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17: Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
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20:
21: <book>
22:
23: <title>BIRD User's Guide
24: <author>
25: Ondrej Filip <it/<feela@network.cz>/,
26: Pavel Machek <it/<pavel@ucw.cz>/,
27: Martin Mares <it/<mj@ucw.cz>/,
28: Ondrej Zajicek <it/<santiago@crfreenet.org>/
29: </author>
30:
31: <abstract>
32: This document contains user documentation for the BIRD Internet Routing Daemon project.
33: </abstract>
34:
35: <!-- Table of contents -->
36: <toc>
37:
38: <!-- Begin the document -->
39:
40:
41: <chapt>Introduction
42: <label id="intro">
43:
44: <sect>What is BIRD
45: <label id="what-is-bird">
46:
47: <p>The name `BIRD' is actually an acronym standing for `BIRD Internet Routing
48: Daemon'. Let's take a closer look at the meaning of the name:
49:
50: <p><em/BIRD/: Well, we think we have already explained that. It's an acronym
51: standing for `BIRD Internet Routing Daemon', you remember, don't you? :-)
52:
53: <p><em/Internet Routing/: It's a program (well, a daemon, as you are going to
54: discover in a moment) which works as a dynamic router in an Internet type
55: network (that is, in a network running either the IPv4 or the IPv6 protocol).
56: Routers are devices which forward packets between interconnected networks in
57: order to allow hosts not connected directly to the same local area network to
58: communicate with each other. They also communicate with the other routers in the
59: Internet to discover the topology of the network which allows them to find
60: optimal (in terms of some metric) rules for forwarding of packets (which are
61: called routing tables) and to adapt themselves to the changing conditions such
62: as outages of network links, building of new connections and so on. Most of
63: these routers are costly dedicated devices running obscure firmware which is
64: hard to configure and not open to any changes (on the other hand, their special
65: hardware design allows them to keep up with lots of high-speed network
66: interfaces, better than general-purpose computer does). Fortunately, most
67: operating systems of the UNIX family allow an ordinary computer to act as a
68: router and forward packets belonging to the other hosts, but only according to a
69: statically configured table.
70:
71: <p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program
72: running on background which does the dynamic part of Internet routing, that is
73: it communicates with the other routers, calculates routing tables and sends them
74: to the OS kernel which does the actual packet forwarding. There already exist
75: other such routing daemons: routed (RIP only), GateD (non-free),
76: <HTMLURL URL="http://www.zebra.org" name="Zebra"> and
77: <HTMLURL URL="http://sourceforge.net/projects/mrt" name="MRTD">,
78: but their capabilities are limited and they are relatively hard to configure
79: and maintain.
80:
81: <p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
82: to support all the routing technology used in the today's Internet or planned to
83: be used in near future and to have a clean extensible architecture allowing new
84: routing protocols to be incorporated easily. Among other features, BIRD
85: supports:
86:
87: <itemize>
88: <item>both IPv4 and IPv6 protocols
89: <item>multiple routing tables
90: <item>the Border Gateway Protocol (BGPv4)
91: <item>the Routing Information Protocol (RIPv2)
92: <item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
93: <item>the Router Advertisements for IPv6 hosts
94: <item>a virtual protocol for exchange of routes between different
95: routing tables on a single host
96: <item>a command-line interface allowing on-line control and inspection
97: of status of the daemon
98: <item>soft reconfiguration (no need to use complex online commands to
99: change the configuration, just edit the configuration file and
100: notify BIRD to re-read it and it will smoothly switch itself to
101: the new configuration, not disturbing routing protocols unless
102: they are affected by the configuration changes)
103: <item>a powerful language for route filtering
104: </itemize>
105:
106: <p>BIRD has been developed at the Faculty of Math and Physics, Charles
107: University, Prague, Czech Republic as a student project. It can be freely
108: distributed under the terms of the GNU General Public License.
109:
110: <p>BIRD has been designed to work on all UNIX-like systems. It has been
111: developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD
112: and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively
113: easy due to its highly modular architecture.
114:
115: <p>BIRD supports either IPv4 or IPv6 protocol, but have to be compiled separately
116: for each one. Therefore, a dualstack router would run two instances of BIRD (one
117: for IPv4 and one for IPv6), with completely separate setups (configuration
118: files, tools ...).
119:
120:
121: <sect>Installing BIRD
122: <label id="install">
123:
124: <p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make)
125: and Perl, installing BIRD should be as easy as:
126:
127: <code>
128: ./configure
129: make
130: make install
131: vi /usr/local/etc/bird.conf
132: bird
133: </code>
134:
135: <p>You can use <tt>./configure --help</tt> to get a list of configure
136: options. The most important ones are: <tt/--enable-ipv6/ which enables building
137: of an IPv6 version of BIRD, <tt/--with-protocols=/ to produce a slightly smaller
138: BIRD executable by configuring out routing protocols you don't use, and
139: <tt/--prefix=/ to install BIRD to a place different from <file>/usr/local</file>.
140:
141:
142: <sect>Running BIRD
143: <label id="argv">
144:
145: <p>You can pass several command-line options to bird:
146:
147: <descrip>
148: <tag><label id="argv-config">-c <m/config name/</tag>
149: use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>.
150:
151: <tag><label id="argv-debug">-d</tag>
152: enable debug messages and run bird in foreground.
153:
154: <tag><label id="argv-log-file">-D <m/filename of debug log/</tag>
155: log debugging information to given file instead of stderr.
156:
157: <tag><label id="argv-foreground">-f</tag>
158: run bird in foreground.
159:
160: <tag><label id="argv-group">-g <m/group/</tag>
161: use that group ID, see the next section for details.
162:
163: <tag><label id="argv-help">-h, --help</tag>
164: display command-line options to bird.
165:
166: <tag><label id="argv-local">-l</tag>
167: look for a configuration file and a communication socket in the current
168: working directory instead of in default system locations. However, paths
169: specified by options <cf/-c/, <cf/-s/ have higher priority.
170:
171: <tag><label id="argv-parse">-p</tag>
172: just parse the config file and exit. Return value is zero if the config
173: file is valid, nonzero if there are some errors.
174:
175: <tag><label id="argv-pid">-P <m/name of PID file/</tag>
176: create a PID file with given filename.
177:
178: <tag><label id="argv-recovery">-R</tag>
179: apply graceful restart recovery after start.
180:
181: <tag><label id="argv-socket">-s <m/name of communication socket/</tag>
182: use given filename for a socket for communications with the client,
183: default is <it/prefix/<file>/var/run/bird.ctl</file>.
184:
185: <tag><label id="argv-user">-u <m/user/</tag>
186: drop privileges and use that user ID, see the next section for details.
187:
188: <tag><label id="argv-version">--version</tag>
189: display bird version.
190: </descrip>
191:
192: <p>BIRD writes messages about its work to log files or syslog (according to config).
193:
194:
195: <sect>Privileges
196: <label id="privileges">
197:
198: <p>BIRD, as a routing daemon, uses several privileged operations (like setting
199: routing table and using raw sockets). Traditionally, BIRD is executed and runs
200: with root privileges, which may be prone to security problems. The recommended
201: way is to use a privilege restriction (options <cf/-u/, <cf/-g/). In that case
202: BIRD is executed with root privileges, but it changes its user and group ID to
203: an unprivileged ones, while using Linux capabilities to retain just required
204: privileges (capabilities CAP_NET_*). Note that the control socket is created
205: before the privileges are dropped, but the config file is read after that. The
206: privilege restriction is not implemented in BSD port of BIRD.
207:
208: <p>An unprivileged user (as an argument to <cf/-u/ options) may be the user
209: <cf/nobody/, but it is suggested to use a new dedicated user account (like
210: <cf/bird/). The similar considerations apply for the group option, but there is
211: one more condition -- the users in the same group can use <file/birdc/ to
212: control BIRD.
213:
214: <p>Finally, there is a possibility to use external tools to run BIRD in an
215: environment with restricted privileges. This may need some configuration, but it
216: is generally easy -- BIRD needs just the standard library, privileges to read
217: the config file and create the control socket and the CAP_NET_* capabilities.
218:
219:
220: <chapt>About routing tables
221: <label id="routing-tables">
222:
223: <p>BIRD has one or more routing tables which may or may not be synchronized with
224: OS kernel and which may or may not be synchronized with each other (see the Pipe
225: protocol). Each routing table contains a list of known routes. Each route
226: consists of:
227:
228: <itemize>
229: <item>network prefix this route is for (network address and prefix
230: length -- the number of bits forming the network part of the
231: address; also known as a netmask)
232: <item>preference of this route
233: <item>IP address of router which told us about this route
234: <item>IP address of router we should forward the packets to using this
235: route
236: <item>other attributes common to all routes
237: <item>dynamic attributes defined by protocols which may or may not be
238: present (typically protocol metrics)
239: </itemize>
240:
241: Routing table maintains multiple entries for a network, but at most one entry
242: for one network and one protocol. The entry with the highest preference is used
243: for routing (we will call such an entry the <it/selected route/). If there are
244: more entries with the same preference and they are from the same protocol, the
245: protocol decides (typically according to metrics). If they aren't, an internal
246: ordering is used to break the tie. You can get the list of route attributes in
247: the Route attributes section.
248:
249: <p>Each protocol is connected to a routing table through two filters which can
250: accept, reject and modify the routes. An <it/export/ filter checks routes passed
251: from the routing table to the protocol, an <it/import/ filter checks routes in
252: the opposite direction. When the routing table gets a route from a protocol, it
253: recalculates the selected route and broadcasts it to all protocols connected to
254: the table. The protocols typically send the update to other routers in the
255: network. Note that although most protocols are interested in receiving just
256: selected routes, some protocols (e.g. the <cf/Pipe/ protocol) receive and
257: process all entries in routing tables (accepted by filters).
258:
259: <p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected route
260: from a list of entries for one network. But if the <cf/sorted/ option is
261: activated, these lists of entries are kept completely sorted (according to
262: preference or some protocol-dependent metric). This is needed for some features
263: of some protocols (e.g. <cf/secondary/ option of BGP protocol, which allows to
264: accept not just a selected route, but the first route (in the sorted list) that
265: is accepted by filters), but it is incompatible with some other features (e.g.
266: <cf/deterministic med/ option of BGP protocol, which activates a way of choosing
267: selected route that cannot be described using comparison and ordering). Minor
268: advantage is that routes are shown sorted in <cf/show route/, minor disadvantage
269: is that it is slightly more computationally expensive.
270:
271:
272: <sect>Graceful restart
273: <label id="graceful-restart">
274:
275: <p>When BIRD is started after restart or crash, it repopulates routing tables in
276: an uncoordinated manner, like after clean start. This may be impractical in some
277: cases, because if the forwarding plane (i.e. kernel routing tables) remains
278: intact, then its synchronization with BIRD would temporarily disrupt packet
279: forwarding until protocols converge. Graceful restart is a mechanism that could
280: help with this issue. Generally, it works by starting protocols and letting them
281: repopulate routing tables while deferring route propagation until protocols
282: acknowledge their convergence. Note that graceful restart behavior have to be
283: configured for all relevant protocols and requires protocol-specific support
284: (currently implemented for Kernel and BGP protocols), it is activated for
285: particular boot by option <cf/-R/.
286:
287:
288: <chapt>Configuration
289: <label id="config">
290:
291: <sect>Introduction
292: <label id="config-intro">
293:
294: <p>BIRD is configured using a text configuration file. Upon startup, BIRD reads
295: <it/prefix/<file>/etc/bird.conf</file> (unless the <tt/-c/ command line option
296: is given). Configuration may be changed at user's request: if you modify the
297: config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
298: config. Then there's the client which allows you to talk with BIRD in an
299: extensive way.
300:
301: <p>In the config, everything on a line after <cf/#/ or inside <cf>/* */</cf> is
302: a comment, whitespace characters are treated as a single space. If there's a
303: variable number of options, they are grouped using the <cf/{ }/ brackets. Each
304: option is terminated by a <cf/;/. Configuration is case sensitive. There are two
305: ways how to name symbols (like protocol names, filter names, constants etc.). You
306: can either use a simple string starting with a letter followed by any
307: combination of letters and numbers (e.g. "R123", "myfilter", "bgp5") or you can
308: enclose the name into apostrophes (<cf/'/) and than you can use any combination
309: of numbers, letters. hyphens, dots and colons (e.g. "'1:strange-name'",
310: "'-NAME-'", "'cool::name'").
311:
312: <p>Here is an example of a simple config file. It enables synchronization of
313: routing tables with OS kernel, scans for new network interfaces every 10 seconds
314: and runs RIP on all network interfaces found.
315:
316: <code>
317: protocol kernel {
318: persist; # Don't remove routes on BIRD shutdown
319: scan time 20; # Scan kernel routing table every 20 seconds
320: export all; # Default is export none
321: }
322:
323: protocol device {
324: scan time 10; # Scan interfaces every 10 seconds
325: }
326:
327: protocol rip {
328: export all;
329: import all;
330: interface "*";
331: }
332: </code>
333:
334:
335: <sect>Global options
336: <label id="global-opts">
337:
338: <p><descrip>
339: <tag><label id="opt-include">include "<m/filename/"</tag>
340: This statement causes inclusion of a new file. <m/Filename/ could also
341: be a wildcard, in that case matching files are included in alphabetic
342: order. The maximal depth is 8. Note that this statement could be used
343: anywhere in the config file, not just as a top-level option.
344:
345: <tag><label id="opt-log">log "<m/filename/"|syslog [name <m/name/]|stderr all|{ <m/list of classes/ }</tag>
346: Set logging of messages having the given class (either <cf/all/ or
347: <cf/{ error|trace [, <m/.../] }/ etc.) into selected destination (a file specified
348: as a filename string, syslog with optional name argument, or the stderr
349: output). Classes are:
350: <cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
351: <cf/debug/ for debugging messages,
352: <cf/trace/ when you want to know what happens in the network,
353: <cf/remote/ for messages about misbehavior of remote machines,
354: <cf/auth/ about authentication failures,
355: <cf/bug/ for internal BIRD bugs.
356: You may specify more than one <cf/log/ line to establish logging to
357: multiple destinations. Default: log everything to the system log.
358:
359: <tag><label id="opt-debug-protocols">debug protocols all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
360: Set global defaults of protocol debugging options. See <cf/debug/ in the
361: following section. Default: off.
362:
363: <tag><label id="opt-debug-commands">debug commands <m/number/</tag>
364: Control logging of client connections (0 for no logging, 1 for logging
365: of connects and disconnects, 2 and higher for logging of all client
366: commands). Default: 0.
367:
368: <tag><label id="opt-debug-latency">debug latency <m/switch/</tag>
369: Activate tracking of elapsed time for internal events. Recent events
370: could be examined using <cf/dump events/ command. Default: off.
371:
372: <tag><label id="opt-debug-latency-limit">debug latency limit <m/time/</tag>
373: If <cf/debug latency/ is enabled, this option allows to specify a limit
374: for elapsed time. Events exceeding the limit are logged. Default: 1 s.
375:
376: <tag><label id="opt-watchdog-warn">watchdog warning <m/time/</tag>
377: Set time limit for I/O loop cycle. If one iteration took more time to
378: complete, a warning is logged. Default: 5 s.
379:
380: <tag><label id="opt-watchdog-timeout">watchdog timeout <m/time/</tag>
381: Set time limit for I/O loop cycle. If the limit is breached, BIRD is
382: killed by abort signal. The timeout has effective granularity of
383: seconds, zero means disabled. Default: disabled (0).
384:
385: <tag><label id="opt-mrtdump">mrtdump "<m/filename/"</tag>
386: Set MRTdump file name. This option must be specified to allow MRTdump
387: feature. Default: no dump file.
388:
389: <tag><label id="opt-mrtdump-protocols">mrtdump protocols all|off|{ states|messages [, <m/.../] }</tag>
390: Set global defaults of MRTdump options. See <cf/mrtdump/ in the
391: following section. Default: off.
392:
393: <tag><label id="opt-filter">filter <m/name local variables/{ <m/commands/ }</tag>
394: Define a filter. You can learn more about filters in the following
395: chapter.
396:
397: <tag><label id="opt-function">function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag>
398: Define a function. You can learn more about functions in the following chapter.
399:
400: <tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
401: Define a protocol instance called <cf><m/name/</cf> (or with a name like
402: "rip5" generated automatically if you don't specify any
403: <cf><m/name/</cf>). You can learn more about configuring protocols in
404: their own chapters. When <cf>from <m/name2/</cf> expression is used,
405: initial protocol options are taken from protocol or template
406: <cf><m/name2/</cf> You can run more than one instance of most protocols
407: (like RIP or BGP). By default, no instances are configured.
408:
409: <tag><label id="opt-template">template rip|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
410: Define a protocol template instance called <m/name/ (or with a name like
411: "bgp1" generated automatically if you don't specify any <m/name/).
412: Protocol templates can be used to group common options when many
413: similarly configured protocol instances are to be defined. Protocol
414: instances (and other templates) can use templates by using <cf/from/
415: expression and the name of the template. At the moment templates (and
416: <cf/from/ expression) are not implemented for OSPF protocol.
417:
418: <tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
419: Define a constant. You can use it later in every place you could use a
420: value of the same type. Besides, there are some predefined numeric
421: constants based on /etc/iproute2/rt_* files. A list of defined constants
422: can be seen (together with other symbols) using 'show symbols' command.
423:
424: <tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
425: Set BIRD's router ID. It's a world-wide unique identification of your
426: router, usually one of router's IPv4 addresses. Default: in IPv4
427: version, the lowest IP address of a non-loopback interface. In IPv6
428: version, this option is mandatory.
429:
430: <tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
431: Set BIRD's router ID based on an IP address of an interface specified by
432: an interface pattern. The option is applicable for IPv4 version only.
433: See <ref id="proto-iface" name="interface"> section for detailed
434: description of interface patterns with extended clauses.
435:
436: <tag><label id="opt-listen-bgp">listen bgp [address <m/address/] [port <m/port/] [dual]</tag>
437: This option allows to specify address and port where BGP protocol should
438: listen. It is global option as listening socket is common to all BGP
439: instances. Default is to listen on all addresses (0.0.0.0) and port 179.
440: In IPv6 mode, option <cf/dual/ can be used to specify that BGP socket
441: should accept both IPv4 and IPv6 connections (but even in that case,
442: BIRD would accept IPv6 routes only). Such behavior was default in older
443: versions of BIRD.
444:
445: <tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
446: During graceful restart recovery, BIRD waits for convergence of routing
447: protocols. This option allows to specify a timeout for the recovery to
448: prevent waiting indefinitely if some protocols cannot converge. Default:
449: 240 seconds.
450:
451: <tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
452: This option allows to specify a format of date/time used by BIRD. The
453: first argument specifies for which purpose such format is used.
454: <cf/route/ is a format used in 'show route' command output,
455: <cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
456: used for other commands and <cf/log/ is used in a log file.
457:
458: "<m/format1/" is a format string using <it/strftime(3)/ notation (see
459: <it/man strftime/ for details). <m/limit> and "<m/format2/" allow to
460: specify the second format string for times in past deeper than <m/limit/
461: seconds. There are few shorthands: <cf/iso long/ is a ISO 8601 date/time
462: format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F %T"/.
463: <cf/iso short/ is a variant of ISO 8601 that uses just the time format
464: (hh:mm:ss) for near times (up to 20 hours in the past) and the date
465: format (YYYY-MM-DD) for far times. This is a shorthand for
466: <cf/"%T" 72000 "%F"/.
467:
468: By default, BIRD uses the <cf/iso short/ format for <cf/route/ and
469: <cf/protocol/ times, and the <cf/iso long/ format for <cf/base/ and
470: <cf/log/ times.
471:
472: In pre-1.4.0 versions, BIRD used an short, ad-hoc format for <cf/route/
473: and <cf/protocol/ times, and a <cf/iso long/ similar format (DD-MM-YYYY
474: hh:mm:ss) for <cf/base/ and <cf/log/. These timeformats could be set by
475: <cf/old short/ and <cf/old long/ compatibility shorthands.
476:
477: <tag><label id="opt-table">table <m/name/ [sorted]</tag>
478: Create a new routing table. The default routing table is created
479: implicitly, other routing tables have to be added by this command.
480: Option <cf/sorted/ can be used to enable sorting of routes, see
481: <ref id="dsc-table-sorted" name="sorted table"> description for details.
482:
483: <tag><label id="opt-roa-table">roa table <m/name/ [ { <m/roa table options .../ } ]</tag>
484: Create a new ROA (Route Origin Authorization) table. ROA tables can be
485: used to validate route origination of BGP routes. A ROA table contains
486: ROA entries, each consist of a network prefix, a max prefix length and
487: an AS number. A ROA entry specifies prefixes which could be originated
488: by that AS number. ROA tables could be filled with data from RPKI (<rfc
489: id="6480">) or from public databases like Whois. ROA tables are
490: examined by <cf/roa_check()/ operator in filters.
491:
492: Currently, there is just one option, <cf>roa <m/prefix/ max <m/num/ as
493: <m/num/</cf>, which can be used to populate the ROA table with static
494: ROA entries. The option may be used multiple times. Other entries can be
495: added dynamically by <cf/add roa/ command.
496:
497: <tag><label id="opt-eval">eval <m/expr/</tag>
498: Evaluates given filter expression. It is used by us for testing of filters.
499: </descrip>
500:
501:
502: <sect>Protocol options
503: <label id="protocol-opts">
504:
505: <p>For each protocol instance, you can configure a bunch of options. Some of
506: them (those described in this section) are generic, some are specific to the
507: protocol (see sections talking about the protocols).
508:
509: <p>Several options use a <m/switch/ argument. It can be either <cf/on/,
510: <cf/yes/ or a numeric expression with a non-zero value for the option to be
511: enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
512: disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
513: agreement").
514:
515: <descrip>
516: <tag><label id="proto-preference">preference <m/expr/</tag>
517: Sets the preference of routes generated by this protocol. Default:
518: protocol dependent.
519:
520: <tag><label id="proto-disabled">disabled <m/switch/</tag>
521: Disables the protocol. You can change the disable/enable status from the
522: command line interface without needing to touch the configuration.
523: Disabled protocols are not activated. Default: protocol is enabled.
524:
525: <tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
526: Set protocol debugging options. If asked, each protocol is capable of
527: writing trace messages about its work to the log (with category
528: <cf/trace/). You can either request printing of <cf/all/ trace messages
529: or only of the types selected: <cf/states/ for protocol state changes
530: (protocol going up, down, starting, stopping etc.), <cf/routes/ for
531: routes exchanged with the routing table, <cf/filters/ for details on
532: route filtering, <cf/interfaces/ for interface change events sent to the
533: protocol, <cf/events/ for events internal to the protocol and <cf/packets/
534: for packets sent and received by the protocol. Default: off.
535:
536: <tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
537: Set protocol MRTdump flags. MRTdump is a standard binary format for
538: logging information from routing protocols and daemons. These flags
539: control what kind of information is logged from the protocol to the
540: MRTdump file (which must be specified by global <cf/mrtdump/ option, see
541: the previous section). Although these flags are similar to flags of
542: <cf/debug/ option, their meaning is different and protocol-specific. For
543: BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
544: received BGP messages. Other protocols does not support MRTdump yet.
545:
546: <tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
547: This option can be used to override global router id for a given
548: protocol. Default: uses global router id.
549:
550: <tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/filter expression/</tag>
551: Specify a filter to be used for filtering routes coming from the
552: protocol to the routing table. <cf/all/ is shorthand for <cf/where true/
553: and <cf/none/ is shorthand for <cf/where false/. Default: <cf/all/.
554:
555: <tag><label id="proto-export">export <m/filter/</tag>
556: This is similar to the <cf>import</cf> keyword, except that it works in
557: the direction from the routing table to the protocol. Default: <cf/none/.
558:
559: <tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
560: Usually, if an import filter rejects a route, the route is forgotten.
561: When this option is active, these routes are kept in the routing table,
562: but they are hidden and not propagated to other protocols. But it is
563: possible to show them using <cf/show route filtered/. Note that this
564: option does not work for the pipe protocol. Default: off.
565:
566: <tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
567: Specify an import route limit (a maximum number of routes imported from
568: the protocol) and optionally the action to be taken when the limit is
569: hit. Warn action just prints warning log message. Block action discards
570: new routes coming from the protocol. Restart and disable actions shut
571: the protocol down like appropriate commands. Disable is the default
572: action if an action is not explicitly specified. Note that limits are
573: reset during protocol reconfigure, reload or restart. Default: <cf/off/.
574:
575: <tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
576: Specify an receive route limit (a maximum number of routes received from
577: the protocol and remembered). It works almost identically to <cf>import
578: limit</cf> option, the only difference is that if <cf/import keep
579: filtered/ option is active, filtered routes are counted towards the
580: limit and blocked routes are forgotten, as the main purpose of the
581: receive limit is to protect routing tables from overflow. Import limit,
582: on the contrary, counts accepted routes only and routes blocked by the
583: limit are handled like filtered routes. Default: <cf/off/.
584:
585: <tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
586: Specify an export route limit, works similarly to the <cf>import
587: limit</cf> option, but for the routes exported to the protocol. This
588: option is experimental, there are some problems in details of its
589: behavior -- the number of exported routes can temporarily exceed the
590: limit without triggering it during protocol reload, exported routes
591: counter ignores route blocking and block action also blocks route
592: updates of already accepted routes -- and these details will probably
593: change in the future. Default: <cf/off/.
594:
595: <tag><label id="proto-description">description "<m/text/"</tag>
596: This is an optional description of the protocol. It is displayed as a
597: part of the output of 'show route all' command.
598:
599: <tag><label id="proto-table">table <m/name/</tag>
600: Connect this protocol to a non-default routing table.
601: </descrip>
602:
603: <p>There are several options that give sense only with certain protocols:
604:
605: <descrip>
606: <tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
607: Specifies a set of interfaces on which the protocol is activated with
608: given interface-specific options. A set of interfaces specified by one
609: interface option is described using an interface pattern. The interface
610: pattern consists of a sequence of clauses (separated by commas), each
611: clause is a mask specified as a shell-like pattern. Interfaces are
612: matched by their name.
613:
614: An interface matches the pattern if it matches any of its clauses. If
615: the clause begins with <cf/-/, matching interfaces are excluded. Patterns
616: are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
617: means eth0 and all non-ethernets.
618:
619: Some protocols (namely OSPFv2 and Direct) support extended clauses that
620: may contain a mask, a prefix, or both of them. An interface matches such
621: clause if its name matches the mask (if specified) and its address
622: matches the prefix (if specified). Extended clauses are used when the
623: protocol handles multiple addresses on an interface independently.
624:
625: An interface option can be used more times with different interface-specific
626: options, in that case for given interface the first matching interface
627: option is used.
628:
629: This option is allowed in Babel, BFD, Direct, OSPF, RAdv and RIP
630: protocols, but in OSPF protocol it is used in the <cf/area/ subsection.
631:
632: Default: none.
633:
634: Examples:
635:
636: <cf>interface "*" { type broadcast; };</cf> - start the protocol on all
637: interfaces with <cf>type broadcast</cf> option.
638:
639: <cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
640: protocol on enumerated interfaces with <cf>type ptp</cf> option.
641:
642: <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
643: on all interfaces that have address from 192.168.0.0/16, but not from
644: 192.168.1.0/24.
645:
646: <cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
647: on all interfaces that have address from 192.168.0.0/16, but not from
648: 192.168.1.0/24.
649:
650: <cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
651: ethernet interfaces that have address from 192.168.1.0/24.
652:
653: <tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
654: This option specifies the value of ToS/DS/Class field in IP headers of
655: the outgoing protocol packets. This may affect how the protocol packets
656: are processed by the network relative to the other network traffic. With
657: <cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
658: octet (but two bits reserved for ECN are ignored). With <cf/dscp/
659: keyword, the value (0-63) is used just for the DS field in the octet.
660: Default value is 0xc0 (DSCP 0x30 - CS6).
661:
662: <tag><label id="proto-tx-priority">tx priority <m/num/</tag>
663: This option specifies the local packet priority. This may affect how the
664: protocol packets are processed in the local TX queues. This option is
665: Linux specific. Default value is 7 (highest priority, privileged traffic).
666:
667: <tag><label id="proto-pass">password "<m/password/" [ { <m>password options</m> } ]</tag>
668: Specifies a password that can be used by the protocol as a shared secret
669: key. Password option can be used more times to specify more passwords.
670: If more passwords are specified, it is a protocol-dependent decision
671: which one is really used. Specifying passwords does not mean that
672: authentication is enabled, authentication can be enabled by separate,
673: protocol-dependent <cf/authentication/ option.
674:
675: This option is allowed in BFD, OSPF and RIP protocols. BGP has also
676: <cf/password/ option, but it is slightly different and described
677: separately.
678: Default: none.
679: </descrip>
680:
681: <p>Password option can contain section with some (not necessary all) password sub-options:
682:
683: <descrip>
684: <tag><label id="proto-pass-id">id <M>num</M></tag>
685: ID of the password, (1-255). If it is not used, BIRD will choose ID based
686: on an order of the password item in the interface. For example, second
687: password item in one interface will have default ID 2. ID is used by
688: some routing protocols to identify which password was used to
689: authenticate protocol packets.
690:
691: <tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
692: The start time of the usage of the password for packet signing.
693: The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
694:
695: <tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
696: The last time of the usage of the password for packet signing.
697:
698: <tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
699: The start time of the usage of the password for packet verification.
700:
701: <tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
702: The last time of the usage of the password for packet verification.
703:
704: <tag><label id="proto-pass-from">from "<m/time/"</tag>
705: Shorthand for setting both <cf/generate from/ and <cf/accept from/.
706:
707: <tag><label id="proto-pass-to">to "<m/time/"</tag>
708: Shorthand for setting both <cf/generate to/ and <cf/accept to/.
709:
710: <tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 )</tag>
711: The message authentication algorithm for the password when cryptographic
712: authentication is enabled. The default value depends on the protocol.
713: For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3
714: protocol it is HMAC-SHA-256.
715:
716: </descrip>
717:
718: <chapt>Remote control
719: <label id="remote-control">
720:
721: <p>You can use the command-line client <file>birdc</file> to talk with a running
722: BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
723: changed with the <tt/-s/ option given to both the server and the client). The
724: commands can perform simple actions such as enabling/disabling of protocols,
725: telling BIRD to show various information, telling it to show routing table
726: filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
727: get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
728: client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
729: be passed to the client, to make it dump numeric return codes along with the
730: messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
731: own applications could do that, too -- the format of communication between BIRD
732: and <file/birdc/ is stable (see the programmer's documentation).
733:
734: <p>There is also lightweight variant of BIRD client called <file/birdcl/, which
735: does not support command line editing and history and has minimal dependencies.
736: This is useful for running BIRD in resource constrained environments, where
737: Readline library (required for regular BIRD client) is not available.
738:
739: <p>Many commands have the <m/name/ of the protocol instance as an argument.
740: This argument can be omitted if there exists only a single instance.
741:
742: <p>Here is a brief list of supported functions:
743:
744: <descrip>
745: <tag><label id="cli-show-status">show status</tag>
746: Show router status, that is BIRD version, uptime and time from last
747: reconfiguration.
748:
749: <tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
750: Show the list of interfaces. For each interface, print its type, state,
751: MTU and addresses assigned.
752:
753: <tag><label id="cli-show-protocols">show protocols [all]</tag>
754: Show list of protocol instances along with tables they are connected to
755: and protocol status, possibly giving verbose information, if <cf/all/ is
756: specified.
757:
758: <tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
759: Show detailed information about OSPF interfaces.
760:
761: <tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
762: Show a list of OSPF neighbors and a state of adjacency to them.
763:
764: <tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
765: Show detailed information about OSPF areas based on a content of the
766: link-state database. It shows network topology, stub networks,
767: aggregated networks and routers from other areas and external routes.
768: The command shows information about reachable network nodes, use option
769: <cf/all/ to show information about all network nodes in the link-state
770: database.
771:
772: <tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
773: Show a topology of OSPF areas based on a content of the link-state
774: database. It is just a stripped-down version of 'show ospf state'.
775:
776: <tag><label id="cli-show-ospf-lsadb">show ospf lsadb [global | area <m/id/ | link] [type <m/num/] [lsid <m/id/] [self | router <m/id/] [<m/name/] </tag>
777: Show contents of an OSPF LSA database. Options could be used to filter
778: entries.
779:
780: <tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
781: Show detailed information about RIP interfaces.
782:
783: <tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
784: Show a list of RIP neighbors and associated state.
785:
786: <tag><label id="cli-show-static">show static [<m/name/]</tag>
787: Show detailed information about static routes.
788:
789: <tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/]</tag>
790: Show information about BFD sessions.
791:
792: <tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
793: Show the list of symbols defined in the configuration (names of
794: protocols, routing tables etc.).
795:
796: <tag><label id="cli-show-route">show route [[for] <m/prefix/|<m/IP/] [table <m/t/] [filter <m/f/|where <m/c/] [(export|preexport|noexport) <m/p/] [protocol <m/p/] [<m/options/]</tag>
797: Show contents of a routing table (by default of the main one or the
798: table attached to a respective protocol), that is routes, their metrics
799: and (in case the <cf/all/ switch is given) all their attributes.
800:
801: <p>You can specify a <m/prefix/ if you want to print routes for a
802: specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
803: the entry which will be used for forwarding of packets to the given
804: destination. By default, all routes for each network are printed with
805: the selected one at the top, unless <cf/primary/ is given in which case
806: only the selected route is shown.
807:
808: <p>You can also ask for printing only routes processed and accepted by
809: a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
810: </cf> or matching a given condition (<cf>where <m/condition/</cf>).
811:
812: The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
813: printing of routes that are exported to the specified protocol.
814: With <cf/preexport/, the export filter of the protocol is skipped.
815: With <cf/noexport/, routes rejected by the export filter are printed
816: instead. Note that routes not exported to the protocol for other reasons
817: (e.g. secondary routes or routes imported from that protocol) are not
818: printed even with <cf/noexport/.
819:
820: <p>You can also select just routes added by a specific protocol.
821: <cf>protocol <m/p/</cf>.
822:
823: <p>If BIRD is configured to keep filtered routes (see <cf/import keep
824: filtered/ option), you can show them instead of routes by using
825: <cf/filtered/ switch.
826:
827: <p>The <cf/stats/ switch requests showing of route statistics (the
828: number of networks, number of routes before and after filtering). If
829: you use <cf/count/ instead, only the statistics will be printed.
830:
831: <tag><label id="cli-show-roa">show roa [<m/prefix/ | in <m/prefix/ | for <m/prefix/] [as <m/num/] [table <m/t/]</tag>
832: Show contents of a ROA table (by default of the first one). You can
833: specify a <m/prefix/ to print ROA entries for a specific network. If you
834: use <cf>for <m/prefix/</cf>, you'll get all entries relevant for route
835: validation of the network prefix; i.e., ROA entries whose prefixes cover
836: the network prefix. Or you can use <cf>in <m/prefix/</cf> to get ROA
837: entries covered by the network prefix. You could also use <cf/as/ option
838: to show just entries for given AS.
839:
840: <tag><label id="cli-add-roa">add roa <m/prefix/ max <m/num/ as <m/num/ [table <m/t/]</tag>
841: Add a new ROA entry to a ROA table. Such entry is called <it/dynamic/
842: compared to <it/static/ entries specified in the config file. These
843: dynamic entries survive reconfiguration.
844:
845: <tag><label id="cli-delete-roa">delete roa <m/prefix/ max <m/num/ as <m/num/ [table <m/t/]</tag>
846: Delete the specified ROA entry from a ROA table. Only dynamic ROA
847: entries (i.e., the ones added by <cf/add roa/ command) can be deleted.
848:
849: <tag><label id="cli-flush-roa">flush roa [table <m/t/]</tag>
850: Remove all dynamic ROA entries from a ROA table.
851:
852: <tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
853: Reload configuration from a given file. BIRD will smoothly switch itself
854: to the new configuration, protocols are reconfigured if possible,
855: restarted otherwise. Changes in filters usually lead to restart of
856: affected protocols.
857:
858: If <cf/soft/ option is used, changes in filters does not cause BIRD to
859: restart affected protocols, therefore already accepted routes (according
860: to old filters) would be still propagated, but new routes would be
861: processed according to the new filters.
862:
863: If <cf/timeout/ option is used, config timer is activated. The new
864: configuration could be either confirmed using <cf/configure confirm/
865: command, or it will be reverted to the old one when the config timer
866: expires. This is useful for cases when reconfiguration breaks current
867: routing and a router becomes inaccessible for an administrator. The
868: config timeout expiration is equivalent to <cf/configure undo/
869: command. The timeout duration could be specified, default is 300 s.
870:
871: <tag><label id="cli-configure-confirm">configure confirm</tag>
872: Deactivate the config undo timer and therefore confirm the current
873: configuration.
874:
875: <tag><label id="cli-configure-undo">configure undo</tag>
876: Undo the last configuration change and smoothly switch back to the
877: previous (stored) configuration. If the last configuration change was
878: soft, the undo change is also soft. There is only one level of undo, but
879: in some specific cases when several reconfiguration requests are given
880: immediately in a row and the intermediate ones are skipped then the undo
881: also skips them back.
882:
883: <tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
884: Read and parse given config file, but do not use it. useful for checking
885: syntactic and some semantic validity of an config file.
886:
887: <tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
888: Enable, disable or restart a given protocol instance, instances matching
889: the <cf><m/pattern/</cf> or <cf/all/ instances.
890:
891: <tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
892: Reload a given protocol instance, that means re-import routes from the
893: protocol instance and re-export preferred routes to the instance. If
894: <cf/in/ or <cf/out/ options are used, the command is restricted to one
895: direction (re-import or re-export).
896:
897: This command is useful if appropriate filters have changed but the
898: protocol instance was not restarted (or reloaded), therefore it still
899: propagates the old set of routes. For example when <cf/configure soft/
900: command was used to change filters.
901:
902: Re-export always succeeds, but re-import is protocol-dependent and might
903: fail (for example, if BGP neighbor does not support route-refresh
904: extension). In that case, re-export is also skipped. Note that for the
905: pipe protocol, both directions are always reloaded together (<cf/in/ or
906: <cf/out/ options are ignored in that case).
907:
908: <tag><label id="cli-down">down</tag>
909: Shut BIRD down.
910:
911: <tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
912: Control protocol debugging.
913:
914: <tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
915: Dump contents of internal data structures to the debugging output.
916:
917: <tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
918: Control echoing of log messages to the command-line output.
919: See <ref id="opt-log" name="log option"> for a list of log classes.
920:
921: <tag><label id="cli-eval">eval <m/expr/</tag>
922: Evaluate given expression.
923: </descrip>
924:
925:
926: <chapt>Filters
927: <label id="filters">
928:
929: <sect>Introduction
930: <label id="filters-intro">
931:
932: <p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
933: There are two objects in this language: filters and functions. Filters are
934: interpreted by BIRD core when a route is being passed between protocols and
935: routing tables. The filter language contains control structures such as if's and
936: switches, but it allows no loops. An example of a filter using many features can
937: be found in <file>filter/test.conf</file>.
938:
939: <p>Filter gets the route, looks at its attributes and modifies some of them if
940: it wishes. At the end, it decides whether to pass the changed route through
941: (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
942: this:
943:
944: <code>
945: filter not_too_far
946: int var;
947: {
948: if defined( rip_metric ) then
949: var = rip_metric;
950: else {
951: var = 1;
952: rip_metric = 1;
953: }
954: if rip_metric > 10 then
955: reject "RIP metric is too big";
956: else
957: accept "ok";
958: }
959: </code>
960:
961: <p>As you can see, a filter has a header, a list of local variables, and a body.
962: The header consists of the <cf/filter/ keyword followed by a (unique) name of
963: filter. The list of local variables consists of <cf><M>type name</M>;</cf>
964: pairs where each pair defines one local variable. The body consists of <cf>
965: { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
966: can group several statements to a single compound statement by using braces
967: (<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
968: block of code conditional.
969:
970: <p>BIRD supports functions, so that you don't have to repeat the same blocks of
971: code over and over. Functions can have zero or more parameters and they can have
972: local variables. Recursion is not allowed. Function definitions look like this:
973:
974: <code>
975: function name ()
976: int local_variable;
977: {
978: local_variable = 5;
979: }
980:
981: function with_parameters (int parameter)
982: {
983: print parameter;
984: }
985: </code>
986:
987: <p>Unlike in C, variables are declared after the <cf/function/ line, but before
988: the first <cf/{/. You can't declare variables in nested blocks. Functions are
989: called like in C: <cf>name(); with_parameters(5);</cf>. Function may return
990: values using the <cf>return <m/[expr]/</cf> command. Returning a value exits
991: from current function (this is similar to C).
992:
993: <p>Filters are declared in a way similar to functions except they can't have
994: explicit parameters. They get a route table entry as an implicit parameter, it
995: is also passed automatically to any functions called. The filter must terminate
996: with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in
997: filter, the route is rejected.
998:
999: <p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1000: from the command line client. An example session might look like:
1001:
1002: <code>
1003: pavel@bug:~/bird$ ./birdc -s bird.ctl
1004: BIRD 0.0.0 ready.
1005: bird> show route
1006: 10.0.0.0/8 dev eth0 [direct1 23:21] (240)
1007: 195.113.30.2/32 dev tunl1 [direct1 23:21] (240)
1008: 127.0.0.0/8 dev lo [direct1 23:21] (240)
1009: bird> show route ?
1010: show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1011: bird> show route filter { if 127.0.0.5 ˜ net then accept; }
1012: 127.0.0.0/8 dev lo [direct1 23:21] (240)
1013: bird>
1014: </code>
1015:
1016:
1017: <sect>Data types
1018: <label id="data-types">
1019:
1020: <p>Each variable and each value has certain type. Booleans, integers and enums
1021: are incompatible with each other (that is to prevent you from shooting in the
1022: foot).
1023:
1024: <descrip>
1025: <tag><label id="type-bool">bool</tag>
1026: This is a boolean type, it can have only two values, <cf/true/ and
1027: <cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1028:
1029: <tag><label id="type-int">int</tag>
1030: This is a general integer type. It is an unsigned 32bit type; i.e., you
1031: can expect it to store values from 0 to 4294967295. Overflows are not
1032: checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1033:
1034: <tag><label id="type-pair">pair</tag>
1035: This is a pair of two short integers. Each component can have values
1036: from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1037: The same syntax can also be used to construct a pair from two arbitrary
1038: integer expressions (for example <cf/(1+2,a)/).
1039:
1040: <tag><label id="type-quad">quad</tag>
1041: This is a dotted quad of numbers used to represent router IDs (and
1042: others). Each component can have a value from 0 to 255. Literals of
1043: this type are written like IPv4 addresses.
1044:
1045: <tag><label id="type-string">string</tag>
1046: This is a string of characters. There are no ways to modify strings in
1047: filters. You can pass them between functions, assign them to variables
1048: of type <cf/string/, print such variables, use standard string
1049: comparison operations (e.g. <cf/=, !=, <, >, <=, >=/), but
1050: you can't concatenate two strings. String literals are written as
1051: <cf/"This is a string constant"/. Additionally matching (<cf/˜,
1052: !˜/) operators could be used to match a string value against
1053: a shell pattern (represented also as a string).
1054:
1055: <tag><label id="type-ip">ip</tag>
1056: This type can hold a single IP address. Depending on the compile-time
1057: configuration of BIRD you are using, it is either an IPv4 or IPv6
1058: address. IP addresses are written in the standard notation
1059: (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special operator
1060: <cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out all but
1061: first <cf><M>num</M></cf> bits from the IP address. So
1062: <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1063:
1064: <tag><label id="type-prefix">prefix</tag>
1065: This type can hold a network prefix consisting of IP address and prefix
1066: length. Prefix literals are written as <cf><m/ipaddress//<m/pxlen/</cf>,
1067: or <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
1068: operators on prefixes: <cf/.ip/ which extracts the IP address from the
1069: pair, and <cf/.len/, which separates prefix length from the pair.
1070: So <cf>1.2.0.0/16.len = 16</cf> is true.
1071:
1072: <tag><label id="type-ec">ec</tag>
1073: This is a specialized type used to represent BGP extended community
1074: values. It is essentially a 64bit value, literals of this type are
1075: usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1076: <cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1077: route target / route origin communities), the format and possible values
1078: of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1079: used kind. Similarly to pairs, ECs can be constructed using expressions
1080: for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1081: <cf/myas/ is an integer variable).
1082:
1083: <tag><label id="type-lc">lc</tag>
1084: This is a specialized type used to represent BGP large community
1085: values. It is essentially a triplet of 32bit values, where the first
1086: value is reserved for the AS number of the issuer, while meaning of
1087: remaining parts is defined by the issuer. Literals of this type are
1088: written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1089: pairs, LCs can be constructed using expressions for its parts, (e.g.
1090: <cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1091:
1092: <tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1093: Filters recognize four types of sets. Sets are similar to strings: you
1094: can pass them around but you can't modify them. Literals of type <cf>int
1095: set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1096: values and ranges are permitted in sets.
1097:
1098: For pair sets, expressions like <cf/(123,*)/ can be used to denote
1099: ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1100: <cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1101: <cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1102: such expressions are translated to a set of intervals, which may be
1103: memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1104: (1,4..20), (2,4..20), ... (65535, 4..20)/.
1105:
1106: EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1107: 10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1108: (like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1109: for ASNs).
1110:
1111: Also LC sets use similar expressions like pair sets. You can use ranges
1112: and wildcards, but if one field uses that, more specific (later) fields
1113: must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1114: is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1115: valid.
1116:
1117: You can also use expressions for int, pair, EC and LC set values.
1118: However, it must be possible to evaluate these expressions before daemon
1119: boots. So you can use only constants inside them. E.g.
1120:
1121: <code>
1122: define one=1;
1123: define myas=64500;
1124: int set odds;
1125: pair set ps;
1126: ec set es;
1127:
1128: odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1129: ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1130: es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1131: </code>
1132:
1133: Sets of prefixes are special: their literals does not allow ranges, but
1134: allows prefix patterns that are written
1135: as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1136: Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1137: pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1138: first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1139: identical and <cf>len1 <= ip1 <= len2</cf>. A valid prefix pattern
1140: has to satisfy <cf>low <= high</cf>, but <cf/pxlen/ is not
1141: constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1142: prefix set literal if it matches any prefix pattern in the prefix set
1143: literal.
1144:
1145: There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1146: is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1147: (where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1148: network prefix <cf><m/address//<m/len/</cf> and all its subnets.
1149: <cf><m/address//<m/len/-</cf> is a shorthand for
1150: <cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1151: <cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1152: that contain it).
1153:
1154: 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}
1155: ]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1156: <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1157: <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1158: matches all prefixes (regardless of IP address) whose prefix length is
1159: 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1160: address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{15,17} ]</cf>
1161: is true, but <cf>1.0.0.0/16 ˜ [ 1.0.0.0/8- ]</cf> is false.
1162:
1163: Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1164: in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1165: <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1166: <cf>192.168.0.0/16{24,32}</cf>.
1167:
1168: <tag><label id="type-enum">enum</tag>
1169: Enumeration types are fixed sets of possibilities. You can't define your
1170: own variables of such type, but some route attributes are of enumeration
1171: type. Enumeration types are incompatible with each other.
1172:
1173: <tag><label id="type-bgppath">bgppath</tag>
1174: BGP path is a list of autonomous system numbers. You can't write
1175: literals of this type. There are several special operators on bgppaths:
1176:
1177: <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1178:
1179: <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1180:
1181: <cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1182:
1183: Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1184: ASN, for example if the path contains an AS set element as the first (or
1185: the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1186: may be used to get last ASN before any AS set.
1187:
1188: <cf><m/P/.len</cf> returns the length of path <m/P/.
1189:
1190: <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1191: returns the result.
1192:
1193: <cf>delete(<m/P/,<m/A/)</cf> deletes all instances of ASN <m/A/ from
1194: from path <m/P/ and returns the result. <m/A/ may also be an integer
1195: set, in that case the operator deletes all ASNs from path <m/P/ that are
1196: also members of set <m/A/.
1197:
1198: <cf>filter(<m/P/,<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1199: not members of integer set <m/A/. I.e., <cf/filter/ do the same as
1200: <cf/delete/ with inverted set <m/A/.
1201:
1202: Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1203: <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1204: (for example <cf/bgp_path/). Similarly for <cf/delete/ and <cf/filter/.
1205:
1206: <tag><label id="type-bgpmask">bgpmask</tag>
1207: BGP masks are patterns used for BGP path matching (using <cf>path
1208: ˜ [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1209: as used by UNIX shells. Autonomous system numbers match themselves,
1210: <cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1211: <cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1212: is 4 3 2 1, then: <tt>bgp_path ˜ [= * 4 3 * =]</tt> is true,
1213: but <tt>bgp_path ˜ [= * 4 5 * =]</tt> is false. BGP mask
1214: expressions can also contain integer expressions enclosed in parenthesis
1215: and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>. You can
1216: also use ranges, for example <tt>[= * 3..5 2 100..200 * =]</tt>.
1217: There is also old (deprecated) syntax that uses / .. / instead of [= .. =]
1218: and ? instead of *.
1219:
1220: <tag><label id="type-clist">clist</tag>
1221: Clist is similar to a set, except that unlike other sets, it can be
1222: modified. The type is used for community list (a set of pairs) and for
1223: cluster list (a set of quads). There exist no literals of this type.
1224: There are three special operators on clists:
1225:
1226: <cf><m/C/.len</cf> returns the length of clist <m/C/.
1227:
1228: <cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1229: returns the result. If item <m/P/ is already in clist <m/C/, it does
1230: nothing. <m/P/ may also be a clist, in that case all its members are
1231: added; i.e., it works as clist union.
1232:
1233: <cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1234: <m/C/ and returns the result. If clist <m/C/ does not contain item
1235: <m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1236: case the operator deletes all items from clist <m/C/ that are also
1237: members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1238: analogously; i.e., it works as clist difference.
1239:
1240: <cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist <m/C/ that are
1241: not members of pair (or quad) set <m/P/. I.e., <cf/filter/ do the same
1242: as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1243: works analogously; i.e., it works as clist intersection.
1244:
1245: Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1246: <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for
1247: example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.
1248:
1249: <tag><label id="type-eclist">eclist</tag>
1250: Eclist is a data type used for BGP extended community lists. Eclists
1251: are very similar to clists, but they are sets of ECs instead of pairs.
1252: The same operations (like <cf/add/, <cf/delete/ or <cf/˜/ and
1253: <cf/!˜/ membership operators) can be used to modify or test
1254: eclists, with ECs instead of pairs as arguments.
1255:
1256: <tag/lclist/
1257: Lclist is a data type used for BGP large community lists. Like eclists,
1258: lclists are very similar to clists, but they are sets of LCs instead of
1259: pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/˜/
1260: and <cf/!˜/ membership operators) can be used to modify or test
1261: lclists, with LCs instead of pairs as arguments.
1262: </descrip>
1263:
1264:
1265: <sect>Operators
1266: <label id="operators">
1267:
1268: <p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1269: parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a<b, a>=b)/.
1270: Logical operations include unary not (<cf/!/), and (<cf/&&/) and or
1271: (<cf/||/). Special operators include (<cf/˜/,
1272: <cf/!˜/) for "is (not) element of a set" operation - it can be used on
1273: element and set of elements of the same type (returning true if element is
1274: contained in the given set), or on two strings (returning true if first string
1275: matches a shell-like pattern stored in second string) or on IP and prefix
1276: (returning true if IP is within the range defined by that prefix), or on prefix
1277: and prefix (returning true if first prefix is more specific than second one) or
1278: on bgppath and bgpmask (returning true if the path matches the mask) or on
1279: number and bgppath (returning true if the number is in the path) or on bgppath
1280: and int (number) set (returning true if any ASN from the path is in the set) or
1281: on pair/quad and clist (returning true if the pair/quad is element of the
1282: clist) or on clist and pair/quad set (returning true if there is an element of
1283: the clist that is also a member of the pair/quad set).
1284:
1285: <p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1286: examines a ROA table and does <rfc id="6483"> route origin validation for a
1287: given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1288: checks current route (which should be from BGP to have AS_PATH argument) in the
1289: specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1290: ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1291: ROAs but none of them match. There is also an extended variant
1292: <cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1293: prefix and an ASN as arguments.
1294:
1295:
1296: <sect>Control structures
1297: <label id="control-structures">
1298:
1299: <p>Filters support two control structures: conditions and case switches.
1300:
1301: <p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/command1/;
1302: else <m/command2/;</cf> and you can use <cf>{ <m/command_1/; <m/command_2/;
1303: <M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1304: omitted. If the <cf><m>boolean expression</m></cf> is true, <m/command1/ is
1305: executed, otherwise <m/command2/ is executed.
1306:
1307: <p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1308: <m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1309: ... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1310: on the left side of the ˜ operator and anything that could be a member of
1311: a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1312: grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1313: between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1314: neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1315:
1316: <p>Here is example that uses <cf/if/ and <cf/case/ structures:
1317:
1318: <code>
1319: case arg1 {
1320: 2: print "two"; print "I can do more commands without {}";
1321: 3 .. 5: print "three to five";
1322: else: print "something else";
1323: }
1324:
1325: if 1234 = i then printn "."; else {
1326: print "not 1234";
1327: print "You need {} around multiple commands";
1328: }
1329: </code>
1330:
1331:
1332: <sect>Route attributes
1333: <label id="route-attributes">
1334:
1335: <p>A filter is implicitly passed a route, and it can access its attributes just
1336: like it accesses variables. Attempts to access undefined attribute result in a
1337: runtime error; you can check if an attribute is defined by using the
1338: <cf>defined( <m>attribute</m> )</cf> operator. One notable exception to this
1339: rule are attributes of clist type, where undefined value is regarded as empty
1340: clist for most purposes.
1341:
1342: <descrip>
1343: <tag><label id="rta-net"><m/prefix/ net</tag>
1344: Network the route is talking about. Read-only. (See the chapter about
1345: routing tables.)
1346:
1347: <tag><label id="rta-scope"><m/enum/ scope</tag>
1348: The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1349: local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1350: link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1351: <cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1352: interpreted by BIRD and can be used to mark routes in filters. The
1353: default value for new routes is <cf/SCOPE_UNIVERSE/.
1354:
1355: <tag><label id="rta-preference"><m/int/ preference</tag>
1356: Preference of the route. Valid values are 0-65535. (See the chapter
1357: about routing tables.)
1358:
1359: <tag><label id="rta-from"><m/ip/ from</tag>
1360: The router which the route has originated from.
1361:
1362: <tag><label id="rta-gw"><m/ip/ gw</tag>
1363: Next hop packets routed using this route should be forwarded to.
1364:
1365: <tag><label id="rta-proto"><m/string/ proto</tag>
1366: The name of the protocol which the route has been imported from.
1367: Read-only.
1368:
1369: <tag><label id="rta-source"><m/enum/ source</tag>
1370: what protocol has told me about this route. Possible values:
1371: <cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
1372: <cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/,
1373: <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/,
1374: <cf/RTS_PIPE/, <cf/RTS_BABEL/.
1375:
1376: <tag><label id="rta-cast"><m/enum/ cast</tag>
1377: Route type (Currently <cf/RTC_UNICAST/ for normal routes,
1378: <cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will be used in
1379: the future for broadcast, multicast and anycast routes). Read-only.
1380:
1381: <tag><label id="rta-dest"><m/enum/ dest</tag>
1382: Type of destination the packets should be sent to
1383: (<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1384: <cf/RTD_DEVICE/ for routing to a directly-connected network,
1385: <cf/RTD_MULTIPATH/ for multipath destinations,
1386: <cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1387: <cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
1388: returned with ICMP host unreachable / ICMP administratively prohibited
1389: messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
1390: <cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
1391:
1392: <tag><label id="rta-ifname"><m/string/ ifname</tag>
1393: Name of the outgoing interface. Sink routes (like blackhole, unreachable
1394: or prohibit) and multipath routes have no interface associated with
1395: them, so <cf/ifname/ returns an empty string for such routes. Read-only.
1396:
1397: <tag><label id="rta-ifindex"><m/int/ ifindex</tag>
1398: Index of the outgoing interface. System wide index of the interface. May
1399: be used for interface matching, however indexes might change on interface
1400: creation/removal. Zero is returned for routes with undefined outgoing
1401: interfaces. Read-only.
1402:
1403: <tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
1404: The optional attribute that can be used to specify a distance to the
1405: network for routes that do not have a native protocol metric attribute
1406: (like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
1407: compare internal distances to boundary routers (see below). It is also
1408: used when the route is exported to OSPF as a default value for OSPF type
1409: 1 metric.
1410: </descrip>
1411:
1412: <p>There also exist some protocol-specific attributes which are described in the
1413: corresponding protocol sections.
1414:
1415:
1416: <sect>Other statements
1417: <label id="other-statements">
1418:
1419: <p>The following statements are available:
1420:
1421: <descrip>
1422: <tag><label id="assignment"><m/variable/ = <m/expr/</tag>
1423: Set variable to a given value.
1424:
1425: <tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
1426: Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1427:
1428: <tag><label id="return">return <m/expr/</tag>
1429: Return <cf><m>expr</m></cf> from the current function, the function ends
1430: at this point.
1431:
1432: <tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
1433: Prints given expressions; useful mainly while debugging filters. The
1434: <cf/printn/ variant does not terminate the line.
1435:
1436: <tag><label id="quitbird">quitbird</tag>
1437: Terminates BIRD. Useful when debugging the filter interpreter.
1438: </descrip>
1439:
1440:
1441: <chapt>Protocols
1442: <label id="protocols">
1443:
1444: <sect>Babel
1445: <label id="babel">
1446:
1447: <sect1>Introduction
1448: <label id="babel-intro">
1449:
1450: <p>The Babel protocol
1451: (<rfc id="6126">) is a loop-avoiding distance-vector routing protocol that is
1452: robust and efficient both in ordinary wired networks and in wireless mesh
1453: networks. Babel is conceptually very simple in its operation and "just works"
1454: in its default configuration, though some configuration is possible and in some
1455: cases desirable.
1456:
1457: <p>While the Babel protocol is dual stack (i.e., can carry both IPv4 and IPv6
1458: routes over the same IPv6 transport), BIRD presently implements only the IPv6
1459: subset of the protocol. No Babel extensions are implemented, but the BIRD
1460: implementation can coexist with implementations using the extensions (and will
1461: just ignore extension messages).
1462:
1463: <p>The Babel protocol implementation in BIRD is currently in alpha stage.
1464:
1465: <sect1>Configuration
1466: <label id="babel-config">
1467:
1468: <p>Babel supports no global configuration options apart from those common to all
1469: other protocols, but supports the following per-interface configuration options:
1470:
1471: <code>
1472: protocol babel [<name>] {
1473: interface <interface pattern> {
1474: type <wired|wireless>;
1475: rxcost <number>;
1476: hello interval <number>;
1477: update interval <number>;
1478: port <number>;
1479: tx class|dscp <number>;
1480: tx priority <number>;
1481: rx buffer <number>;
1482: tx length <number>;
1483: check link <switch>;
1484: };
1485: }
1486: </code>
1487:
1488: <descrip>
1489: <tag><label id="babel-type">type wired|wireless </tag>
1490: This option specifies the interface type: Wired or wireless. Wired
1491: interfaces are considered more reliable, and so the default hello
1492: interval is higher, and a neighbour is considered unreachable after only
1493: a small number of "hello" packets are lost. On wireless interfaces,
1494: hello packets are sent more often, and the ETX link quality estimation
1495: technique is used to compute the metrics of routes discovered over this
1496: interface. This technique will gradually degrade the metric of routes
1497: when packets are lost rather than the more binary up/down mechanism of
1498: wired type links. Default: <cf/wired/.
1499:
1500: <tag><label id="babel-rxcost">rxcost <m/num/</tag>
1501: This specifies the RX cost of the interface. The route metrics will be
1502: computed from this value with a mechanism determined by the interface
1503: <cf/type/. Default: 96 for wired interfaces, 256 for wireless.
1504:
1505: <tag><label id="babel-hello">hello interval <m/num/</tag>
1506: Interval at which periodic "hello" messages are sent on this interface,
1507: in seconds. Default: 4 seconds.
1508:
1509: <tag><label id="babel-update">update interval <m/num/</tag>
1510: Interval at which periodic (full) updates are sent. Default: 4 times the
1511: hello interval.
1512:
1513: <tag><label id="babel-port">port <m/number/</tag>
1514: This option selects an UDP port to operate on. The default is to operate
1515: on port 6696 as specified in the Babel RFC.
1516:
1517: <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
1518: These options specify the ToS/DiffServ/Traffic class/Priority of the
1519: outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
1520: option for detailed description.
1521:
1522: <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
1523: This option specifies the size of buffers used for packet processing.
1524: The buffer size should be bigger than maximal size of received packets.
1525: The default value is the interface MTU, and the value will be clamped to a
1526: minimum of 512 bytes + IP packet overhead.
1527:
1528: <tag><label id="babel-tx-length">tx length <m/number/</tag>
1529: This option specifies the maximum length of generated Babel packets. To
1530: avoid IP fragmentation, it should not exceed the interface MTU value.
1531: The default value is the interface MTU value, and the value will be
1532: clamped to a minimum of 512 bytes + IP packet overhead.
1533:
1534: <tag><label id="babel-check-link">check link <m/switch/</tag>
1535: If set, the hardware link state (as reported by OS) is taken into
1536: consideration. When the link disappears (e.g. an ethernet cable is
1537: unplugged), neighbors are immediately considered unreachable and all
1538: routes received from them are withdrawn. It is possible that some
1539: hardware drivers or platforms do not implement this feature. Default:
1540: yes.
1541: </descrip>
1542:
1543: <sect1>Attributes
1544: <label id="babel-attr">
1545:
1546: <p>Babel defines just one attribute: the internal babel metric of the route. It
1547: is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
1548: (65535).
1549:
1550: <sect1>Example
1551: <label id="babel-exam">
1552:
1553: <p><code>
1554: protocol babel {
1555: interface "eth*" {
1556: type wired;
1557: };
1558: interface "wlan0", "wlan1" {
1559: type wireless;
1560: hello interval 1;
1561: rxcost 512;
1562: };
1563: interface "tap0";
1564:
1565: # This matches the default of babeld: redistribute all addresses
1566: # configured on local interfaces, plus re-distribute all routes received
1567: # from other babel peers.
1568:
1569: export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1570: }
1571: </code>
1572:
1573:
1574: <sect>BFD
1575: <label id="bfd">
1576:
1577: <sect1>Introduction
1578: <label id="bfd-intro">
1579:
1580: <p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
1581: is an independent tool providing liveness and failure detection. Routing
1582: protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
1583: liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
1584: seconds by default in OSPF, could be set down to several seconds). BFD offers
1585: universal, fast and low-overhead mechanism for failure detection, which could be
1586: attached to any routing protocol in an advisory role.
1587:
1588: <p>BFD consists of mostly independent BFD sessions. Each session monitors an
1589: unicast bidirectional path between two BFD-enabled routers. This is done by
1590: periodically sending control packets in both directions. BFD does not handle
1591: neighbor discovery, BFD sessions are created on demand by request of other
1592: protocols (like OSPF or BGP), which supply appropriate information like IP
1593: addresses and associated interfaces. When a session changes its state, these
1594: protocols are notified and act accordingly (e.g. break an OSPF adjacency when
1595: the BFD session went down).
1596:
1597: <p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
1598: advanced features like the echo mode or authentication are not implemented), IP
1599: transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
1600: interaction with client protocols as defined in <rfc id="5882">.
1601:
1602: <p>Note that BFD implementation in BIRD is currently a new feature in
1603: development, expect some rough edges and possible UI and configuration changes
1604: in the future. Also note that we currently support at most one protocol instance.
1605:
1606: <p>BFD packets are sent with a dynamic source port number. Linux systems use by
1607: default a bit different dynamic port range than the IANA approved one
1608: (49152-65535). If you experience problems with compatibility, please adjust
1609: <cf>/proc/sys/net/ipv4/ip_local_port_range</cf>
1610:
1611: <sect1>Configuration
1612: <label id="bfd-config">
1613:
1614: <p>BFD configuration consists mainly of multiple definitions of interfaces.
1615: Most BFD config options are session specific. When a new session is requested
1616: and dynamically created, it is configured from one of these definitions. For
1617: sessions to directly connected neighbors, <cf/interface/ definitions are chosen
1618: based on the interface associated with the session, while <cf/multihop/
1619: definition is used for multihop sessions. If no definition is relevant, the
1620: session is just created with the default configuration. Therefore, an empty BFD
1621: configuration is often sufficient.
1622:
1623: <p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
1624: also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
1625:
1626: <p>Some of BFD session options require <m/time/ value, which has to be specified
1627: with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
1628: are allowed as units, practical minimum values are usually in order of tens of
1629: milliseconds.
1630:
1631: <code>
1632: protocol bfd [<name>] {
1633: interface <interface pattern> {
1634: interval <time>;
1635: min rx interval <time>;
1636: min tx interval <time>;
1637: idle tx interval <time>;
1638: multiplier <num>;
1639: passive <switch>;
1640: authentication none;
1641: authentication simple;
1642: authentication [meticulous] keyed md5|sha1;
1643: password "<text>";
1644: password "<text>" {
1645: id <num>;
1646: generate from "<date>";
1647: generate to "<date>";
1648: accept from "<date>";
1649: accept to "<date>";
1650: from "<date>";
1651: to "<date>";
1652: };
1653: };
1654: multihop {
1655: interval <time>;
1656: min rx interval <time>;
1657: min tx interval <time>;
1658: idle tx interval <time>;
1659: multiplier <num>;
1660: passive <switch>;
1661: };
1662: neighbor <ip> [dev "<interface>"] [local <ip>] [multihop <switch>];
1663: }
1664: </code>
1665:
1666: <descrip>
1667: <tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
1668: Interface definitions allow to specify options for sessions associated
1669: with such interfaces and also may contain interface specific options.
1670: See <ref id="proto-iface" name="interface"> common option for a detailed
1671: description of interface patterns. Note that contrary to the behavior of
1672: <cf/interface/ definitions of other protocols, BFD protocol would accept
1673: sessions (in default configuration) even on interfaces not covered by
1674: such definitions.
1675:
1676: <tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
1677: Multihop definitions allow to specify options for multihop BFD sessions,
1678: in the same manner as <cf/interface/ definitions are used for directly
1679: connected sessions. Currently only one such definition (for all multihop
1680: sessions) could be used.
1681:
1682: <tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
1683: BFD sessions are usually created on demand as requested by other
1684: protocols (like OSPF or BGP). This option allows to explicitly add
1685: a BFD session to the specified neighbor regardless of such requests.
1686:
1687: The session is identified by the IP address of the neighbor, with
1688: optional specification of used interface and local IP. By default
1689: the neighbor must be directly connected, unless the session is
1690: configured as multihop. Note that local IP must be specified for
1691: multihop sessions.
1692: </descrip>
1693:
1694: <p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
1695:
1696: <descrip>
1697: <tag><label id="bfd-interval">interval <m/time/</tag>
1698: BFD ensures availability of the forwarding path associated with the
1699: session by periodically sending BFD control packets in both
1700: directions. The rate of such packets is controlled by two options,
1701: <cf/min rx interval/ and <cf/min tx interval/ (see below). This option
1702: is just a shorthand to set both of these options together.
1703:
1704: <tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
1705: This option specifies the minimum RX interval, which is announced to the
1706: neighbor and used there to limit the neighbor's rate of generated BFD
1707: control packets. Default: 10 ms.
1708:
1709: <tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
1710: This option specifies the desired TX interval, which controls the rate
1711: of generated BFD control packets (together with <cf/min rx interval/
1712: announced by the neighbor). Note that this value is used only if the BFD
1713: session is up, otherwise the value of <cf/idle tx interval/ is used
1714: instead. Default: 100 ms.
1715:
1716: <tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
1717: In order to limit unnecessary traffic in cases where a neighbor is not
1718: available or not running BFD, the rate of generated BFD control packets
1719: is lower when the BFD session is not up. This option specifies the
1720: desired TX interval in such cases instead of <cf/min tx interval/.
1721: Default: 1 s.
1722:
1723: <tag><label id="bfd-multiplier">multiplier <m/num/</tag>
1724: Failure detection time for BFD sessions is based on established rate of
1725: BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
1726: multiplier, which is essentially (ignoring jitter) a number of missed
1727: packets after which the session is declared down. Note that rates and
1728: multipliers could be different in each direction of a BFD session.
1729: Default: 5.
1730:
1731: <tag><label id="bfd-passive">passive <m/switch/</tag>
1732: Generally, both BFD session endpoints try to establish the session by
1733: sending control packets to the other side. This option allows to enable
1734: passive mode, which means that the router does not send BFD packets
1735: until it has received one from the other side. Default: disabled.
1736:
1737: <tag>authentication none</tag>
1738: No passwords are sent in BFD packets. This is the default value.
1739:
1740: <tag>authentication simple</tag>
1741: Every packet carries 16 bytes of password. Received packets lacking this
1742: password are ignored. This authentication mechanism is very weak.
1743:
1744: <tag>authentication [meticulous] keyed md5|sha1</tag>
1745: An authentication code is appended to each packet. The cryptographic
1746: algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
1747: for all keys (on one interface), in contrast to OSPF or RIP, where it
1748: is a per-key option. Passwords (keys) are not sent open via network.
1749:
1750: The <cf/meticulous/ variant means that cryptographic sequence numbers
1751: are increased for each sent packet, while in the basic variant they are
1752: increased about once per second. Generally, the <cf/meticulous/ variant
1753: offers better resistance to replay attacks but may require more
1754: computation.
1755:
1756: <tag>password "<M>text</M>"</tag>
1757: Specifies a password used for authentication. See <ref id="dsc-pass"
1758: name="password"> common option for detailed description. Note that
1759: password option <cf/algorithm/ is not available in BFD protocol. The
1760: algorithm is selected by <cf/authentication/ option for all passwords.
1761:
1762: </descrip>
1763:
1764: <sect1>Example
1765: <label id="bfd-exam">
1766:
1767: <p><code>
1768: protocol bfd {
1769: interface "eth*" {
1770: min rx interval 20 ms;
1771: min tx interval 50 ms;
1772: idle tx interval 300 ms;
1773: };
1774: interface "gre*" {
1775: interval 200 ms;
1776: multiplier 10;
1777: passive;
1778: };
1779: multihop {
1780: interval 200 ms;
1781: multiplier 10;
1782: };
1783:
1784: neighbor 192.168.1.10;
1785: neighbor 192.168.2.2 dev "eth2";
1786: neighbor 192.168.10.1 local 192.168.1.1 multihop;
1787: }
1788: </code>
1789:
1790:
1791: <sect>BGP
1792: <label id="bgp">
1793:
1794: <p>The Border Gateway Protocol is the routing protocol used for backbone level
1795: routing in the today's Internet. Contrary to other protocols, its convergence
1796: does not rely on all routers following the same rules for route selection,
1797: making it possible to implement any routing policy at any router in the network,
1798: the only restriction being that if a router advertises a route, it must accept
1799: and forward packets according to it.
1800:
1801: <p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
1802: is a part of the network with common management and common routing policy. It is
1803: identified by a unique 16-bit number (ASN). Routers within each AS usually
1804: exchange AS-internal routing information with each other using an interior
1805: gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
1806: the AS communicate global (inter-AS) network reachability information with their
1807: neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
1808: received information to other routers in the AS via interior BGP (iBGP).
1809:
1810: <p>Each BGP router sends to its neighbors updates of the parts of its routing
1811: table it wishes to export along with complete path information (a list of AS'es
1812: the packet will travel through if it uses the particular route) in order to
1813: avoid routing loops.
1814:
1815: <p>BIRD supports all requirements of the BGP4 standard as defined in
1816: <rfc id="4271"> It also supports the community attributes (<rfc id="1997">),
1817: capability negotiation (<rfc id="5492">), MD5 password authentication (<rfc
1818: id="2385">), extended communities (<rfc id="4360">), route reflectors (<rfc
1819: id="4456">), graceful restart (<rfc id="4724">), multiprotocol extensions
1820: (<rfc id="4760">), 4B AS numbers (<rfc id="4893">), and 4B AS numbers in
1821: extended communities (<rfc id="5668">).
1822:
1823:
1824: For IPv6, it uses the standard multiprotocol extensions defined in
1825: <rfc id="4760"> and applied to IPv6 according to <rfc id="2545">.
1826:
1827: <sect1>Route selection rules
1828: <label id="bgp-route-select-rules">
1829:
1830: <p>BGP doesn't have any simple metric, so the rules for selection of an optimal
1831: route among multiple BGP routes with the same preference are a bit more complex
1832: and they are implemented according to the following algorithm. It starts the
1833: first rule, if there are more "best" routes, then it uses the second rule to
1834: choose among them and so on.
1835:
1836: <itemize>
1837: <item>Prefer route with the highest Local Preference attribute.
1838: <item>Prefer route with the shortest AS path.
1839: <item>Prefer IGP origin over EGP and EGP origin over incomplete.
1840: <item>Prefer the lowest value of the Multiple Exit Discriminator.
1841: <item>Prefer routes received via eBGP over ones received via iBGP.
1842: <item>Prefer routes with lower internal distance to a boundary router.
1843: <item>Prefer the route with the lowest value of router ID of the
1844: advertising router.
1845: </itemize>
1846:
1847: <sect1>IGP routing table
1848: <label id="bgp-igp-routing-table">
1849:
1850: <p>BGP is mainly concerned with global network reachability and with routes to
1851: other autonomous systems. When such routes are redistributed to routers in the
1852: AS via BGP, they contain IP addresses of a boundary routers (in route attribute
1853: NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
1854: determine immediate next hops for routes and to know their internal distances to
1855: boundary routers for the purpose of BGP route selection. In BIRD, there is
1856: usually one routing table used for both IGP routes and BGP routes.
1857:
1858: <sect1>Configuration
1859: <label id="bgp-config">
1860:
1861: <p>Each instance of the BGP corresponds to one neighboring router. This allows
1862: to set routing policy and all the other parameters differently for each neighbor
1863: using the following configuration parameters:
1864:
1865: <descrip>
1866: <tag><label id="bgp-local">local [<m/ip/] as <m/number/</tag>
1867: Define which AS we are part of. (Note that contrary to other IP routers,
1868: BIRD is able to act as a router located in multiple AS'es simultaneously,
1869: but in such cases you need to tweak the BGP paths manually in the filters
1870: to get consistent behavior.) Optional <cf/ip/ argument specifies a source
1871: address, equivalent to the <cf/source address/ option (see below). This
1872: parameter is mandatory.
1873:
1874: <tag><label id="bgp-neighbor">neighbor [<m/ip/] [port <m/number/] [as <m/number/]</tag>
1875: Define neighboring router this instance will be talking to and what AS
1876: it is located in. In case the neighbor is in the same AS as we are, we
1877: automatically switch to iBGP. Optionally, the remote port may also be
1878: specified. The parameter may be used multiple times with different
1879: sub-options (e.g., both <cf/neighbor 10.0.0.1 as 65000;/ and
1880: <cf/neighbor 10.0.0.1; neighbor as 65000;/ are valid). This parameter is
1881: mandatory.
1882:
1883: <tag><label id="bgp-iface">interface <m/string/</tag>
1884: Define interface we should use for link-local BGP IPv6 sessions.
1885: Interface can also be specified as a part of <cf/neighbor address/
1886: (e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). It is an error to use
1887: this parameter for non link-local sessions.
1888:
1889: <tag><label id="bgp-direct">direct</tag>
1890: Specify that the neighbor is directly connected. The IP address of the
1891: neighbor must be from a directly reachable IP range (i.e. associated
1892: with one of your router's interfaces), otherwise the BGP session
1893: wouldn't start but it would wait for such interface to appear. The
1894: alternative is the <cf/multihop/ option. Default: enabled for eBGP.
1895:
1896: <tag><label id="bgp-multihop">multihop [<m/number/]</tag>
1897: Configure multihop BGP session to a neighbor that isn't directly
1898: connected. Accurately, this option should be used if the configured
1899: neighbor IP address does not match with any local network subnets. Such
1900: IP address have to be reachable through system routing table. The
1901: alternative is the <cf/direct/ option. For multihop BGP it is
1902: recommended to explicitly configure the source address to have it
1903: stable. Optional <cf/number/ argument can be used to specify the number
1904: of hops (used for TTL). Note that the number of networks (edges) in a
1905: path is counted; i.e., if two BGP speakers are separated by one router,
1906: the number of hops is 2. Default: enabled for iBGP.
1907:
1908: <tag><label id="bgp-source-address">source address <m/ip/</tag>
1909: Define local address we should use for next hop calculation and as a
1910: source address for the BGP session. Default: the address of the local
1911: end of the interface our neighbor is connected to.
1912:
1913: <tag><label id="bgp-next-hop-self">next hop self</tag>
1914: Avoid calculation of the Next Hop attribute and always advertise our own
1915: source address as a next hop. This needs to be used only occasionally to
1916: circumvent misconfigurations of other routers. Default: disabled.
1917:
1918: <tag><label id="bgp-next-hop-keep">next hop keep</tag>
1919: Forward the received Next Hop attribute even in situations where the
1920: local address should be used instead, like when the route is sent to an
1921: interface with a different subnet. Default: disabled.
1922:
1923: <tag><label id="bgp-missing-lladdr">missing lladdr self|drop|ignore</tag>
1924: Next Hop attribute in BGP-IPv6 sometimes contains just the global IPv6
1925: address, but sometimes it has to contain both global and link-local IPv6
1926: addresses. This option specifies what to do if BIRD have to send both
1927: addresses but does not know link-local address. This situation might
1928: happen when routes from other protocols are exported to BGP, or when
1929: improper updates are received from BGP peers. <cf/self/ means that BIRD
1930: advertises its own local address instead. <cf/drop/ means that BIRD
1931: skips that prefixes and logs error. <cf/ignore/ means that BIRD ignores
1932: the problem and sends just the global address (and therefore forms
1933: improper BGP update). Default: <cf/self/, unless BIRD is configured as a
1934: route server (option <cf/rs client/), in that case default is <cf/ignore/,
1935: because route servers usually do not forward packets themselves.
1936:
1937: <tag><label id="bgp-gateway">gateway direct|recursive</tag>
1938: For received routes, their <cf/gw/ (immediate next hop) attribute is
1939: computed from received <cf/bgp_next_hop/ attribute. This option
1940: specifies how it is computed. Direct mode means that the IP address from
1941: <cf/bgp_next_hop/ is used if it is directly reachable, otherwise the
1942: neighbor IP address is used. Recursive mode means that the gateway is
1943: computed by an IGP routing table lookup for the IP address from
1944: <cf/bgp_next_hop/. Note that there is just one level of indirection in
1945: recursive mode - the route obtained by the lookup must not be recursive
1946: itself, to prevent mutually recursive routes.
1947:
1948: Recursive mode is the behavior specified by the BGP
1949: standard. Direct mode is simpler, does not require any routes in a
1950: routing table, and was used in older versions of BIRD, but does not
1951: handle well nontrivial iBGP setups and multihop. Recursive mode is
1952: incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
1953: <cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
1954:
1955: <tag><label id="bgp-igp-table">igp table <m/name/</tag>
1956: Specifies a table that is used as an IGP routing table. Default: the
1957: same as the table BGP is connected to.
1958:
1959: <tag><label id="bgp-check-link">check link <M>switch</M></tag>
1960: BGP could use hardware link state into consideration. If enabled,
1961: BIRD tracks the link state of the associated interface and when link
1962: disappears (e.g. an ethernet cable is unplugged), the BGP session is
1963: immediately shut down. Note that this option cannot be used with
1964: multihop BGP. Default: disabled.
1965:
1966: <tag><label id="bgp-bfd">bfd <M>switch</M></tag>
1967: BGP could use BFD protocol as an advisory mechanism for neighbor
1968: liveness and failure detection. If enabled, BIRD setups a BFD session
1969: for the BGP neighbor and tracks its liveness by it. This has an
1970: advantage of an order of magnitude lower detection times in case of
1971: failure. Note that BFD protocol also has to be configured, see
1972: <ref id="bfd" name="BFD"> section for details. Default: disabled.
1973:
1974: <tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
1975: Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
1976: protects against spoofed packets by ignoring received packets with a
1977: smaller than expected TTL. To work properly, GTSM have to be enabled on
1978: both sides of a BGP session. If both <cf/ttl security/ and
1979: <cf/multihop/ options are enabled, <cf/multihop/ option should specify
1980: proper hop value to compute expected TTL. Kernel support required:
1981: Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
1982: Note that full (ICMP protection, for example) <rfc id="5082"> support is
1983: provided by Linux only. Default: disabled.
1984:
1985: <tag><label id="bgp-pass">password <m/string/</tag>
1986: Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
1987: used on BSD systems, see also <cf/setkey/ option below. Default: no
1988: authentication.
1989:
1990: <tag><label id="bgp-setkey">setkey <m/switch/</tag>
1991: On BSD systems, keys for TCP MD5 authentication are stored in the global
1992: SA/SP database, which can be accessed by external utilities (e.g.
1993: setkey(8)). BIRD configures security associations in the SA/SP database
1994: automatically based on <cf/password/ options (see above), this option
1995: allows to disable automatic updates by BIRD when manual configuration by
1996: external utilities is preferred. Note that automatic SA/SP database
1997: updates are currently implemented only for FreeBSD. Passwords have to be
1998: set manually by an external utility on NetBSD and OpenBSD. Default:
1999: enabled (ignored on non-FreeBSD).
2000:
2001: <tag><label id="bgp-passive">passive <m/switch/</tag>
2002: Standard BGP behavior is both initiating outgoing connections and
2003: accepting incoming connections. In passive mode, outgoing connections
2004: are not initiated. Default: off.
2005:
2006: <tag><label id="bgp-rr-client">rr client</tag>
2007: Be a route reflector and treat the neighbor as a route reflection
2008: client. Default: disabled.
2009:
2010: <tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2011: Route reflectors use cluster id to avoid route reflection loops. When
2012: there is one route reflector in a cluster it usually uses its router id
2013: as a cluster id, but when there are more route reflectors in a cluster,
2014: these need to be configured (using this option) to use a common cluster
2015: id. Clients in a cluster need not know their cluster id and this option
2016: is not allowed for them. Default: the same as router id.
2017:
2018: <tag><label id="bgp-rs-client">rs client</tag>
2019: Be a route server and treat the neighbor as a route server client.
2020: A route server is used as a replacement for full mesh EBGP routing in
2021: Internet exchange points in a similar way to route reflectors used in
2022: IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2023: uses ad-hoc implementation, which behaves like plain EBGP but reduces
2024: modifications to advertised route attributes to be transparent (for
2025: example does not prepend its AS number to AS PATH attribute and
2026: keeps MED attribute). Default: disabled.
2027:
2028: <tag><label id="bgp-secondary">secondary <m/switch/</tag>
2029: Usually, if an export filter rejects a selected route, no other route is
2030: propagated for that network. This option allows to try the next route in
2031: order until one that is accepted is found or all routes for that network
2032: are rejected. This can be used for route servers that need to propagate
2033: different tables to each client but do not want to have these tables
2034: explicitly (to conserve memory). This option requires that the connected
2035: routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
2036:
2037: <tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
2038: Standard BGP can propagate only one path (route) per destination network
2039: (usually the selected one). This option controls the add-path protocol
2040: extension, which allows to advertise any number of paths to a
2041: destination. Note that to be active, add-path has to be enabled on both
2042: sides of the BGP session, but it could be enabled separately for RX and
2043: TX direction. When active, all available routes accepted by the export
2044: filter are advertised to the neighbor. Default: off.
2045:
2046: <tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2047: BGP prevents routing loops by rejecting received routes with the local
2048: AS number in the AS path. This option allows to loose or disable the
2049: check. Optional <cf/number/ argument can be used to specify the maximum
2050: number of local ASNs in the AS path that is allowed for received
2051: routes. When the option is used without the argument, the check is
2052: completely disabled and you should ensure loop-free behavior by some
2053: other means. Default: 0 (no local AS number allowed).
2054:
2055: <tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
2056: After the initial route exchange, BGP protocol uses incremental updates
2057: to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
2058: changes its import filter, or if there is suspicion of inconsistency) it
2059: is necessary to do a new complete route exchange. BGP protocol extension
2060: Route Refresh (<rfc id="2918">) allows BGP speaker to request
2061: re-advertisement of all routes from its neighbor. BGP protocol
2062: extension Enhanced Route Refresh (<rfc id="7313">) specifies explicit
2063: begin and end for such exchanges, therefore the receiver can remove
2064: stale routes that were not advertised during the exchange. This option
2065: specifies whether BIRD advertises these capabilities and supports
2066: related procedures. Note that even when disabled, BIRD can send route
2067: refresh requests. Default: on.
2068:
2069: <tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
2070: When a BGP speaker restarts or crashes, neighbors will discard all
2071: received paths from the speaker, which disrupts packet forwarding even
2072: when the forwarding plane of the speaker remains intact. <rfc
2073: id="4724"> specifies an optional graceful restart mechanism to
2074: alleviate this issue. This option controls the mechanism. It has three
2075: states: Disabled, when no support is provided. Aware, when the graceful
2076: restart support is announced and the support for restarting neighbors
2077: is provided, but no local graceful restart is allowed (i.e.
2078: receiving-only role). Enabled, when the full graceful restart
2079: support is provided (i.e. both restarting and receiving role). Note
2080: that proper support for local graceful restart requires also
2081: configuration of other protocols. Default: aware.
2082:
2083: <tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
2084: The restart time is announced in the BGP graceful restart capability
2085: and specifies how long the neighbor would wait for the BGP session to
2086: re-establish after a restart before deleting stale routes. Default:
2087: 120 seconds.
2088:
2089: <tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
2090: <rfc id="1997"> demands that BGP speaker should process well-known
2091: communities like no-export (65535, 65281) or no-advertise (65535,
2092: 65282). For example, received route carrying a no-adverise community
2093: should not be advertised to any of its neighbors. If this option is
2094: enabled (which is by default), BIRD has such behavior automatically (it
2095: is evaluated when a route is exported to the BGP protocol just before
2096: the export filter). Otherwise, this integrated processing of
2097: well-known communities is disabled. In that case, similar behavior can
2098: be implemented in the export filter. Default: on.
2099:
2100: <tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
2101: BGP protocol was designed to use 2B AS numbers and was extended later to
2102: allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
2103: option it can be persuaded not to advertise it and to maintain old-style
2104: sessions with its neighbors. This might be useful for circumventing bugs
2105: in neighbor's implementation of 4B AS extension. Even when disabled
2106: (off), BIRD behaves internally as AS4-aware BGP router. Default: on.
2107:
2108: <tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
2109: The BGP protocol uses maximum message length of 4096 bytes. This option
2110: provides an extension to allow extended messages with length up
2111: to 65535 bytes. Default: off.
2112:
2113: <tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
2114: Use capability advertisement to advertise optional capabilities. This is
2115: standard behavior for newer BGP implementations, but there might be some
2116: older BGP implementations that reject such connection attempts. When
2117: disabled (off), features that request it (4B AS support) are also
2118: disabled. Default: on, with automatic fallback to off when received
2119: capability-related error.
2120:
2121: <tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag>
2122: Advertise IPv4 multiprotocol capability. This is not a correct behavior
2123: according to the strict interpretation of <rfc id="4760">, but it is
2124: widespread and required by some BGP implementations (Cisco and Quagga).
2125: This option is relevant to IPv4 mode with enabled capability
2126: advertisement only. Default: on.
2127:
2128: <tag><label id="bgp-route-limit">route limit <m/number/</tag>
2129: The maximal number of routes that may be imported from the protocol. If
2130: the route limit is exceeded, the connection is closed with an error.
2131: Limit is currently implemented as <cf>import limit <m/number/ action
2132: restart</cf>. This option is obsolete and it is replaced by
2133: <ref id="proto-import-limit" name="import limit option">. Default: no limit.
2134:
2135: <tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
2136: When an error is encountered (either locally or by the other side),
2137: disable the instance automatically and wait for an administrator to fix
2138: the problem manually. Default: off.
2139:
2140: <tag><label id="bgp-hold-time">hold time <m/number/</tag>
2141: Time in seconds to wait for a Keepalive message from the other side
2142: before considering the connection stale. Default: depends on agreement
2143: with the neighboring router, we prefer 240 seconds if the other side is
2144: willing to accept it.
2145:
2146: <tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
2147: Value of the hold timer used before the routers have a chance to exchange
2148: open messages and agree on the real value. Default: 240 seconds.
2149:
2150: <tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
2151: Delay in seconds between sending of two consecutive Keepalive messages.
2152: Default: One third of the hold time.
2153:
2154: <tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
2155: Delay in seconds between protocol startup and the first attempt to
2156: connect. Default: 5 seconds.
2157:
2158: <tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
2159: Time in seconds to wait before retrying a failed attempt to connect.
2160: Default: 120 seconds.
2161:
2162: <tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
2163: Minimum and maximum delay in seconds between a protocol failure (either
2164: local or reported by the peer) and automatic restart. Doesn't apply
2165: when <cf/disable after error/ is configured. If consecutive errors
2166: happen, the delay is increased exponentially until it reaches the
2167: maximum. Default: 60, 300.
2168:
2169: <tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
2170: Maximum time in seconds between two protocol failures to treat them as a
2171: error sequence which makes <cf/error wait time/ increase exponentially.
2172: Default: 300 seconds.
2173:
2174: <tag><label id="bgp-path-metric">path metric <m/switch/</tag>
2175: Enable comparison of path lengths when deciding which BGP route is the
2176: best one. Default: on.
2177:
2178: <tag><label id="bgp-med-metric">med metric <m/switch/</tag>
2179: Enable comparison of MED attributes (during best route selection) even
2180: between routes received from different ASes. This may be useful if all
2181: MED attributes contain some consistent metric, perhaps enforced in
2182: import filters of AS boundary routers. If this option is disabled, MED
2183: attributes are compared only if routes are received from the same AS
2184: (which is the standard behavior). Default: off.
2185:
2186: <tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
2187: BGP route selection algorithm is often viewed as a comparison between
2188: individual routes (e.g. if a new route appears and is better than the
2189: current best one, it is chosen as the new best one). But the proper
2190: route selection, as specified by <rfc id="4271">, cannot be fully
2191: implemented in that way. The problem is mainly in handling the MED
2192: attribute. BIRD, by default, uses an simplification based on individual
2193: route comparison, which in some cases may lead to temporally dependent
2194: behavior (i.e. the selection is dependent on the order in which routes
2195: appeared). This option enables a different (and slower) algorithm
2196: implementing proper <rfc id="4271"> route selection, which is
2197: deterministic. Alternative way how to get deterministic behavior is to
2198: use <cf/med metric/ option. This option is incompatible with <ref
2199: id="dsc-table-sorted" name="sorted tables">. Default: off.
2200:
2201: <tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
2202: Enable comparison of internal distances to boundary routers during best
2203: route selection. Default: on.
2204:
2205: <tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
2206: Standard route selection algorithm breaks ties by comparing router IDs.
2207: This changes the behavior to prefer older routes (when both are external
2208: and from different peer). For details, see <rfc id="5004">. Default: off.
2209:
2210: <tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
2211: Value of the Multiple Exit Discriminator to be used during route
2212: selection when the MED attribute is missing. Default: 0.
2213:
2214: <tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
2215: A default value for the Local Preference attribute. It is used when
2216: a new Local Preference attribute is attached to a route by the BGP
2217: protocol itself (for example, if a route is received through eBGP and
2218: therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
2219: versions of BIRD).
2220: </descrip>
2221:
2222: <sect1>Attributes
2223: <label id="bgp-attr">
2224:
2225: <p>BGP defines several route attributes. Some of them (those marked with
2226: `<tt/I/' in the table below) are available on internal BGP connections only,
2227: some of them (marked with `<tt/O/') are optional.
2228:
2229: <descrip>
2230: <tag><label id="rta-bgp-path">bgppath bgp_path/</tag>
2231: Sequence of AS numbers describing the AS path the packet will travel
2232: through when forwarded according to the particular route. In case of
2233: internal BGP it doesn't contain the number of the local AS.
2234:
2235: <tag><label id="rta-bgp-local-pref">int bgp_local_pref/ [I]</tag>
2236: Local preference value used for selection among multiple BGP routes (see
2237: the selection rules above). It's used as an additional metric which is
2238: propagated through the whole local AS.
2239:
2240: <tag><label id="rta-bgp-med">int bgp_med/ [O]</tag>
2241: The Multiple Exit Discriminator of the route is an optional attribute
2242: which is used on external (inter-AS) links to convey to an adjacent AS
2243: the optimal entry point into the local AS. The received attribute is
2244: also propagated over internal BGP links. The attribute value is zeroed
2245: when a route is exported to an external BGP instance to ensure that the
2246: attribute received from a neighboring AS is not propagated to other
2247: neighboring ASes. A new value might be set in the export filter of an
2248: external BGP instance. See <rfc id="4451"> for further discussion of
2249: BGP MED attribute.
2250:
2251: <tag><label id="rta-bgp-origin">enum bgp_origin/</tag>
2252: Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
2253: in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
2254: from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
2255: <cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
2256:
2257: <tag><label id="rta-bgp-next-hop">ip bgp_next_hop/</tag>
2258: Next hop to be used for forwarding of packets to this destination. On
2259: internal BGP connections, it's an address of the originating router if
2260: it's inside the local AS or a boundary router the packet will leave the
2261: AS through if it's an exterior route, so each BGP speaker within the AS
2262: has a chance to use the shortest interior path possible to this point.
2263:
2264: <tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr/ [O]</tag>
2265: This is an optional attribute which carries no value, but the sole
2266: presence of which indicates that the route has been aggregated from
2267: multiple routes by some router on the path from the originator.
2268:
2269: <!-- we don't handle aggregators right since they are of a very obscure type
2270: <tag>bgp_aggregator</tag>
2271: -->
2272: <tag><label id="rta-bgp-community">clist bgp_community/ [O]</tag>
2273: List of community values associated with the route. Each such value is a
2274: pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
2275: integers, the first of them containing the number of the AS which
2276: defines the community and the second one being a per-AS identifier.
2277: There are lots of uses of the community mechanism, but generally they
2278: are used to carry policy information like "don't export to USA peers".
2279: As each AS can define its own routing policy, it also has a complete
2280: freedom about which community attributes it defines and what will their
2281: semantics be.
2282:
2283: <tag><label id="rta-bgp-ext-community">eclist bgp_ext_community/ [O]</tag>
2284: List of extended community values associated with the route. Extended
2285: communities have similar usage as plain communities, but they have an
2286: extended range (to allow 4B ASNs) and a nontrivial structure with a type
2287: field. Individual community values are represented using an <cf/ec/ data
2288: type inside the filters.
2289:
2290: <tag><label id="rta-bgp-large-community">lclist <cf/bgp_large_community/ [O]</tag>
2291: List of large community values associated with the route. Large BGP
2292: communities is another variant of communities, but contrary to extended
2293: communities they behave very much the same way as regular communities,
2294: just larger -- they are uniform untyped triplets of 32bit numbers.
2295: Individual community values are represented using an <cf/lc/ data type
2296: inside the filters.
2297:
2298: <tag><label id="rta-bgp-originator-id">quad bgp_originator_id/ [I, O]</tag>
2299: This attribute is created by the route reflector when reflecting the
2300: route and contains the router ID of the originator of the route in the
2301: local AS.
2302:
2303: <tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list/ [I, O]</tag>
2304: This attribute contains a list of cluster IDs of route reflectors. Each
2305: route reflector prepends its cluster ID when reflecting the route.
2306: </descrip>
2307:
2308: <sect1>Example
2309: <label id="bgp-exam">
2310:
2311: <p><code>
2312: protocol bgp {
2313: local as 65000; # Use a private AS number
2314: neighbor 198.51.100.130 as 64496; # Our neighbor ...
2315: multihop; # ... which is connected indirectly
2316: export filter { # We use non-trivial export rules
2317: if source = RTS_STATIC then { # Export only static routes
2318: # Assign our community
2319: bgp_community.add((65000,64501));
2320: # Artificially increase path length
2321: # by advertising local AS number twice
2322: if bgp_path ~ [= 65000 =] then
2323: bgp_path.prepend(65000);
2324: accept;
2325: }
2326: reject;
2327: };
2328: import all;
2329: source address 198.51.100.14; # Use a non-standard source address
2330: }
2331: </code>
2332:
2333:
2334: <sect>Device
2335: <label id="device">
2336:
2337: <p>The Device protocol is not a real routing protocol. It doesn't generate any
2338: routes and it only serves as a module for getting information about network
2339: interfaces from the kernel.
2340:
2341: <p>Except for very unusual circumstances, you probably should include this
2342: protocol in the configuration since almost all other protocols require network
2343: interfaces to be defined for them to work with.
2344:
2345: <sect1>Configuration
2346: <label id="device-config">
2347:
2348: <p><descrip>
2349:
2350: <tag><label id="device-scan-time">scan time <m/number/</tag>
2351: Time in seconds between two scans of the network interface list. On
2352: systems where we are notified about interface status changes
2353: asynchronously (such as newer versions of Linux), we need to scan the
2354: list only in order to avoid confusion by lost notification messages,
2355: so the default time is set to a large value.
2356:
2357: <tag><label id="device-primary">primary [ "<m/mask/" ] <m/prefix/</tag>
2358: If a network interface has more than one network address, BIRD has to
2359: choose one of them as a primary one. By default, BIRD chooses the
2360: lexicographically smallest address as the primary one.
2361:
2362: This option allows to specify which network address should be chosen as
2363: a primary one. Network addresses that match <m/prefix/ are preferred to
2364: non-matching addresses. If more <cf/primary/ options are used, the first
2365: one has the highest preference. If "<m/mask/" is specified, then such
2366: <cf/primary/ option is relevant only to matching network interfaces.
2367:
2368: In all cases, an address marked by operating system as secondary cannot
2369: be chosen as the primary one.
2370: </descrip>
2371:
2372: <p>As the Device protocol doesn't generate any routes, it cannot have
2373: any attributes. Example configuration looks like this:
2374:
2375: <p><code>
2376: protocol device {
2377: scan time 10; # Scan the interfaces often
2378: primary "eth0" 192.168.1.1;
2379: primary 192.168.0.0/16;
2380: }
2381: </code>
2382:
2383:
2384: <sect>Direct
2385: <label id="direct">
2386:
2387: <p>The Direct protocol is a simple generator of device routes for all the
2388: directly connected networks according to the list of interfaces provided by the
2389: kernel via the Device protocol.
2390:
2391: <p>The question is whether it is a good idea to have such device routes in BIRD
2392: routing table. OS kernel usually handles device routes for directly connected
2393: networks by itself so we don't need (and don't want) to export these routes to
2394: the kernel protocol. OSPF protocol creates device routes for its interfaces
2395: itself and BGP protocol is usually used for exporting aggregate routes. Although
2396: there are some use cases that use the direct protocol (like abusing eBGP as an
2397: IGP routing protocol), in most cases it is not needed to have these device
2398: routes in BIRD routing table and to use the direct protocol.
2399:
2400: <p>There is one notable case when you definitely want to use the direct protocol
2401: -- running BIRD on BSD systems. Having high priority device routes for directly
2402: connected networks from the direct protocol protects kernel device routes from
2403: being overwritten or removed by IGP routes during some transient network
2404: conditions, because a lower priority IGP route for the same network is not
2405: exported to the kernel routing table. This is an issue on BSD systems only, as
2406: on Linux systems BIRD cannot change non-BIRD route in the kernel routing table.
2407:
2408: <p>There are just few configuration options for the Direct protocol:
2409:
2410: <p><descrip>
2411: <tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
2412: By default, the Direct protocol will generate device routes for all the
2413: interfaces available. If you want to restrict it to some subset of
2414: interfaces or addresses (e.g. if you're using multiple routing tables
2415: for policy routing and some of the policy domains don't contain all
2416: interfaces), just use this clause. See <ref id="proto-iface" name="interface">
2417: common option for detailed description. The Direct protocol uses
2418: extended interface clauses.
2419:
2420: <tag><label id="direct-check-link">check link <m/switch/</tag>
2421: If enabled, a hardware link state (reported by OS) is taken into
2422: consideration. Routes for directly connected networks are generated only
2423: if link up is reported and they are withdrawn when link disappears
2424: (e.g., an ethernet cable is unplugged). Default value is no.
2425: </descrip>
2426:
2427: <p>Direct device routes don't contain any specific attributes.
2428:
2429: <p>Example config might look like this:
2430:
2431: <p><code>
2432: protocol direct {
2433: interface "-arc*", "*"; # Exclude the ARCnets
2434: }
2435: </code>
2436:
2437:
2438: <sect>Kernel
2439: <label id="krt">
2440:
2441: <p>The Kernel protocol is not a real routing protocol. Instead of communicating
2442: with other routers in the network, it performs synchronization of BIRD's routing
2443: tables with the OS kernel. Basically, it sends all routing table updates to the
2444: kernel and from time to time it scans the kernel tables to see whether some
2445: routes have disappeared (for example due to unnoticed up/down transition of an
2446: interface) or whether an `alien' route has been added by someone else (depending
2447: on the <cf/learn/ switch, such routes are either ignored or accepted to our
2448: table).
2449:
2450: <p>Unfortunately, there is one thing that makes the routing table synchronization
2451: a bit more complicated. In the kernel routing table there are also device routes
2452: for directly connected networks. These routes are usually managed by OS itself
2453: (as a part of IP address configuration) and we don't want to touch that. They
2454: are completely ignored during the scan of the kernel tables and also the export
2455: of device routes from BIRD tables to kernel routing tables is restricted to
2456: prevent accidental interference. This restriction can be disabled using
2457: <cf/device routes/ switch.
2458:
2459: <p>If your OS supports only a single routing table, you can configure only one
2460: instance of the Kernel protocol. If it supports multiple tables (in order to
2461: allow policy routing; such an OS is for example Linux), you can run as many
2462: instances as you want, but each of them must be connected to a different BIRD
2463: routing table and to a different kernel table.
2464:
2465: <p>Because the kernel protocol is partially integrated with the connected
2466: routing table, there are two limitations - it is not possible to connect more
2467: kernel protocols to the same routing table and changing route destination
2468: (gateway) in an export filter of a kernel protocol does not work. Both
2469: limitations can be overcome using another routing table and the pipe protocol.
2470:
2471: <sect1>Configuration
2472: <label id="krt-config">
2473:
2474: <p><descrip>
2475: <tag><label id="krt-persist">persist <m/switch/</tag>
2476: Tell BIRD to leave all its routes in the routing tables when it exits
2477: (instead of cleaning them up).
2478:
2479: <tag><label id="krt-scan-time">scan time <m/number/</tag>
2480: Time in seconds between two consecutive scans of the kernel routing
2481: table.
2482:
2483: <tag><label id="krt-learn">learn <m/switch/</tag>
2484: Enable learning of routes added to the kernel routing tables by other
2485: routing daemons or by the system administrator. This is possible only on
2486: systems which support identification of route authorship.
2487:
2488: <tag><label id="krt-device-routes">device routes <m/switch/</tag>
2489: Enable export of device routes to the kernel routing table. By default,
2490: such routes are rejected (with the exception of explicitly configured
2491: device routes from the static protocol) regardless of the export filter
2492: to protect device routes in kernel routing table (managed by OS itself)
2493: from accidental overwriting or erasing.
2494:
2495: <tag><label id="krt-kernel-table">kernel table <m/number/</tag>
2496: Select which kernel table should this particular instance of the Kernel
2497: protocol work with. Available only on systems supporting multiple
2498: routing tables.
2499:
2500: <tag><label id="krt-metric">metric <m/number/</tag> (Linux)
2501: Use specified value as a kernel metric (priority) for all routes sent to
2502: the kernel. When multiple routes for the same network are in the kernel
2503: routing table, the Linux kernel chooses one with lower metric. Also,
2504: routes with different metrics do not clash with each other, therefore
2505: using dedicated metric value is a reliable way to avoid overwriting
2506: routes from other sources (e.g. kernel device routes). Metric 0 has a
2507: special meaning of undefined metric, in which either OS default is used,
2508: or per-route metric can be set using <cf/krt_metric/ attribute. Default:
2509: 0 (undefined).
2510:
2511: <tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
2512: Participate in graceful restart recovery. If this option is enabled and
2513: a graceful restart recovery is active, the Kernel protocol will defer
2514: synchronization of routing tables until the end of the recovery. Note
2515: that import of kernel routes to BIRD is not affected.
2516:
2517: <tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
2518: Usually, only best routes are exported to the kernel protocol. With path
2519: merging enabled, both best routes and equivalent non-best routes are
2520: merged during export to generate one ECMP (equal-cost multipath) route
2521: for each network. This is useful e.g. for BGP multipath. Note that best
2522: routes are still pivotal for route export (responsible for most
2523: properties of resulting ECMP routes), while exported non-best routes are
2524: responsible just for additional multipath next hops. This option also
2525: allows to specify a limit on maximal number of nexthops in one route. By
2526: default, multipath merging is disabled. If enabled, default value of the
2527: limit is 16.
2528: </descrip>
2529:
2530: <sect1>Attributes
2531: <label id="krt-attr">
2532:
2533: <p>The Kernel protocol defines several attributes. These attributes are
2534: translated to appropriate system (and OS-specific) route attributes. We support
2535: these attributes:
2536:
2537: <descrip>
2538: <tag><label id="rta-krt-source">int krt_source/</tag>
2539: The original source of the imported kernel route. The value is
2540: system-dependent. On Linux, it is a value of the protocol field of the
2541: route. See /etc/iproute2/rt_protos for common values. On BSD, it is
2542: based on STATIC and PROTOx flags. The attribute is read-only.
2543:
2544: <tag><label id="rta-krt-metric">int krt_metric/</tag> (Linux)
2545: The kernel metric of the route. When multiple same routes are in a
2546: kernel routing table, the Linux kernel chooses one with lower metric.
2547: Note that preferred way to set kernel metric is to use protocol option
2548: <cf/metric/, unless per-route metric values are needed.
2549:
2550: <tag><label id="rta-krt-prefsrc">ip krt_prefsrc/</tag> (Linux)
2551: The preferred source address. Used in source address selection for
2552: outgoing packets. Has to be one of the IP addresses of the router.
2553:
2554: <tag><label id="rta-krt-realm">int krt_realm/</tag> (Linux)
2555: The realm of the route. Can be used for traffic classification.
2556:
2557: <tag><label id="rta-krt-scope">int krt_scope/</tag> (Linux IPv4)
2558: The scope of the route. Valid values are 0-254, although Linux kernel
2559: may reject some values depending on route type and nexthop. It is
2560: supposed to represent `indirectness' of the route, where nexthops of
2561: routes are resolved through routes with a higher scope, but in current
2562: kernels anything below <it/link/ (253) is treated as <it/global/ (0).
2563: When not present, global scope is implied for all routes except device
2564: routes, where link scope is used by default.
2565: </descrip>
2566:
2567: <p>In Linux, there is also a plenty of obscure route attributes mostly focused
2568: on tuning TCP performance of local connections. BIRD supports most of these
2569: attributes, see Linux or iproute2 documentation for their meaning. Attributes
2570: <cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, others have type int.
2571: Supported attributes are:
2572:
2573: <cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
2574: <cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
2575: <cf/krt_sstresh/, <cf/krt_lock_sstresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
2576: <cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
2577: <cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
2578: <cf/krt_initcwnd/, <cf/krt_initrwnd/, <cf/krt_quickack/,
2579: <cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
2580:
2581: <sect1>Example
2582: <label id="krt-exam">
2583:
2584: <p>A simple configuration can look this way:
2585:
2586: <p><code>
2587: protocol kernel {
2588: export all;
2589: }
2590: </code>
2591:
2592: <p>Or for a system with two routing tables:
2593:
2594: <p><code>
2595: protocol kernel { # Primary routing table
2596: learn; # Learn alien routes from the kernel
2597: persist; # Don't remove routes on bird shutdown
2598: scan time 10; # Scan kernel routing table every 10 seconds
2599: import all;
2600: export all;
2601: }
2602:
2603: protocol kernel { # Secondary routing table
2604: table auxtable;
2605: kernel table 100;
2606: export all;
2607: }
2608: </code>
2609:
2610:
2611: <sect>OSPF
2612: <label id="ospf">
2613:
2614: <sect1>Introduction
2615: <label id="ospf-intro">
2616:
2617: <p>Open Shortest Path First (OSPF) is a quite complex interior gateway
2618: protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
2619: the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
2620: state (a.k.a. shortest path first) protocol -- each router maintains a database
2621: describing the autonomous system's topology. Each participating router has an
2622: identical copy of the database and all routers run the same algorithm
2623: calculating a shortest path tree with themselves as a root. OSPF chooses the
2624: least cost path as the best path.
2625:
2626: <p>In OSPF, the autonomous system can be split to several areas in order to
2627: reduce the amount of resources consumed for exchanging the routing information
2628: and to protect the other areas from incorrect routing data. Topology of the area
2629: is hidden to the rest of the autonomous system.
2630:
2631: <p>Another very important feature of OSPF is that it can keep routing information
2632: from other protocols (like Static or BGP) in its link state database as external
2633: routes. Each external route can be tagged by the advertising router, making it
2634: possible to pass additional information between routers on the boundary of the
2635: autonomous system.
2636:
2637: <p>OSPF quickly detects topological changes in the autonomous system (such as
2638: router interface failures) and calculates new loop-free routes after a short
2639: period of convergence. Only a minimal amount of routing traffic is involved.
2640:
2641: <p>Each router participating in OSPF routing periodically sends Hello messages
2642: to all its interfaces. This allows neighbors to be discovered dynamically. Then
2643: the neighbors exchange theirs parts of the link state database and keep it
2644: identical by flooding updates. The flooding process is reliable and ensures that
2645: each router detects all changes.
2646:
2647: <sect1>Configuration
2648: <label id="ospf-config">
2649:
2650: <p>In the main part of configuration, there can be multiple definitions of OSPF
2651: areas, each with a different id. These definitions includes many other switches
2652: and multiple definitions of interfaces. Definition of interface may contain many
2653: switches and constant definitions and list of neighbors on nonbroadcast
2654: networks.
2655:
2656: <code>
2657: protocol ospf <name> {
2658: rfc1583compat <switch>;
2659: instance id <num>;
2660: stub router <switch>;
2661: tick <num>;
2662: ecmp <switch> [limit <num>];
2663: merge external <switch>;
2664: area <id> {
2665: stub;
2666: nssa;
2667: summary <switch>;
2668: default nssa <switch>;
2669: default cost <num>;
2670: default cost2 <num>;
2671: translator <switch>;
2672: translator stability <num>;
2673:
2674: networks {
2675: <prefix>;
2676: <prefix> hidden;
2677: }
2678: external {
2679: <prefix>;
2680: <prefix> hidden;
2681: <prefix> tag <num>;
2682: }
2683: stubnet <prefix>;
2684: stubnet <prefix> {
2685: hidden <switch>;
2686: summary <switch>;
2687: cost <num>;
2688: }
2689: interface <interface pattern> [instance <num>] {
2690: cost <num>;
2691: stub <switch>;
2692: hello <num>;
2693: poll <num>;
2694: retransmit <num>;
2695: priority <num>;
2696: wait <num>;
2697: dead count <num>;
2698: dead <num>;
2699: secondary <switch>;
2700: rx buffer [normal|large|<num>];
2701: tx length <num>;
2702: type [broadcast|bcast|pointopoint|ptp|
2703: nonbroadcast|nbma|pointomultipoint|ptmp];
2704: link lsa suppression <switch>;
2705: strict nonbroadcast <switch>;
2706: real broadcast <switch>;
2707: ptp netmask <switch>;
2708: check link <switch>;
2709: bfd <switch>;
2710: ecmp weight <num>;
2711: ttl security [<switch>; | tx only]
2712: tx class|dscp <num>;
2713: tx priority <num>;
2714: authentication none|simple|cryptographic;
2715: password "<text>";
2716: password "<text>" {
2717: id <num>;
2718: generate from "<date>";
2719: generate to "<date>";
2720: accept from "<date>";
2721: accept to "<date>";
2722: from "<date>";
2723: to "<date>";
2724: algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2725: };
2726: neighbors {
2727: <ip>;
2728: <ip> eligible;
2729: };
2730: };
2731: virtual link <id> [instance <num>] {
2732: hello <num>;
2733: retransmit <num>;
2734: wait <num>;
2735: dead count <num>;
2736: dead <num>;
2737: authentication none|simple|cryptographic;
2738: password "<text>";
2739: password "<text>" {
2740: id <num>;
2741: generate from "<date>";
2742: generate to "<date>";
2743: accept from "<date>";
2744: accept to "<date>";
2745: from "<date>";
2746: to "<date>";
2747: algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2748: };
2749: };
2750: };
2751: }
2752: </code>
2753:
2754: <descrip>
2755: <tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
2756: This option controls compatibility of routing table calculation with
2757: <rfc id="1583">. Default value is no.
2758:
2759: <tag><label id="ospf-instance-id">instance id <m/num/</tag>
2760: When multiple OSPF protocol instances are active on the same links, they
2761: should use different instance IDs to distinguish their packets. Although
2762: it could be done on per-interface basis, it is often preferred to set
2763: one instance ID to whole OSPF domain/topology (e.g., when multiple
2764: instances are used to represent separate logical topologies on the same
2765: physical network). This option specifies the default instance ID for all
2766: interfaces of the OSPF instance. Note that this option, if used, must
2767: precede interface definitions. Default value is 0.
2768:
2769: <tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
2770: This option configures the router to be a stub router, i.e., a router
2771: that participates in the OSPF topology but does not allow transit
2772: traffic. In OSPFv2, this is implemented by advertising maximum metric
2773: for outgoing links. In OSPFv3, the stub router behavior is announced by
2774: clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
2775: Default value is no.
2776:
2777: <tag><label id="ospf-tick">tick <M>num</M></tag>
2778: The routing table calculation and clean-up of areas' databases is not
2779: performed when a single link state change arrives. To lower the CPU
2780: utilization, it's processed later at periodical intervals of <m/num/
2781: seconds. The default value is 1.
2782:
2783: <tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
2784: This option specifies whether OSPF is allowed to generate ECMP
2785: (equal-cost multipath) routes. Such routes are used when there are
2786: several directions to the destination, each with the same (computed)
2787: cost. This option also allows to specify a limit on maximum number of
2788: nexthops in one route. By default, ECMP is disabled. If enabled,
2789: default value of the limit is 16.
2790:
2791: <tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
2792: This option specifies whether OSPF should merge external routes from
2793: different routers/LSAs for the same destination. When enabled together
2794: with <cf/ecmp/, equal-cost external routes will be combined to multipath
2795: routes in the same way as regular routes. When disabled, external routes
2796: from different LSAs are treated as separate even if they represents the
2797: same destination. Default value is no.
2798:
2799: <tag><label id="ospf-area">area <M>id</M></tag>
2800: This defines an OSPF area with given area ID (an integer or an IPv4
2801: address, similarly to a router ID). The most important area is the
2802: backbone (ID 0) to which every other area must be connected.
2803:
2804: <tag><label id="ospf-stub">stub</tag>
2805: This option configures the area to be a stub area. External routes are
2806: not flooded into stub areas. Also summary LSAs can be limited in stub
2807: areas (see option <cf/summary/). By default, the area is not a stub
2808: area.
2809:
2810: <tag><label id="ospf-nssa">nssa</tag>
2811: This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
2812: is a variant of a stub area which allows a limited way of external route
2813: propagation. Global external routes are not propagated into a NSSA, but
2814: an external route can be imported into NSSA as a (area-wide) NSSA-LSA
2815: (and possibly translated and/or aggregated on area boundary). By
2816: default, the area is not NSSA.
2817:
2818: <tag><label id="ospf-summary">summary <M>switch</M></tag>
2819: This option controls propagation of summary LSAs into stub or NSSA
2820: areas. If enabled, summary LSAs are propagated as usual, otherwise just
2821: the default summary route (0.0.0.0/0) is propagated (this is sometimes
2822: called totally stubby area). If a stub area has more area boundary
2823: routers, propagating summary LSAs could lead to more efficient routing
2824: at the cost of larger link state database. Default value is no.
2825:
2826: <tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
2827: When <cf/summary/ option is enabled, default summary route is no longer
2828: propagated to the NSSA. In that case, this option allows to originate
2829: default route as NSSA-LSA to the NSSA. Default value is no.
2830:
2831: <tag><label id="ospf-default-cost">default cost <M>num</M></tag>
2832: This option controls the cost of a default route propagated to stub and
2833: NSSA areas. Default value is 1000.
2834:
2835: <tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
2836: When a default route is originated as NSSA-LSA, its cost can use either
2837: type 1 or type 2 metric. This option allows to specify the cost of a
2838: default route in type 2 metric. By default, type 1 metric (option
2839: <cf/default cost/) is used.
2840:
2841: <tag><label id="ospf-translator">translator <M>switch</M></tag>
2842: This option controls translation of NSSA-LSAs into external LSAs. By
2843: default, one translator per NSSA is automatically elected from area
2844: boundary routers. If enabled, this area boundary router would
2845: unconditionally translate all NSSA-LSAs regardless of translator
2846: election. Default value is no.
2847:
2848: <tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
2849: This option controls the translator stability interval (in seconds).
2850: When the new translator is elected, the old one keeps translating until
2851: the interval is over. Default value is 40.
2852:
2853: <tag><label id="ospf-networks">networks { <m/set/ }</tag>
2854: Definition of area IP ranges. This is used in summary LSA origination.
2855: Hidden networks are not propagated into other areas.
2856:
2857: <tag><label id="ospf-external">external { <m/set/ }</tag>
2858: Definition of external area IP ranges for NSSAs. This is used for
2859: NSSA-LSA translation. Hidden networks are not translated into external
2860: LSAs. Networks can have configured route tag.
2861:
2862: <tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
2863: Stub networks are networks that are not transit networks between OSPF
2864: routers. They are also propagated through an OSPF area as a part of a
2865: link state database. By default, BIRD generates a stub network record
2866: for each primary network address on each OSPF interface that does not
2867: have any OSPF neighbors, and also for each non-primary network address
2868: on each OSPF interface. This option allows to alter a set of stub
2869: networks propagated by this router.
2870:
2871: Each instance of this option adds a stub network with given network
2872: prefix to the set of propagated stub network, unless option <cf/hidden/
2873: is used. It also suppresses default stub networks for given network
2874: prefix. When option <cf/summary/ is used, also default stub networks
2875: that are subnetworks of given stub network are suppressed. This might be
2876: used, for example, to aggregate generated stub networks.
2877:
2878: <tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
2879: Defines that the specified interfaces belong to the area being defined.
2880: See <ref id="proto-iface" name="interface"> common option for detailed
2881: description. In OSPFv2, extended interface clauses are used, because
2882: each network prefix is handled as a separate virtual interface.
2883:
2884: You can specify alternative instance ID for the interface definition,
2885: therefore it is possible to have several instances of that interface
2886: with different options or even in different areas. For OSPFv2, instance
2887: ID support is an extension (<rfc id="6549">) and is supposed to be set
2888: per-protocol. For OSPFv3, it is an integral feature.
2889:
2890: <tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
2891: Virtual link to router with the router id. Virtual link acts as a
2892: point-to-point interface belonging to backbone. The actual area is used
2893: as a transport area. This item cannot be in the backbone. Like with
2894: <cf/interface/ option, you could also use several virtual links to one
2895: destination with different instance IDs.
2896:
2897: <tag><label id="ospf-cost">cost <M>num</M></tag>
2898: Specifies output cost (metric) of an interface. Default value is 10.
2899:
2900: <tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
2901: If set to interface it does not listen to any packet and does not send
2902: any hello. Default value is no.
2903:
2904: <tag><label id="ospf-hello">hello <M>num</M></tag>
2905: Specifies interval in seconds between sending of Hello messages. Beware,
2906: all routers on the same network need to have the same hello interval.
2907: Default value is 10.
2908:
2909: <tag><label id="ospf-poll">poll <M>num</M></tag>
2910: Specifies interval in seconds between sending of Hello messages for some
2911: neighbors on NBMA network. Default value is 20.
2912:
2913: <tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
2914: Specifies interval in seconds between retransmissions of unacknowledged
2915: updates. Default value is 5.
2916:
2917: <tag><label id="ospf-priority">priority <M>num</M></tag>
2918: On every multiple access network (e.g., the Ethernet) Designated Router
2919: and Backup Designated router are elected. These routers have some special
2920: functions in the flooding process. Higher priority increases preferences
2921: in this election. Routers with priority 0 are not eligible. Default
2922: value is 1.
2923:
2924: <tag><label id="ospf-wait">wait <M>num</M></tag>
2925: After start, router waits for the specified number of seconds between
2926: starting election and building adjacency. Default value is 4*<m/hello/.
2927:
2928: <tag><label id="ospf-dead-count">dead count <M>num</M></tag>
2929: When the router does not receive any messages from a neighbor in
2930: <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
2931:
2932: <tag><label id="ospf-dead">dead <M>num</M></tag>
2933: When the router does not receive any messages from a neighbor in
2934: <m/dead/ seconds, it will consider the neighbor down. If both directives
2935: <cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
2936:
2937: <tag><label id="ospf-secondary">secondary <M>switch</M></tag>
2938: On BSD systems, older versions of BIRD supported OSPFv2 only for the
2939: primary IP address of an interface, other IP ranges on the interface
2940: were handled as stub networks. Since v1.4.1, regular operation on
2941: secondary IP addresses is supported, but disabled by default for
2942: compatibility. This option allows to enable it. The option is a
2943: transitional measure, will be removed in the next major release as the
2944: behavior will be changed. On Linux systems, the option is irrelevant, as
2945: operation on non-primary addresses is already the regular behavior.
2946:
2947: <tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
2948: This option allows to specify the size of buffers used for packet
2949: processing. The buffer size should be bigger than maximal size of any
2950: packets. By default, buffers are dynamically resized as needed, but a
2951: fixed value could be specified. Value <cf/large/ means maximal allowed
2952: packet size - 65535.
2953:
2954: <tag><label id="ospf-tx-length">tx length <M>num</M></tag>
2955: Transmitted OSPF messages that contain large amount of information are
2956: segmented to separate OSPF packets to avoid IP fragmentation. This
2957: option specifies the soft ceiling for the length of generated OSPF
2958: packets. Default value is the MTU of the network interface. Note that
2959: larger OSPF packets may still be generated if underlying OSPF messages
2960: cannot be splitted (e.g. when one large LSA is propagated).
2961:
2962: <tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
2963: BIRD detects a type of a connected network automatically, but sometimes
2964: it's convenient to force use of a different type manually. On broadcast
2965: networks (like ethernet), flooding and Hello messages are sent using
2966: multicasts (a single packet for all the neighbors). A designated router
2967: is elected and it is responsible for synchronizing the link-state
2968: databases and originating network LSAs. This network type cannot be used
2969: on physically NBMA networks and on unnumbered networks (networks without
2970: proper IP prefix).
2971:
2972: <tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
2973: Point-to-point networks connect just 2 routers together. No election is
2974: performed and no network LSA is originated, which makes it simpler and
2975: faster to establish. This network type is useful not only for physically
2976: PtP ifaces (like PPP or tunnels), but also for broadcast networks used
2977: as PtP links. This network type cannot be used on physically NBMA
2978: networks.
2979:
2980: <tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
2981: On NBMA networks, the packets are sent to each neighbor separately
2982: because of lack of multicast capabilities. Like on broadcast networks,
2983: a designated router is elected, which plays a central role in propagation
2984: of LSAs. This network type cannot be used on unnumbered networks.
2985:
2986: <tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
2987: This is another network type designed to handle NBMA networks. In this
2988: case the NBMA network is treated as a collection of PtP links. This is
2989: useful if not every pair of routers on the NBMA network has direct
2990: communication, or if the NBMA network is used as an (possibly
2991: unnumbered) PtP link.
2992:
2993: <tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
2994: In OSPFv3, link LSAs are generated for each link, announcing link-local
2995: IPv6 address of the router to its local neighbors. These are useless on
2996: PtP or PtMP networks and this option allows to suppress the link LSA
2997: origination for such interfaces. The option is ignored on other than PtP
2998: or PtMP interfaces. Default value is no.
2999:
3000: <tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
3001: If set, don't send hello to any undefined neighbor. This switch is
3002: ignored on other than NBMA or PtMP interfaces. Default value is no.
3003:
3004: <tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
3005: In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
3006: packets are sent as IP multicast packets. This option changes the
3007: behavior to using old-fashioned IP broadcast packets. This may be useful
3008: as a workaround if IP multicast for some reason does not work or does
3009: not work reliably. This is a non-standard option and probably is not
3010: interoperable with other OSPF implementations. Default value is no.
3011:
3012: <tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
3013: In <cf/type ptp/ network configurations, OSPFv2 implementations should
3014: ignore received netmask field in hello packets and should send hello
3015: packets with zero netmask field on unnumbered PtP links. But some OSPFv2
3016: implementations perform netmask checking even for PtP links. This option
3017: specifies whether real netmask will be used in hello packets on <cf/type
3018: ptp/ interfaces. You should ignore this option unless you meet some
3019: compatibility problems related to this issue. Default value is no for
3020: unnumbered PtP links, yes otherwise.
3021:
3022: <tag><label id="ospf-check-link">check link <M>switch</M></tag>
3023: If set, a hardware link state (reported by OS) is taken into consideration.
3024: When a link disappears (e.g. an ethernet cable is unplugged), neighbors
3025: are immediately considered unreachable and only the address of the iface
3026: (instead of whole network prefix) is propagated. It is possible that
3027: some hardware drivers or platforms do not implement this feature.
3028: Default value is no.
3029:
3030: <tag><label id="ospf-bfd">bfd <M>switch</M></tag>
3031: OSPF could use BFD protocol as an advisory mechanism for neighbor
3032: liveness and failure detection. If enabled, BIRD setups a BFD session
3033: for each OSPF neighbor and tracks its liveness by it. This has an
3034: advantage of an order of magnitude lower detection times in case of
3035: failure. Note that BFD protocol also has to be configured, see
3036: <ref id="bfd" name="BFD"> section for details. Default value is no.
3037:
3038: <tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3039: TTL security is a feature that protects routing protocols from remote
3040: spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3041: destined to neighbors. Because TTL is decremented when packets are
3042: forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3043: locations. Note that this option would interfere with OSPF virtual
3044: links.
3045:
3046: If this option is enabled, the router will send OSPF packets with TTL
3047: 255 and drop received packets with TTL less than 255. If this option si
3048: set to <cf/tx only/, TTL 255 is used for sent packets, but is not
3049: checked for received packets. Default value is no.
3050:
3051: <tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
3052: These options specify the ToS/DiffServ/Traffic class/Priority of the
3053: outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
3054: option for detailed description.
3055:
3056: <tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
3057: When ECMP (multipath) routes are allowed, this value specifies a
3058: relative weight used for nexthops going through the iface. Allowed
3059: values are 1-256. Default value is 1.
3060:
3061: <tag><label id="ospf-auth-none">authentication none</tag>
3062: No passwords are sent in OSPF packets. This is the default value.
3063:
3064: <tag><label id="ospf-auth-simple">authentication simple</tag>
3065: Every packet carries 8 bytes of password. Received packets lacking this
3066: password are ignored. This authentication mechanism is very weak.
3067: This option is not available in OSPFv3.
3068:
3069: <tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
3070: An authentication code is appended to every packet. The specific
3071: cryptographic algorithm is selected by option <cf/algorithm/ for each
3072: key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
3073: and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
3074: network, so this mechanism is quite secure. Packets can still be read by
3075: an attacker.
3076:
3077: <tag><label id="ospf-pass">password "<M>text</M>"</tag>
3078: Specifies a password used for authentication. See
3079: <ref id="proto-pass" name="password"> common option for detailed
3080: description.
3081:
3082: <tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
3083: A set of neighbors to which Hello messages on NBMA or PtMP networks are
3084: to be sent. For NBMA networks, some of them could be marked as eligible.
3085: In OSPFv3, link-local addresses should be used, using global ones is
3086: possible, but it is nonstandard and might be problematic. And definitely,
3087: link-local and global addresses should not be mixed.
3088: </descrip>
3089:
3090: <sect1>Attributes
3091: <label id="ospf-attr">
3092:
3093: <p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
3094:
3095: <p>Metric is ranging from 1 to infinity (65535). External routes use
3096: <cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
3097: with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
3098: <cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
3099: <cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
3100: 2/ is stored in attribute <cf/ospf_metric2/. If you specify both metrics only
3101: metric1 is used.
3102:
3103: <p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
3104: integer which is used when exporting routes to other protocols; otherwise, it
3105: doesn't affect routing inside the OSPF domain at all. The fourth attribute
3106: <cf/ospf_router_id/ is a router ID of the router advertising that route /
3107: network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
3108: <cf/ospf_tag = 0/.
3109:
3110: <sect1>Example
3111: <label id="ospf-exam">
3112:
3113: <p><code>
3114: protocol ospf MyOSPF {
3115: rfc1583compat yes;
3116: tick 2;
3117: export filter {
3118: if source = RTS_BGP then {
3119: ospf_metric1 = 100;
3120: accept;
3121: }
3122: reject;
3123: };
3124: area 0.0.0.0 {
3125: interface "eth*" {
3126: cost 11;
3127: hello 15;
3128: priority 100;
3129: retransmit 7;
3130: authentication simple;
3131: password "aaa";
3132: };
3133: interface "ppp*" {
3134: cost 100;
3135: authentication cryptographic;
3136: password "abc" {
3137: id 1;
3138: generate to "22-04-2003 11:00:06";
3139: accept from "17-01-2001 12:01:05";
3140: algorithm hmac sha384;
3141: };
3142: password "def" {
3143: id 2;
3144: generate to "22-07-2005 17:03:21";
3145: accept from "22-02-2001 11:34:06";
3146: algorithm hmac sha512;
3147: };
3148: };
3149: interface "arc0" {
3150: cost 10;
3151: stub yes;
3152: };
3153: interface "arc1";
3154: };
3155: area 120 {
3156: stub yes;
3157: networks {
3158: 172.16.1.0/24;
3159: 172.16.2.0/24 hidden;
3160: }
3161: interface "-arc0" , "arc*" {
3162: type nonbroadcast;
3163: authentication none;
3164: strict nonbroadcast yes;
3165: wait 120;
3166: poll 40;
3167: dead count 8;
3168: neighbors {
3169: 192.168.120.1 eligible;
3170: 192.168.120.2;
3171: 192.168.120.10;
3172: };
3173: };
3174: };
3175: }
3176: </code>
3177:
3178:
3179: <sect>Pipe
3180: <label id="pipe">
3181:
3182: <sect1>Introduction
3183: <label id="pipe-intro">
3184:
3185: <p>The Pipe protocol serves as a link between two routing tables, allowing
3186: routes to be passed from a table declared as primary (i.e., the one the pipe is
3187: connected to using the <cf/table/ configuration keyword) to the secondary one
3188: (declared using <cf/peer table/) and vice versa, depending on what's allowed by
3189: the filters. Export filters control export of routes from the primary table to
3190: the secondary one, import filters control the opposite direction.
3191:
3192: <p>The Pipe protocol may work in the transparent mode mode or in the opaque
3193: mode. In the transparent mode, the Pipe protocol retransmits all routes from
3194: one table to the other table, retaining their original source and attributes.
3195: If import and export filters are set to accept, then both tables would have
3196: the same content. The transparent mode is the default mode.
3197:
3198: <p>In the opaque mode, the Pipe protocol retransmits optimal route from one
3199: table to the other table in a similar way like other protocols send and receive
3200: routes. Retransmitted route will have the source set to the Pipe protocol, which
3201: may limit access to protocol specific route attributes. This mode is mainly for
3202: compatibility, it is not suggested for new configs. The mode can be changed by
3203: <tt/mode/ option.
3204:
3205: <p>The primary use of multiple routing tables and the Pipe protocol is for
3206: policy routing, where handling of a single packet doesn't depend only on its
3207: destination address, but also on its source address, source interface, protocol
3208: type and other similar parameters. In many systems (Linux being a good example),
3209: the kernel allows to enforce routing policies by defining routing rules which
3210: choose one of several routing tables to be used for a packet according to its
3211: parameters. Setting of these rules is outside the scope of BIRD's work (on
3212: Linux, you can use the <tt/ip/ command), but you can create several routing
3213: tables in BIRD, connect them to the kernel ones, use filters to control which
3214: routes appear in which tables and also you can employ the Pipe protocol for
3215: exporting a selected subset of one table to another one.
3216:
3217: <sect1>Configuration
3218: <label id="pipe-config">
3219:
3220: <p><descrip>
3221: <tag><label id="pipe-peer-table">peer table <m/table/</tag>
3222: Defines secondary routing table to connect to. The primary one is
3223: selected by the <cf/table/ keyword.
3224:
3225: <tag><label id="pipe-mode">mode opaque|transparent</tag>
3226: Specifies the mode for the pipe to work in. Default is transparent.
3227: </descrip>
3228:
3229: <sect1>Attributes
3230: <label id="pipe-attr">
3231:
3232: <p>The Pipe protocol doesn't define any route attributes.
3233:
3234: <sect1>Example
3235: <label id="pipe-exam">
3236:
3237: <p>Let's consider a router which serves as a boundary router of two different
3238: autonomous systems, each of them connected to a subset of interfaces of the
3239: router, having its own exterior connectivity and wishing to use the other AS as
3240: a backup connectivity in case of outage of its own exterior line.
3241:
3242: <p>Probably the simplest solution to this situation is to use two routing tables
3243: (we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
3244: packets having arrived from interfaces belonging to the first AS will be routed
3245: according to <cf/as1/ and similarly for the second AS. Thus we have split our
3246: router to two logical routers, each one acting on its own routing table, having
3247: its own routing protocols on its own interfaces. In order to use the other AS's
3248: routes for backup purposes, we can pass the routes between the tables through a
3249: Pipe protocol while decreasing their preferences and correcting their BGP paths
3250: to reflect the AS boundary crossing.
3251:
3252: <code>
3253: table as1; # Define the tables
3254: table as2;
3255:
3256: protocol kernel kern1 { # Synchronize them with the kernel
3257: table as1;
3258: kernel table 1;
3259: }
3260:
3261: protocol kernel kern2 {
3262: table as2;
3263: kernel table 2;
3264: }
3265:
3266: protocol bgp bgp1 { # The outside connections
3267: table as1;
3268: local as 1;
3269: neighbor 192.168.0.1 as 1001;
3270: export all;
3271: import all;
3272: }
3273:
3274: protocol bgp bgp2 {
3275: table as2;
3276: local as 2;
3277: neighbor 10.0.0.1 as 1002;
3278: export all;
3279: import all;
3280: }
3281:
3282: protocol pipe { # The Pipe
3283: table as1;
3284: peer table as2;
3285: export filter {
3286: if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks
3287: if preference>10 then preference = preference-10;
3288: if source=RTS_BGP then bgp_path.prepend(1);
3289: accept;
3290: }
3291: reject;
3292: };
3293: import filter {
3294: if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks
3295: if preference>10 then preference = preference-10;
3296: if source=RTS_BGP then bgp_path.prepend(2);
3297: accept;
3298: }
3299: reject;
3300: };
3301: }
3302: </code>
3303:
3304:
3305: <sect>RAdv
3306: <label id="radv">
3307:
3308: <sect1>Introduction
3309: <label id="radv-intro">
3310:
3311: <p>The RAdv protocol is an implementation of Router Advertisements, which are
3312: used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
3313: time intervals or as an answer to a request) advertisement packets to connected
3314: networks. These packets contain basic information about a local network (e.g. a
3315: list of network prefixes), which allows network hosts to autoconfigure network
3316: addresses and choose a default route. BIRD implements router behavior as defined
3317: in <rfc id="4861"> and also the DNS extensions from <rfc id="6106">.
3318:
3319: <sect1>Configuration
3320: <label id="radv-config">
3321:
3322: <p>There are several classes of definitions in RAdv configuration -- interface
3323: definitions, prefix definitions and DNS definitions:
3324:
3325: <descrip>
3326: <tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3327: Interface definitions specify a set of interfaces on which the
3328: protocol is activated and contain interface specific options.
3329: See <ref id="proto-iface" name="interface"> common options for
3330: detailed description.
3331:
3332: <tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
3333: Prefix definitions allow to modify a list of advertised prefixes. By
3334: default, the advertised prefixes are the same as the network prefixes
3335: assigned to the interface. For each network prefix, the matching prefix
3336: definition is found and its options are used. If no matching prefix
3337: definition is found, the prefix is used with default options.
3338:
3339: Prefix definitions can be either global or interface-specific. The
3340: second ones are part of interface options. The prefix definition
3341: matching is done in the first-match style, when interface-specific
3342: definitions are processed before global definitions. As expected, the
3343: prefix definition is matching if the network prefix is a subnet of the
3344: prefix in prefix definition.
3345:
3346: <tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
3347: RDNSS definitions allow to specify a list of advertised recursive DNS
3348: servers together with their options. As options are seldom necessary,
3349: there is also a short variant <cf>rdnss <m/address/</cf> that just
3350: specifies one DNS server. Multiple definitions are cumulative. RDNSS
3351: definitions may also be interface-specific when used inside interface
3352: options. By default, interface uses both global and interface-specific
3353: options, but that can be changed by <cf/rdnss local/ option.
3354: dsc-iface
3355: <tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
3356: DNSSL definitions allow to specify a list of advertised DNS search
3357: domains together with their options. Like <cf/rdnss/ above, multiple
3358: definitions are cumulative, they can be used also as interface-specific
3359: options and there is a short variant <cf>dnssl <m/domain/</cf> that just
3360: specifies one DNS search domain.
3361:
3362: <tag><label id="radv-trigger">trigger <m/prefix/</tag>
3363: RAdv protocol could be configured to change its behavior based on
3364: availability of routes. When this option is used, the protocol waits in
3365: suppressed state until a <it/trigger route/ (for the specified network)
3366: is exported to the protocol, the protocol also returnsd to suppressed
3367: state if the <it/trigger route/ disappears. Note that route export
3368: depends on specified export filter, as usual. This option could be used,
3369: e.g., for handling failover in multihoming scenarios.
3370:
3371: During suppressed state, router advertisements are generated, but with
3372: some fields zeroed. Exact behavior depends on which fields are zeroed,
3373: this can be configured by <cf/sensitive/ option for appropriate
3374: fields. By default, just <cf/default lifetime/ (also called <cf/router
3375: lifetime/) is zeroed, which means hosts cannot use the router as a
3376: default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
3377: also be configured as <cf/sensitive/ for a prefix, which would cause
3378: autoconfigured IPs to be deprecated or even removed.
3379: </descrip>
3380:
3381: <p>Interface specific options:
3382:
3383: <descrip>
3384: <tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
3385: Unsolicited router advertisements are sent in irregular time intervals.
3386: This option specifies the maximum length of these intervals, in seconds.
3387: Valid values are 4-1800. Default: 600
3388:
3389: <tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
3390: This option specifies the minimum length of that intervals, in seconds.
3391: Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
3392: about 1/3 * <cf/max ra interval/.
3393:
3394: <tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
3395: The minimum delay between two consecutive router advertisements, in
3396: seconds. Default: 3
3397:
3398: <tag><label id="radv-iface-managed">managed <m/switch/</tag>
3399: This option specifies whether hosts should use DHCPv6 for IP address
3400: configuration. Default: no
3401:
3402: <tag><label id="radv-iface-other-config">other config <m/switch/</tag>
3403: This option specifies whether hosts should use DHCPv6 to receive other
3404: configuration information. Default: no
3405:
3406: <tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
3407: This option specifies which value of MTU should be used by hosts. 0
3408: means unspecified. Default: 0
3409:
3410: <tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
3411: This option specifies the time (in milliseconds) how long hosts should
3412: assume a neighbor is reachable (from the last confirmation). Maximum is
3413: 3600000, 0 means unspecified. Default 0.
3414:
3415: <tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
3416: This option specifies the time (in milliseconds) how long hosts should
3417: wait before retransmitting Neighbor Solicitation messages. 0 means
3418: unspecified. Default 0.
3419:
3420: <tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
3421: This option specifies which value of Hop Limit should be used by
3422: hosts. Valid values are 0-255, 0 means unspecified. Default: 64
3423:
3424: <tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
3425: This option specifies the time (in seconds) how long (after the receipt
3426: of RA) hosts may use the router as a default router. 0 means do not use
3427: as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3428: Default: 3 * <cf/max ra interval/, <cf/sensitive/ yes.
3429:
3430: <tag><label id="radv-iface-default-preference-low">default preference low|medium|high</tag>
3431: This option specifies the Default Router Preference value to advertise
3432: to hosts. Default: medium.
3433:
3434: <tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
3435: Use only local (interface-specific) RDNSS definitions for this
3436: interface. Otherwise, both global and local definitions are used. Could
3437: also be used to disable RDNSS for given interface if no local definitons
3438: are specified. Default: no.
3439:
3440: <tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
3441: Use only local DNSSL definitions for this interface. See <cf/rdnss local/
3442: option above. Default: no.
3443: </descrip>
3444:
3445:
3446: <p>Prefix specific options
3447:
3448: <descrip>
3449: <tag><label id="radv-prefix-skip">skip <m/switch/</tag>
3450: This option allows to specify that given prefix should not be
3451: advertised. This is useful for making exceptions from a default policy
3452: of advertising all prefixes. Note that for withdrawing an already
3453: advertised prefix it is more useful to advertise it with zero valid
3454: lifetime. Default: no
3455:
3456: <tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
3457: This option specifies whether hosts may use the advertised prefix for
3458: onlink determination. Default: yes
3459:
3460: <tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
3461: This option specifies whether hosts may use the advertised prefix for
3462: stateless autoconfiguration. Default: yes
3463:
3464: <tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
3465: This option specifies the time (in seconds) how long (after the
3466: receipt of RA) the prefix information is valid, i.e., autoconfigured
3467: IP addresses can be assigned and hosts with that IP addresses are
3468: considered directly reachable. 0 means the prefix is no longer
3469: valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3470: Default: 86400 (1 day), <cf/sensitive/ no.
3471:
3472: <tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
3473: This option specifies the time (in seconds) how long (after the
3474: receipt of RA) IP addresses generated from the prefix using stateless
3475: autoconfiguration remain preferred. For <cf/sensitive/ option,
3476: see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
3477: <cf/sensitive/ no.
3478: </descrip>
3479:
3480:
3481: <p>RDNSS specific options:
3482:
3483: <descrip>
3484: <tag><label id="radv-rdnss-ns">ns <m/address/</tag>
3485: This option specifies one recursive DNS server. Can be used multiple
3486: times for multiple servers. It is mandatory to have at least one
3487: <cf/ns/ option in <cf/rdnss/ definition.
3488:
3489: <tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
3490: This option specifies the time how long the RDNSS information may be
3491: used by clients after the receipt of RA. It is expressed either in
3492: seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
3493: interval/. Note that RDNSS information is also invalidated when
3494: <cf/default lifetime/ expires. 0 means these addresses are no longer
3495: valid DNS servers. Default: 3 * <cf/max ra interval/.
3496: </descrip>
3497:
3498:
3499: <p>DNSSL specific options:
3500:
3501: <descrip>
3502: <tag><label id="radv-dnssl-domain">domain <m/address/</tag>
3503: This option specifies one DNS search domain. Can be used multiple times
3504: for multiple domains. It is mandatory to have at least one <cf/domain/
3505: option in <cf/dnssl/ definition.
3506:
3507: <tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
3508: This option specifies the time how long the DNSSL information may be
3509: used by clients after the receipt of RA. Details are the same as for
3510: RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
3511: </descrip>
3512:
3513:
3514: <sect1>Example
3515: <label id="radv-exam">
3516:
3517: <p><code>
3518: protocol radv {
3519: interface "eth2" {
3520: max ra interval 5; # Fast failover with more routers
3521: managed yes; # Using DHCPv6 on eth2
3522: prefix ::/0 {
3523: autonomous off; # So do not autoconfigure any IP
3524: };
3525: };
3526:
3527: interface "eth*"; # No need for any other options
3528:
3529: prefix 2001:0DB8:1234::/48 {
3530: preferred lifetime 0; # Deprecated address range
3531: };
3532:
3533: prefix 2001:0DB8:2000::/48 {
3534: autonomous off; # Do not autoconfigure
3535: };
3536:
3537: rdnss 2001:0DB8:1234::10; # Short form of RDNSS
3538:
3539: rdnss {
3540: lifetime mult 10;
3541: ns 2001:0DB8:1234::11;
3542: ns 2001:0DB8:1234::12;
3543: };
3544:
3545: dnssl {
3546: lifetime 3600;
3547: domain "abc.com";
3548: domain "xyz.com";
3549: };
3550: }
3551: </code>
3552:
3553:
3554: <sect>RIP
3555: <label id="rip">
3556:
3557: <sect1>Introduction
3558: <label id="rip-intro">
3559:
3560: <p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
3561: where each router broadcasts (to all its neighbors) distances to all networks it
3562: can reach. When a router hears distance to another network, it increments it and
3563: broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
3564: network goes unreachable, routers keep telling each other that its distance is
3565: the original distance plus 1 (actually, plus interface metric, which is usually
3566: one). After some time, the distance reaches infinity (that's 15 in RIP) and all
3567: routers know that network is unreachable. RIP tries to minimize situations where
3568: counting to infinity is necessary, because it is slow. Due to infinity being 16,
3569: you can't use RIP on networks where maximal distance is higher than 15
3570: hosts.
3571:
3572: <p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
3573: id="2080">), and RIP cryptographic authentication (<rfc id="4822">).
3574:
3575: <p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
3576: convergence, big network load and inability to handle larger networks makes it
3577: pretty much obsolete. It is still usable on very small networks.
3578:
3579: <sect1>Configuration
3580: <label id="rip-config">
3581:
3582: <p>RIP configuration consists mainly of common protocol options and interface
3583: definitions, most RIP options are interface specific.
3584:
3585: <code>
3586: protocol rip [<name>] {
3587: infinity <number>;
3588: ecmp <switch> [limit <number>];
3589: interface <interface pattern> {
3590: metric <number>;
3591: mode multicast|broadcast;
3592: passive <switch>;
3593: address <ip>;
3594: port <number>;
3595: version 1|2;
3596: split horizon <switch>;
3597: poison reverse <switch>;
3598: check zero <switch>;
3599: update time <number>;
3600: timeout time <number>;
3601: garbage time <number>;
3602: ecmp weight <number>;
3603: ttl security <switch>; | tx only;
3604: tx class|dscp <number>;
3605: tx priority <number>;
3606: rx buffer <number>;
3607: tx length <number>;
3608: check link <switch>;
3609: authentication none|plaintext|cryptographic;
3610: password "<text>";
3611: password "<text>" {
3612: id <num>;
3613: generate from "<date>";
3614: generate to "<date>";
3615: accept from "<date>";
3616: accept to "<date>";
3617: from "<date>";
3618: to "<date>";
3619: algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3620: };
3621: };
3622: }
3623: </code>
3624:
3625: <descrip>
3626: <tag><label id="rip-infinity">infinity <M>number</M></tag>
3627: Selects the distance of infinity. Bigger values will make
3628: protocol convergence even slower. The default value is 16.
3629:
3630: <tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
3631: This option specifies whether RIP is allowed to generate ECMP
3632: (equal-cost multipath) routes. Such routes are used when there are
3633: several directions to the destination, each with the same (computed)
3634: cost. This option also allows to specify a limit on maximum number of
3635: nexthops in one route. By default, ECMP is disabled. If enabled,
3636: default value of the limit is 16.
3637:
3638: <tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3639: Interface definitions specify a set of interfaces on which the
3640: protocol is activated and contain interface specific options.
3641: See <ref id="proto-iface" name="interface"> common options for
3642: detailed description.
3643: </descrip>
3644:
3645: <p>Interface specific options:
3646:
3647: <descrip>
3648: <tag><label id="rip-iface-metric">metric <m/num/</tag>
3649: This option specifies the metric of the interface. When a route is
3650: received from the interface, its metric is increased by this value
3651: before further processing. Valid values are 1-255, but values higher
3652: than infinity has no further meaning. Default: 1.
3653:
3654: <tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
3655: This option selects the mode for RIP to use on the interface. The
3656: default is multicast mode for RIPv2 and broadcast mode for RIPv1.
3657: RIPng always uses the multicast mode.
3658:
3659: <tag><label id="rip-iface-passive">passive <m/switch/</tag>
3660: Passive interfaces receive routing updates but do not transmit any
3661: messages. Default: no.
3662:
3663: <tag><label id="rip-iface-address">address <m/ip/</tag>
3664: This option specifies a destination address used for multicast or
3665: broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
3666: (ff02::9) multicast address, or an appropriate broadcast address in the
3667: broadcast mode.
3668:
3669: <tag><label id="rip-iface-port">port <m/number/</tag>
3670: This option selects an UDP port to operate on, the default is the
3671: official RIP (520) or RIPng (521) port.
3672:
3673: <tag><label id="rip-iface-version">version 1|2</tag>
3674: This option selects the version of RIP used on the interface. For RIPv1,
3675: automatic subnet aggregation is not implemented, only classful network
3676: routes and host routes are propagated. Note that BIRD allows RIPv1 to be
3677: configured with features that are defined for RIPv2 only, like
3678: authentication or using multicast sockets. The default is RIPv2 for IPv4
3679: RIP, the option is not supported for RIPng, as no further versions are
3680: defined.
3681:
3682: <tag><label id="rip-iface-version-only">version only <m/switch/</tag>
3683: Regardless of RIP version configured for the interface, BIRD accepts
3684: incoming packets of any RIP version. This option restrict accepted
3685: packets to the configured version. Default: no.
3686:
3687: <tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
3688: Split horizon is a scheme for preventing routing loops. When split
3689: horizon is active, routes are not regularly propagated back to the
3690: interface from which they were received. They are either not propagated
3691: back at all (plain split horizon) or propagated back with an infinity
3692: metric (split horizon with poisoned reverse). Therefore, other routers
3693: on the interface will not consider the router as a part of an
3694: independent path to the destination of the route. Default: yes.
3695:
3696: <tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
3697: When split horizon is active, this option specifies whether the poisoned
3698: reverse variant (propagating routes back with an infinity metric) is
3699: used. The poisoned reverse has some advantages in faster convergence,
3700: but uses more network traffic. Default: yes.
3701:
3702: <tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
3703: Received RIPv1 packets with non-zero values in reserved fields should
3704: be discarded. This option specifies whether the check is performed or
3705: such packets are just processed as usual. Default: yes.
3706:
3707: <tag><label id="rip-iface-update-time">update time <m/number/</tag>
3708: Specifies the number of seconds between periodic updates. A lower number
3709: will mean faster convergence but bigger network load. Default: 30.
3710:
3711: <tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
3712: Specifies the time interval (in seconds) between the last received route
3713: announcement and the route expiration. After that, the network is
3714: considered unreachable, but still is propagated with infinity distance.
3715: Default: 180.
3716:
3717: <tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
3718: Specifies the time interval (in seconds) between the route expiration
3719: and the removal of the unreachable network entry. The garbage interval,
3720: when a route with infinity metric is propagated, is used for both
3721: internal (after expiration) and external (after withdrawal) routes.
3722: Default: 120.
3723:
3724: <tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
3725: When ECMP (multipath) routes are allowed, this value specifies a
3726: relative weight used for nexthops going through the iface. Valid
3727: values are 1-256. Default value is 1.
3728:
3729: <tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
3730: Selects authentication method to be used. <cf/none/ means that packets
3731: are not authenticated at all, <cf/plaintext/ means that a plaintext
3732: password is embedded into each packet, and <cf/cryptographic/ means that
3733: packets are authenticated using some cryptographic hash function
3734: selected by option <cf/algorithm/ for each key. The default
3735: cryptographic algorithm for RIP keys is Keyed-MD5. If you set
3736: authentication to not-none, it is a good idea to add <cf>password</cf>
3737: section. Default: none.
3738:
3739: <tag><label id="rip-iface-pass">password "<m/text/"</tag>
3740: Specifies a password used for authentication. See <ref id="proto-pass"
3741: name="password"> common option for detailed description.
3742:
3743: <tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3744: TTL security is a feature that protects routing protocols from remote
3745: spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3746: destined to neighbors. Because TTL is decremented when packets are
3747: forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3748: locations.
3749:
3750: If this option is enabled, the router will send RIP packets with TTL 255
3751: and drop received packets with TTL less than 255. If this option si set
3752: to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
3753: for received packets. Such setting does not offer protection, but offers
3754: compatibility with neighbors regardless of whether they use ttl
3755: security.
3756:
3757: For RIPng, TTL security is a standard behavior (required by <rfc
3758: id="2080">) and therefore default value is yes. For IPv4 RIP, default
3759: value is no.
3760:
3761: <tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
3762: These options specify the ToS/DiffServ/Traffic class/Priority of the
3763: outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
3764: option for detailed description.
3765:
3766: <tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
3767: This option specifies the size of buffers used for packet processing.
3768: The buffer size should be bigger than maximal size of received packets.
3769: The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
3770:
3771: <tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
3772: This option specifies the maximum length of generated RIP packets. To
3773: avoid IP fragmentation, it should not exceed the interface MTU value.
3774: The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
3775:
3776: <tag><label id="rip-iface-check-link">check link <m/switch/</tag>
3777: If set, the hardware link state (as reported by OS) is taken into
3778: consideration. When the link disappears (e.g. an ethernet cable is
3779: unplugged), neighbors are immediately considered unreachable and all
3780: routes received from them are withdrawn. It is possible that some
3781: hardware drivers or platforms do not implement this feature.
3782: Default: no.
3783: </descrip>
3784:
3785: <sect1>Attributes
3786: <label id="rip-attr">
3787:
3788: <p>RIP defines two route attributes:
3789:
3790: <descrip>
3791: <tag><label id="rta-rip-metric">int rip_metric/</tag>
3792: RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
3793: from different RIP instances are available and all of them have the same
3794: preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
3795: non-RIP route is exported to RIP, the default metric is 1.
3796:
3797: <tag><label id="rta-rip-tag">int rip_tag/</tag>
3798: RIP route tag: a 16-bit number which can be used to carry additional
3799: information with the route (for example, an originating AS number in
3800: case of external routes). When a non-RIP route is exported to RIP, the
3801: default tag is 0.
3802: </descrip>
3803:
3804: <sect1>Example
3805: <label id="rip-exam">
3806:
3807: <p><code>
3808: protocol rip {
3809: debug all;
3810: port 1520;
3811: period 12;
3812: garbage time 60;
3813: interface "eth0" { metric 3; mode multicast; };
3814: interface "eth*" { metric 2; mode broadcast; };
3815: authentication cryptographic;
3816: password "secret-shared-key" { algorithm hmac sha256; };
3817: import filter { print "importing"; accept; };
3818: export filter { print "exporting"; accept; };
3819: }
3820: </code>
3821:
3822:
3823: <sect>Static
3824: <label id="static">
3825:
3826: <p>The Static protocol doesn't communicate with other routers in the network,
3827: but instead it allows you to define routes manually. This is often used for
3828: specifying how to forward packets to parts of the network which don't use
3829: dynamic routing at all and also for defining sink routes (i.e., those telling to
3830: return packets as undeliverable if they are in your IP block, you don't have any
3831: specific destination for them and you don't want to send them out through the
3832: default route to prevent routing loops).
3833:
3834: <p>There are five types of static routes: `classical' routes telling to forward
3835: packets to a neighboring router, multipath routes specifying several (possibly
3836: weighted) neighboring routers, device routes specifying forwarding to hosts on a
3837: directly connected network, recursive routes computing their nexthops by doing
3838: route table lookups for a given IP, and special routes (sink, blackhole etc.)
3839: which specify a special action to be done instead of forwarding the packet.
3840:
3841: <p>When the particular destination is not available (the interface is down or
3842: the next hop of the route is not a neighbor at the moment), Static just
3843: uninstalls the route from the table it is connected to and adds it again as soon
3844: as the destination becomes adjacent again.
3845:
3846: <p>There are three classes of definitions in Static protocol configuration --
3847: global options, static route definitions, and per-route options. Usually, the
3848: definition of the protocol contains mainly a list of static routes.
3849:
3850: <p>Global options:
3851:
3852: <descrip>
3853: <tag><label id="static-check-link">check link <m/switch/</tag>
3854: If set, hardware link states of network interfaces are taken into
3855: consideration. When link disappears (e.g. ethernet cable is unplugged),
3856: static routes directing to that interface are removed. It is possible
3857: that some hardware drivers or platforms do not implement this feature.
3858: Default: off.
3859:
3860: <tag><label id="static-igp-table">igp table <m/name/</tag>
3861: Specifies a table that is used for route table lookups of recursive
3862: routes. Default: the same table as the protocol is connected to.
3863: </descrip>
3864:
3865: <p>Route definitions (each may also contain a block of per-route options):
3866:
3867: <descrip>
3868: <tag><label id="static-route-via-ip">route <m/prefix/ via <m/ip/</tag>
3869: Static route through a neighboring router. For link-local next hops,
3870: interface can be specified as a part of the address (e.g.,
3871: <cf/via fe80::1234%eth0/).
3872:
3873: <tag><label id="static-route-via-mpath">route <m/prefix/ multipath via <m/ip/ [weight <m/num/] [bfd <m/switch/] [via <m/.../]</tag>
3874: Static multipath route. Contains several nexthops (gateways), possibly
3875: with their weights.
3876:
3877: <tag><label id="static-route-via-iface">route <m/prefix/ via <m/"interface"/</tag>
3878: Static device route through an interface to hosts on a directly
3879: connected network.
3880:
3881: <tag><label id="static-route-recursive">route <m/prefix/ recursive <m/ip/</tag>
3882: Static recursive route, its nexthop depends on a route table lookup for
3883: given IP address.
3884:
3885: <tag><label id="static-route-drop">route <m/prefix/ blackhole|unreachable|prohibit</tag>
3886: Special routes specifying to silently drop the packet, return it as
3887: unreachable or return it as administratively prohibited. First two
3888: targets are also known as <cf/drop/ and <cf/reject/.
3889: </descrip>
3890:
3891: <p>Per-route options:
3892:
3893: <descrip>
3894: <tag><label id="static-route-bfd">bfd <m/switch/</tag>
3895: The Static protocol could use BFD protocol for next hop liveness
3896: detection. If enabled, a BFD session to the route next hop is created
3897: and the static route is BFD-controlled -- the static route is announced
3898: only if the next hop liveness is confirmed by BFD. If the BFD session
3899: fails, the static route is removed. Note that this is a bit different
3900: compared to other protocols, which may use BFD as an advisory mechanism
3901: for fast failure detection but ignores it if a BFD session is not even
3902: established.
3903:
3904: This option can be used for static routes with a direct next hop, or
3905: also for for individual next hops in a static multipath route (see
3906: above). Note that BFD protocol also has to be configured, see
3907: <ref id="bfd" name="BFD"> section for details. Default value is no.
3908:
3909: <tag><label id="static-route-filter"><m/filter expression/</tag>
3910: This is a special option that allows filter expressions to be configured
3911: on per-route basis. Can be used multiple times. These expressions are
3912: evaluated when the route is originated, similarly to the import filter
3913: of the static protocol. This is especially useful for configuring route
3914: attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
3915: exported to the OSPF protocol.
3916: </descrip>
3917:
3918: <p>Static routes have no specific attributes.
3919:
3920: <p>Example static config might look like this:
3921:
3922: <p><code>
3923: protocol static {
3924: table testable; # Connect to a non-default routing table
3925: check link; # Advertise routes only if link is up
3926: route 0.0.0.0/0 via 198.51.100.130; # Default route
3927: route 10.0.0.0/8 multipath # Multipath route
3928: via 198.51.100.10 weight 2
3929: via 198.51.100.20 bfd # BFD-controlled next hop
3930: via 192.0.2.1;
3931: route 203.0.113.0/24 unreachable; # Sink route
3932: route 10.2.0.0/24 via "arc0"; # Secondary network
3933: route 192.168.10.0/24 via 198.51.100.100 {
3934: ospf_metric1 = 20; # Set extended attribute
3935: }
3936: route 192.168.10.0/24 via 198.51.100.100 {
3937: ospf_metric2 = 100; # Set extended attribute
3938: ospf_tag = 2; # Set extended attribute
3939: bfd; # BFD-controlled route
3940: }
3941: }
3942: </code>
3943:
3944:
3945: <chapt>Conclusions
3946: <label id="conclusion">
3947:
3948: <sect>Future work
3949: <label id="future-work">
3950:
3951: <p>Although BIRD supports all the commonly used routing protocols, there are
3952: still some features which would surely deserve to be implemented in future
3953: versions of BIRD:
3954:
3955: <itemize>
3956: <item>Opaque LSA's
3957: <item>Route aggregation and flap dampening
3958: <item>Multipath routes
3959: <item>Multicast routing protocols
3960: <item>Ports to other systems
3961: </itemize>
3962:
3963:
3964: <sect>Getting more help
3965: <label id="help">
3966:
3967: <p>If you use BIRD, you're welcome to join the bird-users mailing list
3968: (<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
3969: where you can share your experiences with the other users and consult
3970: your problems with the authors. To subscribe to the list, visit
3971: <HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
3972: The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
3973:
3974: <p>BIRD is a relatively young system and it probably contains some bugs. You can
3975: report any problems to the bird-users list and the authors will be glad to solve
3976: them, but before you do so, please make sure you have read the available
3977: documentation and that you are running the latest version (available at
3978: <HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
3979: (Of course, a patch which fixes the bug is always welcome as an attachment.)
3980:
3981: <p>If you want to understand what is going inside, Internet standards are a good
3982: and interesting reading. You can get them from
3983: <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
3984: nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
3985: name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
3986:
3987: <p><it/Good luck!/
3988:
3989: </book>
3990:
3991: <!--
3992: LocalWords: GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel
3993: LocalWords: linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
3994: LocalWords: router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
3995: LocalWords: len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth
3996: LocalWords: RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek
3997: LocalWords: EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC
3998: LocalWords: OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU
3999: LocalWords: uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc
4000: LocalWords: compat multicasts nonbroadcast pointopoint loopback sym stats
4001: LocalWords: Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt
4002: LocalWords: proto wildcard Ondrej Filip
4003: -->
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