10;
1773 if source=RTS_BGP then bgp_path.prepend(1);
1779 if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks
1780 if preference>10 then preference = preference-10;
1781 if source=RTS_BGP then bgp_path.prepend(2);
1793 <p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol, where each router broadcasts (to all its neighbors)
1794 distances to all networks it can reach. When a router hears distance to another network, it increments
1795 it and broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some network goes
1796 unreachable, routers keep telling each other that its distance is the original distance plus 1 (actually, plus
1797 interface metric, which is usually one). After some time, the distance reaches infinity (that's 15 in
1798 RIP) and all routers know that network is unreachable. RIP tries to minimize situations where
1799 counting to infinity is necessary, because it is slow. Due to infinity being 16, you can't use
1800 RIP on networks where maximal distance is higher than 15 hosts. You can read more about RIP at <HTMLURL
1801 URL="http://www.ietf.org/html.charters/rip-charter.html" name="http://www.ietf.org/html.charters/rip-charter.html">. Both IPv4
1802 (RFC 1723<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1723.txt">)
1803 and IPv6 (RFC 2080<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2080.txt">) versions of RIP are supported by BIRD, historical RIPv1 (RFC 1058<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1058.txt">)is
1804 not currently supported. RIPv4 MD5 authentication (RFC 2082<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2082.txt">) is supported.
1806 <p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
1807 convergence, big network load and inability to handle larger networks
1808 makes it pretty much obsolete. (It is still usable on very small networks.)
1810 <sect1>Configuration
1812 <p>In addition to options common for all to other protocols, RIP supports the following ones:
1815 <tag/authentication none|plaintext|md5/ selects authentication method to be used. <cf/none/ means that
1816 packets are not authenticated at all, <cf/plaintext/ means that a plaintext password is embedded
1817 into each packet, and <cf/md5/ means that packets are authenticated using a MD5 cryptographic
1818 hash. If you set authentication to not-none, it is a good idea to add <cf>password</cf>
1819 section. Default: none.
1821 <tag>honor always|neighbor|never </tag>specifies when should requests for dumping routing table
1822 be honored. (Always, when sent from a host on a directly connected
1823 network or never.) Routing table updates are honored only from
1824 neighbors, that is not configurable. Default: never.
1827 <p>There are two options that can be specified per-interface. First is <cf>metric</cf>, with
1828 default one. Second is <cf>mode multicast|broadcast|quiet|nolisten|version1</cf>, it selects mode for
1829 rip to work in. If nothing is specified, rip runs in multicast mode. <cf>version1</cf> is
1830 currently equivalent to <cf>broadcast</cf>, and it makes RIP talk to a broadcast address even
1831 through multicast mode is possible. <cf>quiet</cf> option means that RIP will not transmit
1832 any periodic messages to this interface and <cf>nolisten</cf> means that RIP will send to this
1833 interface but not listen to it.
1835 <p>The following options generally override behavior specified in RFC. If you use any of these
1836 options, BIRD will no longer be RFC-compliant, which means it will not be able to talk to anything
1837 other than equally configured BIRD. I have warned you.
1840 <tag>port <M>number</M></tag>
1841 selects IP port to operate on, default 520. (This is useful when testing BIRD, if you
1842 set this to an address >1024, you will not need to run bird with UID==0).
1844 <tag>infinity <M>number</M></tag>
1845 selects the value of infinity, default is 16. Bigger values will make protocol convergence
1848 <tag>period <M>number</M>
1849 </tag>specifies the number of seconds between periodic updates. Default is 30 seconds. A lower
1850 number will mean faster convergence but bigger network
1851 load. Do not use values lower than 10.
1853 <tag>timeout time <M>number</M>
1854 </tag>specifies how old route has to be to be considered unreachable. Default is 4*<cf/period/.
1856 <tag>garbage time <M>number</M>
1857 </tag>specifies how old route has to be to be discarded. Default is 10*<cf/period/.
1862 <p>RIP defines two route attributes:
1865 <tag>int <cf/rip_metric/</tag> RIP metric of the route (ranging from 0 to <cf/infinity/).
1866 When routes from different RIP instances are available and all of them have the same
1867 preference, BIRD prefers the route with lowest <cf/rip_metric/.
1868 When importing a non-RIP route, the metric defaults to 5.
1870 <tag>int <cf/rip_tag/</tag> RIP route tag: a 16-bit number which can be used
1871 to carry additional information with the route (for example, an originating AS number
1872 in case of external routes). When importing a non-RIP route, the tag defaults to 0.
1878 protocol rip MyRIP_test {
1883 interface "eth0" { metric 3; mode multicast; };
1884 interface "eth*" { metric 2; mode broadcast; };
1886 authentication none;
1887 import filter { print "importing"; accept; };
1888 export filter { print "exporting"; accept; };
1894 <p>The Static protocol doesn't communicate with other routers in the network,
1895 but instead it allows you to define routes manually. This is often used for
1896 specifying how to forward packets to parts of the network which don't use
1897 dynamic routing at all and also for defining sink routes (i.e., those
1898 telling to return packets as undeliverable if they are in your IP block,
1899 you don't have any specific destination for them and you don't want to send
1900 them out through the default route to prevent routing loops).
1902 <p>There are three types of static routes: `classical' routes telling to
1903 forward packets to a neighboring router, device routes specifying forwarding
1904 to hosts on a directly connected network and special routes (sink, blackhole
1905 etc.) which specify a special action to be done instead of forwarding the
1908 <p>When the particular destination is not available (the interface is down or
1909 the next hop of the route is not a neighbor at the moment), Static just
1910 uninstalls the route from the table it is connected to and adds it again as soon
1911 as the destination becomes adjacent again.
1913 <p>The Static protocol has no configuration options. Instead, the
1914 definition of the protocol contains a list of static routes:
1917 <tag>route <m/prefix/ via <m/ip/</tag> Static route through
1918 a neighboring router.
1919 <tag>route <m/prefix/ via <m/"interface"/</tag> Static device
1920 route through an interface to hosts on a directly connected network.
1921 <tag>route <m/prefix/ drop|reject|prohibit</tag> Special routes
1922 specifying to drop the packet, return it as unreachable or return
1923 it as administratively prohibited.
1926 <p>Static routes have no specific attributes.
1928 <p>Example static config might look like this:
1932 table testable; # Connect to a non-default routing table
1933 route 0.0.0.0/0 via 62.168.0.13; # Default route
1934 route 62.168.0.0/25 reject; # Sink route
1935 route 10.2.0.0/24 via "arc0"; # Secondary network
1943 <p>Although BIRD supports all the commonly used routing protocols,
1944 there are still some features which would surely deserve to be
1945 implemented in future versions of BIRD:
1948 <item>OSPF NSSA areas and opaque LSA's
1949 <item>Route aggregation and flap dampening
1950 <item>Generation of IPv6 router advertisements
1951 <item>Multipath routes
1952 <item>Multicast routing protocols
1953 <item>Ports to other systems
1956 <sect>Getting more help
1958 <p>If you use BIRD, you're welcome to join the bird-users mailing list
1959 (<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">)
1960 where you can share your experiences with the other users and consult
1961 your problems with the authors. To subscribe to the list, just send a
1962 <tt/subscribe bird-users/ command in a body of a mail to
1963 (<HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">).
1964 The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
1966 <p>BIRD is a relatively young system and it probably contains some
1967 bugs. You can report any problems to the bird-users list and the authors
1968 will be glad to solve them, but before you do so,
1969 please make sure you have read the available documentation and that you are running the latest version (available at <HTMLURL
1970 URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, a patch
1971 which fixes the bug is always welcome as an attachment.)
1973 <p>If you want to understand what is going inside, Internet standards are
1974 a good and interesting reading. You can get them from <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc" name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
1981 LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel
1982 LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
1983 LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
1984 LocalWords: len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth
1985 LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek
1986 LocalWords: EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC
1987 LocalWords: OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU
1988 LocalWords: uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc
1989 LocalWords: compat multicasts nonbroadcast pointopoint loopback sym stats
1990 LocalWords: Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt
1991 LocalWords: proto wildcard