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>/
30 This document contains user documentation for the BIRD Internet Routing Daemon project.
33 <!-- Table of contents -->
36 <!-- Begin the document -->
43 The name `BIRD' is actually an acronym standing for `BIRD Internet Routing Daemon'.
44 Let's take a closer look at the meaning of the name:
46 <p><em/BIRD/: Well, we think we have already explained that. It's an acronym standing
47 for `BIRD Internet Routing Daemon', you remember, don't you? :-)
49 <p><em/Internet Routing/: It's a program (well, a daemon, as you are going to discover in a moment)
50 which works as a dynamic router in an Internet type network (that is, in a network running either
51 the IPv4 or the IPv6 protocol). Routers are devices which forward packets between interconnected
52 networks in order to allow hosts not connected directly to the same local area network to
53 communicate with each other. They also communicate with the other routers in the Internet to discover
54 the topology of the network which allows them to find optimal (in terms of some metric) rules for
55 forwarding of packets (which are called routing tables) and to adapt themselves to the
56 changing conditions such as outages of network links, building of new connections and so on. Most of
57 these routers are costly dedicated devices running obscure firmware which is hard to configure and
58 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
59 computer to act as a router and forward packets belonging to the other hosts, but only according to
60 a statically configured table.
62 <p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program running on
63 background which does the dynamic part of Internet routing, that is it communicates
64 with the other routers, calculates routing tables and sends them to the OS kernel
65 which does the actual packet forwarding. There already exist other such routing daemons: routed (RIP only), GateD<HTMLURL URL="http://www.gated.org/">
66 (non-free), Zebra<HTMLURL URL="http://www.zebra.org"> and MRTD<HTMLURL URL="http://www.zcu.cz/ftp/mirrors/mmrz/mrtd">, but their capabilities are limited and
67 they are relatively hard to configure and maintain.
69 <p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
70 to support all the routing technology used in the today's Internet or planned to be
71 used in near future and to have a clean extensible architecture allowing new routing
72 protocols to be incorporated easily. Among other features, BIRD supports:
75 <item>both IPv4 and IPv6 protocols
76 <item>multiple routing tables
77 <item>the Border Gateway Protocol (BGPv4)
78 <item>the Routing Information Protocol (RIPv2)
79 <item>the Open Shortest Path First protocol (OSPFv2)
80 <item>a virtual protocol for exchange of routes between different routing tables on a single host
81 <item>a command-line interface allowing on-line control and inspection
82 of status of the daemon
83 <item>soft reconfiguration (no need to use complex online commands
84 to change the configuration, just edit the configuration file
85 and notify BIRD to re-read it and it will smoothly switch itself
86 to the new configuration, not disturbing routing protocols
87 unless they are affected by the configuration changes)
88 <item>a powerful language for route filtering
91 <p>BIRD has been developed at the Faculty of Math and Physics, Charles University, Prague,
92 Czech Republic as a student project. It can be freely distributed under the terms of the GNU General
95 <p>BIRD has been designed to work on all UNIX-like systems. It has been developed and
96 tested under Linux 2.0 to 2.4, and then ported to FreeBSD and NetBSD, porting to other
97 systems (even non-UNIX ones) should be relatively easy due to its highly modular architecture.
101 <p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make) and Perl, installing BIRD should be as easy as:
107 vi /usr/local/etc/bird.conf
111 <p>You can use <tt>./configure --help</tt> to get a list of configure
112 options. The most important ones are:
113 <tt/--enable-ipv6/ which enables building of an IPv6 version of BIRD,
114 <tt/--with-protocols=/ to produce a slightly smaller BIRD executable by configuring out routing protocols you don't use, and
115 <tt/--prefix=/ to install BIRD to a place different from.
116 <file>/usr/local</file>.
120 <p>You can pass several command-line options to bird:
123 <tag>-c <m/config name/</tag>
124 use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>.
127 enable debug messages and run bird in foreground.
129 <tag>-D <m/filename of debug log/</tag>
130 log debugging information to given file instead of stderr
132 <tag>-s <m/name of communication socket/</tag>
133 use given filename for a socket for communications with the client, default is <it/prefix/<file>/var/run/bird.ctl</file>.
136 <p>BIRD writes messages about its work to log files or syslog (according to config).
138 <chapt>About routing tables
140 <p>BIRD has one or more routing tables which may or may not be
141 synchronized with OS kernel and which may or may not be synchronized with
142 each other (see the Pipe protocol). Each routing table contains a list of
143 known routes. Each route consists of:
146 <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)
147 <item>preference of this route
148 <item>IP address of router which told us about this route
149 <item>IP address of router we should forward the packets to
151 <item>other attributes common to all routes
152 <item>dynamic attributes defined by protocols which may or
153 may not be present (typically protocol metrics)
156 Routing table maintains multiple entries
157 for a network, but at most one entry for one network and one
158 protocol. The entry with the highest preference is used for routing (we
159 will call such an entry the <it/selected route/). If
160 there are more entries with the same preference and they are from the same
161 protocol, the protocol decides (typically according to metrics). If they aren't,
162 an internal ordering is used to break the tie. You can
163 get the list of route attributes in the Route attributes section.
165 <p>Each protocol is connected to a routing table through two filters
166 which can accept, reject and modify the routes. An <it/export/
167 filter checks routes passed from the routing table to the protocol,
168 an <it/import/ filter checks routes in the opposite direction.
169 When the routing table gets a route from a protocol, it recalculates
170 the selected route and broadcasts it to all protocols connected to
171 the table. The protocols typically send the update to other routers
178 <p>BIRD is configured using a text configuration file. Upon startup, BIRD reads <it/prefix/<file>/etc/bird.conf</file> (unless the
179 <tt/-c/ command line option is given). Configuration may be changed at user's request: if you modify
180 the config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
181 config. Then there's the client
182 which allows you to talk with BIRD in an extensive way.
184 <p>In the config, everything on a line after <cf/#/ or inside <cf>/*
185 */</cf> is a comment, whitespace characters are treated as a single space. If there's a variable number of options, they are grouped using
186 the <cf/{ }/ brackets. Each option is terminated by a <cf/;/. Configuration
189 <p>Here is an example of a simple config file. It enables
190 synchronization of routing tables with OS kernel, scans for
191 new network interfaces every 10 seconds and runs RIP on all network interfaces found.
196 persist; # Don't remove routes on BIRD shutdown
197 scan time 20; # Scan kernel routing table every 20 seconds
198 export all; # Default is export none
202 scan time 10; # Scan interfaces every 10 seconds
215 <tag>log "<m/filename/"|syslog|stderr all|{ <m/list of classes/ }</tag>
216 Set logging of messages having the given class (either <cf/all/ or <cf/{
217 error, trace }/ etc.) into selected destination. Classes are:
218 <cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
219 <cf/debug/ for debugging messages,
220 <cf/trace/ when you want to know what happens in the network,
221 <cf/remote/ for messages about misbehavior of remote machines,
222 <cf/auth/ about authentication failures,
223 <cf/bug/ for internal BIRD bugs. You may specify more than one <cf/log/ line to establish logging to multiple
224 destinations. Default: log everything to the system log.
226 <tag>debug protocols all|off|{ states, routes, filters, interfaces, events, packets }</tag>
227 Set global defaults of protocol debugging options. See <cf/debug/ in the following section. Default: off.
229 <tag>debug commands <m/number/</tag>
230 Control logging of client connections (0 for no logging, 1 for
231 logging of connects and disconnects, 2 and higher for logging of
232 all client commands). Default: 0.
234 <tag>filter <m/name local variables/{ <m/commands/ }</tag> Define a filter. You can learn more about filters
235 in the following chapter.
237 <tag>function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag> Define a function. You can learn more
238 about functions in the following chapter.
240 <tag>protocol rip|ospf|bgp|... <m/[name]/ { <m>protocol options</m> }</tag> Define a protocol
241 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
242 about configuring protocols in their own chapters. You can run more than one instance of
243 most protocols (like RIP or BGP). By default, no instances are configured.
245 <tag>define <m/constant/ = (<m/expression/)|<m/number/|<m/IP address/</tag> Define a constant. You can use it later in every place
246 you could use a simple integer or an IP address.
248 <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.
250 <tag>table <m/name/</tag> Create a new routing table. The default
251 routing table is created implicitly, other routing tables have
252 to be added by this command.
254 <tag>eval <m/expr/</tag> Evaluates given filter expression. It
255 is used by us for testing of filters.
258 <sect>Protocol options
260 <p>For each protocol instance, you can configure a bunch of options.
261 Some of them (those described in this section) are generic, some are
262 specific to the protocol (see sections talking about the protocols).
264 <p>Several options use a <cf><m/switch/</cf> argument. It can be either
265 <cf/on/, <cf/yes/ or a numeric expression with a non-zero value for the
266 option to be enabled or <cf/off/, <cf/no/ or a numeric expression evaluating
267 to zero to disable it. An empty <cf><m/switch/</cf> is equivalent to <cf/on/
268 ("silence means agreement").
271 <tag>preference <m/expr/</tag> Sets the preference of routes generated by this protocol. Default: protocol dependent.
273 <tag>disabled <m/switch/</tag> Disables the protocol. You can change the disable/enable status from the command
274 line interface without needing to touch the configuration. Disabled protocols are not activated. Default: protocol is enabled.
276 <tag>debug all|off|{ states, routes, filters, interfaces, events, packets }</tag>
277 Set protocol debugging options. If asked, each protocol is capable of
278 writing trace messages about its work to the log (with category
279 <cf/trace/). You can either request printing of <cf/all/ trace messages
280 or only of the types selected: <cf/states/ for protocol state changes
281 (protocol going up, down, starting, stopping etc.),
282 <cf/routes/ for routes exchanged with the routing table,
283 <cf/filters/ for details on route filtering,
284 <cf/interfaces/ for interface change events sent to the protocol,
285 <cf/events/ for events internal to the protocol and
286 <cf/packets/ for packets sent and received by the protocol. Default: off.
288 <tag>import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/filter expression/</tag>
289 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/.
291 <tag>export <m/filter/</tag> This is similar to the <cf>import</cf> keyword, except that it
292 works in the direction from the routing table to the protocol. Default: <cf/none/.
294 <tag>table <m/name/</tag> Connect this protocol to a non-default routing table.
297 <p>There are several options that give sense only with certain protocols:
300 <tag>passwords { password "<m/password/" from <m/time/ to <m/time/ passive <m/time/ id
301 <m/num/ [...] }</tag> Specifies passwords to be used with this protocol. <cf>Passive <m/time/</cf> is
302 time from which the password is not used for sending, but it is recognized on reception. <cf/id/ is password ID as needed by
303 certain protocols. Format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
305 <tag>interface "<m/mask/"|<m/prefix/ [ { <m/option/ ; [...] } ]</tag> Specifies which
306 interfaces is this protocol active on and allows you to set options on a
307 per-interface basis. Mask is specified as in shell-like patterns, thus <cf>interface
308 "*" { mode broadcast; };</cf> will start the protocol on all interfaces with <cf>mode
309 broadcast;</cf> option. If the first character of mask is <cf/-/, such interfaces are
310 excluded. Masks are parsed left-to-right, thus <cf/interface "-eth*", "*";/ means all but
311 the ethernets. Default: none.
315 <chapt>Remote control
317 <p>You can use the command-line client <file>birdc</file> to talk with
318 a running BIRD. Communication is done using a <file/bird.ctl/ UNIX domain
319 socket (unless changed with the <tt/-s/ option given to both the server and
320 the client). The commands can perform simple actions such as enabling/disabling
321 of protocols, telling BIRD to show various information, telling it to
322 show routing table filtered by filter, or asking BIRD to
323 reconfigure. Press <tt/?/ at any time to get online help. Option
324 <tt/-v/ can be passed to the client, to make it dump numeric return
325 codes along with the messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
326 own applications could do that, too -- the format of communication between
327 BIRD and <file/birdc/ is stable (see the programmer's documentation).
329 <p>Here is a brief list of supported functions:
332 <tag>dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
333 Dump contents of internal data structures to the debugging output.
335 <tag>show status</tag>
336 Show router status, that is BIRD version, uptime and time from last reconfiguration.
338 <tag>show protocols [all]</tag>
339 Show list of protocol instances along with tables they are connected to and protocol status, possibly giving verbose information, if <cf/all/ is specified.
341 <tag>show ospf [interface|neighbors] [<m/name/] ["<m/interface/"]</tag>
342 Show detailed information about OSPF protocol, possibly giving a verbose list of interfaces and neighbors. The <m/name/ of the protocol instance can be omitted if there exists only a single instance.
344 <tag>show static [<m/name/]</tag>
345 Show detailed information about static routes. The <m/name/ of the protocol instance can be omitted if there exists only a single instance.
347 <tag>show interfaces [summary]</tag>
348 Show the list of interfaces. For each interface, print its type, state, MTU and addresses assigned.
350 <tag>show symbols</tag>
351 Show the list of symbols defined in the configuration (names of protocols, routing tables etc.).
353 <tag>show route [[for] <m/prefix/|<m/IP/] [table <m/sym/] [filter <m/f/|where <m/c/] [(import|preimport) <m/p/] [<m/options/]</tag>
354 Show contents of a routing table (by default of the main one),
355 that is routes, their metrics and (in case the <cf/all/ switch is given)
356 all their attributes.
358 <p>You can specify a <m/prefix/ if you want to print routes for a
359 specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
360 the entry which will be used for forwarding of packets to the given
361 destination. By default, all routes for each network are printed with
362 the selected one at the top, unless <cf/primary/ is given in which case
363 only the selected route is shown.
365 <p>You can also ask for printing only routes processed and accepted by
366 a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
367 </cf> or matching a given condition (<cf>where <m/condition/</cf>).
368 The <cf/import/ and <cf/preimport/ switches ask for printing of entries
369 that are imported to the specified protocol. With <cf/preimport/, the
370 import filter of the protocol is skipped.
372 <p>The <cf/stats/ switch requests showing of route statistics (the
373 number of networks, number of routes before and after filtering). If
374 you use <cf/count/ instead, only the statistics will be printed.
376 <tag>enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
377 Enable, disable or restart a given protocol instance, instances matching the <cf><m/pattern/</cf> or <cf/all/ instances.
379 <tag>configure ["<m/config file/"]</tag>
380 Reload configuration from a given file.
385 <tag>debug <m/protocol/|<m/pattern/|all all|off|{ states | routes | filters | events | packets }</tag>
386 Control protocol debugging.
393 <p>BIRD contains a simple programming language. (No, it can't yet read mail :-). There are
394 two objects in this language: filters and functions. Filters are interpreted by BIRD core when a route is
395 being passed between protocols and routing tables. The filter language contains control structures such
396 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>.
398 <p>Filter gets the route, looks at its attributes and
399 modifies some of them if it wishes. At the end, it decides whether to
400 pass the changed route through (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks
407 if defined( rip_metric ) then
413 if rip_metric > 10 then
414 reject "RIP metric is too big";
420 <p>As you can see, a filter has a header, a list of local variables, and a body. The header consists of
421 the <cf/filter/ keyword followed by a (unique) name of filter. The list of local variables consists of
422 <cf><M>type name</M>;</cf> pairs where each pair defines one local variable. The body consists of
423 <cf> { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You can group
424 several statements to a single compound statement by using braces (<cf>{ <M>statements</M> }</cf>) which is useful if
425 you want to make a bigger block of code conditional.
427 <p>BIRD supports functions, so that you don't have to repeat the same blocks of code over and
428 over. Functions can have zero or more parameters and they can have local variables. Recursion is not allowed. Function definitions
438 function with_parameters (int parameter)
444 <p>Unlike in C, variables are declared after the <cf/function/ line, but before the first <cf/{/. You can't declare
445 variables in nested blocks. Functions are called like in C: <cf>name();
446 with_parameters(5);</cf>. Function may return values using the <cf>return <m/[expr]/</cf>
447 command. Returning a value exits from current function (this is similar to C).
449 <p>Filters are declared in a way similar to functions except they can't have explicit
450 parameters. They get a route table entry as an implicit parameter, it is also passed automatically
451 to any functions called. The filter must terminate with either
452 <cf/accept/ or <cf/reject/ statement. If there's a runtime error in filter, the route
455 <p>A nice trick to debug filters is to use <cf>show route filter
456 <m/name/</cf> from the command line client. An example session might look
460 pavel@bug:~/bird$ ./birdc -s bird.ctl
463 10.0.0.0/8 dev eth0 [direct1 23:21] (240)
464 195.113.30.2/32 dev tunl1 [direct1 23:21] (240)
465 127.0.0.0/8 dev lo [direct1 23:21] (240)
467 show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
468 bird> show route filter { if 127.0.0.5 ˜ net then accept; }
469 127.0.0.0/8 dev lo [direct1 23:21] (240)
475 <p>Each variable and each value has certain type. Booleans, integers and enums are
476 incompatible with each other (that is to prevent you from shooting in the foot).
479 <tag/bool/ This is a boolean type, it can have only two values, <cf/true/ and
480 <cf/false/. Boolean is the only type you can use in <cf/if/
483 <tag/int/ This is a general integer type, you can expect it to store signed values from -2000000000
484 to +2000000000. Overflows are not checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
486 <tag/pair/ This is a pair of two short integers. Each component can have values from 0 to
487 65535. Literals of this type is written as <cf/(1234,5678)/.
489 <tag/string/ This is a string of characters. There are no ways to modify strings in
490 filters. You can pass them between functions, assign them to variables of type <cf/string/, print
491 such variables, but you can't concatenate two strings. String literals
492 are written as <cf/"This is a string constant"/.
494 <tag/ip/ This type can hold a single IP address. Depending on the compile-time configuration of BIRD you are using, it
495 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>
496 on values of type ip. It masks out all but first <cf><M>num</M></cf> bits from the IP
497 address. So <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
499 <tag/prefix/ This type can hold a network prefix consisting of IP address and prefix length. Prefix literals are written as
500 <cf><M>ipaddress</M>/<M>pxlen</M></cf>, or
501 <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
502 operators on prefixes:
503 <cf/.ip/ which extracts the IP address from the pair, and <cf/.len/, which separates prefix
504 length from the pair. So <cf>1.2.0.0/16.pxlen = 16</cf> is true.
506 <tag/int|ip|prefix|pair|enum set/
507 Filters recognize four types of sets. Sets are similar to strings: you can pass them around
508 but you can't modify them. Literals of type <cf>set int</cf> look like <cf>
509 [ 1, 2, 5..7 ]</cf>. As you can see, both simple values and ranges are permitted in
510 sets. Sets of prefixes are special: you can specify which prefix lengths should match them by
511 using <cf>[ 1.0.0.0/8+, 2.0.0.0/8-, 3.0.0.0/8{5,6} ]</cf>. <cf>3.0.0.0/8{5,6}</cf> matches
512 prefixes <cf/3.X.X.X/ whose prefix length is 5 to 6. <cf><m>address</m>/<m>num</m>+</cf> is a shorthand for <cf><m>address</m>/{0,<m/num/}</cf>,
513 <cf><m>address</m>/<m/num/-</cf> is a shorthand for <cf><m>address</m>/{0,<m/num-1/}</cf>. For example,
514 <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{ 15 , 17 } ]</cf> is true, but
515 <cf>1.0.0.0/8 ˜ [ 1.0.0.0/8- ]</cf> is false.
518 Enumeration types are fixed sets of possibilities. You can't define your own
519 variables of such type, but some route attributes are of enumeration
520 type. Enumeration types are incompatible with each other.
523 BGP path is a list of autonomous system numbers. You can't write literals of this type.
526 BGP masks are patterns used for BGP path matching
527 (using <cf>path ˜ /2 3 5 ?/</cf> syntax). The masks
528 resemble wildcard patterns as used by UNIX shells. Autonomous
529 system numbers match themselves, <cf/?/ matches any (even empty)
530 sequence of arbitrary AS numbers (<cf/*/ hasn't been chosen, because
531 <cf>/*</cf> starts a comment). For example:
532 <tt>/4 3 2 1/ ˜ /? 4 3 ?/</tt> is true, but
533 <tt>/4 3 2 1/ ˜ /? 4 5 ?/</tt> is false.
535 Community list is similar to set of pairs,
536 except that unlike other sets, it can be modified.
537 There exist no literals of this type.
543 <p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>, parentheses <cf/(a*(b+c))/, comparison
544 <cf/(a=b, a!=b, a<b, a>=b)/. Logical operations include unary not (<cf/!/), and (<cf/&&/) and or (<cf/||/).
545 Special operators include <cf/˜/ for "is element of a set" operation - it can be
546 used on element and set of elements of the same type (returning true if element is contained in the given set), or on IP and prefix (returning true if IP is within the range defined by that prefix), or on
547 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).
550 <sect>Control structures
552 <p>Filters support two control structures: conditions and case switches.
554 <p>Syntax of a condition is: <cf>if
555 <M>boolean expression</M> then <M>command1</M>; else <M>command2</M>;</cf> and you can use <cf>{
556 <M>command_1</M>; <M>command_2</M>; <M>...</M> }</cf> instead of either command. The <cf>else</cf>
557 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.
559 <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case <m/expr/ { else |
560 <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [ ... ] }</cf>. The expression after
561 <cf>case</cf> can be of any type which can be on the left side of the ˜ operator and anything that could
562 be a member of a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/ grouping.
563 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.
565 <p>Here is example that uses <cf/if/ and <cf/case/ structures:
569 2: print "two"; print "I can do more commands without {}";
570 3 .. 5: print "three to five";
571 else: print "something else";
574 if 1234 = i then printn "."; else {
576 print "You need {} around multiple commands";
580 <sect>Route attributes
582 <p>A filter is implicitly passed a route, and it can access its
583 attributes just like it accesses variables. Attempts to access undefined
584 attribute result in a runtime error; you can check if an attribute is
585 defined by using the <cf>defined( <m>attribute</m> )</cf> operator.
588 <tag><m/prefix/ net</tag>
589 Network the route is talking about. Read-only. (See the chapter about routing tables.)
591 <tag><m/enum/ scope</tag>
592 Address scope of the network (<cf/SCOPE_HOST/ for addresses local to this host, <cf/SCOPE_LINK/ for those specific for a physical link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private addresses, <cf/SCOPE_UNIVERSE/ for globally visible addresses).
594 <tag><m/int/ preference</tag>
595 Preference of the route. (See the chapter about routing tables.)
597 <tag><m/ip/ from</tag>
598 The router which the route has originated from. Read-only.
601 Next hop packets routed using this route should be forwarded to.
603 <tag><m/enum/ source</tag>
604 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/.
606 <tag><m/enum/ cast</tag>
607 Route type (<cf/RTC_UNICAST/ for normal routes, <cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ for broadcast, multicast and anycast routes). Read-only.
609 <tag><m/enum/ dest</tag>
610 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.
613 <p>There also exist some protocol-specific attributes which are described in the corresponding protocol sections.
615 <sect>Other statements
617 <p>The following statements are available:
620 <tag><m/variable/ = <m/expr/</tag> Set variable to a given value.
622 <tag>accept|reject [ <m/expr/ ]</tag> Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
624 <tag>return <m/expr/</tag> Return <cf><m>expr</m></cf> from the current function, the function ends at this point.
626 <tag>print|printn <m/expr/ [<m/, expr.../]</tag>
627 Prints given expressions; useful mainly while debugging
628 filters. The <cf/printn/ variant does not terminate the line.
631 Terminates BIRD. Useful when debugging the filter interpreter.
638 <p>The Border Gateway Protocol is the routing protocol used for backbone
639 level routing in the today's Internet. Contrary to the other protocols, its convergence
640 doesn't rely on all routers following the same rules for route selection,
641 making it possible to implement any routing policy at any router in the
642 network, the only restriction being that if a router advertises a route,
643 it must accept and forward packets according to it.
645 <p>BGP works in terms of autonomous systems (often abbreviated as AS). Each
646 AS is a part of the network with common management and common routing policy. It is identified by a unique 16-bit number.
647 Routers within each AS usually communicate with each other using either a interior routing
648 protocol (such as OSPF or RIP) or an interior variant of BGP (called iBGP).
649 Boundary routers at the border of the AS communicate with their peers
650 in the neighboring AS'es via exterior BGP (eBGP).
652 <p>Each BGP router sends to its neighbors updates of the parts of its
653 routing table it wishes to export along with complete path information
654 (a list of AS'es the packet will travel through if it uses the particular
655 route) in order to avoid routing loops.
657 <p>BIRD supports all requirements of the BGP4 standard as defined in
658 RFC 4271<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4271.txt">
659 It also supports the community attributes
660 (RFC 1997<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1997.txt">),
661 capability negotiation
662 (RFC 3392<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc3392.txt">),
663 MD5 password authentication
664 (RFC 2385<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2385.txt">),
666 (RFC 4456<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4456.txt">),
668 (RFC 4893<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4893.txt">).
671 For IPv6, it uses the standard multiprotocol extensions defined in
672 RFC 2283<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2283.txt">
673 including changes described in the
674 latest draft<htmlurl url="ftp://ftp.rfc-editor.org/internet-drafts/draft-ietf-idr-bgp4-multiprotocol-v2-05.txt">
675 and applied to IPv6 according to
676 RFC 2545<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2545.txt">.
678 <sect1>Route selection rules
680 <p>BGP doesn't have any simple metric, so the rules for selection of an optimal
681 route among multiple BGP routes with the same preference are a bit more complex
682 and they are implemented according to the following algorithm. It starts the first
683 rule, if there are more "best" routes, then it uses the second rule to choose
684 among them and so on.
687 <item>Prefer route with the highest Local Preference attribute.
688 <item>Prefer route with the shortest AS path.
689 <item>Prefer IGP origin over EGP and EGP over incomplete.
690 <item>Prefer the lowest value of the Multiple Exit Discriminator.
691 <item>Prefer internal routes over external ones.
692 <item>Prefer the route with the lowest value of router ID of the
698 <p>Each instance of the BGP corresponds to one neighboring router.
699 This allows to set routing policy and all the other parameters differently
700 for each neighbor using the following configuration parameters:
703 <tag>local as <m/number/</tag> Define which AS we are part of. (Note that
704 contrary to other IP routers, BIRD is able to act as a router located
705 in multiple AS'es simultaneously, but in such cases you need to tweak
706 the BGP paths manually in the filters to get consistent behavior.)
707 This parameter is mandatory.
709 <tag>neighbor <m/ip/ as <m/number/</tag> Define neighboring router
710 this instance will be talking to and what AS it's located in. Unless
711 you use the <cf/multihop/ clause, it must be directly connected to one
712 of your router's interfaces. In case the neighbor is in the same AS
713 as we are, we automatically switch to iBGP. This parameter is mandatory.
715 <tag>multihop <m/number/ via <m/ip/</tag> Configure multihop BGP to a
716 neighbor which is connected at most <m/number/ hops far and to which
717 we should route via our direct neighbor with address <m/ip/.
718 Default: switched off.
720 <tag>next hop self</tag> Avoid calculation of the Next Hop attribute
721 and always advertise our own source address (see below) as a next hop.
722 This needs to be used only
723 occasionally to circumvent misconfigurations of other routers.
726 <tag>source address <m/ip/</tag> Define local address we should use
727 for next hop calculation. Default: the address of the local end
728 of the interface our neighbor is connected to.
730 <tag>password <m/string/</tag> Use this password for MD5 authentication
731 of BGP sessions. Default: no authentication.
733 <tag>rr client</tag> Be a route reflector and treat neighbor as
734 route reflection client. Default: disabled.
736 <tag>rr cluster id <m/IPv4 address/</tag> Route reflectors use cluster id
737 to avoid route reflection loops. When there is one route reflector in a cluster
738 it usually uses its router id as a cluster id, but when there are more route
739 reflectors in a cluster, these need to be configured (using this option) to
740 use a common cluster id. Clients in a cluster need not known their cluster
741 id and this option is not allowed to them Default: a same as router id.
743 <tag>enable as4 <m/switch/</tag> BGP protocol was designed to use 2B AS numbers
744 and was extended later to allow 4B AS number. BIRD supports 4B AS extension,
745 but by disabling this option it can be persuaded not to advertise it and
746 to maintain old-style sessions with its neighbors. This might be useful for
747 circumventing bugs in neighbor's implementation of 4B AS extension.
748 Even when disabled (off), BIRD behaves internally as AS4-aware BGP router.
751 <tag>disable after error <m/switch/</tag> When an error is encountered (either
752 locally or by the other side), disable the instance automatically
753 and wait for an administrator to fix the problem manually. Default: off.
755 <tag>hold time <m/number/</tag> Time in seconds to wait for a Keepalive
756 message from the other side before considering the connection stale.
757 Default: depends on agreement with the neighboring router, we prefer
758 240 seconds if the other side is willing to accept it.
760 <tag>startup hold time <m/number/</tag> Value of the hold timer used
761 before the routers have a chance to exchange open messages and agree
762 on the real value. Default: 240 seconds.
764 <tag>keepalive time <m/number/</tag> Delay in seconds between sending
765 of two consecutive Keepalive messages. Default: One third of the hold time.
767 <tag>connect retry time <m/number/</tag> Time in seconds to wait before
768 retrying a failed attempt to connect. Default: 120 seconds.
770 <tag>start delay time <m/number/</tag> Delay in seconds between protocol
771 startup and the first attempt to connect. Default: 5 seconds.
773 <tag>error wait time <m/number/,<m/number/</tag> Minimum and maximum delay in seconds between a protocol
774 failure (either local or reported by the peer) and automatic restart.
775 Doesn't apply when <cf/disable after error/ is configured. If consecutive
776 errors happen, the delay is increased exponentially until it reaches the maximum. Default: 60, 300.
778 <tag>error forget time <m/number/</tag> Maximum time in seconds between two protocol
779 failures to treat them as a error sequence which makes the <cf/error wait time/
780 increase exponentially. Default: 300 seconds.
782 <tag>path metric <m/switch/</tag> Enable comparison of path lengths
783 when deciding which BGP route is the best one. Default: on.
785 <tag>default bgp_med <m/number/</tag> Value of the Multiple Exit
786 Discriminator to be used during route selection when the MED attribute
787 is missing. Default: 0.
789 <tag>default bgp_local_pref <m/number/</tag> Value of the Local Preference
790 to be used during route selection when the Local Preference attribute
791 is missing. Default: 0.
796 <p>BGP defines several route attributes. Some of them (those marked with `<tt/I/' in the
797 table below) are available on internal BGP connections only, some of them (marked
798 with `<tt/O/') are optional.
801 <tag>bgppath <cf/bgp_path/</tag> Sequence of AS numbers describing the AS path
802 the packet will travel through when forwarded according to the particular route. In case of
803 internal BGP it doesn't contain the number of the local AS.
805 <tag>int <cf/bgp_local_pref/ [I]</tag> Local preference value used for
806 selection among multiple BGP routes (see the selection rules above). It's
807 used as an additional metric which is propagated through the whole local AS.
809 <tag>int <cf/bgp_med/ [O]</tag> The Multiple Exit Discriminator of the route
810 is an optional attribute which is used on on external (inter-AS) links to
811 convey to an adjacent AS the optimal entry point into the local AS.
812 The received attribute may be also propagated over internal BGP links
813 (and this is default behavior). The attribute value is zeroed when a route
814 is exported from a routing table to a BGP instance to ensure that the attribute
815 received from a neighboring AS is not propagated to other neighboring ASes.
816 A new value might be set in the export filter of a BGP instance.
817 See RFC 4451<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4451.txt">
818 for further discussion of BGP MED attribute.
820 <tag>enum <cf/bgp_origin/</tag> Origin of the route: either <cf/ORIGIN_IGP/
821 if the route has originated in an interior routing protocol or
822 <cf/ORIGIN_EGP/ if it's been imported from the <tt>EGP</tt> protocol
823 (nowadays it seems to be obsolete) or <cf/ORIGIN_INCOMPLETE/ if the origin
826 <tag>ip <cf/bgp_next_hop/</tag> Next hop to be used for forwarding of packets
827 to this destination. On internal BGP connections, it's an address of the
828 originating router if it's inside the local AS or a boundary router the
829 packet will leave the AS through if it's an exterior route, so each BGP
830 speaker within the AS has a chance to use the shortest interior path
831 possible to this point.
833 <tag>void <cf/bgp_atomic_aggr/ [O]</tag> This is an optional attribute
834 which carries no value, but the sole presence of which indicates that the route
835 has been aggregated from multiple routes by some router on the path from
838 <!-- we don't handle aggregators right since they are of a very obscure type
839 <tag>bgp_aggregator</tag>
841 <tag>clist <cf/bgp_community/ [O]</tag> List of community values associated
842 with the route. Each such value is a pair (represented as a <cf/pair/ data
843 type inside the filters) of 16-bit integers, the first of them containing the number of the AS which defines
844 the community and the second one being a per-AS identifier. There are lots
845 of uses of the community mechanism, but generally they are used to carry
846 policy information like "don't export to USA peers". As each AS can define
847 its own routing policy, it also has a complete freedom about which community
848 attributes it defines and what will their semantics be.
855 local as 65000; # Use a private AS number
856 neighbor 62.168.0.130 as 5588; # Our neighbor ...
857 multihop 20 via 62.168.0.13; # ... which is connected indirectly
858 export filter { # We use non-trivial export rules
859 if source = RTS_STATIC then { # Export only static routes
860 # Assign our community
861 bgp_community.add((65000,5678));
862 # Artificially increase path length
863 # by advertising local AS number twice
864 if bgp_path ~ / 65000 / then
865 bgp_path.prepend(65000);
871 source address 62.168.0.1; # Use a non-standard source address
877 <p>The Device protocol is not a real routing protocol. It doesn't generate
878 any routes and it only serves as a module for getting information about network
879 interfaces from the kernel.
881 <p>Except for very unusual circumstances, you probably should include
882 this protocol in the configuration since almost all other protocols
883 require network interfaces to be defined for them to work with.
885 <p>The only configurable thing is interface scan time:
888 <tag>scan time <m/number/</tag> Time in seconds between two scans
889 of the network interface list. On systems where we are notified about
890 interface status changes asynchronously (such as newer versions of
891 Linux), we need to scan the list only in order to avoid confusion by lost
892 notification messages, so the default time is set to a large value.
895 <p>As the Device protocol doesn't generate any routes, it cannot have
896 any attributes. Example configuration looks really simple:
900 scan time 10; # Scan the interfaces often
906 <p>The Direct protocol is a simple generator of device routes for all the
907 directly connected networks according to the list of interfaces provided
908 by the kernel via the Device protocol.
910 <p>It's highly recommended to include this protocol in your configuration
911 unless you want to use BIRD as a route server or a route reflector, that is
912 on a machine which doesn't forward packets itself and only participates in
913 distribution of routing information.
915 <p>The only configurable thing about direct is what interfaces it watches:
918 <tag>interface <m/pattern [, ...]/</tag> By default, the Direct
919 protocol will generate device routes for all the interfaces
920 available. If you want to restrict it to some subset of interfaces
921 (for example if you're using multiple routing tables for policy
922 routing and some of the policy domains don't contain all interfaces),
923 just use this clause.
926 <p>Direct device routes don't contain any specific attributes.
928 <p>Example config might look like this:
932 interface "-arc*", "*"; # Exclude the ARCnets
938 <p>The Kernel protocol is not a real routing protocol. Instead of communicating
939 the with other routers in the network, it performs synchronization of BIRD's routing
940 tables with the OS kernel. Basically, it sends all routing table updates to the kernel
941 and from time to time it scans the kernel tables to see whether some routes have
942 disappeared (for example due to unnoticed up/down transition of an interface)
943 or whether an `alien' route has been added by someone else (depending on the
944 <cf/learn/ switch, such routes are either deleted or accepted to our
947 <p>If your OS supports only a single routing table, you can configure only one
948 instance of the Kernel protocol. If it supports multiple tables (in order to
949 allow policy routing; such an OS is for example Linux 2.2), you can run as many instances as you want, but each of
950 them must be connected to a different BIRD routing table and to a different
956 <tag>persist <m/switch/</tag> Tell BIRD to leave all its routes in the
957 routing tables when it exits (instead of cleaning them up).
958 <tag>scan time <m/number/</tag> Time in seconds between two consecutive scans of the
959 kernel routing table.
960 <tag>learn <m/switch/</tag> Enable learning of routes added to the kernel
961 routing tables by other routing daemons or by the system administrator.
962 This is possible only on systems which support identification of route
964 <tag>kernel table <m/number/</tag> Select which kernel table should
965 this particular instance of the Kernel protocol work with. Available
966 only on systems supporting multiple routing tables.
969 <p>The Kernel protocol doesn't define any route attributes.
970 <p>A simple configuration can look this way:
979 <p>Or for a system with two routing tables:
982 protocol kernel { # Primary routing table
983 learn; # Learn alien routes from the kernel
984 persist; # Don't remove routes on bird shutdown
985 scan time 10; # Scan kernel routing table every 10 seconds
990 protocol kernel { # Secondary routing table
1001 <p>Open Shortest Path First (OSPF) is a quite complex interior gateway
1002 protocol. The current IPv4 version (OSPFv2) is defined
1003 in RFC 2328<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt">. It's a link
1004 state (a.k.a. shortest path first) protocol -- each router maintains a database
1005 describing the autonomous system's topology. Each participating router
1006 has an identical copy of the database and all routers run the same algorithm
1007 calculating a shortest path tree with themselves as a root.
1008 OSPF chooses the least cost path as the best path.
1009 (OSPFv3 - OSPF for IPv6 is not supported yet.)
1011 <p>In OSPF, the autonomous system can be split to several areas in order
1012 to reduce the amount of resources consumed for exchanging the routing
1013 information and to protect the other areas from incorrect routing data.
1014 Topology of the area is hidden to the rest of the autonomous system.
1016 <p>Another very important feature of OSPF is that
1017 it can keep routing information from other protocols (like Static or BGP)
1018 in its link state database as external routes. Each external route can
1019 be tagged by the advertising router, making it possible to pass additional
1020 information between routers on the boundary of the autonomous system.
1022 <p>OSPF quickly detects topological changes in the autonomous system (such
1023 as router interface failures) and calculates new loop-free routes after a short
1024 period of convergence. Only a minimal amount of
1025 routing traffic is involved.
1027 <p>Each router participating in OSPF routing periodically sends Hello messages
1028 to all its interfaces. This allows neighbors to be discovered dynamically.
1029 Then the neighbors exchange theirs parts of the link state database and keep it
1030 identical by flooding updates. The flooding process is reliable and ensures
1031 that each router detects all changes.
1033 <sect1>Configuration
1035 <p>In the main part of configuration, there can be multiple definitions of
1036 OSPF area witch different id included. These definitions includes many other
1037 switches and multiple definitions of interfaces. Definition of interface
1038 may contain many switches and constant definitions and list of neighbors
1039 on nonbroadcast networks.
1042 protocol ospf <name> {
1043 rfc1583compat <switch>;
1046 stub cost <num>;
1049 <prefix> hidden;
1051 interface <interface pattern>
1054 stub <switch>;
1057 retransmit <num>;
1058 priority <num>;
1060 dead count <num>;
1062 rx buffer [normal|large|<num>];
1063 type [broadcast|nonbroadcast|pointopoint];
1064 strict nonbroadcast <switch>;
1065 authentication [none|simple];
1066 password "<text>";
1068 password "<text>" {
1070 generate from "<date>";
1071 generate to "<date>";
1072 accept from "<date>";
1073 accept to "<date>";
1078 <ip> eligible;
1081 virtual link <id>
1084 retransmit <num>;
1086 dead count <num>;
1088 authentication [none|simple];
1089 password "<text>";
1096 <tag>rfc1583compat <M>switch</M></tag>
1097 This option controls compatibility of routing table
1098 calculation with RFC 1583<htmlurl
1099 url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
1102 <tag>area <M>id</M></tag>
1103 This defines an OSPF area with given area ID (an integer or an IPv4
1104 address, similarly to a router ID).
1105 The most important area is
1106 the backbone (ID 0) to which every other area must be connected.
1108 <tag>stub cost <M>num</M></tag>
1109 No external (except default) routes are flooded into stub areas.
1110 Setting this value marks area stub with defined cost of default route.
1111 Default value is no. (Area is not stub.)
1113 <tag>tick <M>num</M></tag>
1114 The routing table calculation and clean-up of areas' databases
1115 is not performed when a single link state
1116 change arrives. To lower the CPU utilization, it's processed later
1117 at periodical intervals of <m/num/ seconds. The default value is 1.
1119 <tag>networks { <m/set/ }</tag>
1120 Definition of area IP ranges. This is used in summary lsa origination.
1121 Hidden networks are not propagated into other areas.
1123 <tag>interface <M>pattern</M></tag>
1124 Defines that the specified interfaces belong to the area being defined.
1126 <tag>virtual link <M>id</M></tag>
1127 Virtual link to router with the router id. Virtual link acts as a
1128 point-to-point interface belonging to backbone. The actual area is
1129 used as transport area. This item cannot be in the backbone.
1131 <tag>cost <M>num</M></tag>
1132 Specifies output cost (metric) of an interface. Default value is 10.
1134 <tag>stub <M>switch</M></tag>
1135 If set to interface it does not listen to any packet and does not send
1136 any hello. Default value is no.
1138 <tag>hello <M>num</M></tag>
1139 Specifies interval in seconds between sending of Hello messages. Beware, all
1140 routers on the same network need to have the same hello interval.
1141 Default value is 10.
1143 <tag>poll <M>num</M></tag>
1144 Specifies interval in seconds between sending of Hello messages for
1145 some neighbors on NBMA network. Default value is 20.
1147 <tag>retransmit <M>num</M></tag>
1148 Specifies interval in seconds between retransmissions of unacknowledged updates.
1151 <tag>priority <M>num</M></tag>
1152 On every multiple access network (e.g., the Ethernet) Designed Router
1153 and Backup Designed router are elected. These routers have some
1154 special functions in the flooding process. Higher priority increases
1155 preferences in this election. Routers with priority 0 are not
1156 eligible. Default value is 1.
1158 <tag>wait <M>num</M></tag>
1159 After start, router waits for the specified number of seconds between starting
1160 election and building adjacency. Default value is 40.
1162 <tag>dead count <M>num</M></tag>
1163 When the router does not receive any messages from a neighbor in
1164 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
1166 <tag>dead <M>num</M></tag>
1167 When the router does not receive any messages from a neighbor in
1168 <m/dead/ seconds, it will consider the neighbor down. If both directives
1169 <m/dead count/ and <m/dead/ are used, <m/dead/ has precendence.
1171 <tag>rx buffer <M>num</M></tag>
1172 This sets the size of buffer used for receiving packets. The buffer should
1173 be bigger than maximal size of any packets. Value NORMAL (default)
1174 means 2*MTU, value LARGE means maximal allowed packet - 65536.
1176 <tag>type broadcast</tag>
1177 BIRD detects a type of a connected network automatically, but sometimes it's
1178 convenient to force use of a different type manually.
1179 On broadcast networks, flooding and Hello messages are sent using multicasts
1180 (a single packet for all the neighbors).
1182 <tag>type pointopoint</tag>
1183 Point-to-point networks connect just 2 routers together. No election
1184 is performed there which reduces the number of messages sent.
1186 <tag>type nonbroadcast</tag>
1187 On nonbroadcast networks, the packets are sent to each neighbor
1188 separately because of lack of multicast capabilities.
1190 <tag>strict nonbroadcast <M>switch</M></tag>
1191 If set, don't send hello to any undefined neighbor. This switch
1192 is ignored on on any non-NBMA network. Default is No.
1194 <tag>authentication none</tag>
1195 No passwords are sent in OSPF packets. This is the default value.
1197 <tag>authentication simple</tag>
1198 Every packet carries 8 bytes of password. Received packets
1199 lacking this password are ignored. This authentication mechanism is
1202 <tag>authentication cryptographic</tag>
1203 16-byte long md5 digest is appended to every packet. For the digest
1204 generation 16-byte long passwords are used. Those passwords are
1205 not sent via network, so this mechanismus is quite secure.
1206 Packets can still be read by an attacker.
1208 <tag>password "<M>text</M>"</tag>
1209 An 8-byte or 16-byte password used for authentication.
1211 <tag>id <M>num</M></tag>
1212 ID of the password, (0-255). If it's not used, BIRD will choose
1215 <tag>generate from <M>date</M></tag>
1216 The start time of the usage of the password for packet signing.
1218 <tag>generate to <M>date</M></tag>
1219 The last time of the usage of the password for packet signing.
1221 <tag>accept from <M>date</M></tag>
1222 The start time of the usage of the password for packet verification.
1224 <tag>accept to <M>date</M></tag>
1225 The last time of the usage of the password for packet verification.
1227 <tag>neighbors { <m/set/ } </tag>
1228 A set of neighbors to which Hello messages on nonbroadcast networks
1229 are to be sent. Some of them could be marked as eligible.
1235 <p>OSPF defines three route attributes. Each internal route has a <cf/metric/
1236 Metric is ranging from 1 to infinity (65535).
1237 External routes use <cf/metric type 1/ or <cf/metric type 2/.
1238 A <cf/metric of type 1/ is comparable with internal <cf/metric/, a
1239 <cf/metric of type 2/ is always longer
1240 than any <cf/metric of type 1/ or any <cf/internal metric/.
1241 If you specify both metrics only metric1 is used.
1242 Each external route can also carry a <cf/tag/ which is a 32-bit
1243 integer which is used when exporting routes to other protocols;
1244 otherwise, it doesn't affect routing inside the OSPF domain at all.
1245 Default is <cf/metric of type 2 = 10000/ and <cf/tag = 0/.
1252 protocol ospf MyOSPF {
1253 rfc1583compatibility yes;
1256 if source = RTS_BGP then {
1268 authentication simple;
1273 authentication cryptographic;
1277 generate to "22-04-2003 11:00:06";
1278 accept from "17-01-2001 12:01:05";
1282 generate to "22-07-2005 17:03:21";
1283 accept from "22-02-2001 11:34:06";
1297 172.16.2.0/24 hidden;
1299 interface "-arc0" , "arc*" {
1301 authentication none;
1302 strict nonbroadcast yes;
1307 192.168.120.1 eligible;
1320 <p>The Pipe protocol serves as a link between two routing tables, allowing routes to be
1321 passed from a table declared as primary (i.e., the one the pipe is connected to using the
1322 <cf/table/ configuration keyword) to the secondary one (declared using <cf/peer table/)
1323 and vice versa, depending on what's allowed by the filters. Export filters control export
1324 of routes from the primary table to the secondary one, import filters control the opposite
1327 <p>The primary use of multiple routing tables and the Pipe protocol is for policy routing,
1328 where handling of a single packet doesn't depend only on its destination address, but also
1329 on its source address, source interface, protocol type and other similar parameters.
1330 In many systems (Linux 2.2 being a good example), the kernel allows to enforce routing policies
1331 by defining routing rules which choose one of several routing tables to be used for a packet
1332 according to its parameters. Setting of these rules is outside the scope of BIRD's work
1333 (on Linux, you can use the <tt/ip/ command), but you can create several routing tables in BIRD,
1334 connect them to the kernel ones, use filters to control which routes appear in which tables
1335 and also you can employ the Pipe protocol for exporting a selected subset of one table to
1338 <sect1>Configuration
1341 <tag>peer table <m/table/</tag> Define secondary routing table to connect to. The
1342 primary one is selected by the <cf/table/ keyword.
1347 <p>The Pipe protocol doesn't define any route attributes.
1351 <p>Let's consider a router which serves as a boundary router of two different autonomous
1352 systems, each of them connected to a subset of interfaces of the router, having its own
1353 exterior connectivity and wishing to use the other AS as a backup connectivity in case
1354 of outage of its own exterior line.
1356 <p>Probably the simplest solution to this situation is to use two routing tables (we'll
1357 call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that packets having
1358 arrived from interfaces belonging to the first AS will be routed according to <cf/as1/
1359 and similarly for the second AS. Thus we have split our router to two logical routers,
1360 each one acting on its own routing table, having its own routing protocols on its own
1361 interfaces. In order to use the other AS's routes for backup purposes, we can pass
1362 the routes between the tables through a Pipe protocol while decreasing their preferences
1363 and correcting their BGP paths to reflect the AS boundary crossing.
1366 table as1; # Define the tables
1369 protocol kernel kern1 { # Synchronize them with the kernel
1374 protocol kernel kern2 {
1379 protocol bgp bgp1 { # The outside connections
1382 neighbor 192.168.0.1 as 1001;
1390 neighbor 10.0.0.1 as 1002;
1395 protocol pipe { # The Pipe
1399 if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks
1400 if preference>10 then preference = preference-10;
1401 if source=RTS_BGP then bgp_path.prepend(1);
1407 if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks
1408 if preference>10 then preference = preference-10;
1409 if source=RTS_BGP then bgp_path.prepend(2);
1421 <p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol, where each router broadcasts (to all its neighbors)
1422 distances to all networks it can reach. When a router hears distance to another network, it increments
1423 it and broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some network goes
1424 unreachable, routers keep telling each other that its distance is the original distance plus 1 (actually, plus
1425 interface metric, which is usually one). After some time, the distance reaches infinity (that's 15 in
1426 RIP) and all routers know that network is unreachable. RIP tries to minimize situations where
1427 counting to infinity is necessary, because it is slow. Due to infinity being 16, you can't use
1428 RIP on networks where maximal distance is higher than 15 hosts. You can read more about RIP at <HTMLURL
1429 URL="http://www.ietf.org/html.charters/rip-charter.html" name="http://www.ietf.org/html.charters/rip-charter.html">. Both IPv4
1430 (RFC 1723<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1723.txt">)
1431 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
1432 not currently supported. RIPv4 md5 authentication (RFC 2082<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2082.txt">) is supported.
1434 <p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
1435 convergence, big network load and inability to handle larger networks
1436 makes it pretty much obsolete in IPv4 world. (It is still usable on
1437 very small networks.) It is widely used in IPv6 networks,
1438 because there are no good implementations of OSPFv3.
1440 <sect1>Configuration
1442 <p>In addition to options common for all to other protocols, RIP supports the following ones:
1445 <tag/authentication none|plaintext|md5/ selects authentication method to be used. <cf/none/ means that
1446 packets are not authenticated at all, <cf/plaintext/ means that a plaintext password is embedded
1447 into each packet, and <cf/md5/ means that packets are authenticated using a md5 cryptographic
1448 hash. If you set authentication to not-none, it is a good idea to add <cf>passwords { }</cf>
1449 section. Default: none.
1451 <tag>honor always|neighbor|never </tag>specifies when should requests for dumping routing table
1452 be honored. (Always, when sent from a host on a directly connected
1453 network or never.) Routing table updates are honored only from
1454 neighbors, that is not configurable. Default: never.
1457 <p>There are two options that can be specified per-interface. First is <cf>metric</cf>, with
1458 default one. Second is <cf>mode multicast|broadcast|quiet|nolisten|version1</cf>, it selects mode for
1459 rip to work in. If nothing is specified, rip runs in multicast mode. <cf>version1</cf> is
1460 currently equivalent to <cf>broadcast</cf>, and it makes RIP talk to a broadcast address even
1461 through multicast mode is possible. <cf>quiet</cf> option means that RIP will not transmit
1462 any periodic messages to this interface and <cf>nolisten</cf> means that RIP will send to this
1463 interface but not listen to it.
1465 <p>The following options generally override behavior specified in RFC. If you use any of these
1466 options, BIRD will no longer be RFC-compliant, which means it will not be able to talk to anything
1467 other than equally configured BIRD. I have warned you.
1470 <tag>port <M>number</M></tag>
1471 selects IP port to operate on, default 520. (This is useful when testing BIRD, if you
1472 set this to an address >1024, you will not need to run bird with UID==0).
1474 <tag>infinity <M>number</M></tag>
1475 selects the value of infinity, default is 16. Bigger values will make protocol convergence
1478 <tag>period <M>number</M>
1479 </tag>specifies the number of seconds between periodic updates. Default is 30 seconds. A lower
1480 number will mean faster convergence but bigger network
1481 load. Do not use values lower than 10.
1483 <tag>timeout time <M>number</M>
1484 </tag>specifies how old route has to be to be considered unreachable. Default is 4*<cf/period/.
1486 <tag>garbage time <M>number</M>
1487 </tag>specifies how old route has to be to be discarded. Default is 10*<cf/period/.
1492 <p>RIP defines two route attributes:
1495 <tag>int <cf/rip_metric/</tag> RIP metric of the route (ranging from 0 to <cf/infinity/).
1496 When routes from different RIP instances are available and all of them have the same
1497 preference, BIRD prefers the route with lowest <cf/rip_metric/.
1498 When importing a non-RIP route, the metric defaults to 5.
1500 <tag>int <cf/rip_tag/</tag> RIP route tag: a 16-bit number which can be used
1501 to carry additional information with the route (for example, an originating AS number
1502 in case of external routes). When importing a non-RIP route, the tag defaults to 0.
1508 protocol rip MyRIP_test {
1513 interface "eth0" { metric 3; mode multicast; }
1514 "eth1" { metric 2; mode broadcast; };
1516 authentication none;
1517 import filter { print "importing"; accept; };
1518 export filter { print "exporting"; accept; };
1524 <p>The Static protocol doesn't communicate with other routers in the network,
1525 but instead it allows you to define routes manually. This is often used for
1526 specifying how to forward packets to parts of the network which don't use
1527 dynamic routing at all and also for defining sink routes (i.e., those
1528 telling to return packets as undeliverable if they are in your IP block,
1529 you don't have any specific destination for them and you don't want to send
1530 them out through the default route to prevent routing loops).
1532 <p>There are three types of static routes: `classical' routes telling to
1533 forward packets to a neighboring router, device routes specifying forwarding
1534 to hosts on a directly connected network and special routes (sink, blackhole
1535 etc.) which specify a special action to be done instead of forwarding the
1538 <p>When the particular destination is not available (the interface is down or
1539 the next hop of the route is not a neighbor at the moment), Static just
1540 uninstalls the route from the table it is connected to and adds it again as soon
1541 as the destination becomes adjacent again.
1543 <p>The Static protocol has no configuration options. Instead, the
1544 definition of the protocol contains a list of static routes:
1547 <tag>route <m/prefix/ via <m/ip/</tag> Static route through
1548 a neighboring router.
1549 <tag>route <m/prefix/ via <m/"interface"/</tag> Static device
1550 route through an interface to hosts on a directly connected network.
1551 <tag>route <m/prefix/ drop|reject|prohibit</tag> Special routes
1552 specifying to drop the packet, return it as unreachable or return
1553 it as administratively prohibited.
1556 <p>Static routes have no specific attributes.
1558 <p>Example static config might look like this:
1562 table testable; # Connect to a non-default routing table
1563 route 0.0.0.0/0 via 62.168.0.13; # Default route
1564 route 62.168.0.0/25 reject; # Sink route
1565 route 10.2.0.0/24 via "arc0"; # Secondary network
1573 <p>Although BIRD supports all the commonly used routing protocols,
1574 there are still some features which would surely deserve to be
1575 implemented in future versions of BIRD:
1578 <item>OSPF for IPv6 networks
1579 <item>OSPF NSSA areas and opaque LSA's
1580 <item>Route aggregation and flap dampening
1581 <item>Generation of IPv6 router advertisements
1582 <item>Multipath routes
1583 <item>Multicast routing protocols
1584 <item>Ports to other systems
1587 <sect>Getting more help
1589 <p>If you use BIRD, you're welcome to join the bird-users mailing list
1590 (<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">)
1591 where you can share your experiences with the other users and consult
1592 your problems with the authors. To subscribe to the list, just send a
1593 <tt/subscribe bird-users/ command in a body of a mail to
1594 (<HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">).
1595 The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
1597 <p>BIRD is a relatively young system and it probably contains some
1598 bugs. You can report any problems to the bird-users list and the authors
1599 will be glad to solve them, but before you do so,
1600 please make sure you have read the available documentation and that you are running the latest version (available at <HTMLURL
1601 URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, a patch
1602 which fixes the bug is always welcome as an attachment.)
1604 <p>If you want to understand what is going inside, Internet standards are
1605 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">).
1612 LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel
1613 LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
1614 LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
1615 LocalWords: len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth
1616 LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek
1617 LocalWords: EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC
1618 LocalWords: OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU
1619 LocalWords: uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc
1620 LocalWords: compat multicasts nonbroadcast pointopoint loopback sym stats
1621 LocalWords: Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt
1622 LocalWords: proto wildcard