Statistics
| Branch: | Revision:

iof-bird-daemon / doc / bird.sgml @ 9b0a0ba9

History | View | Annotate | Download (181 KB)

1
<!doctype birddoc system>
2

    
3
<!--
4
	BIRD documentation
5

    
6
This documentation can have 4 forms: sgml (this is master copy), html, ASCII
7
text and dvi/postscript (generated from sgml using sgmltools). You should always
8
edit master copy.
9

    
10
This is a slightly modified linuxdoc dtd. Anything in <descrip> tags is
11
considered definition of configuration primitives, <cf> is fragment of
12
configuration within normal text, <m> is "meta" information within fragment of
13
configuration - something in config which is not keyword.
14

    
15
    (set-fill-column 80)
16

    
17
    Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
18

    
19
 -->
20

    
21
<book>
22

    
23
<title>BIRD User's Guide
24
<author>
25
Ondrej Filip <it/&lt;feela@network.cz&gt;/,
26
Pavel Machek <it/&lt;pavel@ucw.cz&gt;/,
27
Martin Mares <it/&lt;mj@ucw.cz&gt;/,
28
Ondrej Zajicek <it/&lt;santiago@crfreenet.org&gt;/
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 &gt; 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 &tilde; 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/=, !=, &lt;, &gt;, &lt;=, &gt;=/), but
1050
	you can't concatenate two strings. String literals are written as
1051
	<cf/"This is a string constant"/. Additionally matching (<cf/&tilde;,
1052
	!&tilde;/) 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 &lt;= ip1 &lt;= len2</cf>. A valid prefix pattern
1140
	has to satisfy <cf>low &lt;= 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 &tilde; [ 1.0.0.0/8{15,17} ]</cf>
1161
	is true, but <cf>1.0.0.0/16 &tilde; [ 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
	&tilde; [= 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 &tilde; [= * 4 3 * =]</tt> is true,
1213
	but <tt>bgp_path &tilde; [= * 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/&tilde;/ and
1253
	<cf/!&tilde;/ membership operators) can be used to modify or test
1254
	eclists, with ECs instead of pairs as arguments.
1255

    
1256
	<tag><label id="type-lclist">lclist/</tag>
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/&tilde;/
1260
	and <cf/!&tilde;/ 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&lt;b, a&gt;=b)/.
1270
Logical operations include unary not (<cf/!/), and (<cf/&amp;&amp;/) and or
1271
(<cf/&verbar;&verbar;/). Special operators include (<cf/&tilde;/,
1272
<cf/!&tilde;/) 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 &tilde; 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 [&lt;name&gt;] {
1633
	interface &lt;interface pattern&gt; {
1634
		interval &lt;time&gt;;
1635
		min rx interval &lt;time&gt;;
1636
		min tx interval &lt;time&gt;;
1637
		idle tx interval &lt;time&gt;;
1638
		multiplier &lt;num&gt;;
1639
		passive &lt;switch&gt;;
1640
		authentication none;
1641
		authentication simple;
1642
		authentication [meticulous] keyed md5|sha1;
1643
		password "&lt;text&gt;";
1644
		password "&lt;text&gt;" {
1645
			id &lt;num&gt;;
1646
			generate from "&lt;date&gt;";
1647
			generate to "&lt;date&gt;";
1648
			accept from "&lt;date&gt;";
1649
			accept to "&lt;date&gt;";
1650
			from "&lt;date&gt;";
1651
			to "&lt;date&gt;";
1652
		};
1653
	};
1654
	multihop {
1655
		interval &lt;time&gt;;
1656
		min rx interval &lt;time&gt;;
1657
		min tx interval &lt;time&gt;;
1658
		idle tx interval &lt;time&gt;;
1659
		multiplier &lt;num&gt;;
1660
		passive &lt;switch&gt;;
1661
	};
1662
	neighbor &lt;ip&gt; [dev "&lt;interface&gt;"] [local &lt;ip&gt;] [multihop &lt;switch&gt;];
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 &lt;name&gt; {
2658
	rfc1583compat &lt;switch&gt;;
2659
	instance id &lt;num&gt;;
2660
	stub router &lt;switch&gt;;
2661
	tick &lt;num&gt;;
2662
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
2663
	merge external &lt;switch&gt;;
2664
	area &lt;id&gt; {
2665
		stub;
2666
		nssa;
2667
		summary &lt;switch&gt;;
2668
		default nssa &lt;switch&gt;;
2669
		default cost &lt;num&gt;;
2670
		default cost2 &lt;num&gt;;
2671
		translator &lt;switch&gt;;
2672
		translator stability &lt;num&gt;;
2673

    
2674
                networks {
2675
			&lt;prefix&gt;;
2676
			&lt;prefix&gt; hidden;
2677
		}
2678
                external {
2679
			&lt;prefix&gt;;
2680
			&lt;prefix&gt; hidden;
2681
			&lt;prefix&gt; tag &lt;num&gt;;
2682
		}
2683
		stubnet &lt;prefix&gt;;
2684
		stubnet &lt;prefix&gt; {
2685
			hidden &lt;switch&gt;;
2686
			summary &lt;switch&gt;;
2687
			cost &lt;num&gt;;
2688
		}
2689
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
2690
			cost &lt;num&gt;;
2691
			stub &lt;switch&gt;;
2692
			hello &lt;num&gt;;
2693
			poll &lt;num&gt;;
2694
			retransmit &lt;num&gt;;
2695
			priority &lt;num&gt;;
2696
			wait &lt;num&gt;;
2697
			dead count &lt;num&gt;;
2698
			dead &lt;num&gt;;
2699
			secondary &lt;switch&gt;;
2700
			rx buffer [normal|large|&lt;num&gt;];
2701
			tx length &lt;num&gt;;
2702
			type [broadcast|bcast|pointopoint|ptp|
2703
				nonbroadcast|nbma|pointomultipoint|ptmp];
2704
			link lsa suppression &lt;switch&gt;;
2705
			strict nonbroadcast &lt;switch&gt;;
2706
			real broadcast &lt;switch&gt;;
2707
			ptp netmask &lt;switch&gt;;
2708
			check link &lt;switch&gt;;
2709
			bfd &lt;switch&gt;;
2710
			ecmp weight &lt;num&gt;;
2711
			ttl security [&lt;switch&gt;; | tx only]
2712
			tx class|dscp &lt;num&gt;;
2713
			tx priority &lt;num&gt;;
2714
			authentication none|simple|cryptographic;
2715
			password "&lt;text&gt;";
2716
			password "&lt;text&gt;" {
2717
				id &lt;num&gt;;
2718
				generate from "&lt;date&gt;";
2719
				generate to "&lt;date&gt;";
2720
				accept from "&lt;date&gt;";
2721
				accept to "&lt;date&gt;";
2722
				from "&lt;date&gt;";
2723
				to "&lt;date&gt;";
2724
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2725
			};
2726
			neighbors {
2727
				&lt;ip&gt;;
2728
				&lt;ip&gt; eligible;
2729
			};
2730
		};
2731
		virtual link &lt;id&gt; [instance &lt;num&gt;] {
2732
			hello &lt;num&gt;;
2733
			retransmit &lt;num&gt;;
2734
			wait &lt;num&gt;;
2735
			dead count &lt;num&gt;;
2736
			dead &lt;num&gt;;
2737
			authentication none|simple|cryptographic;
2738
			password "&lt;text&gt;";
2739
			password "&lt;text&gt;" {
2740
				id &lt;num&gt;;
2741
				generate from "&lt;date&gt;";
2742
				generate to "&lt;date&gt;";
2743
				accept from "&lt;date&gt;";
2744
				accept to "&lt;date&gt;";
2745
				from "&lt;date&gt;";
2746
				to "&lt;date&gt;";
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 [&lt;name&gt;] {
3587
	infinity &lt;number&gt;;
3588
	ecmp &lt;switch&gt; [limit &lt;number&gt;];
3589
	interface &lt;interface pattern&gt; {
3590
		metric &lt;number&gt;;
3591
		mode multicast|broadcast;
3592
		passive &lt;switch&gt;;
3593
		address &lt;ip&gt;;
3594
		port &lt;number&gt;;
3595
		version 1|2;
3596
		split horizon &lt;switch&gt;;
3597
		poison reverse &lt;switch&gt;;
3598
		check zero &lt;switch&gt;;
3599
		update time &lt;number&gt;;
3600
		timeout time &lt;number&gt;;
3601
		garbage time &lt;number&gt;;
3602
		ecmp weight &lt;number&gt;;
3603
		ttl security &lt;switch&gt;; | tx only;
3604
		tx class|dscp &lt;number&gt;;
3605
		tx priority &lt;number&gt;;
3606
		rx buffer &lt;number&gt;;
3607
		tx length &lt;number&gt;;
3608
		check link &lt;switch&gt;;
3609
		authentication none|plaintext|cryptographic;
3610
		password "&lt;text&gt;";
3611
		password "&lt;text&gt;" {
3612
			id &lt;num&gt;;
3613
			generate from "&lt;date&gt;";
3614
			generate to "&lt;date&gt;";
3615
			accept from "&lt;date&gt;";
3616
			accept to "&lt;date&gt;";
3617
			from "&lt;date&gt;";
3618
			to "&lt;date&gt;";
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
-->