Statistics
| Branch: | Revision:

iof-bird-daemon / doc / bird.sgml @ df092aa1

History | View | Annotate | Download (222 KB)

1
<!doctype birddoc system>
2

    
3
<!--
4
	BIRD 2.0 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 2.0 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
Maria Matejka <it/&lt;mq@jmq.cz&gt;/,
29
Ondrej Zajicek <it/&lt;santiago@crfreenet.org&gt;/
30
</author>
31

    
32
<abstract>
33
This document contains user documentation for the BIRD Internet Routing Daemon project.
34
</abstract>
35

    
36
<!-- Table of contents -->
37
<toc>
38

    
39
<!-- Begin the document -->
40

    
41

    
42
<chapt>Introduction
43
<label id="intro">
44

    
45
<sect>What is BIRD
46
<label id="what-is-bird">
47

    
48
<p>The name `BIRD' is actually an acronym standing for `BIRD Internet Routing
49
Daemon'. Let's take a closer look at the meaning of the name:
50

    
51
<p><em/BIRD/: Well, we think we have already explained that. It's an acronym
52
standing for `BIRD Internet Routing Daemon', you remember, don't you? :-)
53

    
54
<p><em/Internet Routing/: It's a program (well, a daemon, as you are going to
55
discover in a moment) which works as a dynamic router in an Internet type
56
network (that is, in a network running either the IPv4 or the IPv6 protocol).
57
Routers are devices which forward packets between interconnected networks in
58
order to allow hosts not connected directly to the same local area network to
59
communicate with each other. They also communicate with the other routers in the
60
Internet to discover the topology of the network which allows them to find
61
optimal (in terms of some metric) rules for forwarding of packets (which are
62
called routing tables) and to adapt themselves to the changing conditions such
63
as outages of network links, building of new connections and so on. Most of
64
these routers are costly dedicated devices running obscure firmware which is
65
hard to configure and not open to any changes (on the other hand, their special
66
hardware design allows them to keep up with lots of high-speed network
67
interfaces, better than general-purpose computer does). Fortunately, most
68
operating systems of the UNIX family allow an ordinary computer to act as a
69
router and forward packets belonging to the other hosts, but only according to a
70
statically configured table.
71

    
72
<p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program
73
running on background which does the dynamic part of Internet routing, that is
74
it communicates with the other routers, calculates routing tables and sends them
75
to the OS kernel which does the actual packet forwarding. There already exist
76
other such routing daemons: routed (RIP only), GateD (non-free),
77
<HTMLURL URL="http://www.zebra.org" name="Zebra"> and
78
<HTMLURL URL="http://sourceforge.net/projects/mrt" name="MRTD">,
79
but their capabilities are limited and they are relatively hard to configure
80
and maintain.
81

    
82
<p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
83
to support all the routing technology used in the today's Internet or planned to
84
be used in near future and to have a clean extensible architecture allowing new
85
routing protocols to be incorporated easily. Among other features, BIRD
86
supports:
87

    
88
<itemize>
89
	<item>both IPv4 and IPv6 protocols
90
	<item>multiple routing tables
91
	<item>the Border Gateway Protocol (BGPv4)
92
	<item>the Routing Information Protocol (RIPv2, RIPng)
93
	<item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
94
	<item>the Babel Routing Protocol
95
	<item>the Router Advertisements for IPv6 hosts
96
	<item>a virtual protocol for exchange of routes between different
97
		routing tables on a single host
98
	<item>a command-line interface allowing on-line control and inspection
99
		of status of the daemon
100
	<item>soft reconfiguration (no need to use complex online commands to
101
		change the configuration, just edit the configuration file and
102
		notify BIRD to re-read it and it will smoothly switch itself to
103
		the new configuration, not disturbing routing protocols unless
104
		they are affected by the configuration changes)
105
	<item>a powerful language for route filtering
106
</itemize>
107

    
108
<p>BIRD has been developed at the Faculty of Math and Physics, Charles
109
University, Prague, Czech Republic as a student project. It can be freely
110
distributed under the terms of the GNU General Public License.
111

    
112
<p>BIRD has been designed to work on all UNIX-like systems. It has been
113
developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD
114
and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively
115
easy due to its highly modular architecture.
116

    
117
<p>BIRD 1.x supported either IPv4 or IPv6 protocol, but had to be compiled separately
118
for each one. BIRD~2 supports both of them with a possibility of further extension.
119
BIRD~2 supports Linux at least 3.16, FreeBSD 10, NetBSD 7.0, and OpenBSD 5.8.
120
Anyway, it will probably work well also on older systems.
121

    
122
<sect>Installing BIRD
123
<label id="install">
124

    
125
<p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make)
126
and Perl, installing BIRD should be as easy as:
127

    
128
<code>
129
	./configure
130
	make
131
	make install
132
	vi /usr/local/etc/bird.conf
133
	bird
134
</code>
135

    
136
<p>You can use <tt>./configure --help</tt> to get a list of configure
137
options. The most important ones are: <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 to stderr, and run bird in foreground.
153

    
154
	<tag><label id="argv-debug-file">-D <m/filename of debug log/</tag>
155
	enable debug messages to given file.
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>Architecture
221
<label id="architecture">
222

    
223
<sect>Routing tables
224
<label id="routing-tables">
225

    
226
<p>The heart of BIRD is a routing table. BIRD has several independent routing tables;
227
each of them contains routes of exactly one <m/nettype/ (see below). There are two
228
default tables -- <cf/master4/ for IPv4 routes and <cf/master6/ for IPv6 routes.
229
Other tables must be explicitly configured.
230

    
231
<p>
232
These routing tables are not kernel forwarding tables. No forwarding is done by
233
BIRD. If you want to forward packets using the routes in BIRD tables, you may
234
use the Kernel protocol (see below) to synchronize them with kernel FIBs.
235

    
236
<p>
237
Every nettype defines a (kind of) primary key on routes. Every route source can
238
supply one route for every possible primary key; new route announcement replaces
239
the old route from the same source, keeping other routes intact. BIRD always
240
chooses the best route for each primary key among the known routes and keeps the
241
others as suboptimal. When the best route is retracted, BIRD re-runs the best
242
route selection algorithm to find the current best route.
243

    
244
<p>
245
The global best route selection algorithm is (roughly) as follows:
246

    
247
<itemize>
248
	<item>Preferences of the routes are compared.
249
	<item>Source protocol instance preferences are compared.
250
	<item>If source protocols are the same (e.g. BGP vs. BGP), the protocol's route selection algorithm is invoked.
251
	<item>If source protocols are different (e.g. BGP vs. OSPF), result of the algorithm is undefined.
252
</itemize>
253

    
254
<p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected
255
route from a list of entries for one network. But if the <cf/sorted/ option is
256
activated, these lists of entries are kept completely sorted (according to
257
preference or some protocol-dependent metric). This is needed for some features
258
of some protocols (e.g. <cf/secondary/ option of BGP protocol, which allows to
259
accept not just a selected route, but the first route (in the sorted list) that
260
is accepted by filters), but it is incompatible with some other features (e.g.
261
<cf/deterministic med/ option of BGP protocol, which activates a way of choosing
262
selected route that cannot be described using comparison and ordering). Minor
263
advantage is that routes are shown sorted in <cf/show route/, minor disadvantage
264
is that it is slightly more computationally expensive.
265

    
266
<sect>Routes and network types
267
<label id="routes">
268

    
269
<p>BIRD works with several types of routes. Some of them are typical IP routes,
270
others are better described as forwarding rules. We call them all routes,
271
regardless of this difference.
272

    
273
<p>Every route consists of several attributes (read more about them in the
274
<ref id="route-attributes" name="Route attributes"> section); the common for all
275
routes are:
276

    
277
<itemize>
278
	<item>IP address of router which told us about this route
279
	<item>Source protocol instance
280
	<item>Route preference
281
	<item>Optional attributes defined by protocols
282
</itemize>
283

    
284
<p>Other attributes depend on nettypes. Some of them are part of the primary key, these are marked (PK).
285

    
286
<sect1>IPv4 and IPv6 routes
287
<label id="ip-routes">
288

    
289
<p>The traditional routes. Configuration keywords are <cf/ipv4/ and <cf/ipv6/.
290

    
291
<itemize>
292
	<item>(PK) Route destination (IP prefix together with its length)
293
	<item>Route next hops (see below)
294
</itemize>
295

    
296
<sect1>IPv6 source-specific routes
297
<label id="ip-sadr-routes">
298

    
299
<p>The IPv6 routes containing both destination and source prefix. They are used
300
for source-specific routing (SSR), also called source-address dependent routing
301
(SADR), see <rfc id="8043">. Currently limited mostly to the Babel protocol.
302
Configuration keyword is <cf/ipv6 sadr/.
303

    
304
<itemize>
305
	<item>(PK) Route destination (IP prefix together with its length)
306
	<item>(PK) Route source (IP prefix together with its length)
307
	<item>Route next hops (see below)
308
</itemize>
309

    
310
<sect1>VPN IPv4 and IPv6 routes
311
<label id="vpn-routes">
312

    
313
<p>Routes for IPv4 and IPv6 with VPN Route Distinguisher (<rfc id="4364">).
314
Configuration keywords are <cf/vpn4/ and <cf/vpn6/.
315

    
316
<itemize>
317
	<item>(PK) Route destination (IP prefix together with its length)
318
	<item>(PK) Route distinguisher (according to <rfc id="4364">)
319
	<item>Route next hops
320
</itemize>
321

    
322
<sect1>Route Origin Authorization for IPv4 and IPv6
323
<label id="roa-routes">
324

    
325
<p>These entries can be used to validate route origination of BGP routes.
326
A ROA entry specifies prefixes which could be originated by an AS number.
327
Their keywords are <cf/roa4/ and <cf/roa6/.
328

    
329
<itemize>
330
	<item>(PK) IP prefix together with its length
331
	<item>(PK) Matching prefix maximal length
332
	<item>(PK) AS number
333
</itemize>
334

    
335
<sect1>Flowspec for IPv4 and IPv6
336
<label id="flow-routes">
337

    
338
<p>Flowspec rules are a form of firewall and traffic flow control rules
339
distributed mostly via BGP. These rules may help the operators stop various
340
network attacks in the beginning before eating up the whole bandwidth.
341
Configuration keywords are <cf/flow4/ and <cf/flow6/.
342

    
343
<itemize>
344
	<item>(PK) IP prefix together with its length
345
	<item>(PK) Flow definition data
346
	<item>Flow action (encoded internally as BGP communities according to <rfc id="5575">)
347
</itemize>
348

    
349
<sect1>MPLS switching rules
350
<label id="mpls-routes">
351

    
352
<p>This nettype is currently a stub before implementing more support of <rfc id="3031">.
353
BIRD currently does not support any label distribution protocol nor any label assignment method.
354
Only the Kernel, Pipe and Static protocols can use MPLS tables.
355
Configuration keyword is <cf/mpls/.
356

    
357
<itemize>
358
	<item>(PK) MPLS label
359
	<item>Route next hops
360
</itemize>
361

    
362
<sect1>Route next hops
363
<label id="route-next-hop">
364

    
365
<p>This is not a nettype. The route next hop is a complex attribute common for many
366
nettypes as you can see before. Every next hop has its assigned device
367
(either assumed from its IP address or set explicitly). It may have also
368
an IP address and an MPLS stack (one or both independently).
369
Maximal MPLS stack depth is set (in compile time) to 8 labels.
370

    
371
<p>Every route (when eligible to have a next hop) can have more than one next hop.
372
In that case, every next hop has also its weight.
373

    
374
<sect>Protocols and channels
375
<label id="protocols-concept">
376

    
377
<p>BIRD protocol is an abstract class of producers and consumers of the routes.
378
Each protocol may run in multiple instances and bind on one side to route
379
tables via channels, on the other side to specified listen sockets (BGP),
380
interfaces (Babel, OSPF, RIP), APIs (Kernel, Direct), or nothing (Static, Pipe).
381

    
382
<p>There are also two protocols that do not have any channels -- BFD and Device.
383
Both of them are kind of service for other protocols.
384

    
385
<p>Each protocol is connected to a routing table through a channel. Some protocols
386
support only one channel (OSPF, RIP), some protocols support more channels (BGP, Direct).
387
Each channel has two filters which can accept, reject and modify the routes.
388
An <it/export/ filter is applied to routes passed from the routing table to the protocol,
389
an <it/import/ filter is applied to routes in the opposite direction.
390

    
391
<sect>Graceful restart
392
<label id="graceful-restart">
393

    
394
<p>When BIRD is started after restart or crash, it repopulates routing tables in
395
an uncoordinated manner, like after clean start. This may be impractical in some
396
cases, because if the forwarding plane (i.e. kernel routing tables) remains
397
intact, then its synchronization with BIRD would temporarily disrupt packet
398
forwarding until protocols converge. Graceful restart is a mechanism that could
399
help with this issue. Generally, it works by starting protocols and letting them
400
repopulate routing tables while deferring route propagation until protocols
401
acknowledge their convergence. Note that graceful restart behavior have to be
402
configured for all relevant protocols and requires protocol-specific support
403
(currently implemented for Kernel and BGP protocols), it is activated for
404
particular boot by option <cf/-R/.
405

    
406

    
407
<chapt>Configuration
408
<label id="config">
409

    
410
<sect>Introduction
411
<label id="config-intro">
412

    
413
<p>BIRD is configured using a text configuration file. Upon startup, BIRD reads
414
<it/prefix/<file>/etc/bird.conf</file> (unless the <tt/-c/ command line option
415
is given). Configuration may be changed at user's request: if you modify the
416
config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
417
config. Then there's the client which allows you to talk with BIRD in an
418
extensive way.
419

    
420
<p>In the config, everything on a line after <cf/#/ or inside <cf>/* */</cf> is
421
a comment, whitespace characters are treated as a single space. If there's a
422
variable number of options, they are grouped using the <cf/{ }/ brackets. Each
423
option is terminated by a <cf/;/. Configuration is case sensitive. There are two
424
ways how to name symbols (like protocol names, filter names, constants etc.).
425
You can either use a simple string starting with a letter followed by any
426
combination of letters and numbers (e.g. <cf/R123/, <cf/myfilter/, <cf/bgp5/) or
427
you can enclose the name into apostrophes (<cf/'/) and than you can use any
428
combination of numbers, letters. hyphens, dots and colons (e.g.
429
<cf/'1:strange-name'/, <cf/'-NAME-'/, <cf/'cool::name'/).
430

    
431
<p>Here is an example of a simple config file. It enables synchronization of
432
routing tables with OS kernel, learns network interfaces and runs RIP on all
433
network interfaces found.
434

    
435
<code>
436
protocol kernel {
437
	ipv4 {
438
		export all;	# Default is export none
439
	};
440
	persist;		# Don't remove routes on BIRD shutdown
441
}
442

    
443
protocol device {
444
}
445

    
446
protocol rip {
447
	ipv4 {
448
		import all;
449
		export all;
450
	};
451
	interface "*";
452
}
453
</code>
454

    
455

    
456
<sect>Global options
457
<label id="global-opts">
458

    
459
<p><descrip>
460
	<tag><label id="opt-include">include "<m/filename/";</tag>
461
	This statement causes inclusion of a new file. The <m/filename/ could
462
	also be a wildcard, in that case matching files are included in
463
	alphabetic order. The maximal depth is 8. Note that this statement can
464
	be used anywhere in the config file, even inside other options, but
465
	always on the beginning of line. In the following example, the first
466
	semicolon belongs to the <cf/include/, the second to <cf/ipv6 table/.
467
	If the <file/tablename.conf/ contains exactly one token (the name of the
468
	table), this construction is correct:
469
<code>
470
ipv6 table
471
include "tablename.conf";;
472
</code>
473

    
474
	<tag><label id="opt-log">log "<m/filename/" [<m/limit/ "<m/backup/"] | syslog [name <m/name/] | stderr all|{ <m/list of classes/ }</tag>
475
	Set logging of messages having the given class (either <cf/all/ or <cf>{
476
	error|trace [, <m/.../] }</cf> etc.) into selected destination - a file
477
	specified as a filename string (with optional log rotation information),
478
	syslog (with optional name argument), or the stderr output.
479

    
480
	Classes are:
481
	<cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
482
	<cf/debug/ for debugging messages,
483
	<cf/trace/ when you want to know what happens in the network,
484
	<cf/remote/ for messages about misbehavior of remote machines,
485
	<cf/auth/ about authentication failures,
486
	<cf/bug/ for internal BIRD bugs.
487

    
488
	Logging directly to file supports basic log rotation -- there is an
489
	optional log file limit and a backup filename, when log file reaches the
490
	limit, the current log file is renamed to the backup filename and a new
491
	log file is created.
492

    
493
	You may specify more than one <cf/log/ line to establish logging to
494
	multiple destinations. Default: log everything to the system log, or
495
	to the debug output if debugging is enabled by <cf/-d//<cf/-D/
496
	command-line option.
497

    
498
	<tag><label id="opt-debug-protocols">debug protocols all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
499
	Set global defaults of protocol debugging options. See <cf/debug/ in the
500
	following section. Default: off.
501

    
502
	<tag><label id="opt-debug-commands">debug commands <m/number/</tag>
503
	Control logging of client connections (0 for no logging, 1 for logging
504
	of connects and disconnects, 2 and higher for logging of all client
505
	commands). Default: 0.
506

    
507
	<tag><label id="opt-debug-latency">debug latency <m/switch/</tag>
508
	Activate tracking of elapsed time for internal events. Recent events
509
	could be examined using <cf/dump events/ command. Default: off.
510

    
511
	<tag><label id="opt-debug-latency-limit">debug latency limit <m/time/</tag>
512
	If <cf/debug latency/ is enabled, this option allows to specify a limit
513
	for elapsed time. Events exceeding the limit are logged. Default: 1 s.
514

    
515
	<tag><label id="opt-watchdog-warn">watchdog warning <m/time/</tag>
516
	Set time limit for I/O loop cycle. If one iteration took more time to
517
	complete, a warning is logged. Default: 5 s.
518

    
519
	<tag><label id="opt-watchdog-timeout">watchdog timeout <m/time/</tag>
520
	Set time limit for I/O loop cycle. If the limit is breached, BIRD is
521
	killed by abort signal. The timeout has effective granularity of
522
	seconds, zero means disabled. Default: disabled (0).
523

    
524
	<tag><label id="opt-mrtdump">mrtdump "<m/filename/"</tag>
525
	Set MRTdump file name. This option must be specified to allow MRTdump
526
	feature. Default: no dump file.
527

    
528
	<tag><label id="opt-mrtdump-protocols">mrtdump protocols all|off|{ states|messages [, <m/.../] }</tag>
529
	Set global defaults of MRTdump options. See <cf/mrtdump/ in the
530
	following section. Default: off.
531

    
532
	<tag><label id="opt-filter">filter <m/name local variables/{ <m/commands/ }</tag>
533
	Define a filter. You can learn more about filters in the following
534
	chapter.
535

    
536
	<tag><label id="opt-function">function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag>
537
	Define a function. You can learn more about functions in the following chapter.
538

    
539
	<tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
540
	Define a protocol instance called <cf><m/name/</cf> (or with a name like
541
	"rip5" generated automatically if you don't specify any
542
	<cf><m/name/</cf>). You can learn more about configuring protocols in
543
	their own chapters. When <cf>from <m/name2/</cf> expression is used,
544
	initial protocol options are taken from protocol or template
545
	<cf><m/name2/</cf> You can run more than one instance of most protocols
546
	(like RIP or BGP). By default, no instances are configured.
547

    
548
	<tag><label id="opt-template">template rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
549
	Define a protocol template instance called <m/name/ (or with a name like
550
	"bgp1" generated automatically if you don't specify any	<m/name/).
551
	Protocol templates can be used to group common options when many
552
	similarly configured protocol instances are to be defined. Protocol
553
	instances (and other templates) can use templates by using <cf/from/
554
	expression and the name of the template. At the moment templates (and
555
	<cf/from/ expression) are not implemented for OSPF protocol.
556

    
557
	<tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
558
	Define a constant. You can use it later in every place you could use a
559
	value of the same type. Besides, there are some predefined numeric
560
	constants based on /etc/iproute2/rt_* files. A list of defined constants
561
	can be seen (together with other symbols) using 'show symbols' command.
562

    
563
	<tag><label id="opt-attribute">attribute <m/type/ <m/name/</tag>
564
	Declare a custom route attribute. You can set and get it in filters like
565
	any other route atribute. This feature is intended for marking routes
566
	in import filters for export filtering purposes instead of locally
567
	assigned BGP communities which have to be deleted in export filters.
568

    
569
	<tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
570
	Set BIRD's router ID. It's a world-wide unique identification of your
571
	router, usually one of router's IPv4 addresses. Default: the lowest
572
	IPv4 address of a non-loopback interface.
573

    
574
	<tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
575
	Set BIRD's router ID based on an IPv4 address of an interface specified by
576
	an interface pattern.
577
	See <ref id="proto-iface" name="interface"> section for detailed
578
	description of interface patterns with extended clauses.
579

    
580
	<tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
581
	During graceful restart recovery, BIRD waits for convergence of routing
582
	protocols. This option allows to specify a timeout for the recovery to
583
	prevent waiting indefinitely if some protocols cannot converge. Default:
584
	240 seconds.
585

    
586
	<tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
587
	This option allows to specify a format of date/time used by BIRD. The
588
	first argument specifies for which purpose such format is used.
589
	<cf/route/ is a format used in 'show route' command output,
590
	<cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
591
	used for other commands and <cf/log/ is used in a log file.
592

    
593
	"<m/format1/" is a format string using <it/strftime(3)/ notation (see
594
	<it/man strftime/ for details). It is extended to support sub-second
595
	time part with variable precision (up to microseconds) using "%f"
596
	conversion code (e.g., "%T.%3f" is hh:mm:ss.sss time). <m/limit/ and
597
	"<m/format2/" allow to specify the second format string for times in
598
	past deeper than <m/limit/ seconds.
599

    
600
	There are several shorthands: <cf/iso long/ is a ISO 8601 date/time
601
	format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F
602
	%T"/. Similarly, <cf/iso long ms/ and <cf/iso long us/ are ISO 8601
603
	date/time formats with millisecond or microsecond precision.
604
	<cf/iso short/ is a variant of ISO 8601 that uses just the time format
605
	(hh:mm:ss) for near times (up to 20 hours in the past) and the date
606
	format (YYYY-MM-DD) for far times. This is a shorthand for <cf/"%T"
607
	72000 "%F"/. And there are also <cf/iso short ms/ and <cf/iso short us/
608
	high-precision variants of that.
609

    
610
	By default, BIRD uses the <cf/iso short ms/ format for <cf/route/ and
611
	<cf/protocol/ times, and the <cf/iso long ms/ format for <cf/base/ and
612
	<cf/log/ times.
613

    
614
	<tag><label id="opt-table"><m/nettype/ table <m/name/ [sorted]</tag>
615
	Create a new routing table. The default routing tables <cf/master4/ and
616
	<cf/master6/ are created implicitly, other routing tables have to be
617
	added by this command.  Option <cf/sorted/ can be used to enable sorting
618
	of routes, see <ref id="dsc-table-sorted" name="sorted table">
619
	description for details.
620

    
621
	<tag><label id="opt-eval">eval <m/expr/</tag>
622
	Evaluates given filter expression. It is used by the developers for testing of filters.
623
</descrip>
624

    
625

    
626
<sect>Protocol options
627
<label id="protocol-opts">
628

    
629
<p>For each protocol instance, you can configure a bunch of options. Some of
630
them (those described in this section) are generic, some are specific to the
631
protocol (see sections talking about the protocols).
632

    
633
<p>Several options use a <m/switch/ argument. It can be either <cf/on/,
634
<cf/yes/ or a numeric expression with a non-zero value for the option to be
635
enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
636
disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
637
agreement").
638

    
639
<descrip>
640
	<tag><label id="proto-disabled">disabled <m/switch/</tag>
641
	Disables the protocol. You can change the disable/enable status from the
642
	command line interface without needing to touch the configuration.
643
	Disabled protocols are not activated. Default: protocol is enabled.
644

    
645
	<tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
646
	Set protocol debugging options. If asked, each protocol is capable of
647
	writing trace messages about its work to the log (with category
648
	<cf/trace/). You can either request printing of <cf/all/ trace messages
649
	or only of the types selected: <cf/states/ for protocol state changes
650
	(protocol going up, down, starting, stopping etc.), <cf/routes/ for
651
	routes exchanged with the routing table, <cf/filters/ for details on
652
	route filtering, <cf/interfaces/ for interface change events sent to the
653
	protocol, <cf/events/ for events internal to the protocol and <cf/packets/
654
	for packets sent and received by the protocol. Default: off.
655

    
656
	<tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
657
	Set protocol MRTdump flags. MRTdump is a standard binary format for
658
	logging information from routing protocols and daemons. These flags
659
	control what kind of information is logged from the protocol to the
660
	MRTdump file (which must be specified by global <cf/mrtdump/ option, see
661
	the previous section). Although these flags are similar to flags of
662
	<cf/debug/ option, their meaning is different and protocol-specific. For
663
	BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
664
	received BGP messages. Other protocols does not support MRTdump yet.
665

    
666
	<tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
667
	This option can be used to override global router id for a given
668
	protocol. Default: uses global router id.
669

    
670
	<tag><label id="proto-description">description "<m/text/"</tag>
671
	This is an optional description of the protocol. It is displayed as a
672
	part of the output of 'show protocols all' command.
673

    
674
	<tag><label id="proto-vrf">vrf "<m/text/"</tag>
675
	Associate the protocol with specific VRF. The protocol will be
676
	restricted to interfaces assigned to the VRF and will use sockets bound
677
	to the VRF. Appropriate VRF interface must exist on OS level. For kernel
678
	protocol, an appropriate table still must be explicitly selected by
679
	<cf/table/ option. Note that for proper VRF support it is necessary to
680
	use Linux kernel version at least 4.14, older versions have limited VRF
681
	implementation.
682

    
683
	<tag><label id="proto-channel"><m/channel name/ [{<m/channel config/}]</tag>
684
	Every channel must be explicitly stated. See the protocol-specific
685
	configuration for the list of supported channel names. See the
686
	<ref id="channel-opts" name="channel configuration section"> for channel
687
	definition.
688
</descrip>
689

    
690
<p>There are several options that give sense only with certain protocols:
691

    
692
<descrip>
693
	<tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
694
	Specifies a set of interfaces on which the protocol is activated with
695
	given interface-specific options. A set of interfaces specified by one
696
	interface option is described using an interface pattern. The interface
697
	pattern consists of a sequence of clauses (separated by commas), each
698
	clause is a mask specified as a shell-like pattern. Interfaces are
699
	matched by their name.
700

    
701
	An interface matches the pattern if it matches any of its clauses. If
702
	the clause begins with <cf/-/, matching interfaces are excluded. Patterns
703
	are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
704
	means eth0 and all non-ethernets.
705

    
706
	Some protocols (namely OSPFv2 and Direct) support extended clauses that
707
	may contain a mask, a prefix, or both of them. An interface matches such
708
	clause if its name matches the mask (if specified) and its address
709
	matches the prefix (if specified). Extended clauses are used when the
710
	protocol handles multiple addresses on an interface independently.
711

    
712
	An interface option can be used more times with different interface-specific
713
	options, in that case for given interface the first matching interface
714
	option is used.
715

    
716
	This option is allowed in Babel, BFD, Device, Direct, OSPF, RAdv and RIP
717
	protocols. In OSPF protocol it is used in the <cf/area/ subsection.
718

    
719
	Default: none.
720

    
721
	Examples:
722

    
723
	<cf>interface "*" { type broadcast; };</cf> - start the protocol on all
724
	interfaces with <cf>type broadcast</cf> option.
725

    
726
	<cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
727
	protocol on enumerated interfaces with <cf>type ptp</cf> option.
728

    
729
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
730
	on all interfaces that have address from 192.168.0.0/16, but not from
731
	192.168.1.0/24.
732

    
733
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
734
	on all interfaces that have address from 192.168.0.0/16, but not from
735
	192.168.1.0/24.
736

    
737
	<cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
738
	ethernet interfaces that have address from 192.168.1.0/24.
739

    
740
	<tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
741
	This option specifies the value of ToS/DS/Class field in IP headers of
742
	the outgoing protocol packets. This may affect how the protocol packets
743
	are processed by the network relative to the other network traffic. With
744
	<cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
745
	octet (but two bits reserved for ECN are ignored). With	<cf/dscp/
746
	keyword, the value (0-63) is used just for the DS field in the octet.
747
	Default value is 0xc0 (DSCP 0x30 - CS6).
748

    
749
	<tag><label id="proto-tx-priority">tx priority <m/num/</tag>
750
	This option specifies the local packet priority. This may affect how the
751
	protocol packets are processed in the local TX queues. This option is
752
	Linux specific. Default value is 7 (highest priority, privileged traffic).
753

    
754
	<tag><label id="proto-pass">password "<m/password/" [ { <m>password options</m> } ]</tag>
755
	Specifies a password that can be used by the protocol as a shared secret
756
	key. Password option can be used more times to specify more passwords.
757
	If more passwords are specified, it is a protocol-dependent decision
758
	which one is really used. Specifying passwords does not mean that
759
	authentication is enabled, authentication can be enabled by separate,
760
	protocol-dependent <cf/authentication/ option.
761

    
762
	This option is allowed in BFD, OSPF and RIP protocols. BGP has also
763
	<cf/password/ option, but it is slightly different and described
764
	separately.
765
	Default: none.
766
</descrip>
767

    
768
<p>Password option can contain section with some (not necessary all) password sub-options:
769

    
770
<descrip>
771
	<tag><label id="proto-pass-id">id <M>num</M></tag>
772
	ID of the password, (1-255). If it is not used, BIRD will choose ID based
773
	on an order of the password item in the interface. For example, second
774
	password item in one interface will have default ID 2. ID is used by
775
	some routing protocols to identify which password was used to
776
	authenticate protocol packets.
777

    
778
	<tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
779
	The start time of the usage of the password for packet signing.
780
	The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
781

    
782
	<tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
783
	The last time of the usage of the password for packet signing.
784

    
785
	<tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
786
	The start time of the usage of the password for packet verification.
787

    
788
	<tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
789
	The last time of the usage of the password for packet verification.
790

    
791
	<tag><label id="proto-pass-from">from "<m/time/"</tag>
792
	Shorthand for setting both <cf/generate from/ and <cf/accept from/.
793

    
794
	<tag><label id="proto-pass-to">to "<m/time/"</tag>
795
	Shorthand for setting both <cf/generate to/ and <cf/accept to/.
796

    
797
	<tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 )</tag>
798
	The message authentication algorithm for the password when cryptographic
799
	authentication is enabled. The default value depends on the protocol.
800
	For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3
801
	protocol it is HMAC-SHA-256.
802

    
803
</descrip>
804

    
805

    
806
<sect>Channel options
807
<label id="channel-opts">
808

    
809
<p>Every channel belongs to a protocol and is configured inside its block. The
810
minimal channel config is empty, then it uses default values. The name of the
811
channel implies its nettype. Channel definitions can be inherited from protocol
812
templates. Multiple definitions of the same channel are forbidden, but channels
813
inherited from templates can be updated by new definitions.
814

    
815
<descrip>
816
	<tag><label id="proto-table">table <m/name/</tag>
817
	Specify a table to which the channel is connected. Default: the first
818
	table of given nettype.
819

    
820
	<tag><label id="proto-preference">preference <m/expr/</tag>
821
	Sets the preference of routes generated by the protocol and imported
822
	through this channel. Default: protocol dependent.
823

    
824
	<tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/boolean filter expression/</tag>
825
	Specify a filter to be used for filtering routes coming from the
826
	protocol to the routing table. <cf/all/ is for keeping all routes,
827
	<cf/none/ is for dropping all routes. Default: <cf/all/ (except for
828
	EBGP).
829

    
830
	<tag><label id="proto-export">export <m/filter/</tag>
831
	This is similar to the <cf>import</cf> keyword, except that it works in
832
	the direction from the routing table to the protocol. Default: <cf/none/
833
	(except for EBGP).
834

    
835
	<tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
836
	Usually, if an import filter rejects a route, the route is forgotten.
837
	When this option is active, these routes are kept in the routing table,
838
	but they are hidden and not propagated to other protocols. But it is
839
	possible to show them using <cf/show route filtered/. Note that this
840
	option does not work for the pipe protocol. Default: off.
841

    
842
	<tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
843
	Specify an import route limit (a maximum number of routes imported from
844
	the protocol) and optionally the action to be taken when the limit is
845
	hit. Warn action just prints warning log message. Block action discards
846
	new routes coming from the protocol. Restart and disable actions shut
847
	the protocol down like appropriate commands. Disable is the default
848
	action if an action is not explicitly specified. Note that limits are
849
	reset during protocol reconfigure, reload or restart. Default: <cf/off/.
850

    
851
	<tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
852
	Specify an receive route limit (a maximum number of routes received from
853
	the protocol and remembered). It works almost identically to <cf>import
854
	limit</cf> option, the only difference is that if <cf/import keep
855
	filtered/ option is active, filtered routes are counted towards the
856
	limit and blocked routes are forgotten, as the main purpose of the
857
	receive limit is to protect routing tables from overflow. Import limit,
858
	on the contrary, counts accepted routes only and routes blocked by the
859
	limit are handled like filtered routes. Default: <cf/off/.
860

    
861
	<tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
862
	Specify an export route limit, works similarly to the <cf>import
863
	limit</cf> option, but for the routes exported to the protocol. This
864
	option is experimental, there are some problems in details of its
865
	behavior -- the number of exported routes can temporarily exceed the
866
	limit without triggering it during protocol reload, exported routes
867
	counter ignores route blocking and block action also blocks route
868
	updates of already accepted routes -- and these details will probably
869
	change in the future. Default: <cf/off/.
870
</descrip>
871

    
872
<p>This is a trivial example of RIP configured for IPv6 on all interfaces:
873
<code>
874
protocol rip ng {
875
	ipv6;
876
	interface "*";
877
}
878
</code>
879

    
880
<p>This is a non-trivial example.
881
<code>
882
protocol rip ng {
883
	ipv6 {
884
		table mytable6;
885
		import filter { ... };
886
		export filter { ... };
887
		import limit 50;
888
	};
889
	interface "*";
890
}
891
</code>
892

    
893
<p>And this is even more complicated example using templates.
894
<code>
895
template bgp {
896
	local 198.51.100.14 as 65000;
897

    
898
	ipv4 {
899
		table mytable4;
900
		import filter { ... };
901
		export none;
902
	};
903
	ipv6 {
904
		table mytable6;
905
		import filter { ... };
906
		export none;
907
	};
908
}
909

    
910
protocol bgp from  {
911
	neighbor 198.51.100.130 as 64496;
912

    
913
	# IPv4 channel is inherited as-is, while IPv6
914
	# channel is adjusted by export filter option
915
	ipv6 {
916
		export filter { ... };
917
	};
918
}
919
</code>
920

    
921

    
922
<chapt>Remote control
923
<label id="remote-control">
924

    
925
<p>You can use the command-line client <file>birdc</file> to talk with a running
926
BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
927
changed with the <tt/-s/ option given to both the server and the client). The
928
commands can perform simple actions such as enabling/disabling of protocols,
929
telling BIRD to show various information, telling it to show routing table
930
filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
931
get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
932
client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
933
be passed to the client, to make it dump numeric return codes along with the
934
messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
935
own applications could do that, too -- the format of communication between BIRD
936
and <file/birdc/ is stable (see the programmer's documentation).
937

    
938
<p>There is also lightweight variant of BIRD client called <file/birdcl/, which
939
does not support command line editing and history and has minimal dependencies.
940
This is useful for running BIRD in resource constrained environments, where
941
Readline library (required for regular BIRD client) is not available.
942

    
943
<p>Many commands have the <m/name/ of the protocol instance as an argument.
944
This argument can be omitted if there exists only a single instance.
945

    
946
<p>Here is a brief list of supported functions:
947

    
948
<descrip>
949
	<tag><label id="cli-show-status">show status</tag>
950
	Show router status, that is BIRD version, uptime and time from last
951
	reconfiguration.
952

    
953
	<tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
954
	Show the list of interfaces. For each interface, print its type, state,
955
	MTU and addresses assigned.
956

    
957
	<tag><label id="cli-show-protocols">show protocols [all]</tag>
958
	Show list of protocol instances along with tables they are connected to
959
	and protocol status, possibly giving verbose information, if <cf/all/ is
960
	specified.
961

    
962
	<!-- TODO: Move these protocol-specific remote control commands to the protocol sections -->
963
	<tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
964
	Show detailed information about OSPF interfaces.
965

    
966
	<tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
967
	Show a list of OSPF neighbors and a state of adjacency to them.
968

    
969
	<tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
970
	Show detailed information about OSPF areas based on a content of the
971
	link-state database. It shows network topology, stub networks,
972
	aggregated networks and routers from other areas and external routes.
973
	The command shows information about reachable network nodes, use option
974
	<cf/all/ to show information about all network nodes in the link-state
975
	database.
976

    
977
	<tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
978
	Show a topology of OSPF areas based on a content of the link-state
979
	database. It is just a stripped-down version of 'show ospf state'.
980

    
981
	<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>
982
	Show contents of an OSPF LSA database. Options could be used to filter
983
	entries.
984

    
985
	<tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
986
	Show detailed information about RIP interfaces.
987

    
988
	<tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
989
	Show a list of RIP neighbors and associated state.
990

    
991
	<tag><label id="cli-show-static">show static [<m/name/]</tag>
992
	Show detailed information about static routes.
993

    
994
	<tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/]</tag>
995
	Show information about BFD sessions.
996

    
997
	<tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
998
	Show the list of symbols defined in the configuration (names of
999
	protocols, routing tables etc.).
1000

    
1001
	<tag><label id="cli-show-route">show route [[for] <m/prefix/|<m/IP/] [table (<m/t/ | all)] [filter <m/f/|where <m/c/] [(export|preexport|noexport) <m/p/] [protocol <m/p/] [(stats|count)] [<m/options/]</tag>
1002
	Show contents of specified routing tables, that is routes, their metrics
1003
	and (in case the <cf/all/ switch is given) all their attributes.
1004

    
1005
	<p>You can specify a <m/prefix/ if you want to print routes for a
1006
	specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
1007
	the entry which will be used for forwarding of packets to the given
1008
	destination. By default, all routes for each network are printed with
1009
	the selected one at the top, unless <cf/primary/ is given in which case
1010
	only the selected route is shown.
1011

    
1012
	<p>The <cf/show route/ command can process one or multiple routing
1013
	tables. The set of selected tables is determined on three levels: First,
1014
	tables can be explicitly selected by <cf/table/ switch, which could be
1015
	used multiple times, all tables are specified by <cf/table all/. Second,
1016
	tables can be implicitly selected by channels or protocols that are
1017
	arguments of several other switches (e.g., <cf/export/, <cf/protocol/).
1018
	Last, the set of default tables is used: <cf/master4/, <cf/master6/ and
1019
	each first table of any other network type.
1020

    
1021
	<p>You can also ask for printing only routes processed and accepted by
1022
	a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
1023
	</cf> or matching a given condition (<cf>where <m/condition/</cf>).
1024

    
1025
	The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
1026
	printing of routes that are exported to the specified protocol or
1027
	channel. With <cf/preexport/, the export filter of the channel is
1028
	skipped. With <cf/noexport/, routes rejected by the export filter are
1029
	printed instead. Note that routes not exported for other reasons
1030
	(e.g. secondary routes or routes imported from that protocol) are not
1031
	printed even with <cf/noexport/. These switches also imply that
1032
	associated routing tables are selected instead of default ones.
1033

    
1034
	<p>You can also select just routes added by a specific protocol.
1035
	<cf>protocol <m/p/</cf>. This switch also implies that associated
1036
	routing tables are selected instead of default ones.
1037

    
1038
	<p>If BIRD is configured to keep filtered routes (see <cf/import keep
1039
	filtered/ option), you can show them instead of routes by using
1040
	<cf/filtered/ switch.
1041

    
1042
	<p>The <cf/stats/ switch requests showing of route statistics (the
1043
	number of networks, number of routes before and after filtering). If
1044
	you use <cf/count/ instead, only the statistics will be printed.
1045

    
1046
	<tag><label id="cli-mrt-dump">mrt dump table <m/name/|"<m/pattern/" to "<m/filename/" [filter <m/f/|where <m/c/]</tag>
1047
	Dump content of a routing table to a specified file in MRT table dump
1048
	format. See <ref id="mrt" name="MRT protocol"> for details.
1049

    
1050
	<tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
1051
	Reload configuration from a given file. BIRD will smoothly switch itself
1052
	to the new configuration, protocols are reconfigured if possible,
1053
	restarted otherwise. Changes in filters usually lead to restart of
1054
	affected protocols.
1055

    
1056
	If <cf/soft/ option is used, changes in filters does not cause BIRD to
1057
	restart affected protocols, therefore already accepted routes (according
1058
	to old filters) would be still propagated, but new routes would be
1059
	processed according to the new filters.
1060

    
1061
	If <cf/timeout/ option is used, config timer is activated. The new
1062
	configuration could be either confirmed using <cf/configure confirm/
1063
	command, or it will be reverted to the old one when the config timer
1064
	expires. This is useful for cases when reconfiguration breaks current
1065
	routing and a router becomes inaccessible for an administrator. The
1066
	config timeout expiration is equivalent to <cf/configure undo/
1067
	command. The timeout duration could be specified, default is 300 s.
1068

    
1069
	<tag><label id="cli-configure-confirm">configure confirm</tag>
1070
	Deactivate the config undo timer and therefore confirm the current
1071
	configuration.
1072

    
1073
	<tag><label id="cli-configure-undo">configure undo</tag>
1074
	Undo the last configuration change and smoothly switch back to the
1075
	previous (stored) configuration. If the last configuration change was
1076
	soft, the undo change is also soft. There is only one level of undo, but
1077
	in some specific cases when several reconfiguration requests are given
1078
	immediately in a row and the intermediate ones are skipped then the undo
1079
	also skips them back.
1080

    
1081
	<tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
1082
	Read and parse given config file, but do not use it. useful for checking
1083
	syntactic and some semantic validity of an config file.
1084

    
1085
	<tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
1086
	Enable, disable or restart a given protocol instance, instances matching
1087
	the <cf><m/pattern/</cf> or <cf/all/ instances.
1088

    
1089
	<tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
1090
	Reload a given protocol instance, that means re-import routes from the
1091
	protocol instance and re-export preferred routes to the instance. If
1092
	<cf/in/ or <cf/out/ options are used, the command is restricted to one
1093
	direction (re-import or re-export).
1094

    
1095
	This command is useful if appropriate filters have changed but the
1096
	protocol instance was not restarted (or reloaded), therefore it still
1097
	propagates the old set of routes. For example when <cf/configure soft/
1098
	command was used to change filters.
1099

    
1100
	Re-export always succeeds, but re-import is protocol-dependent and might
1101
	fail (for example, if BGP neighbor does not support route-refresh
1102
	extension). In that case, re-export is also skipped. Note that for the
1103
	pipe protocol, both directions are always reloaded together (<cf/in/ or
1104
	<cf/out/ options are ignored in that case).
1105

    
1106
	<tag><label id="cli-down">down</tag>
1107
	Shut BIRD down.
1108

    
1109
	<tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
1110
	Control protocol debugging.
1111

    
1112
	<tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
1113
	Dump contents of internal data structures to the debugging output.
1114

    
1115
	<tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
1116
	Control echoing of log messages to the command-line output.
1117
	See <ref id="opt-log" name="log option"> for a list of log classes.
1118

    
1119
	<tag><label id="cli-eval">eval <m/expr/</tag>
1120
	Evaluate given expression.
1121
</descrip>
1122

    
1123

    
1124
<chapt>Filters
1125
<label id="filters">
1126

    
1127
<sect>Introduction
1128
<label id="filters-intro">
1129

    
1130
<p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
1131
There are two objects in this language: filters and functions. Filters are
1132
interpreted by BIRD core when a route is being passed between protocols and
1133
routing tables. The filter language contains control structures such as if's and
1134
switches, but it allows no loops. An example of a filter using many features can
1135
be found in <file>filter/test.conf</file>.
1136

    
1137
<p>Filter gets the route, looks at its attributes and modifies some of them if
1138
it wishes. At the end, it decides whether to pass the changed route through
1139
(using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
1140
this:
1141

    
1142
<code>
1143
filter not_too_far
1144
int var;
1145
{
1146
	if defined( rip_metric ) then
1147
		var = rip_metric;
1148
	else {
1149
		var = 1;
1150
		rip_metric = 1;
1151
	}
1152
	if rip_metric &gt; 10 then
1153
		reject "RIP metric is too big";
1154
	else
1155
		accept "ok";
1156
}
1157
</code>
1158

    
1159
<p>As you can see, a filter has a header, a list of local variables, and a body.
1160
The header consists of the <cf/filter/ keyword followed by a (unique) name of
1161
filter. The list of local variables consists of <cf><M>type name</M>;</cf>
1162
pairs where each pair declares one local variable. The body consists of <cf>
1163
{ <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
1164
can group several statements to a single compound statement by using braces
1165
(<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
1166
block of code conditional.
1167

    
1168
<p>BIRD supports functions, so that you don't have to repeat the same blocks of
1169
code over and over. Functions can have zero or more parameters and they can have
1170
local variables. Recursion is not allowed. Function definitions look like this:
1171

    
1172
<code>
1173
function name ()
1174
int local_variable;
1175
{
1176
	local_variable = 5;
1177
}
1178

    
1179
function with_parameters (int parameter)
1180
{
1181
	print parameter;
1182
}
1183
</code>
1184

    
1185
<p>Unlike in C, variables are declared after the <cf/function/ line, but before
1186
the first <cf/{/. You can't declare variables in nested blocks. Functions are
1187
called like in C: <cf>name(); with_parameters(5);</cf>. Function may return
1188
values using the <cf>return <m/[expr]/</cf> command. Returning a value exits
1189
from current function (this is similar to C).
1190

    
1191
<p>Filters are defined in a way similar to functions except they can't have
1192
explicit parameters. They get a route table entry as an implicit parameter, it
1193
is also passed automatically to any functions called. The filter must terminate
1194
with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in
1195
filter, the route is rejected.
1196

    
1197
<p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1198
from the command line client. An example session might look like:
1199

    
1200
<code>
1201
pavel@bug:~/bird$ ./birdc -s bird.ctl
1202
BIRD 0.0.0 ready.
1203
bird> show route
1204
10.0.0.0/8         dev eth0 [direct1 23:21] (240)
1205
195.113.30.2/32    dev tunl1 [direct1 23:21] (240)
1206
127.0.0.0/8        dev lo [direct1 23:21] (240)
1207
bird> show route ?
1208
show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1209
bird> show route filter { if 127.0.0.5 &tilde; net then accept; }
1210
127.0.0.0/8        dev lo [direct1 23:21] (240)
1211
bird>
1212
</code>
1213

    
1214

    
1215
<sect>Data types
1216
<label id="data-types">
1217

    
1218
<p>Each variable and each value has certain type. Booleans, integers and enums
1219
are incompatible with each other (that is to prevent you from shooting in the
1220
foot).
1221

    
1222
<descrip>
1223
	<tag><label id="type-bool">bool</tag>
1224
	This is a boolean type, it can have only two values, <cf/true/ and
1225
	<cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1226

    
1227
	<tag><label id="type-int">int</tag>
1228
	This is a general integer type. It is an unsigned 32bit type; i.e., you
1229
	can expect it to store values from 0 to 4294967295. Overflows are not
1230
	checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1231

    
1232
	<tag><label id="type-pair">pair</tag>
1233
	This is a pair of two short integers. Each component can have values
1234
	from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1235
	The same syntax can also be used to construct a pair from two arbitrary
1236
	integer expressions (for example <cf/(1+2,a)/).
1237

    
1238
	<tag><label id="type-quad">quad</tag>
1239
	This is a dotted quad of numbers used to represent router IDs (and
1240
	others). Each component can have a value from 0 to 255. Literals of
1241
	this type are written like IPv4 addresses.
1242

    
1243
	<tag><label id="type-string">string</tag>
1244
	This is a string of characters. There are no ways to modify strings in
1245
	filters. You can pass them between functions, assign them to variables
1246
	of type <cf/string/, print such variables, use standard string
1247
	comparison operations (e.g. <cf/=, !=, &lt;, &gt;, &lt;=, &gt;=/), but
1248
	you can't concatenate two strings. String literals are written as
1249
	<cf/"This is a string constant"/. Additionally matching (<cf/&tilde;,
1250
	!&tilde;/) operators could be used to match a string value against
1251
	a shell pattern (represented also as a string).
1252

    
1253
	<tag><label id="type-ip">ip</tag>
1254
	This type can hold a single IP address. The IPv4 addresses are stored as
1255
	IPv4-Mapped IPv6 addresses so one data type for both of them is used.
1256
	Whether the address is IPv4 or not may be checked by <cf>.is_ip4</cf>
1257
	which returns <cf/bool/. IP addresses are written in the standard
1258
	notation (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special
1259
	operator <cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out
1260
	all but first <cf><M>num</M></cf> bits from the IP address. So
1261
	<cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1262

    
1263
	<tag><label id="type-prefix">prefix</tag>
1264
	This type can hold a network prefix consisting of IP address, prefix
1265
	length and several other values. This is the key in route tables.
1266

    
1267
	Prefixes may be of several types, which can be determined by the special
1268
	operator <cf/.type/. The type may be:
1269

    
1270
	<cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
1271
	are written as <cf><m/ipaddress//<m/pxlen/</cf>. There are two special
1272
	operators on these: <cf/.ip/ which extracts the IP address from the
1273
	pair, and <cf/.len/, which separates prefix length from the pair.
1274
	So <cf>1.2.0.0/16.len = 16</cf> is true.
1275

    
1276
	<cf/NET_IP6_SADR/ nettype holds both destination and source IPv6
1277
	prefix. The literals are written as <cf><m/ipaddress//<m/pxlen/ from
1278
	<m/ipaddress//<m/pxlen/</cf>, where the first part is the destination
1279
	prefix and the second art is the source prefix. They support the same
1280
	operators as IP prefixes, but just for the destination part.
1281

    
1282
	<cf/NET_VPN4/ and <cf/NET_VPN6/ prefixes hold an IP prefix with VPN
1283
	Route Distinguisher (<rfc id="4364">). They support the same special
1284
	operators as IP prefixes, and also <cf/.rd/ which extracts the Route
1285
	Distinguisher. Their literals are written
1286
	as <cf><m/vpnrd/ <m/ipprefix/</cf>
1287

    
1288
	<cf/NET_ROA4/ and <cf/NET_ROA6/ prefixes hold an IP prefix range
1289
	together with an ASN. They support the same special operators as IP
1290
	prefixes, and also <cf/.maxlen/ which extracts maximal prefix length,
1291
	and <cf/.asn/ which extracts the ASN.
1292

    
1293
	<cf/NET_FLOW4/ and <cf/NET_FLOW6/ hold an IP prefix together with a
1294
	flowspec rule. Filters currently don't support flowspec parsing.
1295

    
1296
	<cf/NET_MPLS/ holds a single MPLS label and its handling is currently
1297
	not implemented.
1298

    
1299
	<tag><label id="type-vpnrd">vpnrd</tag>
1300
	This is a route distinguisher according to <rfc id="4364">. There are
1301
	three kinds of RD's: <cf><m/asn/:<m/32bit int/</cf>, <cf><m/asn4/:<m/16bit int/</cf>
1302
	and <cf><m/IPv4 address/:<m/32bit int/</cf>
1303

    
1304
	<tag><label id="type-ec">ec</tag>
1305
	This is a specialized type used to represent BGP extended community
1306
	values. It is essentially a 64bit value, literals of this type are
1307
	usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1308
	<cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1309
	route target / route origin communities), the format and possible values
1310
	of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1311
	used kind. Similarly to pairs, ECs can be constructed using expressions
1312
	for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1313
	<cf/myas/ is an integer variable).
1314

    
1315
	<tag><label id="type-lc">lc</tag>
1316
	This is a specialized type used to represent BGP large community
1317
	values. It is essentially a triplet of 32bit values, where the first
1318
	value is reserved for the AS number of the issuer, while meaning of
1319
	remaining parts is defined by the issuer. Literals of this type are
1320
	written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1321
	pairs, LCs can be constructed using expressions for its parts, (e.g.
1322
	<cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1323

    
1324
	<tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1325
	Filters recognize four types of sets. Sets are similar to strings: you
1326
	can pass them around but you can't modify them. Literals of type <cf>int
1327
	set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1328
	values and ranges are permitted in sets.
1329

    
1330
	For pair sets, expressions like <cf/(123,*)/ can be used to denote
1331
	ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1332
	<cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1333
	<cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1334
	such expressions are translated to a set of intervals, which may be
1335
	memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1336
	(1,4..20), (2,4..20), ... (65535, 4..20)/.
1337

    
1338
	EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1339
	10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1340
	(like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1341
	for ASNs).
1342

    
1343
	Also LC sets use similar expressions like pair sets. You can use ranges
1344
	and wildcards, but if one field uses that, more specific (later) fields
1345
	must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1346
	is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1347
	valid.
1348

    
1349
	You can also use expressions for int, pair, EC and LC set values.
1350
	However, it must be possible to evaluate these expressions before daemon
1351
	boots. So you can use only constants inside them. E.g.
1352

    
1353
	<code>
1354
	 define one=1;
1355
	 define myas=64500;
1356
	 int set odds;
1357
	 pair set ps;
1358
	 ec set es;
1359

    
1360
	 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1361
	 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1362
	 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1363
	</code>
1364

    
1365
	Sets of prefixes are special: their literals does not allow ranges, but
1366
	allows prefix patterns that are written
1367
	as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1368
	Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1369
	pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1370
	first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1371
	identical and <cf>len1 &lt;= ip1 &lt;= len2</cf>. A valid prefix pattern
1372
	has to satisfy <cf>low &lt;= high</cf>, but <cf/pxlen/ is not
1373
	constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1374
	prefix set literal if it matches any prefix pattern in the prefix set
1375
	literal.
1376

    
1377
	There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1378
	is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1379
	(where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1380
	network prefix <cf><m/address//<m/len/</cf> and all its	subnets.
1381
	<cf><m/address//<m/len/-</cf> is a shorthand for
1382
	<cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1383
	<cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1384
	that contain it).
1385

    
1386
	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}
1387
	]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1388
	<cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1389
	<cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1390
	matches all prefixes (regardless of IP address) whose prefix length is
1391
	20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1392
	address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 &tilde; [ 1.0.0.0/8{15,17} ]</cf>
1393
	is true, but <cf>1.0.0.0/16 &tilde; [ 1.0.0.0/8- ]</cf> is false.
1394

    
1395
	Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1396
	in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1397
	<cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1398
	<cf>192.168.0.0/16{24,32}</cf>.
1399

    
1400
	It is possible to mix IPv4 and IPv6 prefixes/addresses in a prefix/ip set
1401
	but its behavior may change between versions without any warning; don't do
1402
	it unless you are more than sure what you are doing. (Really, don't do it.)
1403

    
1404
	<tag><label id="type-enum">enum</tag>
1405
	Enumeration types are fixed sets of possibilities. You can't define your
1406
	own variables of such type, but some route attributes are of enumeration
1407
	type. Enumeration types are incompatible with each other.
1408

    
1409
	<tag><label id="type-bgppath">bgppath</tag>
1410
	BGP path is a list of autonomous system numbers. You can't write
1411
	literals of this type. There are several special operators on bgppaths:
1412

    
1413
	<cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1414

    
1415
	<cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1416

    
1417
	<cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1418

    
1419
	Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1420
	ASN, for example if the path contains an AS set element as the first (or
1421
	the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1422
	may be used to get last ASN before any AS set.
1423

    
1424
	<cf><m/P/.len</cf> returns the length of path <m/P/.
1425

    
1426
	<cf><m/P/.empty</cf> makes the path <m/P/ empty.
1427

    
1428
	<cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1429
	returns the result.
1430

    
1431
	<cf>delete(<m/P/,<m/A/)</cf> deletes all instances of ASN <m/A/ from
1432
	from path <m/P/ and returns the result. <m/A/ may also be an integer
1433
	set, in that case the operator deletes all ASNs from path <m/P/ that are
1434
	also members of set <m/A/.
1435

    
1436
	<cf>filter(<m/P/,<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1437
	not members of integer set <m/A/. I.e., <cf/filter/ do the same as
1438
	<cf/delete/ with inverted set <m/A/.
1439

    
1440
	Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1441
	<cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1442
	(for example <cf/bgp_path/). Similarly for <cf/delete/ and <cf/filter/.
1443

    
1444
	<tag><label id="type-bgpmask">bgpmask</tag>
1445
	BGP masks are patterns used for BGP path matching (using <cf>path
1446
	&tilde; [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1447
	as used by UNIX shells. Autonomous system numbers match themselves,
1448
	<cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1449
	<cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1450
 	is 4 3 2 1, then: <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true,
1451
	but <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false. BGP mask
1452
	expressions can also contain integer expressions enclosed in parenthesis
1453
	and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>. You can
1454
        also use ranges, for example <tt>[= * 3..5 2 100..200 * =]</tt>.
1455

    
1456
	<tag><label id="type-clist">clist</tag>
1457
	Clist is similar to a set, except that unlike other sets, it can be
1458
	modified. The type is used for community list (a set of pairs) and for
1459
	cluster list (a set of quads). There exist no literals of this type.
1460
	There are three special operators on clists:
1461

    
1462
	<cf><m/C/.len</cf> returns the length of clist <m/C/.
1463

    
1464
	<cf><m/C/.empty</cf> makes the list <m/C/ empty.
1465

    
1466
	<cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1467
	returns the result. If item <m/P/ is already in clist <m/C/, it does
1468
	nothing. <m/P/ may also be a clist, in that case all its members are
1469
	added; i.e., it works as clist union.
1470

    
1471
	<cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1472
	<m/C/ and returns the result. If clist <m/C/ does not contain item
1473
	<m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1474
	case the operator deletes all items from clist <m/C/ that are also
1475
	members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1476
	analogously; i.e., it works as clist difference.
1477

    
1478
	<cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist <m/C/ that are
1479
	not members of pair (or quad) set <m/P/. I.e., <cf/filter/ do the same
1480
	as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1481
	works analogously; i.e., it works as clist intersection.
1482

    
1483
	Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1484
	<cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for
1485
	example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.
1486

    
1487
	<tag><label id="type-eclist">eclist</tag>
1488
	Eclist is a data type used for BGP extended community lists. Eclists
1489
	are very similar to clists, but they are sets of ECs instead of pairs.
1490
	The same operations (like <cf/add/, <cf/delete/ or <cf/&tilde;/ and
1491
	<cf/!&tilde;/ membership operators) can be used to modify or test
1492
	eclists, with ECs instead of pairs as arguments.
1493

    
1494
	<tag><label id="type-lclist">lclist/</tag>
1495
	Lclist is a data type used for BGP large community lists. Like eclists,
1496
	lclists are very similar to clists, but they are sets of LCs instead of
1497
	pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/&tilde;/
1498
	and <cf/!&tilde;/ membership operators) can be used to modify or test
1499
	lclists, with LCs instead of pairs as arguments.
1500
</descrip>
1501

    
1502

    
1503
<sect>Operators
1504
<label id="operators">
1505

    
1506
<p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1507
parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a&lt;b, a&gt;=b)/.
1508
Logical operations include unary not (<cf/!/), and (<cf/&amp;&amp;/), and or
1509
(<cf/&verbar;&verbar;/). Special operators include (<cf/&tilde;/,
1510
<cf/!&tilde;/) for "is (not) element of a set" operation - it can be used on
1511
element and set of elements of the same type (returning true if element is
1512
contained in the given set), or on two strings (returning true if first string
1513
matches a shell-like pattern stored in second string) or on IP and prefix
1514
(returning true if IP is within the range defined by that prefix), or on prefix
1515
and prefix (returning true if first prefix is more specific than second one) or
1516
on bgppath and bgpmask (returning true if the path matches the mask) or on
1517
number and bgppath (returning true if the number is in the path) or on bgppath
1518
and int (number) set (returning true if any ASN from the path is in the set) or
1519
on pair/quad and clist (returning true if the pair/quad is element of the
1520
clist) or on clist and pair/quad set (returning true if there is an element of
1521
the clist that is also a member of the pair/quad set).
1522

    
1523
<p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1524
examines a ROA table and does <rfc id="6483"> route origin validation for a
1525
given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1526
checks current route (which should be from BGP to have AS_PATH argument) in the
1527
specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1528
ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1529
ROAs but none of them match. There is also an extended variant
1530
<cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1531
prefix and an ASN as arguments.
1532

    
1533

    
1534
<sect>Control structures
1535
<label id="control-structures">
1536

    
1537
<p>Filters support two control structures: conditions and case switches.
1538

    
1539
<p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/commandT/;
1540
else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/;
1541
<M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1542
omitted. If the <cf><m>boolean expression</m></cf> is true, <m/commandT/ is
1543
executed, otherwise <m/commandF/ is executed.
1544

    
1545
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1546
<m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1547
... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1548
on the left side of the &tilde; operator and anything that could be a member of
1549
a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1550
grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1551
between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1552
neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1553

    
1554
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
1555

    
1556
<code>
1557
case arg1 {
1558
	2: print "two"; print "I can do more commands without {}";
1559
	3 .. 5: print "three to five";
1560
	else: print "something else";
1561
}
1562

    
1563
if 1234 = i then printn "."; else {
1564
  print "not 1234";
1565
  print "You need {} around multiple commands";
1566
}
1567
</code>
1568

    
1569

    
1570
<sect>Route attributes
1571
<label id="route-attributes">
1572

    
1573
<p>A filter is implicitly passed a route, and it can access its attributes just
1574
like it accesses variables. There are common route attributes, protocol-specific
1575
route attributes and custom route attributes. Most common attributes are
1576
mandatory (always defined), while remaining are optional.  Attempts to access
1577
undefined attribute result in a runtime error; you can check if an attribute is
1578
defined by using the <cf>defined( <m>attribute</m> )</cf> operator. One notable
1579
exception to this rule are attributes of bgppath and *clist types, where
1580
undefined value is regarded as empty bgppath/*clist for most purposes.
1581

    
1582
Attributes can be defined by just setting them in filters. Custom attributes
1583
have to be first declared by <ref id="opt-attribute" name="attribute"> global
1584
option. You can also undefine optional attribute back to non-existence by using
1585
the <cf>unset( <m/attribute/ )</cf> operator.
1586

    
1587
Common route attributes are:
1588

    
1589
<descrip>
1590
	<tag><label id="rta-net"><m/prefix/ net</tag>
1591
	The network prefix or anything else the route is talking about. The
1592
	primary key of the routing table. Read-only. (See the <ref id="routes"
1593
	name="chapter about routes">.)
1594

    
1595
	<tag><label id="rta-scope"><m/enum/ scope</tag>
1596
	The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1597
	local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1598
	link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1599
	<cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1600
	interpreted by BIRD and can be used to mark routes in filters. The
1601
	default value for new routes is <cf/SCOPE_UNIVERSE/.
1602

    
1603
	<tag><label id="rta-preference"><m/int/ preference</tag>
1604
	Preference of the route. Valid values are 0-65535. (See the chapter
1605
	about routing tables.)
1606

    
1607
	<tag><label id="rta-from"><m/ip/ from</tag>
1608
	The router which the route has originated from.
1609

    
1610
	<tag><label id="rta-gw"><m/ip/ gw</tag>
1611
	Next hop packets routed using this route should be forwarded to.
1612

    
1613
	<tag><label id="rta-proto"><m/string/ proto</tag>
1614
	The name of the protocol which the route has been imported from.
1615
	Read-only.
1616

    
1617
	<tag><label id="rta-source"><m/enum/ source</tag>
1618
	what protocol has told me about this route. Possible values:
1619
	<cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
1620
	<cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/,
1621
	<cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/,
1622
	<cf/RTS_PIPE/, <cf/RTS_BABEL/.
1623

    
1624
	<tag><label id="rta-dest"><m/enum/ dest</tag>
1625
	Type of destination the packets should be sent to
1626
	(<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1627
	<cf/RTD_DEVICE/ for routing to a directly-connected network,
1628
	<cf/RTD_MULTIPATH/ for multipath destinations,
1629
	<cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1630
	<cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
1631
	returned with ICMP host unreachable / ICMP administratively prohibited
1632
	messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
1633
	<cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
1634

    
1635
	<tag><label id="rta-ifname"><m/string/ ifname</tag>
1636
	Name of the outgoing interface. Sink routes (like blackhole, unreachable
1637
	or prohibit) and multipath routes have no interface associated with
1638
	them, so <cf/ifname/ returns an empty string for such routes. Setting it
1639
	would also change route to a direct one (remove gateway).
1640

    
1641
	<tag><label id="rta-ifindex"><m/int/ ifindex</tag>
1642
	Index of the outgoing interface. System wide index of the interface. May
1643
	be used for interface matching, however indexes might change on interface
1644
	creation/removal. Zero is returned for routes with undefined outgoing
1645
	interfaces. Read-only.
1646

    
1647
	<tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
1648
	The optional attribute that can be used to specify a distance to the
1649
	network for routes that do not have a native protocol metric attribute
1650
	(like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
1651
	compare internal distances to boundary routers (see below).
1652
</descrip>
1653

    
1654
<p>Protocol-specific route attributes are described in the corresponding
1655
protocol sections.
1656

    
1657

    
1658
<sect>Other statements
1659
<label id="other-statements">
1660

    
1661
<p>The following statements are available:
1662

    
1663
<descrip>
1664
	<tag><label id="assignment"><m/variable/ = <m/expr/</tag>
1665
	Set variable (or route attribute) to a given value.
1666

    
1667
	<tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
1668
	Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1669

    
1670
	<tag><label id="return">return <m/expr/</tag>
1671
	Return <cf><m>expr</m></cf> from the current function, the function ends
1672
	at this point.
1673

    
1674
	<tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
1675
	Prints given expressions; useful mainly while debugging filters. The
1676
	<cf/printn/ variant does not terminate the line.
1677

    
1678
	<tag><label id="quitbird">quitbird</tag>
1679
	Terminates BIRD. Useful when debugging the filter interpreter.
1680
</descrip>
1681

    
1682

    
1683
<chapt>Protocols
1684
<label id="protocols">
1685

    
1686
<sect>Babel
1687
<label id="babel">
1688

    
1689
<sect1>Introduction
1690
<label id="babel-intro">
1691

    
1692
<p>The Babel protocol
1693
(<rfc id="6126">) is a loop-avoiding distance-vector routing protocol that is
1694
robust and efficient both in ordinary wired networks and in wireless mesh
1695
networks. Babel is conceptually very simple in its operation and "just works"
1696
in its default configuration, though some configuration is possible and in some
1697
cases desirable.
1698

    
1699
<p>The Babel protocol is dual stack; i.e., it can carry both IPv4 and IPv6
1700
routes over the same IPv6 transport. For sending and receiving Babel packets,
1701
only a link-local IPv6 address is needed.
1702

    
1703
<p>BIRD implements an extension for IPv6 source-specific routing (SSR or SADR),
1704
but must be configured accordingly to use it. SADR-enabled Babel router can
1705
interoperate with non-SADR Babel router, but the later would ignore routes
1706
with specific (non-zero) source prefix.
1707

    
1708
<sect1>Configuration
1709
<label id="babel-config">
1710

    
1711
<p>The Babel protocol support both IPv4 and IPv6 channels; both can be
1712
configured simultaneously. It can also be configured with <ref
1713
id="ip-sadr-routes" name="IPv6 SADR"> channel instead of regular IPv6
1714
channel, in such case SADR support is enabled. Babel supports no global
1715
configuration options apart from those common to all other protocols, but
1716
supports the following per-interface configuration options:
1717

    
1718
<code>
1719
protocol babel [<name>] {
1720
	ipv4 { <channel config> };
1721
	ipv6 [sadr] { <channel config> };
1722
        randomize router id <switch>;
1723
	interface <interface pattern> {
1724
		type <wired|wireless>;
1725
		rxcost <number>;
1726
		limit <number>;
1727
		hello interval <time>;
1728
		update interval <time>;
1729
		port <number>;
1730
		tx class|dscp <number>;
1731
		tx priority <number>;
1732
		rx buffer <number>;
1733
		tx length <number>;
1734
		check link <switch>;
1735
		next hop ipv4 <address>;
1736
		next hop ipv6 <address>;
1737
	};
1738
}
1739
</code>
1740

    
1741
<descrip>
1742
      <tag><label id="babel-channel">ipv4 | ipv6 [sadr] <m/channel config/</tag>
1743
      The supported channels are IPv4, IPv6, and IPv6 SADR.
1744

    
1745
      <tag><label id="babel-random-router-id">randomize router id <m/switch/</tag>
1746
      If enabled, Bird will randomize the top 32 bits of its router ID whenever
1747
      the protocol instance starts up. If a Babel node restarts, it loses its
1748
      sequence number, which can cause its routes to be rejected by peers until
1749
      the state is cleared out by other nodes in the network (which can take on
1750
      the order of minutes). Enabling this option causes Bird to pick a random
1751
      router ID every time it starts up, which avoids this problem at the cost
1752
      of not having stable router IDs in the network. Default: no.
1753

    
1754
      <tag><label id="babel-type">type wired|wireless </tag>
1755
      This option specifies the interface type: Wired or wireless. On wired
1756
      interfaces a neighbor is considered unreachable after a small number of
1757
      Hello packets are lost, as described by <cf/limit/ option. On wireless
1758
      interfaces the ETX link quality estimation technique is used to compute
1759
      the metrics of routes discovered over this interface. This technique will
1760
      gradually degrade the metric of routes when packets are lost rather than
1761
      the more binary up/down mechanism of wired type links. Default:
1762
      <cf/wired/.
1763

    
1764
      <tag><label id="babel-rxcost">rxcost <m/num/</tag>
1765
      This option specifies the nominal RX cost of the interface. The effective
1766
      neighbor costs for route metrics will be computed from this value with a
1767
      mechanism determined by the interface <cf/type/. Note that in contrast to
1768
      other routing protocols like RIP or OSPF, the <cf/rxcost/ specifies the
1769
      cost of RX instead of TX, so it affects primarily neighbors' route
1770
      selection and not local route selection. Default: 96 for wired interfaces,
1771
      256 for wireless.
1772

    
1773
      <tag><label id="babel-limit">limit <m/num/</tag>
1774
      BIRD keeps track of received Hello messages from each neighbor to
1775
      establish neighbor reachability. For wired type interfaces, this option
1776
      specifies how many of last 16 hellos have to be correctly received in
1777
      order to neighbor is assumed to be up. The option is ignored on wireless
1778
      type interfaces, where gradual cost degradation is used instead of sharp
1779
      limit. Default: 12.
1780

    
1781
      <tag><label id="babel-hello">hello interval <m/time/ s|ms</tag>
1782
      Interval at which periodic Hello messages are sent on this interface,
1783
      with time units. Default: 4 seconds.
1784

    
1785
      <tag><label id="babel-update">update interval <m/time/ s|ms</tag>
1786
      Interval at which periodic (full) updates are sent, with time
1787
      units. Default: 4 times the hello interval.
1788

    
1789
      <tag><label id="babel-port">port <m/number/</tag>
1790
      This option selects an UDP port to operate on. The default is to operate
1791
      on port 6696 as specified in the Babel RFC.
1792

    
1793
      <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
1794
      These options specify the ToS/DiffServ/Traffic class/Priority of the
1795
      outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
1796
      option for detailed description.
1797

    
1798
      <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
1799
      This option specifies the size of buffers used for packet processing.
1800
      The buffer size should be bigger than maximal size of received packets.
1801
      The default value is the interface MTU, and the value will be clamped to a
1802
      minimum of 512 bytes + IP packet overhead.
1803

    
1804
      <tag><label id="babel-tx-length">tx length <m/number/</tag>
1805
      This option specifies the maximum length of generated Babel packets. To
1806
      avoid IP fragmentation, it should not exceed the interface MTU value.
1807
      The default value is the interface MTU value, and the value will be
1808
      clamped to a minimum of 512 bytes + IP packet overhead.
1809

    
1810
      <tag><label id="babel-check-link">check link <m/switch/</tag>
1811
      If set, the hardware link state (as reported by OS) is taken into
1812
      consideration. When the link disappears (e.g. an ethernet cable is
1813
      unplugged), neighbors are immediately considered unreachable and all
1814
      routes received from them are withdrawn. It is possible that some
1815
      hardware drivers or platforms do not implement this feature. Default:
1816
      yes.
1817

    
1818
      <tag><label id="babel-next-hop-ipv4">next hop ipv4 <m/address/</tag>
1819
      Set the next hop address advertised for IPv4 routes advertised on this
1820
      interface. Default: the preferred IPv4 address of the interface.
1821

    
1822
      <tag><label id="babel-next-hop-ipv6">next hop ipv6 <m/address/</tag>
1823
      Set the next hop address advertised for IPv6 routes advertised on this
1824
      interface. If not set, the same link-local address that is used as the
1825
      source for Babel packets will be used. In normal operation, it should not
1826
      be necessary to set this option.
1827
</descrip>
1828

    
1829
<sect1>Attributes
1830
<label id="babel-attr">
1831

    
1832
<p>Babel defines just one attribute: the internal babel metric of the route. It
1833
is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
1834
(65535).
1835

    
1836
<sect1>Example
1837
<label id="babel-exam">
1838

    
1839
<p><code>
1840
protocol babel {
1841
	interface "eth*" {
1842
		type wired;
1843
	};
1844
	interface "wlan0", "wlan1" {
1845
		type wireless;
1846
		hello interval 1;
1847
		rxcost 512;
1848
	};
1849
	interface "tap0";
1850

    
1851
	# This matches the default of babeld: redistribute all addresses
1852
	# configured on local interfaces, plus re-distribute all routes received
1853
	# from other babel peers.
1854

    
1855
	ipv4 {
1856
		export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1857
	};
1858
	ipv6 {
1859
		export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1860
	};
1861
}
1862
</code>
1863

    
1864
<sect1>Known issues
1865
<label id="babel-issues">
1866

    
1867
<p>When retracting a route, Babel generates an unreachable route for a little
1868
while (according to RFC). The interaction of this behavior with other protocols
1869
is not well tested and strange things may happen.
1870

    
1871

    
1872
<sect>BFD
1873
<label id="bfd">
1874

    
1875
<sect1>Introduction
1876
<label id="bfd-intro">
1877

    
1878
<p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
1879
is an independent tool providing liveness and failure detection. Routing
1880
protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
1881
liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
1882
seconds by default in OSPF, could be set down to several seconds). BFD offers
1883
universal, fast and low-overhead mechanism for failure detection, which could be
1884
attached to any routing protocol in an advisory role.
1885

    
1886
<p>BFD consists of mostly independent BFD sessions. Each session monitors an
1887
unicast bidirectional path between two BFD-enabled routers. This is done by
1888
periodically sending control packets in both directions. BFD does not handle
1889
neighbor discovery, BFD sessions are created on demand by request of other
1890
protocols (like OSPF or BGP), which supply appropriate information like IP
1891
addresses and associated interfaces. When a session changes its state, these
1892
protocols are notified and act accordingly (e.g. break an OSPF adjacency when
1893
the BFD session went down).
1894

    
1895
<p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
1896
advanced features like the echo mode or authentication are not implemented), IP
1897
transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
1898
interaction with client protocols as defined in <rfc id="5882">.
1899
We currently support at most one protocol instance.
1900

    
1901
<p>BFD packets are sent with a dynamic source port number. Linux systems use by
1902
default a bit different dynamic port range than the IANA approved one
1903
(49152-65535). If you experience problems with compatibility, please adjust
1904
<cf>/proc/sys/net/ipv4/ip_local_port_range</cf>
1905

    
1906
<sect1>Configuration
1907
<label id="bfd-config">
1908

    
1909
<p>BFD configuration consists mainly of multiple definitions of interfaces.
1910
Most BFD config options are session specific. When a new session is requested
1911
and dynamically created, it is configured from one of these definitions. For
1912
sessions to directly connected neighbors, <cf/interface/ definitions are chosen
1913
based on the interface associated with the session, while <cf/multihop/
1914
definition is used for multihop sessions. If no definition is relevant, the
1915
session is just created with the default configuration. Therefore, an empty BFD
1916
configuration is often sufficient.
1917

    
1918
<p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
1919
also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
1920

    
1921
<p>Some of BFD session options require <m/time/ value, which has to be specified
1922
with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
1923
are allowed as units, practical minimum values are usually in order of tens of
1924
milliseconds.
1925

    
1926
<code>
1927
protocol bfd [&lt;name&gt;] {
1928
	interface &lt;interface pattern&gt; {
1929
		interval &lt;time&gt;;
1930
		min rx interval &lt;time&gt;;
1931
		min tx interval &lt;time&gt;;
1932
		idle tx interval &lt;time&gt;;
1933
		multiplier &lt;num&gt;;
1934
		passive &lt;switch&gt;;
1935
		authentication none;
1936
		authentication simple;
1937
		authentication [meticulous] keyed md5|sha1;
1938
		password "&lt;text&gt;";
1939
		password "&lt;text&gt;" {
1940
			id &lt;num&gt;;
1941
			generate from "&lt;date&gt;";
1942
			generate to "&lt;date&gt;";
1943
			accept from "&lt;date&gt;";
1944
			accept to "&lt;date&gt;";
1945
			from "&lt;date&gt;";
1946
			to "&lt;date&gt;";
1947
		};
1948
	};
1949
	multihop {
1950
		interval &lt;time&gt;;
1951
		min rx interval &lt;time&gt;;
1952
		min tx interval &lt;time&gt;;
1953
		idle tx interval &lt;time&gt;;
1954
		multiplier &lt;num&gt;;
1955
		passive &lt;switch&gt;;
1956
	};
1957
	neighbor &lt;ip&gt; [dev "&lt;interface&gt;"] [local &lt;ip&gt;] [multihop &lt;switch&gt;];
1958
}
1959
</code>
1960

    
1961
<descrip>
1962
	<tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
1963
	Interface definitions allow to specify options for sessions associated
1964
	with such interfaces and also may contain interface specific options.
1965
	See <ref id="proto-iface" name="interface"> common option for a detailed
1966
	description of interface patterns. Note that contrary to the behavior of
1967
	<cf/interface/ definitions of other protocols, BFD protocol would accept
1968
	sessions (in default configuration) even on interfaces not covered by
1969
	such definitions.
1970

    
1971
	<tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
1972
	Multihop definitions allow to specify options for multihop BFD sessions,
1973
	in the same manner as <cf/interface/ definitions are used for directly
1974
	connected sessions. Currently only one such definition (for all multihop
1975
	sessions) could be used.
1976

    
1977
	<tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
1978
	BFD sessions are usually created on demand as requested by other
1979
	protocols (like OSPF or BGP). This option allows to explicitly add
1980
	a BFD session to the specified neighbor regardless of such requests.
1981

    
1982
	The session is identified by the IP address of the neighbor, with
1983
	optional specification of used interface and local IP. By default
1984
	the neighbor must be directly connected, unless the session is
1985
	configured as multihop. Note that local IP must be specified for
1986
	multihop sessions.
1987
</descrip>
1988

    
1989
<p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
1990

    
1991
<descrip>
1992
	<tag><label id="bfd-interval">interval <m/time/</tag>
1993
	BFD ensures availability of the forwarding path associated with the
1994
	session by periodically sending BFD control packets in both
1995
	directions. The rate of such packets is controlled by two options,
1996
	<cf/min rx interval/ and <cf/min tx interval/ (see below). This option
1997
	is just a shorthand to set both of these options together.
1998

    
1999
	<tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
2000
	This option specifies the minimum RX interval, which is announced to the
2001
	neighbor and used there to limit the neighbor's rate of generated BFD
2002
	control packets. Default: 10 ms.
2003

    
2004
	<tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
2005
	This option specifies the desired TX interval, which controls the rate
2006
	of generated BFD control packets (together with <cf/min rx interval/
2007
	announced by the neighbor). Note that this value is used only if the BFD
2008
	session is up, otherwise the value of <cf/idle tx interval/ is used
2009
	instead. Default: 100 ms.
2010

    
2011
	<tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
2012
	In order to limit unnecessary traffic in cases where a neighbor is not
2013
	available or not running BFD, the rate of generated BFD control packets
2014
	is lower when the BFD session is not up. This option specifies the
2015
	desired TX interval in such cases instead of <cf/min tx interval/.
2016
	Default: 1 s.
2017

    
2018
	<tag><label id="bfd-multiplier">multiplier <m/num/</tag>
2019
	Failure detection time for BFD sessions is based on established rate of
2020
	BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
2021
	multiplier, which is essentially (ignoring jitter) a number of missed
2022
	packets after which the session is declared down. Note that rates and
2023
	multipliers could be different in each direction of a BFD session.
2024
	Default: 5.
2025

    
2026
	<tag><label id="bfd-passive">passive <m/switch/</tag>
2027
	Generally, both BFD session endpoints try to establish the session by
2028
	sending control packets to the other side. This option allows to enable
2029
	passive mode, which means that the router does not send BFD packets
2030
	until it has received one from the other side. Default: disabled.
2031

    
2032
	<tag>authentication none</tag>
2033
	No passwords are sent in BFD packets. This is the default value.
2034

    
2035
	<tag>authentication simple</tag>
2036
	Every packet carries 16 bytes of password. Received packets lacking this
2037
	password are ignored. This authentication mechanism is very weak.
2038

    
2039
	<tag>authentication [meticulous] keyed md5|sha1</tag>
2040
	An authentication code is appended to each packet. The cryptographic
2041
	algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
2042
	for all keys (on one interface), in contrast to OSPF or RIP, where it
2043
	is a per-key option. Passwords (keys) are not sent open via network.
2044

    
2045
	The <cf/meticulous/ variant means that cryptographic sequence numbers
2046
	are increased for each sent packet, while in the basic variant they are
2047
	increased about once per second. Generally, the <cf/meticulous/ variant
2048
	offers better resistance to replay attacks but may require more
2049
	computation.
2050

    
2051
	<tag>password "<M>text</M>"</tag>
2052
	Specifies a password used for authentication. See <ref id="proto-pass"
2053
	name="password"> common option for detailed description. Note that
2054
	password option <cf/algorithm/ is not available in BFD protocol. The
2055
	algorithm is selected by <cf/authentication/ option for all passwords.
2056

    
2057
</descrip>
2058

    
2059
<sect1>Example
2060
<label id="bfd-exam">
2061

    
2062
<p><code>
2063
protocol bfd {
2064
	interface "eth*" {
2065
		min rx interval 20 ms;
2066
		min tx interval 50 ms;
2067
		idle tx interval 300 ms;
2068
	};
2069
	interface "gre*" {
2070
		interval 200 ms;
2071
		multiplier 10;
2072
		passive;
2073
	};
2074
	multihop {
2075
		interval 200 ms;
2076
		multiplier 10;
2077
	};
2078

    
2079
	neighbor 192.168.1.10;
2080
	neighbor 192.168.2.2 dev "eth2";
2081
	neighbor 192.168.10.1 local 192.168.1.1 multihop;
2082
}
2083
</code>
2084

    
2085

    
2086
<sect>BGP
2087
<label id="bgp">
2088

    
2089
<p>The Border Gateway Protocol is the routing protocol used for backbone level
2090
routing in the today's Internet. Contrary to other protocols, its convergence
2091
does not rely on all routers following the same rules for route selection,
2092
making it possible to implement any routing policy at any router in the network,
2093
the only restriction being that if a router advertises a route, it must accept
2094
and forward packets according to it.
2095

    
2096
<p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
2097
is a part of the network with common management and common routing policy. It is
2098
identified by a unique 16-bit number (ASN). Routers within each AS usually
2099
exchange AS-internal routing information with each other using an interior
2100
gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
2101
the AS communicate global (inter-AS) network reachability information with their
2102
neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
2103
received information to other routers in the AS via interior BGP (iBGP).
2104

    
2105
<p>Each BGP router sends to its neighbors updates of the parts of its routing
2106
table it wishes to export along with complete path information (a list of AS'es
2107
the packet will travel through if it uses the particular route) in order to
2108
avoid routing loops.
2109

    
2110
<sect1>Supported standards
2111
<label id="bgp-standards">
2112

    
2113
<p>
2114
<itemize>
2115
<item> <rfc id="4271"> - Border Gateway Protocol 4 (BGP)
2116
<item> <rfc id="1997"> - BGP Communities Attribute
2117
<item> <rfc id="2385"> - Protection of BGP Sessions via TCP MD5 Signature
2118
<item> <rfc id="2545"> - Use of BGP Multiprotocol Extensions for IPv6
2119
<item> <rfc id="2918"> - Route Refresh Capability
2120
<item> <rfc id="3107"> - Carrying Label Information in BGP
2121
<item> <rfc id="4360"> - BGP Extended Communities Attribute
2122
<item> <rfc id="4364"> - BGP/MPLS IPv4 Virtual Private Networks
2123
<item> <rfc id="4456"> - BGP Route Reflection
2124
<item> <rfc id="4486"> - Subcodes for BGP Cease Notification Message
2125
<item> <rfc id="4659"> - BGP/MPLS IPv6 Virtual Private Networks
2126
<item> <rfc id="4724"> - Graceful Restart Mechanism for BGP
2127
<item> <rfc id="4760"> - Multiprotocol extensions for BGP
2128
<item> <rfc id="4798"> - Connecting IPv6 Islands over IPv4 MPLS
2129
<item> <rfc id="5065"> - AS confederations for BGP
2130
<item> <rfc id="5082"> - Generalized TTL Security Mechanism
2131
<item> <rfc id="5492"> - Capabilities Advertisement with BGP
2132
<item> <rfc id="5549"> - Advertising IPv4 NLRI with an IPv6 Next Hop
2133
<item> <rfc id="5575"> - Dissemination of Flow Specification Rules
2134
<item> <rfc id="5668"> - 4-Octet AS Specific BGP Extended Community
2135
<item> <rfc id="6286"> - AS-Wide Unique BGP Identifier
2136
<item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error
2137
<item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers
2138
<item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP
2139
<item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages
2140
<item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP
2141
<item> <rfc id="7947"> - Internet Exchange BGP Route Server
2142
<item> <rfc id="8092"> - BGP Large Communities Attribute
2143
<item> <rfc id="8203"> - BGP Administrative Shutdown Communication
2144
<item> <rfc id="8212"> - Default EBGP Route Propagation Behavior without Policies
2145
</itemize>
2146

    
2147
<sect1>Route selection rules
2148
<label id="bgp-route-select-rules">
2149

    
2150
<p>BGP doesn't have any simple metric, so the rules for selection of an optimal
2151
route among multiple BGP routes with the same preference are a bit more complex
2152
and they are implemented according to the following algorithm. It starts the
2153
first rule, if there are more "best" routes, then it uses the second rule to
2154
choose among them and so on.
2155

    
2156
<itemize>
2157
	<item>Prefer route with the highest Local Preference attribute.
2158
	<item>Prefer route with the shortest AS path.
2159
	<item>Prefer IGP origin over EGP and EGP origin over incomplete.
2160
	<item>Prefer the lowest value of the Multiple Exit Discriminator.
2161
	<item>Prefer routes received via eBGP over ones received via iBGP.
2162
	<item>Prefer routes with lower internal distance to a boundary router.
2163
	<item>Prefer the route with the lowest value of router ID of the
2164
	advertising router.
2165
</itemize>
2166

    
2167
<sect1>IGP routing table
2168
<label id="bgp-igp-routing-table">
2169

    
2170
<p>BGP is mainly concerned with global network reachability and with routes to
2171
other autonomous systems. When such routes are redistributed to routers in the
2172
AS via BGP, they contain IP addresses of a boundary routers (in route attribute
2173
NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
2174
determine immediate next hops for routes and to know their internal distances to
2175
boundary routers for the purpose of BGP route selection. In BIRD, there is
2176
usually one routing table used for both IGP routes and BGP routes.
2177

    
2178
<sect1>Protocol configuration
2179
<label id="bgp-proto-config">
2180

    
2181
<p>Each instance of the BGP corresponds to one neighboring router. This allows
2182
to set routing policy and all the other parameters differently for each neighbor
2183
using the following configuration parameters:
2184

    
2185
<descrip>
2186
	<tag><label id="bgp-local">local [<m/ip/] [port <m/number/] [as <m/number/]</tag>
2187
	Define which AS we are part of. (Note that contrary to other IP routers,
2188
	BIRD is able to act as a router located in multiple AS'es simultaneously,
2189
	but in such cases you need to tweak the BGP paths manually in the filters
2190
	to get consistent behavior.) Optional <cf/ip/ argument specifies a source
2191
	address, equivalent to the <cf/source address/ option (see below).
2192
	Optional <cf/port/ argument specifies the local BGP port instead of
2193
	standard port 179. The parameter may be used multiple times with
2194
	different sub-options (e.g., both <cf/local 10.0.0.1 as 65000;/ and
2195
	<cf/local 10.0.0.1; local as 65000;/ are valid). This parameter is
2196
	mandatory.
2197

    
2198
	<tag><label id="bgp-neighbor">neighbor [<m/ip/] [port <m/number/] [as <m/number/] [internal|external]</tag>
2199
	Define neighboring router this instance will be talking to and what AS
2200
	it is located in. In case the neighbor is in the same AS as we are, we
2201
	automatically switch to IBGP. Alternatively, it is possible to specify
2202
	just <cf/internal/ or </cf/external/ instead of AS number, in that case
2203
	either local AS number, or any external AS number is accepted.
2204
	Optionally, the remote port may also be specified. Like <cf/local/
2205
	parameter, this parameter may also be used multiple times with different
2206
	sub-options. This parameter is mandatory.
2207

    
2208
	<tag><label id="bgp-iface">interface <m/string/</tag>
2209
	Define interface we should use for link-local BGP IPv6 sessions.
2210
	Interface can also be specified as a part of <cf/neighbor address/
2211
	(e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). The option may also be
2212
	used for non link-local sessions when it is necessary to explicitly
2213
	specify an interface, but only for direct (not multihop) sessions.
2214

    
2215
	<tag><label id="bgp-direct">direct</tag>
2216
	Specify that the neighbor is directly connected. The IP address of the
2217
	neighbor must be from a directly reachable IP range (i.e. associated
2218
	with one of your router's interfaces), otherwise the BGP session
2219
	wouldn't start but it would wait for such interface to appear. The
2220
	alternative is the <cf/multihop/ option. Default: enabled for eBGP.
2221

    
2222
	<tag><label id="bgp-multihop">multihop [<m/number/]</tag>
2223
	Configure multihop BGP session to a neighbor that isn't directly
2224
	connected. Accurately, this option should be used if the configured
2225
	neighbor IP address does not match with any local network subnets. Such
2226
	IP address have to be reachable through system routing table. The
2227
	alternative is the <cf/direct/ option. For multihop BGP it is
2228
	recommended to explicitly configure the source address to have it
2229
	stable. Optional <cf/number/ argument can be used to specify the number
2230
	of hops (used for TTL). Note that the number of networks (edges) in a
2231
	path is counted; i.e., if two BGP speakers are separated by one router,
2232
	the number of hops is 2. Default: enabled for iBGP.
2233

    
2234
	<tag><label id="bgp-source-address">source address <m/ip/</tag>
2235
	Define local address we should use as a source address for the BGP
2236
	session. Default: the address of the local end of the interface our
2237
	neighbor is connected to.
2238

    
2239
	<tag><label id="bgp-strict-bind">strict bind <m/switch/</tag>
2240
	Specify whether BGP listening socket should be bound to a specific local
2241
	address (the same as the <cf/source address/) and associated interface,
2242
	or to all addresses. Binding to a specific address could be useful in
2243
	cases like running multiple BIRD instances on a machine, each using its
2244
	IP address. Note that listening sockets bound to a specific address and
2245
	to all addresses collide, therefore either all BGP protocols (of the
2246
	same address family and using the same local port) should have set
2247
	<cf/strict bind/, or none of them. Default: disabled.
2248

    
2249
	<tag><label id="bgp-check-link">check link <M>switch</M></tag>
2250
	BGP could use hardware link state into consideration.  If enabled,
2251
	BIRD tracks the link state of the associated interface and when link
2252
	disappears (e.g. an ethernet cable is unplugged), the BGP session is
2253
	immediately shut down. Note that this option cannot be used with
2254
	multihop BGP. Default: enabled for direct BGP, disabled otherwise.
2255

    
2256
	<tag><label id="bgp-bfd">bfd <M>switch</M>|graceful</tag>
2257
	BGP could use BFD protocol as an advisory mechanism for neighbor
2258
	liveness and failure detection. If enabled, BIRD setups a BFD session
2259
	for the BGP neighbor and tracks its liveness by it. This has an
2260
	advantage of an order of magnitude lower detection times in case of
2261
	failure. When a neighbor failure is detected, the BGP session is
2262
	restarted. Optionally, it can be configured (by <cf/graceful/ argument)
2263
	to trigger graceful restart instead of regular restart. Note that BFD
2264
	protocol also has to be configured, see <ref id="bfd" name="BFD">
2265
	section for details. Default: disabled.
2266

    
2267
	<tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
2268
	Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
2269
	protects against spoofed packets by ignoring received packets with a
2270
	smaller than expected TTL. To work properly, GTSM have to be enabled on
2271
	both sides of a BGP session. If both <cf/ttl security/ and
2272
	<cf/multihop/ options are enabled, <cf/multihop/ option should specify
2273
	proper hop value to compute expected TTL. Kernel support required:
2274
	Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
2275
	Note that full (ICMP protection, for example) <rfc id="5082"> support is
2276
	provided by Linux only. Default: disabled.
2277

    
2278
	<tag><label id="bgp-password">password <m/string/</tag>
2279
	Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
2280
	used on BSD systems, see also <cf/setkey/ option below. Default: no
2281
	authentication.
2282

    
2283
	<tag><label id="bgp-setkey">setkey <m/switch/</tag>
2284
	On BSD systems, keys for TCP MD5 authentication are stored in the global
2285
	SA/SP database, which can be accessed by external utilities (e.g.
2286
	setkey(8)). BIRD configures security associations in the SA/SP database
2287
	automatically based on <cf/password/ options (see above), this option
2288
	allows to disable automatic updates by BIRD when manual configuration by
2289
	external utilities is preferred. Note that automatic SA/SP database
2290
	updates are currently implemented only for FreeBSD. Passwords have to be
2291
	set manually by an external utility on NetBSD and OpenBSD. Default:
2292
	enabled (ignored on non-FreeBSD).
2293

    
2294
	<tag><label id="bgp-passive">passive <m/switch/</tag>
2295
	Standard BGP behavior is both initiating outgoing connections and
2296
	accepting incoming connections. In passive mode, outgoing connections
2297
	are not initiated. Default: off.
2298

    
2299
	<tag><label id="bgp-confederation">confederation <m/number/</tag>
2300
	BGP confederations (<rfc id="5065">) are collections of autonomous
2301
	systems that act as one entity to external systems, represented by one
2302
	confederation identifier (instead of AS numbers). This option allows to
2303
	enable BGP confederation behavior and to specify the local confederation
2304
	identifier. When BGP confederations are used, all BGP speakers that are
2305
	members of the BGP confederation should have the same confederation
2306
	identifier configured. Default: 0 (no confederation).
2307

    
2308
	<tag><label id="bgp-confederation-member">confederation member <m/switch/</tag>
2309
	When BGP confederations are used, this option allows to specify whether
2310
	the BGP neighbor is a member of the same confederation as the local BGP
2311
	speaker. The option is unnecessary (and ignored) for IBGP sessions, as
2312
	the same AS number implies the same confederation. Default: no.
2313

    
2314
	<tag><label id="bgp-rr-client">rr client</tag>
2315
	Be a route reflector and treat the neighbor as a route reflection
2316
	client. Default: disabled.
2317

    
2318
	<tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2319
	Route reflectors use cluster id to avoid route reflection loops. When
2320
	there is one route reflector in a cluster it usually uses its router id
2321
	as a cluster id, but when there are more route reflectors in a cluster,
2322
	these need to be configured (using this option) to use a common cluster
2323
	id. Clients in a cluster need not know their cluster id and this option
2324
	is not allowed for them. Default: the same as router id.
2325

    
2326
	<tag><label id="bgp-rs-client">rs client</tag>
2327
	Be a route server and treat the neighbor as a route server client.
2328
	A route server is used as a replacement for full mesh EBGP routing in
2329
	Internet exchange points in a similar way to route reflectors used in
2330
	IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2331
	uses ad-hoc implementation, which behaves like plain EBGP but reduces
2332
	modifications to advertised route attributes to be transparent (for
2333
	example does not prepend its AS number to AS PATH attribute and
2334
	keeps MED attribute). Default: disabled.
2335

    
2336
	<tag><label id="bgp-allow-local-pref">allow bgp_local_pref <m/switch/</tag>
2337
	A standard BGP implementation do not send the Local Preference attribute
2338
	to eBGP neighbors and ignore this attribute if received from eBGP
2339
	neighbors, as per <rfc id="4271">.  When this option is enabled on an
2340
	eBGP session, this attribute will be sent to and accepted from the peer,
2341
	which is useful for example if you have a setup like in <rfc id="7938">.
2342
	The option does not affect iBGP sessions. Default: off.
2343

    
2344
	<tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2345
	BGP prevents routing loops by rejecting received routes with the local
2346
	AS number in the AS path. This option allows to loose or disable the
2347
	check. Optional <cf/number/ argument can be used to specify the maximum
2348
	number of local ASNs in the AS path that is allowed for received
2349
	routes. When the option is used without the argument, the check is
2350
	completely disabled and you should ensure loop-free behavior by some
2351
	other means. Default: 0 (no local AS number allowed).
2352

    
2353
	<tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
2354
	After the initial route exchange, BGP protocol uses incremental updates
2355
	to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
2356
	changes its import filter, or if there is suspicion of inconsistency) it
2357
	is necessary to do a new complete route exchange. BGP protocol extension
2358
	Route Refresh (<rfc id="2918">) allows BGP speaker to request
2359
	re-advertisement of all routes from its neighbor. BGP protocol
2360
	extension Enhanced Route Refresh (<rfc id="7313">) specifies explicit
2361
	begin and end for such exchanges, therefore the receiver can remove
2362
	stale routes that were not advertised during the exchange. This option
2363
	specifies whether BIRD advertises these capabilities and supports
2364
	related procedures. Note that even when disabled, BIRD can send route
2365
	refresh requests.  Default: on.
2366

    
2367
	<tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
2368
	When a BGP speaker restarts or crashes, neighbors will discard all
2369
	received paths from the speaker, which disrupts packet forwarding even
2370
	when the forwarding plane of the speaker remains intact. <rfc id="4724">
2371
	specifies an optional graceful restart mechanism to alleviate this
2372
	issue. This option controls the mechanism. It has three states:
2373
	Disabled, when no support is provided. Aware, when the graceful restart
2374
	support is announced and the support for restarting neighbors is
2375
	provided, but no local graceful restart is allowed (i.e. receiving-only
2376
	role). Enabled, when the full graceful restart support is provided
2377
	(i.e. both restarting and receiving role). Restarting role could be also
2378
	configured per-channel. Note that proper support for local graceful
2379
	restart requires also configuration of other protocols. Default: aware.
2380

    
2381
	<tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
2382
	The restart time is announced in the BGP graceful restart capability
2383
	and specifies how long the neighbor would wait for the BGP session to
2384
	re-establish after a restart before deleting stale routes. Default:
2385
	120 seconds.
2386

    
2387
	<tag><label id="bgp-long-lived-graceful-restart">long lived graceful restart <m/switch/|aware</tag>
2388
	The long-lived graceful restart is an extension of the traditional
2389
	<ref id="bgp-graceful-restart" name="BGP graceful restart">, where stale
2390
	routes are kept even after the <ref id="bgp-graceful-restart-time"
2391
	name="restart time"> expires for additional long-lived stale time, but
2392
	they are marked with the LLGR_STALE community, depreferenced, and
2393
	withdrawn from routers not supporting LLGR. Like traditional BGP
2394
	graceful restart, it has three states: disabled, aware (receiving-only),
2395
	and enabled. Note that long-lived graceful restart requires at least
2396
	aware level of traditional BGP graceful restart. Default: aware, unless
2397
	graceful restart is disabled.
2398

    
2399
	<tag><label id="bgp-long-lived-stale-time">long lived stale time <m/number/</tag>
2400
	The long-lived stale time is announced in the BGP long-lived graceful
2401
	restart capability and specifies how long the neighbor would keep stale
2402
	routes depreferenced during long-lived graceful restart until either the
2403
	session is re-stablished and synchronized or the stale time expires and
2404
	routes are removed. Default: 3600 seconds.
2405

    
2406
	<tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
2407
	<rfc id="1997"> demands that BGP speaker should process well-known
2408
	communities like no-export (65535, 65281) or no-advertise (65535,
2409
	65282). For example, received route carrying a no-adverise community
2410
	should not be advertised to any of its neighbors. If this option is
2411
	enabled (which is by default), BIRD has such behavior automatically (it
2412
	is evaluated when a route is exported to the BGP protocol just before
2413
	the export filter).  Otherwise, this integrated processing of
2414
	well-known communities is disabled. In that case, similar behavior can
2415
	be implemented in the export filter.  Default: on.
2416

    
2417
	<tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
2418
	BGP protocol was designed to use 2B AS numbers and was extended later to
2419
	allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
2420
	option it can be persuaded not to advertise it and to maintain old-style
2421
	sessions with its neighbors. This might be useful for circumventing bugs
2422
	in neighbor's implementation of 4B AS extension. Even when disabled
2423
	(off), BIRD behaves internally as AS4-aware BGP router. Default: on.
2424

    
2425
	<tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
2426
	The BGP protocol uses maximum message length of 4096 bytes. This option
2427
	provides an extension to allow extended messages with length up
2428
	to 65535 bytes. Default: off.
2429

    
2430
	<tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
2431
	Use capability advertisement to advertise optional capabilities. This is
2432
	standard behavior for newer BGP implementations, but there might be some
2433
	older BGP implementations that reject such connection attempts. When
2434
	disabled (off), features that request it (4B AS support) are also
2435
	disabled. Default: on, with automatic fallback to off when received
2436
	capability-related error.
2437

    
2438
	<tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag>
2439
	Advertise IPv4 multiprotocol capability. This is not a correct behavior
2440
	according to the strict interpretation of <rfc id="4760">, but it is
2441
	widespread and required by some BGP implementations (Cisco and Quagga).
2442
	This option is relevant to IPv4 mode with enabled capability
2443
	advertisement only. Default: on.
2444

    
2445
	<tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
2446
	When an error is encountered (either locally or by the other side),
2447
	disable the instance automatically and wait for an administrator to fix
2448
	the problem manually. Default: off.
2449

    
2450
	<tag><label id="bgp-disable-after-cease">disable after cease <m/switch/|<m/set-of-flags/</tag>
2451
	When a Cease notification is received, disable the instance
2452
	automatically and wait for an administrator to fix the problem manually.
2453
	When used with <m/switch/ argument, it means handle every Cease subtype
2454
	with the exception of <cf/connection collision/. Default: off.
2455

    
2456
	The <m/set-of-flags/ allows to narrow down relevant Cease subtypes. The
2457
	syntax is <cf>{<m/flag/ [, <m/.../] }</cf>, where flags are: <cf/cease/,
2458
	<cf/prefix limit hit/, <cf/administrative shutdown/,
2459
	<cf/peer deconfigured/, <cf/administrative reset/,
2460
	<cf/connection rejected/, <cf/configuration change/,
2461
	<cf/connection collision/, <cf/out of resources/.
2462

    
2463
	<tag><label id="bgp-hold-time">hold time <m/number/</tag>
2464
	Time in seconds to wait for a Keepalive message from the other side
2465
	before considering the connection stale. Default: depends on agreement
2466
	with the neighboring router, we prefer 240 seconds if the other side is
2467
	willing to accept it.
2468

    
2469
	<tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
2470
	Value of the hold timer used before the routers have a chance to exchange
2471
	open messages and agree on the real value. Default: 240	seconds.
2472

    
2473
	<tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
2474
	Delay in seconds between sending of two consecutive Keepalive messages.
2475
	Default: One third of the hold time.
2476

    
2477
	<tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
2478
	Delay in seconds between protocol startup and the first attempt to
2479
	connect. Default: 5 seconds.
2480

    
2481
	<tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
2482
	Time in seconds to wait before retrying a failed attempt to connect.
2483
	Default: 120 seconds.
2484

    
2485
	<tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
2486
	Minimum and maximum delay in seconds between a protocol failure (either
2487
	local or reported by the peer) and automatic restart. Doesn't apply
2488
	when <cf/disable after error/ is configured. If consecutive errors
2489
	happen, the delay is increased exponentially until it reaches the
2490
	maximum. Default: 60, 300.
2491

    
2492
	<tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
2493
	Maximum time in seconds between two protocol failures to treat them as a
2494
	error sequence which makes <cf/error wait time/ increase exponentially.
2495
	Default: 300 seconds.
2496

    
2497
	<tag><label id="bgp-path-metric">path metric <m/switch/</tag>
2498
	Enable comparison of path lengths when deciding which BGP route is the
2499
	best one. Default: on.
2500

    
2501
	<tag><label id="bgp-med-metric">med metric <m/switch/</tag>
2502
	Enable comparison of MED attributes (during best route selection) even
2503
	between routes received from different ASes. This may be useful if all
2504
	MED attributes contain some consistent metric, perhaps enforced in
2505
	import filters of AS boundary routers. If this option is disabled, MED
2506
	attributes are compared only if routes are received from the same AS
2507
	(which is the standard behavior). Default: off.
2508

    
2509
	<tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
2510
	BGP route selection algorithm is often viewed as a comparison between
2511
	individual routes (e.g. if a new route appears and is better than the
2512
	current best one, it is chosen as the new best one). But the proper
2513
	route selection, as specified by <rfc id="4271">, cannot be fully
2514
	implemented in that way. The problem is mainly in handling the MED
2515
	attribute. BIRD, by default, uses an simplification based on individual
2516
	route comparison, which in some cases may lead to temporally dependent
2517
	behavior (i.e. the selection is dependent on the order in which routes
2518
	appeared). This option enables a different (and slower) algorithm
2519
	implementing proper <rfc id="4271"> route selection, which is
2520
	deterministic. Alternative way how to get deterministic behavior is to
2521
	use <cf/med metric/ option. This option is incompatible with <ref
2522
	id="dsc-table-sorted" name="sorted tables">.  Default: off.
2523

    
2524
	<tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
2525
	Enable comparison of internal distances to boundary routers during best
2526
	route selection. Default: on.
2527

    
2528
	<tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
2529
	Standard route selection algorithm breaks ties by comparing router IDs.
2530
	This changes the behavior to prefer older routes (when both are external
2531
	and from different peer). For details, see <rfc id="5004">. Default: off.
2532

    
2533
	<tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
2534
	Value of the Multiple Exit Discriminator to be used during route
2535
	selection when the MED attribute is missing. Default: 0.
2536

    
2537
	<tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
2538
	A default value for the Local Preference attribute. It is used when
2539
	a new Local Preference attribute is attached to a route by the BGP
2540
	protocol itself (for example, if a route is received through eBGP and
2541
	therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
2542
	versions of BIRD).
2543
</descrip>
2544

    
2545
<sect1>Channel configuration
2546
<label id="bgp-channel-config">
2547

    
2548
<p>BGP supports several AFIs and SAFIs over one connection. Every AFI/SAFI
2549
announced to the peer corresponds to one channel. The table of supported AFI/SAFIs
2550
together with their appropriate channels follows.
2551

    
2552
<table loc="h">
2553
<tabular ca="l|l|l|r|r">
2554
  <bf/Channel name/   | <bf/Table nettype/ | <bf/IGP table allowed/  | <bf/AFI/ | <bf/SAFI/
2555
@<hline>
2556
  <cf/ipv4/	      | <cf/ipv4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 1
2557
@ <cf/ipv6/           | <cf/ipv6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 1
2558
@ <cf/ipv4 multicast/ | <cf/ipv4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 2
2559
@ <cf/ipv6 multicast/ | <cf/ipv6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 2
2560
@ <cf/ipv4 mpls/      | <cf/ipv4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 4
2561
@ <cf/ipv6 mpls/      | <cf/ipv6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 4
2562
@ <cf/vpn4 mpls/      | <cf/vpn4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 128
2563
@ <cf/vpn6 mpls/      | <cf/vpn6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 128
2564
@ <cf/vpn4 multicast/ | <cf/vpn4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 129
2565
@ <cf/vpn6 multicast/ | <cf/vpn6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 129
2566
@ <cf/flow4/	      | <cf/flow4/         | ---                     | 1        | 133
2567
@ <cf/flow6/          | <cf/flow6/         | ---                     | 2        | 133
2568
</tabular>
2569
</table>
2570

    
2571
<p>Due to <rfc id="8212">, external BGP protocol requires explicit configuration
2572
of import and export policies (in contrast to other protocols, where default
2573
policies of <cf/import all/ and <cf/export none/ are used in absence of explicit
2574
configuration). Note that blanket policies like <cf/all/ or <cf/none/ can still
2575
be used in explicit configuration.
2576

    
2577
<p>BGP channels have additional config options (together with the common ones):
2578

    
2579
<descrip>
2580
	<tag><label id="bgp-mandatory">mandatory <m/switch/</tag>
2581
	When local and neighbor sets of configured AFI/SAFI pairs differ,
2582
	capability negotiation ensures that a common subset is used. For
2583
	mandatory channels their associated AFI/SAFI must be negotiated
2584
	(i.e., also announced by the neighbor), otherwise BGP session
2585
	negotiation fails with <it/'Required capability missing'/ error.
2586
	Regardless, at least one AFI/SAFI must be negotiated in order to BGP
2587
	session be successfully established. Default: off.
2588

    
2589
	<tag><label id="bgp-next-hop-keep">next hop keep <m/switch/|ibgp|ebgp</tag>
2590
	Do not modify the Next Hop attribute and advertise the current one
2591
	unchanged even in cases where our own local address should be used
2592
	instead. This is necessary when the BGP speaker does not forward network
2593
	traffic (route servers and some route reflectors) and also can be useful
2594
	in some other cases (e.g. multihop EBGP sessions). Can be enabled for
2595
	all routes, or just for routes received from IBGP / EBGP neighbors.
2596
	Default: disabled for regular BGP, enabled for route servers,
2597
	<cf/ibgp/ for route reflectors.
2598

    
2599
	<tag><label id="bgp-next-hop-self">next hop self <m/switch/|ibgp|ebgp</tag>
2600
	Always advertise our own local address as a next hop, even in cases
2601
	where the current Next Hop attribute should be used unchanged. This is
2602
	sometimes used for routes propagated from EBGP to IBGP when IGP routing
2603
	does not cover inter-AS links, therefore IP addreses of EBGP neighbors
2604
	are not resolvable through IGP. Can be enabled for all routes, or just
2605
	for routes received from IBGP / EBGP neighbors. Default: disabled.
2606

    
2607
	<tag><label id="bgp-next-hop-address">next hop address <m/ip/</tag>
2608
	Specify which address to use when our own local address should be
2609
	announced in the Next Hop attribute. Default: the source address of the
2610
	BGP session (if acceptable), or the preferred address of an associated
2611
	interface.
2612

    
2613
	<tag><label id="bgp-missing-lladdr">missing lladdr self|drop|ignore</tag>
2614
	Next Hop attribute in BGP-IPv6 sometimes contains just the global IPv6
2615
	address, but sometimes it has to contain both global and link-local IPv6
2616
	addresses. This option specifies what to do if BIRD have to send both
2617
	addresses but does not know link-local address. This situation might
2618
	happen when routes from other protocols are exported to BGP, or when
2619
	improper updates are received from BGP peers. <cf/self/ means that BIRD
2620
	advertises its own local address instead. <cf/drop/ means that BIRD
2621
	skips that prefixes and logs error. <cf/ignore/ means that BIRD ignores
2622
	the problem and sends just the global address (and therefore forms
2623
	improper BGP update). Default: <cf/self/, unless BIRD is configured as a
2624
	route server (option <cf/rs client/), in that case default is <cf/ignore/,
2625
	because route servers usually do not forward packets themselves.
2626

    
2627
	<tag><label id="bgp-gateway">gateway direct|recursive</tag>
2628
	For received routes, their <cf/gw/ (immediate next hop) attribute is
2629
	computed from received <cf/bgp_next_hop/ attribute. This option
2630
	specifies how it is computed. Direct mode means that the IP address from
2631
	<cf/bgp_next_hop/ is used if it is directly reachable, otherwise the
2632
	neighbor IP address is used. Recursive mode means that the gateway is
2633
	computed by an IGP routing table lookup for the IP address from
2634
	<cf/bgp_next_hop/. Note that there is just one level of indirection in
2635
	recursive mode - the route obtained by the lookup must not be recursive
2636
	itself, to prevent mutually recursive routes.
2637

    
2638
	Recursive mode is the behavior specified by the BGP
2639
	standard. Direct mode is simpler, does not require any routes in a
2640
	routing table, and was used in older versions of BIRD, but does not
2641
	handle well nontrivial iBGP setups and multihop. Recursive mode is
2642
	incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
2643
	<cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
2644

    
2645
	<tag><label id="bgp-igp-table">igp table <m/name/</tag>
2646
	Specifies a table that is used as an IGP routing table. The type of this
2647
	table must be as allowed in the table above. This option is allowed once
2648
	for every allowed table type. Default: the same as the main table
2649
	the channel is connected to (if eligible).
2650

    
2651
	<tag><label id="bgp-import-table">import table <m/switch/</tag>
2652
	A BGP import table contains all received routes from given BGP neighbor,
2653
	before application of import filters. It is also called <em/Adj-RIB-In/
2654
	in BGP terminology. BIRD BGP by default operates without import tables,
2655
	in which case received routes are just processed by import filters,
2656
	accepted ones are stored in the master table, and the rest is forgotten.
2657
	Enabling <cf/import table/ allows to store unprocessed routes, which can
2658
	be examined later by <cf/show route/, and can be used to reconfigure
2659
	import filters without full route refresh. Default: off.
2660

    
2661
	<tag><label id="bgp-secondary">secondary <m/switch/</tag>
2662
	Usually, if an export filter rejects a selected route, no other route is
2663
	propagated for that network. This option allows to try the next route in
2664
	order until one that is accepted is found or all routes for that network
2665
	are rejected. This can be used for route servers that need to propagate
2666
	different tables to each client but do not want to have these tables
2667
	explicitly (to conserve memory). This option requires that the connected
2668
	routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
2669

    
2670
	<tag><label id="bgp-extended-next-hop">extended next hop <m/switch/</tag>
2671
	BGP expects that announced next hops have the same address family as
2672
	associated network prefixes. This option provides an extension to use
2673
	IPv4 next hops with IPv6 prefixes and vice versa. For IPv4 / VPNv4
2674
	channels, the behavior is controlled by the Extended Next Hop Encoding
2675
	capability, as described in <rfc id="5549">. For IPv6 / VPNv6 channels,
2676
	just IPv4-mapped IPv6 addresses are used, as described in
2677
	<rfc id="4798"> and <rfc id="4659">. Default: off.
2678

    
2679
	<tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
2680
	Standard BGP can propagate only one path (route) per destination network
2681
	(usually the selected one). This option controls the add-path protocol
2682
	extension, which allows to advertise any number of paths to a
2683
	destination. Note that to be active, add-path has to be enabled on both
2684
	sides of the BGP session, but it could be enabled separately for RX and
2685
	TX direction. When active, all available routes accepted by the export
2686
	filter are advertised to the neighbor. Default: off.
2687

    
2688
	<tag><label id="bgp-graceful-restart-c">graceful restart <m/switch/</tag>
2689
	Although BGP graceful restart is configured mainly by protocol-wide
2690
	<ref id="bgp-graceful-restart" name="options">, it is possible to
2691
	configure restarting role per AFI/SAFI pair by this channel option.
2692
	The option is ignored if graceful restart is disabled by protocol-wide
2693
	option. Default: off in aware mode, on in full mode.
2694

    
2695
	<tag><label id="bgp-long-lived-graceful-restart-c">long lived graceful restart <m/switch/</tag>
2696
	BGP long-lived graceful restart is configured mainly by protocol-wide
2697
	<ref id="bgp-long-lived-graceful-restart" name="options">, but the
2698
	restarting role can be set per AFI/SAFI pair by this channel option.
2699
	The option is ignored if long-lived graceful restart is disabled by
2700
	protocol-wide option. Default: off in aware mode, on in full mode.
2701

    
2702
	<tag><label id="bgp-long-lived-stale-time-c">long lived stale time <m/number/</tag>
2703
	Like previous graceful restart channel options, this option allows to
2704
	set <ref id="bgp-long-lived-stale-time" name="long lived stale time">
2705
	per AFI/SAFI pair instead of per protocol. Default: set by protocol-wide
2706
	option.
2707
</descrip>
2708

    
2709
<sect1>Attributes
2710
<label id="bgp-attr">
2711

    
2712
<p>BGP defines several route attributes. Some of them (those marked with
2713
`<tt/I/' in the table below) are available on internal BGP connections only,
2714
some of them (marked with `<tt/O/') are optional.
2715

    
2716
<descrip>
2717
	<tag><label id="rta-bgp-path">bgppath bgp_path</tag>
2718
	Sequence of AS numbers describing the AS path the packet will travel
2719
	through when forwarded according to the particular route. In case of
2720
	internal BGP it doesn't contain the number of the local AS.
2721

    
2722
	<tag><label id="rta-bgp-local-pref">int bgp_local_pref [I]</tag>
2723
	Local preference value used for selection among multiple BGP routes (see
2724
	the selection rules above). It's used as an additional metric which is
2725
	propagated through the whole local AS.
2726

    
2727
	<tag><label id="rta-bgp-med">int bgp_med [O]</tag>
2728
	The Multiple Exit Discriminator of the route is an optional attribute
2729
	which is used on external (inter-AS) links to convey to an adjacent AS
2730
	the optimal entry point into the local AS. The received attribute is
2731
	also propagated over internal BGP links. The attribute value is zeroed
2732
	when a route is exported to an external BGP instance to ensure that the
2733
	attribute received from a neighboring AS is not propagated to other
2734
	neighboring ASes. A new value might be set in the export filter of an
2735
	external BGP instance. See <rfc id="4451"> for further discussion of
2736
	BGP MED attribute.
2737

    
2738
	<tag><label id="rta-bgp-origin">enum bgp_origin</tag>
2739
	Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
2740
	in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
2741
	from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
2742
	<cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
2743

    
2744
	<tag><label id="rta-bgp-next-hop">ip bgp_next_hop</tag>
2745
	Next hop to be used for forwarding of packets to this destination. On
2746
	internal BGP connections, it's an address of the originating router if
2747
	it's inside the local AS or a boundary router the packet will leave the
2748
	AS through if it's an exterior route, so each BGP speaker within the AS
2749
	has a chance to use the shortest interior path possible to this point.
2750

    
2751
	<tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr [O]</tag>
2752
	This is an optional attribute which carries no value, but the sole
2753
	presence of which indicates that the route has been aggregated from
2754
	multiple routes by some router on the path from the originator.
2755

    
2756
<!-- we don't handle aggregators right since they are of a very obscure type
2757
	<tag>bgp_aggregator</tag>
2758
-->
2759
	<tag><label id="rta-bgp-community">clist bgp_community [O]</tag>
2760
	List of community values associated with the route. Each such value is a
2761
	pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
2762
	integers, the first of them containing the number of the AS which
2763
	defines the community and the second one being a per-AS identifier.
2764
	There are lots of uses of the community mechanism, but generally they
2765
	are used to carry policy information like "don't export to USA peers".
2766
	As each AS can define its own routing policy, it also has a complete
2767
	freedom about which community attributes it defines and what will their
2768
	semantics be.
2769

    
2770
	<tag><label id="rta-bgp-ext-community">eclist bgp_ext_community [O]</tag>
2771
	List of extended community values associated with the route. Extended
2772
	communities have similar usage as plain communities, but they have an
2773
	extended range (to allow 4B ASNs) and a nontrivial structure with a type
2774
	field. Individual community values are represented using an <cf/ec/ data
2775
	type inside the filters.
2776

    
2777
	<tag><label id="rta-bgp-large-community">lclist bgp_large_community [O]</tag>
2778
	List of large community values associated with the route. Large BGP
2779
	communities is another variant of communities, but contrary to extended
2780
	communities they behave very much the same way as regular communities,
2781
	just larger -- they are uniform untyped triplets of 32bit numbers.
2782
	Individual community values are represented using an <cf/lc/ data type
2783
	inside the filters.
2784

    
2785
	<tag><label id="rta-bgp-originator-id">quad bgp_originator_id [I, O]</tag>
2786
	This attribute is created by the route reflector when reflecting the
2787
	route and contains the router ID of the originator of the route in the
2788
	local AS.
2789

    
2790
	<tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list [I, O]</tag>
2791
	This attribute contains a list of cluster IDs of route reflectors. Each
2792
	route reflector prepends its cluster ID when reflecting the route.
2793
</descrip>
2794

    
2795
<sect1>Example
2796
<label id="bgp-exam">
2797

    
2798
<p><code>
2799
protocol bgp {
2800
	local 198.51.100.14 as 65000;	     # Use a private AS number
2801
	neighbor 198.51.100.130 as 64496;    # Our neighbor ...
2802
	multihop;			     # ... which is connected indirectly
2803
	ipv4 {
2804
		export filter {			     # We use non-trivial export rules
2805
			if source = RTS_STATIC then { # Export only static routes
2806
				# Assign our community
2807
				bgp_community.add((65000,64501));
2808
				# Artificially increase path length
2809
				# by advertising local AS number twice
2810
				if bgp_path ~ [= 65000 =] then
2811
					bgp_path.prepend(65000);
2812
				accept;
2813
			}
2814
			reject;
2815
		};
2816
		import all;
2817
		next hop self; # advertise this router as next hop
2818
		igp table myigptable4; # IGP table for routes with IPv4 nexthops
2819
		igp table myigptable6; # IGP table for routes with IPv6 nexthops
2820
	};
2821
	ipv6 {
2822
		export filter mylargefilter; # We use a named filter
2823
		import all;
2824
		missing lladdr self;
2825
		igp table myigptable4; # IGP table for routes with IPv4 nexthops
2826
		igp table myigptable6; # IGP table for routes with IPv6 nexthops
2827
	};
2828
	ipv4 multicast {
2829
		import all;
2830
		export filter someotherfilter;
2831
		table mymulticasttable4; # Another IPv4 table, dedicated for multicast
2832
		igp table myigptable4;
2833
	};
2834
}
2835
</code>
2836

    
2837

    
2838
<sect>Device
2839
<label id="device">
2840

    
2841
<p>The Device protocol is not a real routing protocol. It doesn't generate any
2842
routes and it only serves as a module for getting information about network
2843
interfaces from the kernel. This protocol supports no channel.
2844

    
2845
<p>Except for very unusual circumstances, you probably should include this
2846
protocol in the configuration since almost all other protocols require network
2847
interfaces to be defined for them to work with.
2848

    
2849
<sect1>Configuration
2850
<label id="device-config">
2851

    
2852
<p><descrip>
2853
	<tag><label id="device-scan-time">scan time <m/number/</tag>
2854
	Time in seconds between two scans of the network interface list. On
2855
	systems where we are notified about interface status changes
2856
	asynchronously (such as newer versions of Linux), we need to scan the
2857
	list only in order to avoid confusion by lost notification messages,
2858
	so the default time is set to a large value.
2859

    
2860
	<tag><label id="device-iface">interface <m/pattern/ [, <m/.../]</tag>
2861
	By default, the Device protocol handles all interfaces without any
2862
	configuration. Interface definitions allow to specify optional
2863
	parameters for specific interfaces. See <ref id="proto-iface"
2864
	name="interface"> common option for detailed description. Currently only
2865
	one interface option is available:
2866

    
2867
	<tag><label id="device-preferred">preferred <m/ip/</tag>
2868
	If a network interface has more than one IP address, BIRD chooses one of
2869
	them as a preferred one. Preferred IP address is used as source address
2870
	for packets or announced next hop by routing protocols. Precisely, BIRD
2871
	chooses one preferred IPv4 address, one preferred IPv6 address and one
2872
	preferred link-local IPv6 address. By default, BIRD chooses the first
2873
	found IP address as the preferred one.
2874

    
2875
	This option allows to specify which IP address should be preferred. May
2876
	be used multiple times for different address classes (IPv4, IPv6, IPv6
2877
	link-local). In all cases, an address marked by operating system as
2878
	secondary cannot be chosen as the primary one.
2879
</descrip>
2880

    
2881
<p>As the Device protocol doesn't generate any routes, it cannot have
2882
any attributes. Example configuration looks like this:
2883

    
2884
<p><code>
2885
protocol device {
2886
	scan time 10;		# Scan the interfaces often
2887
	interface "eth0" {
2888
		preferred 192.168.1.1;
2889
		preferred 2001:db8:1:10::1;
2890
	};
2891
}
2892
</code>
2893

    
2894

    
2895
<sect>Direct
2896
<label id="direct">
2897

    
2898
<p>The Direct protocol is a simple generator of device routes for all the
2899
directly connected networks according to the list of interfaces provided by the
2900
kernel via the Device protocol. The Direct protocol supports both IPv4 and IPv6
2901
channels; both can be configured simultaneously. It can also be configured with
2902
<ref id="ip-sadr-routes" name="IPv6 SADR"> channel instead of regular IPv6
2903
channel in order to be used together with SADR-enabled Babel protocol.
2904

    
2905
<p>The question is whether it is a good idea to have such device routes in BIRD
2906
routing table. OS kernel usually handles device routes for directly connected
2907
networks by itself so we don't need (and don't want) to export these routes to
2908
the kernel protocol. OSPF protocol creates device routes for its interfaces
2909
itself and BGP protocol is usually used for exporting aggregate routes. But the
2910
Direct protocol is necessary for distance-vector protocols like RIP or Babel to
2911
announce local networks.
2912

    
2913
<p>There are just few configuration options for the Direct protocol:
2914

    
2915
<p><descrip>
2916
	<tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
2917
	By default, the Direct protocol will generate device routes for all the
2918
	interfaces available. If you want to restrict it to some subset of
2919
	interfaces or addresses (e.g. if you're using multiple routing tables
2920
	for policy routing and some of the policy domains don't contain all
2921
	interfaces), just use this clause. See <ref id="proto-iface" name="interface">
2922
	common option for detailed description. The Direct protocol uses
2923
	extended interface clauses.
2924

    
2925
	<tag><label id="direct-check-link">check link <m/switch/</tag>
2926
	If enabled, a hardware link state (reported by OS) is taken into
2927
	consideration. Routes for directly connected networks are generated only
2928
	if link up is reported and they are withdrawn when link disappears
2929
	(e.g., an ethernet cable is unplugged). Default value is no.
2930
</descrip>
2931

    
2932
<p>Direct device routes don't contain any specific attributes.
2933

    
2934
<p>Example config might look like this:
2935

    
2936
<p><code>
2937
protocol direct {
2938
	ipv4;
2939
	ipv6;
2940
	interface "-arc*", "*";		# Exclude the ARCnets
2941
}
2942
</code>
2943

    
2944

    
2945
<sect>Kernel
2946
<label id="krt">
2947

    
2948
<p>The Kernel protocol is not a real routing protocol. Instead of communicating
2949
with other routers in the network, it performs synchronization of BIRD's routing
2950
tables with the OS kernel. Basically, it sends all routing table updates to the
2951
kernel and from time to time it scans the kernel tables to see whether some
2952
routes have disappeared (for example due to unnoticed up/down transition of an
2953
interface) or whether an `alien' route has been added by someone else (depending
2954
on the <cf/learn/ switch, such routes are either ignored or accepted to our
2955
table).
2956

    
2957
<p>Note that routes created by OS kernel itself, namely direct routes
2958
representing IP subnets of associated interfaces, are not imported even with
2959
<cf/learn/ enabled. You can use <ref id="direct" name="Direct protocol"> to
2960
generate these direct routes.
2961

    
2962
<p>If your OS supports only a single routing table, you can configure only one
2963
instance of the Kernel protocol. If it supports multiple tables (in order to
2964
allow policy routing; such an OS is for example Linux), you can run as many
2965
instances as you want, but each of them must be connected to a different BIRD
2966
routing table and to a different kernel table.
2967

    
2968
<p>Because the kernel protocol is partially integrated with the connected
2969
routing table, there are two limitations - it is not possible to connect more
2970
kernel protocols to the same routing table and changing route destination
2971
(gateway) in an export filter of a kernel protocol does not work. Both
2972
limitations can be overcome using another routing table and the pipe protocol.
2973

    
2974
<p>The Kernel protocol supports both IPv4 and IPv6 channels; only one channel
2975
can be configured in each protocol instance. On Linux, it also supports <ref
2976
id="ip-sadr-routes" name="IPv6 SADR"> and <ref id="mpls-routes" name="MPLS">
2977
channels.
2978

    
2979
<sect1>Configuration
2980
<label id="krt-config">
2981

    
2982
<p><descrip>
2983
	<tag><label id="krt-persist">persist <m/switch/</tag>
2984
	Tell BIRD to leave all its routes in the routing tables when it exits
2985
	(instead of cleaning them up).
2986

    
2987
	<tag><label id="krt-scan-time">scan time <m/number/</tag>
2988
	Time in seconds between two consecutive scans of the kernel routing
2989
	table.
2990

    
2991
	<tag><label id="krt-learn">learn <m/switch/</tag>
2992
	Enable learning of routes added to the kernel routing tables by other
2993
	routing daemons or by the system administrator. This is possible only on
2994
	systems which support identification of route authorship.
2995

    
2996
	<tag><label id="krt-kernel-table">kernel table <m/number/</tag>
2997
	Select which kernel table should this particular instance of the Kernel
2998
	protocol work with. Available only on systems supporting multiple
2999
	routing tables.
3000

    
3001
	<tag><label id="krt-metric">metric <m/number/</tag> (Linux)
3002
	Use specified value as a kernel metric (priority) for all routes sent to
3003
	the kernel. When multiple routes for the same network are in the kernel
3004
	routing table, the Linux kernel chooses one with lower metric. Also,
3005
	routes with different metrics do not clash with each other, therefore
3006
	using dedicated metric value is a reliable way to avoid overwriting
3007
	routes from other sources (e.g. kernel device routes). Metric 0 has a
3008
	special meaning of undefined metric, in which either OS default is used,
3009
	or per-route metric can be set using <cf/krt_metric/ attribute. Default:
3010
	32.
3011

    
3012
	<tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
3013
	Participate in graceful restart recovery. If this option is enabled and
3014
	a graceful restart recovery is active, the Kernel protocol will defer
3015
	synchronization of routing tables until the end of the recovery. Note
3016
	that import of kernel routes to BIRD is not affected.
3017

    
3018
	<tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
3019
	Usually, only best routes are exported to the kernel protocol. With path
3020
	merging enabled, both best routes and equivalent non-best routes are
3021
	merged during export to generate one ECMP (equal-cost multipath) route
3022
	for each network. This is useful e.g. for BGP multipath. Note that best
3023
	routes are still pivotal for route export (responsible for most
3024
	properties of resulting ECMP routes), while exported non-best routes are
3025
	responsible just for additional multipath next hops. This option also
3026
	allows to specify a limit on maximal number of nexthops in one route. By
3027
	default, multipath merging is disabled. If enabled, default value of the
3028
	limit is 16.
3029
</descrip>
3030

    
3031
<sect1>Attributes
3032
<label id="krt-attr">
3033

    
3034
<p>The Kernel protocol defines several attributes. These attributes are
3035
translated to appropriate system (and OS-specific) route attributes. We support
3036
these attributes:
3037

    
3038
<descrip>
3039
	<tag><label id="rta-krt-source">int krt_source</tag>
3040
	The original source of the imported kernel route. The value is
3041
	system-dependent. On Linux, it is a value of the protocol field of the
3042
	route. See /etc/iproute2/rt_protos for common values. On BSD, it is
3043
	based on STATIC and PROTOx flags. The attribute is read-only.
3044

    
3045
	<tag><label id="rta-krt-metric">int krt_metric</tag> (Linux)
3046
	The kernel metric of the route. When multiple same routes are in a
3047
	kernel routing table, the Linux kernel chooses one with lower metric.
3048
	Note that preferred way to set kernel metric is to use protocol option
3049
	<cf/metric/, unless per-route metric values are needed.
3050

    
3051
	<tag><label id="rta-krt-prefsrc">ip krt_prefsrc</tag> (Linux)
3052
	The preferred source address. Used in source address selection for
3053
	outgoing packets. Has to be one of the IP addresses of the router.
3054

    
3055
	<tag><label id="rta-krt-realm">int krt_realm</tag> (Linux)
3056
	The realm of the route. Can be used for traffic classification.
3057

    
3058
	<tag><label id="rta-krt-scope">int krt_scope</tag> (Linux IPv4)
3059
	The scope of the route. Valid values are 0-254, although Linux kernel
3060
	may reject some values depending on route type and nexthop. It is
3061
	supposed to represent `indirectness' of the route, where nexthops of
3062
	routes are resolved through routes with a higher scope, but in current
3063
	kernels anything below <it/link/ (253) is treated as <it/global/ (0).
3064
	When not present, global scope is implied for all routes except device
3065
	routes, where link scope is used by default.
3066
</descrip>
3067

    
3068
<p>In Linux, there is also a plenty of obscure route attributes mostly focused
3069
on tuning TCP performance of local connections. BIRD supports most of these
3070
attributes, see Linux or iproute2 documentation for their meaning. Attributes
3071
<cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, others have type int.
3072
Supported attributes are:
3073

    
3074
<cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
3075
<cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
3076
<cf/krt_sstresh/, <cf/krt_lock_sstresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
3077
<cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
3078
<cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
3079
<cf/krt_initcwnd/, <cf/krt_initrwnd/, <cf/krt_quickack/,
3080
<cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
3081

    
3082
<sect1>Example
3083
<label id="krt-exam">
3084

    
3085
<p>A simple configuration can look this way:
3086

    
3087
<p><code>
3088
protocol kernel {
3089
	export all;
3090
}
3091
</code>
3092

    
3093
<p>Or for a system with two routing tables:
3094

    
3095
<p><code>
3096
protocol kernel {		# Primary routing table
3097
	learn;			# Learn alien routes from the kernel
3098
	persist;		# Don't remove routes on bird shutdown
3099
	scan time 10;		# Scan kernel routing table every 10 seconds
3100
	ipv4 {
3101
		import all;
3102
		export all;
3103
	};
3104
}
3105

    
3106
protocol kernel {		# Secondary routing table
3107
	kernel table 100;
3108
	ipv4 {
3109
		table auxtable;
3110
		export all;
3111
	};
3112
}
3113
</code>
3114

    
3115

    
3116
<sect>MRT
3117
<label id="mrt">
3118

    
3119
<sect1>Introduction
3120
<label id="mrt-intro">
3121

    
3122
<p>The MRT protocol is a component responsible for handling the Multi-Threaded
3123
Routing Toolkit (MRT) routing information export format, which is mainly used
3124
for collecting and analyzing of routing information from BGP routers. The MRT
3125
protocol can be configured to do periodic dumps of routing tables, created MRT
3126
files can be analyzed later by other tools. Independent MRT table dumps can also
3127
be requested from BIRD client. There is also a feature to save incoming BGP
3128
messages in MRT files, but it is controlled by <ref id="proto-mrtdump"
3129
name="mrtdump"> options independently of MRT protocol, although that might
3130
change in the future.
3131

    
3132
BIRD implements the main MRT format specification as defined in <rfc id="6396">
3133
and the ADD_PATH extension (<rfc id="8050">).
3134

    
3135
<sect1>Configuration
3136
<label id="mrt-config">
3137

    
3138
<p>MRT configuration consists of several statements describing routing table
3139
dumps. Multiple independent periodic dumps can be done as multiple MRT protocol
3140
instances. The MRT protocol does not use channels. There are two mandatory
3141
statements: <cf/filename/ and <cf/period/.
3142

    
3143
The behavior can be modified by following configuration parameters:
3144

    
3145
<descrip>
3146
	<tag><label id="mrt-table">table <m/name/ | "<m/pattern/"</tag>
3147
	Specify a routing table (or a set of routing tables described by a
3148
	wildcard pattern) that are to be dumped by the MRT protocol instance.
3149
	Default: the master table.
3150

    
3151
	<tag><label id="mrt-filter">filter { <m/filter commands/ }</tag>
3152
	The MRT protocol allows to specify a filter that is applied to routes as
3153
	they are dumped. Rejected routes are ignored and not saved to the MRT
3154
	dump file. Default: no filter.
3155

    
3156
	<tag><label id="mrt-where">where <m/filter expression/</tag>
3157
	An alternative way to specify a filter for the MRT protocol.
3158

    
3159
	<tag><label id="mrt-filename">filename "<m/filename/"</tag>
3160
	Specify a filename for MRT dump files. The filename may contain time
3161
	format sequences with <it/strftime(3)/ notation (see <it/man strftime/
3162
	for details), there is also a sequence "%N" that is expanded to the name
3163
	of dumped table. Therefore, each periodic dump of each table can be
3164
	saved to a different file. Mandatory, see example below.
3165

    
3166
	<tag><label id="mrt-period">period <m/number/</tag>
3167
	Specify the time interval (in seconds) between periodic dumps.
3168
	Mandatory.
3169

    
3170
	<tag><label id="mrt-always-add-path">always add path <m/switch/</tag>
3171
	The MRT format uses special records (specified in <rfc id="8050">) for
3172
	routes received using BGP ADD_PATH extension to keep Path ID, while
3173
	other routes use regular records. This has advantage of better
3174
	compatibility with tools that do not know special records, but it loses
3175
	information about which route is the best route. When this option is
3176
	enabled, both ADD_PATH and non-ADD_PATH routes are stored in ADD_PATH
3177
	records and order of routes for network is preserved. Default: disabled.
3178
</descrip>
3179

    
3180
<sect1>Example
3181
<label id="mrt-exam">
3182

    
3183
<p><code>
3184
protocol mrt {
3185
	table "tab*";
3186
	where source = RTS_BGP;
3187
	filename "/var/log/bird/%N_%F_%T.mrt";
3188
	period 300;
3189
}
3190
</code>
3191

    
3192

    
3193
<sect>OSPF
3194
<label id="ospf">
3195

    
3196
<sect1>Introduction
3197
<label id="ospf-intro">
3198

    
3199
<p>Open Shortest Path First (OSPF) is a quite complex interior gateway
3200
protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
3201
the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
3202
state (a.k.a. shortest path first) protocol -- each router maintains a database
3203
describing the autonomous system's topology. Each participating router has an
3204
identical copy of the database and all routers run the same algorithm
3205
calculating a shortest path tree with themselves as a root. OSPF chooses the
3206
least cost path as the best path.
3207

    
3208
<p>In OSPF, the autonomous system can be split to several areas in order to
3209
reduce the amount of resources consumed for exchanging the routing information
3210
and to protect the other areas from incorrect routing data. Topology of the area
3211
is hidden to the rest of the autonomous system.
3212

    
3213
<p>Another very important feature of OSPF is that it can keep routing information
3214
from other protocols (like Static or BGP) in its link state database as external
3215
routes. Each external route can be tagged by the advertising router, making it
3216
possible to pass additional information between routers on the boundary of the
3217
autonomous system.
3218

    
3219
<p>OSPF quickly detects topological changes in the autonomous system (such as
3220
router interface failures) and calculates new loop-free routes after a short
3221
period of convergence. Only a minimal amount of routing traffic is involved.
3222

    
3223
<p>Each router participating in OSPF routing periodically sends Hello messages
3224
to all its interfaces. This allows neighbors to be discovered dynamically. Then
3225
the neighbors exchange theirs parts of the link state database and keep it
3226
identical by flooding updates. The flooding process is reliable and ensures that
3227
each router detects all changes.
3228

    
3229
<sect1>Configuration
3230
<label id="ospf-config">
3231

    
3232
<p>First, the desired OSPF version can be specified by using <cf/ospf v2/ or
3233
<cf/ospf v3/ as a protocol type. By default, OSPFv2 is used. In the main part of
3234
configuration, there can be multiple definitions of OSPF areas, each with a
3235
different id. These definitions includes many other switches and multiple
3236
definitions of interfaces. Definition of interface may contain many switches and
3237
constant definitions and list of neighbors on nonbroadcast networks.
3238

    
3239
<p>OSPFv2 needs one IPv4 channel. OSPFv3 needs either one IPv6 channel, or one
3240
IPv4 channel (<rfc id="5838">). Therefore, it is possible to use OSPFv3 for both
3241
IPv4 and Pv6 routing, but it is necessary to have two protocol instances anyway.
3242
If no channel is configured, appropriate channel is defined with default
3243
parameters.
3244

    
3245
<code>
3246
protocol ospf [v2|v3] &lt;name&gt; {
3247
	rfc1583compat &lt;switch&gt;;
3248
	rfc5838 &lt;switch&gt;;
3249
	instance id &lt;num&gt;;
3250
	stub router &lt;switch&gt;;
3251
	tick &lt;num&gt;;
3252
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
3253
	merge external &lt;switch&gt;;
3254
	area &lt;id&gt; {
3255
		stub;
3256
		nssa;
3257
		summary &lt;switch&gt;;
3258
		default nssa &lt;switch&gt;;
3259
		default cost &lt;num&gt;;
3260
		default cost2 &lt;num&gt;;
3261
		translator &lt;switch&gt;;
3262
		translator stability &lt;num&gt;;
3263

    
3264
                networks {
3265
			&lt;prefix&gt;;
3266
			&lt;prefix&gt; hidden;
3267
		}
3268
                external {
3269
			&lt;prefix&gt;;
3270
			&lt;prefix&gt; hidden;
3271
			&lt;prefix&gt; tag &lt;num&gt;;
3272
		}
3273
		stubnet &lt;prefix&gt;;
3274
		stubnet &lt;prefix&gt; {
3275
			hidden &lt;switch&gt;;
3276
			summary &lt;switch&gt;;
3277
			cost &lt;num&gt;;
3278
		}
3279
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
3280
			cost &lt;num&gt;;
3281
			stub &lt;switch&gt;;
3282
			hello &lt;num&gt;;
3283
			poll &lt;num&gt;;
3284
			retransmit &lt;num&gt;;
3285
			priority &lt;num&gt;;
3286
			wait &lt;num&gt;;
3287
			dead count &lt;num&gt;;
3288
			dead &lt;num&gt;;
3289
			secondary &lt;switch&gt;;
3290
			rx buffer [normal|large|&lt;num&gt;];
3291
			tx length &lt;num&gt;;
3292
			type [broadcast|bcast|pointopoint|ptp|
3293
				nonbroadcast|nbma|pointomultipoint|ptmp];
3294
			link lsa suppression &lt;switch&gt;;
3295
			strict nonbroadcast &lt;switch&gt;;
3296
			real broadcast &lt;switch&gt;;
3297
			ptp netmask &lt;switch&gt;;
3298
			check link &lt;switch&gt;;
3299
			bfd &lt;switch&gt;;
3300
			ecmp weight &lt;num&gt;;
3301
			ttl security [&lt;switch&gt;; | tx only]
3302
			tx class|dscp &lt;num&gt;;
3303
			tx priority &lt;num&gt;;
3304
			authentication none|simple|cryptographic;
3305
			password "&lt;text&gt;";
3306
			password "&lt;text&gt;" {
3307
				id &lt;num&gt;;
3308
				generate from "&lt;date&gt;";
3309
				generate to "&lt;date&gt;";
3310
				accept from "&lt;date&gt;";
3311
				accept to "&lt;date&gt;";
3312
				from "&lt;date&gt;";
3313
				to "&lt;date&gt;";
3314
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3315
			};
3316
			neighbors {
3317
				&lt;ip&gt;;
3318
				&lt;ip&gt; eligible;
3319
			};
3320
		};
3321
		virtual link &lt;id&gt; [instance &lt;num&gt;] {
3322
			hello &lt;num&gt;;
3323
			retransmit &lt;num&gt;;
3324
			wait &lt;num&gt;;
3325
			dead count &lt;num&gt;;
3326
			dead &lt;num&gt;;
3327
			authentication none|simple|cryptographic;
3328
			password "&lt;text&gt;";
3329
			password "&lt;text&gt;" {
3330
				id &lt;num&gt;;
3331
				generate from "&lt;date&gt;";
3332
				generate to "&lt;date&gt;";
3333
				accept from "&lt;date&gt;";
3334
				accept to "&lt;date&gt;";
3335
				from "&lt;date&gt;";
3336
				to "&lt;date&gt;";
3337
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3338
			};
3339
		};
3340
	};
3341
}
3342
</code>
3343

    
3344
<descrip>
3345
	<tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
3346
	This option controls compatibility of routing table calculation with
3347
	<rfc id="1583">. Default value is no.
3348

    
3349
	<tag><label id="ospf-rfc5838">rfc5838 <m/switch/</tag>
3350
	Basic OSPFv3 is limited to IPv6 unicast routing. The <rfc id="5838">
3351
	extension defines support for more address families (IPv4, IPv6, both
3352
	unicast and multicast). The extension is enabled by default, but can be
3353
	disabled if necessary, as it restricts the range of available instance
3354
	IDs. Default value is yes.
3355

    
3356
	<tag><label id="ospf-instance-id">instance id <m/num/</tag>
3357
	When multiple OSPF protocol instances are active on the same links, they
3358
	should use different instance IDs to distinguish their packets. Although
3359
	it could be done on per-interface basis, it is often preferred to set
3360
	one instance ID to whole OSPF domain/topology (e.g., when multiple
3361
	instances are used to represent separate logical topologies on the same
3362
	physical network). This option specifies the instance ID for all
3363
	interfaces of the OSPF instance, but can be overridden by
3364
	<cf/interface/ option. Default value is 0 unless OSPFv3-AF extended
3365
	address families are used, see <rfc id="5838"> for that case.
3366

    
3367
	<tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
3368
	This option configures the router to be a stub router, i.e., a router
3369
	that participates in the OSPF topology but does not allow transit
3370
	traffic. In OSPFv2, this is implemented by advertising maximum metric
3371
	for outgoing links. In OSPFv3, the stub router behavior is announced by
3372
	clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
3373
	Default value is no.
3374

    
3375
	<tag><label id="ospf-tick">tick <M>num</M></tag>
3376
	The routing table calculation and clean-up of areas' databases is not
3377
	performed when a single link state change arrives. To lower the CPU
3378
	utilization, it's processed later at periodical intervals of <m/num/
3379
	seconds. The default value is 1.
3380

    
3381
	<tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
3382
	This option specifies whether OSPF is allowed to generate ECMP
3383
	(equal-cost multipath) routes. Such routes are used when there are
3384
	several directions to the destination, each with the same (computed)
3385
	cost. This option also allows to specify a limit on maximum number of
3386
	nexthops in one route. By default, ECMP is enabled if supported by
3387
	Kernel. Default value of the limit is 16.
3388

    
3389
	<tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
3390
	This option specifies whether OSPF should merge external routes from
3391
	different routers/LSAs for the same destination. When enabled together
3392
	with <cf/ecmp/, equal-cost external routes will be combined to multipath
3393
	routes in the same way as regular routes. When disabled, external routes
3394
	from different LSAs are treated as separate even if they represents the
3395
	same destination. Default value is no.
3396

    
3397
	<tag><label id="ospf-area">area <M>id</M></tag>
3398
	This defines an OSPF area with given area ID (an integer or an IPv4
3399
	address, similarly to a router ID). The most important area is the
3400
	backbone (ID 0) to which every other area must be connected.
3401

    
3402
	<tag><label id="ospf-stub">stub</tag>
3403
	This option configures the area to be a stub area. External routes are
3404
	not flooded into stub areas. Also summary LSAs can be limited in stub
3405
	areas (see option <cf/summary/). By default, the area is not a stub
3406
	area.
3407

    
3408
	<tag><label id="ospf-nssa">nssa</tag>
3409
	This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
3410
	is a variant of a stub area which allows a limited way of external route
3411
	propagation. Global external routes are not propagated into a NSSA, but
3412
	an external route can be imported into NSSA as a (area-wide) NSSA-LSA
3413
	(and possibly translated and/or aggregated on area boundary). By
3414
	default, the area is not NSSA.
3415

    
3416
	<tag><label id="ospf-summary">summary <M>switch</M></tag>
3417
	This option controls propagation of summary LSAs into stub or NSSA
3418
	areas. If enabled, summary LSAs are propagated as usual, otherwise just
3419
	the default summary route (0.0.0.0/0) is propagated (this is sometimes
3420
	called totally stubby area). If a stub area has more area boundary
3421
	routers, propagating summary LSAs could lead to more efficient routing
3422
	at the cost of larger link state database. Default value is no.
3423

    
3424
	<tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
3425
	When <cf/summary/ option is enabled, default summary route is no longer
3426
	propagated to the NSSA. In that case, this option allows to originate
3427
	default route as NSSA-LSA to the NSSA. Default value is no.
3428

    
3429
	<tag><label id="ospf-default-cost">default cost <M>num</M></tag>
3430
	This option controls the cost of a default route propagated to stub and
3431
	NSSA areas. Default value is 1000.
3432

    
3433
	<tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
3434
	When a default route is originated as NSSA-LSA, its cost can use either
3435
	type 1 or type 2 metric. This option allows to specify the cost of a
3436
	default route in type 2 metric. By default, type 1 metric (option
3437
	<cf/default cost/) is used.
3438

    
3439
	<tag><label id="ospf-translator">translator <M>switch</M></tag>
3440
	This option controls translation of NSSA-LSAs into external LSAs. By
3441
	default, one translator per NSSA is automatically elected from area
3442
	boundary routers. If enabled, this area boundary router would
3443
	unconditionally translate all NSSA-LSAs regardless of translator
3444
	election. Default value is no.
3445

    
3446
	<tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
3447
	This option controls the translator stability interval (in seconds).
3448
	When the new translator is elected, the old one keeps translating until
3449
	the interval is over. Default value is 40.
3450

    
3451
	<tag><label id="ospf-networks">networks { <m/set/ }</tag>
3452
	Definition of area IP ranges. This is used in summary LSA origination.
3453
	Hidden networks are not propagated into other areas.
3454

    
3455
	<tag><label id="ospf-external">external { <m/set/ }</tag>
3456
	Definition of external area IP ranges for NSSAs. This is used for
3457
	NSSA-LSA translation. Hidden networks are not translated into external
3458
	LSAs. Networks can have configured route tag.
3459

    
3460
	<tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
3461
	Stub networks are networks that are not transit networks between OSPF
3462
	routers. They are also propagated through an OSPF area as a part of a
3463
	link state database. By default, BIRD generates a stub network record
3464
	for each primary network address on each OSPF interface that does not
3465
	have any OSPF neighbors, and also for each non-primary network address
3466
	on each OSPF interface. This option allows to alter a set of stub
3467
	networks propagated by this router.
3468

    
3469
	Each instance of this option adds a stub network with given network
3470
	prefix to the set of propagated stub network, unless option <cf/hidden/
3471
	is used. It also suppresses default stub networks for given network
3472
	prefix. When option <cf/summary/ is used, also default stub networks
3473
	that are subnetworks of given stub network are suppressed. This might be
3474
	used, for example, to aggregate generated stub networks.
3475

    
3476
	<tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
3477
	Defines that the specified interfaces belong to the area being defined.
3478
	See <ref id="proto-iface" name="interface"> common option for detailed
3479
	description. In OSPFv2, extended interface clauses are used, because
3480
	each network prefix is handled as a separate virtual interface.
3481

    
3482
	You can specify alternative instance ID for the interface definition,
3483
	therefore it is possible to have several instances of that interface
3484
	with different options or even in different areas. For OSPFv2, instance
3485
	ID support is an extension (<rfc id="6549">) and is supposed to be set
3486
	per-protocol. For OSPFv3, it is an integral feature.
3487

    
3488
	<tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
3489
	Virtual link to router with the router id. Virtual link acts as a
3490
	point-to-point interface belonging to backbone. The actual area is used
3491
	as a transport area. This item cannot be in the backbone. Like with
3492
	<cf/interface/ option, you could also use several virtual links to one
3493
	destination with different instance IDs.
3494

    
3495
	<tag><label id="ospf-cost">cost <M>num</M></tag>
3496
	Specifies output cost (metric) of an interface. Default value is 10.
3497

    
3498
	<tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
3499
	If set to interface it does not listen to any packet and does not send
3500
	any hello. Default value is no.
3501

    
3502
	<tag><label id="ospf-hello">hello <M>num</M></tag>
3503
	Specifies interval in seconds between sending of Hello messages. Beware,
3504
	all routers on the same network need to have the same hello interval.
3505
	Default value is 10.
3506

    
3507
	<tag><label id="ospf-poll">poll <M>num</M></tag>
3508
	Specifies interval in seconds between sending of Hello messages for some
3509
	neighbors on NBMA network. Default value is 20.
3510

    
3511
	<tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
3512
	Specifies interval in seconds between retransmissions of unacknowledged
3513
	updates. Default value is 5.
3514

    
3515
	<tag><label id="ospf-transmit-delay">transmit delay <M>num</M></tag>
3516
	Specifies estimated transmission delay of link state updates send over
3517
	the interface. The value is added to LSA age of LSAs propagated through
3518
	it. Default value is 1.
3519

    
3520
	<tag><label id="ospf-priority">priority <M>num</M></tag>
3521
	On every multiple access network (e.g., the Ethernet) Designated Router
3522
	and Backup Designated router are elected. These routers have some special
3523
	functions in the flooding process. Higher priority increases preferences
3524
	in this election. Routers with priority 0 are not eligible. Default
3525
	value is 1.
3526

    
3527
	<tag><label id="ospf-wait">wait <M>num</M></tag>
3528
	After start, router waits for the specified number of seconds between
3529
	starting election and building adjacency. Default value is 4*<m/hello/.
3530

    
3531
	<tag><label id="ospf-dead-count">dead count <M>num</M></tag>
3532
	When the router does not receive any messages from a neighbor in
3533
	<m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
3534

    
3535
	<tag><label id="ospf-dead">dead <M>num</M></tag>
3536
	When the router does not receive any messages from a neighbor in
3537
	<m/dead/ seconds, it will consider the neighbor down. If both directives
3538
	<cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
3539

    
3540
	<tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
3541
	This option allows to specify the size of buffers used for packet
3542
	processing. The buffer size should be bigger than maximal size of any
3543
	packets. By default, buffers are dynamically resized as needed, but a
3544
	fixed value could be specified. Value <cf/large/ means maximal allowed
3545
	packet size - 65535.
3546

    
3547
	<tag><label id="ospf-tx-length">tx length <M>num</M></tag>
3548
	Transmitted OSPF messages that contain large amount of information are
3549
	segmented to separate OSPF packets to avoid IP fragmentation. This
3550
	option specifies the soft ceiling for the length of generated OSPF
3551
	packets. Default value is the MTU of the network interface. Note that
3552
	larger OSPF packets may still be generated if underlying OSPF messages
3553
	cannot be splitted (e.g. when one large LSA is propagated).
3554

    
3555
	<tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
3556
	BIRD detects a type of a connected network automatically, but sometimes
3557
	it's convenient to force use of a different type manually. On broadcast
3558
	networks (like ethernet), flooding and Hello messages are sent using
3559
	multicasts (a single packet for all the neighbors). A designated router
3560
	is elected and it is responsible for synchronizing the link-state
3561
	databases and originating network LSAs. This network type cannot be used
3562
	on physically NBMA networks and on unnumbered networks (networks without
3563
	proper IP prefix).
3564

    
3565
	<tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
3566
	Point-to-point networks connect just 2 routers together. No election is
3567
	performed and no network LSA is originated, which makes it simpler and
3568
	faster to establish. This network type is useful not only for physically
3569
	PtP ifaces (like PPP or tunnels), but also for broadcast networks used
3570
	as PtP links. This network type cannot be used on physically NBMA
3571
	networks.
3572

    
3573
	<tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
3574
	On NBMA networks, the packets are sent to each neighbor separately
3575
	because of lack of multicast capabilities. Like on broadcast networks,
3576
	a designated router is elected, which plays a central role in propagation
3577
	of LSAs. This network type cannot be used on unnumbered networks.
3578

    
3579
	<tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
3580
	This is another network type designed to handle NBMA networks. In this
3581
	case the NBMA network is treated as a collection of PtP links. This is
3582
	useful if not every pair of routers on the NBMA network has direct
3583
	communication, or if the NBMA network is used as an (possibly
3584
	unnumbered) PtP link.
3585

    
3586
	<tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
3587
	In OSPFv3, link LSAs are generated for each link, announcing link-local
3588
	IPv6 address of the router to its local neighbors. These are useless on
3589
	PtP or PtMP networks and this option allows to suppress the link LSA
3590
	origination for such interfaces. The option is ignored on other than PtP
3591
	or PtMP interfaces. Default value is no.
3592

    
3593
	<tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
3594
	If set, don't send hello to any undefined neighbor. This switch is
3595
	ignored on other than NBMA or PtMP interfaces. Default value is no.
3596

    
3597
	<tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
3598
	In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
3599
	packets are sent as IP multicast packets. This option changes the
3600
	behavior to using old-fashioned IP broadcast packets. This may be useful
3601
	as a workaround if IP multicast for some reason does not work or does
3602
	not work reliably. This is a non-standard option and probably is not
3603
	interoperable with other OSPF implementations. Default value is no.
3604

    
3605
	<tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
3606
	In <cf/type ptp/ network configurations, OSPFv2 implementations should
3607
	ignore received netmask field in hello packets and should send hello
3608
	packets with zero netmask field on unnumbered PtP links. But some OSPFv2
3609
	implementations perform netmask checking even for PtP links. This option
3610
	specifies whether real netmask will be used in hello packets on <cf/type
3611
 	ptp/ interfaces. You should ignore this option unless you meet some
3612
	compatibility problems related to this issue. Default value is no for
3613
	unnumbered PtP links, yes otherwise.
3614

    
3615
	<tag><label id="ospf-check-link">check link <M>switch</M></tag>
3616
	If set, a hardware link state (reported by OS) is taken into consideration.
3617
	When a link disappears (e.g. an ethernet cable is unplugged), neighbors
3618
	are immediately considered unreachable and only the address of the iface
3619
	(instead of whole network prefix) is propagated. It is possible that
3620
	some hardware drivers or platforms do not implement this feature.
3621
	Default value is yes.
3622

    
3623
	<tag><label id="ospf-bfd">bfd <M>switch</M></tag>
3624
	OSPF could use BFD protocol as an advisory mechanism for neighbor
3625
	liveness and failure detection. If enabled, BIRD setups a BFD session
3626
	for each OSPF neighbor and tracks its liveness by it. This has an
3627
	advantage of an order of magnitude lower detection times in case of
3628
	failure. Note that BFD protocol also has to be configured, see
3629
	<ref id="bfd" name="BFD"> section for details. Default value is no.
3630

    
3631
	<tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3632
	TTL security is a feature that protects routing protocols from remote
3633
	spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3634
	destined to neighbors. Because TTL is decremented when packets are
3635
	forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3636
	locations. Note that this option would interfere with OSPF virtual
3637
	links.
3638

    
3639
	If this option is enabled, the router will send OSPF packets with TTL
3640
	255 and drop received packets with TTL less than 255. If this option si
3641
	set to <cf/tx only/, TTL 255 is used for sent packets, but is not
3642
	checked for received packets. Default value is no.
3643

    
3644
	<tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
3645
	These options specify the ToS/DiffServ/Traffic class/Priority of the
3646
	outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
3647
	option for detailed description.
3648

    
3649
	<tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
3650
	When ECMP (multipath) routes are allowed, this value specifies a
3651
	relative weight used for nexthops going through the iface. Allowed
3652
	values are 1-256. Default value is 1.
3653

    
3654
	<tag><label id="ospf-auth-none">authentication none</tag>
3655
	No passwords are sent in OSPF packets. This is the default value.
3656

    
3657
	<tag><label id="ospf-auth-simple">authentication simple</tag>
3658
	Every packet carries 8 bytes of password. Received packets lacking this
3659
	password are ignored. This authentication mechanism is very weak.
3660
	This option is not available in OSPFv3.
3661

    
3662
	<tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
3663
	An authentication code is appended to every packet. The specific
3664
	cryptographic algorithm is selected by option <cf/algorithm/ for each
3665
	key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
3666
	and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
3667
	network, so this mechanism is quite secure. Packets can still be read by
3668
	an attacker.
3669

    
3670
	<tag><label id="ospf-pass">password "<M>text</M>"</tag>
3671
	Specifies a password used for authentication. See
3672
	<ref id="proto-pass" name="password"> common option for detailed
3673
	description.
3674

    
3675
	<tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
3676
	A set of neighbors to which Hello messages on NBMA or PtMP networks are
3677
	to be sent. For NBMA networks, some of them could be marked as eligible.
3678
	In OSPFv3, link-local addresses should be used, using global ones is
3679
	possible, but it is nonstandard and might be problematic. And definitely,
3680
	link-local and global addresses should not be mixed.
3681
</descrip>
3682

    
3683
<sect1>Attributes
3684
<label id="ospf-attr">
3685

    
3686
<p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
3687

    
3688
<p>Metric is ranging from 1 to infinity (65535). External routes use
3689
<cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
3690
with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
3691
<cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
3692
<cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
3693
2/ is stored in attribute <cf/ospf_metric2/.
3694

    
3695
When both metrics are specified then <cf/metric of type 2/ is used. This is
3696
relevant e.g. when a type 2 external route is propagated from one OSPF domain to
3697
another and <cf/ospf_metric1/ is an internal distance to the original ASBR,
3698
while <cf/ospf_metric2/ stores the type 2 metric. Note that in such cases if
3699
<cf/ospf_metric1/ is non-zero then <cf/ospf_metric2/ is increased by one to
3700
ensure monotonicity of metric, as internal distance is reset to zero when an
3701
external route is announced.
3702

    
3703
<p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
3704
integer which is used when exporting routes to other protocols; otherwise, it
3705
doesn't affect routing inside the OSPF domain at all. The fourth attribute
3706
<cf/ospf_router_id/ is a router ID of the router advertising that route /
3707
network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
3708
<cf/ospf_tag = 0/.
3709

    
3710
<sect1>Example
3711
<label id="ospf-exam">
3712

    
3713
<p><code>
3714
protocol ospf MyOSPF {
3715
	ipv4 {
3716
		export filter {
3717
			if source = RTS_BGP then {
3718
				ospf_metric1 = 100;
3719
				accept;
3720
			}
3721
			reject;
3722
		};
3723
	};
3724
	area 0.0.0.0 {
3725
		interface "eth*" {
3726
			cost 11;
3727
			hello 15;
3728
			priority 100;
3729
			retransmit 7;
3730
			authentication simple;
3731
			password "aaa";
3732
		};
3733
		interface "ppp*" {
3734
			cost 100;
3735
			authentication cryptographic;
3736
			password "abc" {
3737
				id 1;
3738
				generate to "22-04-2003 11:00:06";
3739
				accept from "17-01-2001 12:01:05";
3740
				algorithm hmac sha384;
3741
			};
3742
			password "def" {
3743
				id 2;
3744
				generate to "22-07-2005 17:03:21";
3745
				accept from "22-02-2001 11:34:06";
3746
				algorithm hmac sha512;
3747
			};
3748
		};
3749
		interface "arc0" {
3750
			cost 10;
3751
			stub yes;
3752
		};
3753
		interface "arc1";
3754
	};
3755
	area 120 {
3756
		stub yes;
3757
		networks {
3758
			172.16.1.0/24;
3759
			172.16.2.0/24 hidden;
3760
		}
3761
		interface "-arc0" , "arc*" {
3762
			type nonbroadcast;
3763
			authentication none;
3764
			strict nonbroadcast yes;
3765
			wait 120;
3766
			poll 40;
3767
			dead count 8;
3768
			neighbors {
3769
				192.168.120.1 eligible;
3770
				192.168.120.2;
3771
				192.168.120.10;
3772
			};
3773
		};
3774
	};
3775
}
3776
</code>
3777

    
3778
<sect>Perf
3779
<label id="perf">
3780

    
3781
<sect1>Introduction
3782
<label id="perf-intro">
3783

    
3784
<p>The Perf protocol is a generator of fake routes together with a time measurement
3785
framework. Its purpose is to check BIRD performance and to benchmark filters.
3786

    
3787
<p>Import mode of this protocol runs in several steps. In each step, it generates 2^x routes,
3788
imports them into the appropriate table and withdraws them. The exponent x is configurable.
3789
It runs the benchmark several times for the same x, then it increases x by one
3790
until it gets too high, then it stops.
3791

    
3792
<p>Export mode of this protocol repeats route refresh from table and measures how long it takes.
3793

    
3794
<p>Output data is logged on info level. There is a Perl script <cf>proto/perf/parse.pl</cf>
3795
which may be handy to parse the data and draw some plots.
3796

    
3797
<p>Implementation of this protocol is experimental. Use with caution and do not keep
3798
any instance of Perf in production configs for long time. The config interface is also unstable
3799
and may change in future versions without warning.
3800

    
3801
<sect1>Configuration
3802
<label id="perf-config">
3803

    
3804
<p><descrip>
3805
	<tag><label id="perf-mode">mode import|export</tag>
3806
	Set perf mode. Default: import
3807

    
3808
	<tag><label id="perf-repeat">repeat <m/number/</tag>
3809
	Run this amount of iterations of the benchmark for every amount step. Default: 4
3810

    
3811
	<tag><label id="perf-from">exp from <m/number/</tag>
3812
	Begin benchmarking on this exponent for number of generated routes in one step.
3813
	Default: 10
3814

    
3815
	<tag><label id="perf-to">exp to <m/number/</tag>
3816
	Stop benchmarking on this exponent. Default: 20
3817

    
3818
	<tag><label id="perf-threshold-min">threshold min <m/time/</tag>
3819
	If a run for the given exponent took less than this time for route import,
3820
	increase the exponent immediately. Default: 1 ms
3821

    
3822
	<tag><label id="perf-threshold-max">threshold max <m/time/</tag>
3823
	If every run for the given exponent took at least this time for route import,
3824
	stop benchmarking. Default: 500 ms
3825
</descrip>
3826

    
3827
<sect>Pipe
3828
<label id="pipe">
3829

    
3830
<sect1>Introduction
3831
<label id="pipe-intro">
3832

    
3833
<p>The Pipe protocol serves as a link between two routing tables, allowing
3834
routes to be passed from a table declared as primary (i.e., the one the pipe is
3835
connected to using the <cf/table/ configuration keyword) to the secondary one
3836
(declared using <cf/peer table/) and vice versa, depending on what's allowed by
3837
the filters. Export filters control export of routes from the primary table to
3838
the secondary one, import filters control the opposite direction. Both tables
3839
must be of the same nettype.
3840

    
3841
<p>The Pipe protocol retransmits all routes from one table to the other table,
3842
retaining their original source and attributes. If import and export filters
3843
are set to accept, then both tables would have the same content.
3844

    
3845
<p>The primary use of multiple routing tables and the Pipe protocol is for
3846
policy routing, where handling of a single packet doesn't depend only on its
3847
destination address, but also on its source address, source interface, protocol
3848
type and other similar parameters. In many systems (Linux being a good example),
3849
the kernel allows to enforce routing policies by defining routing rules which
3850
choose one of several routing tables to be used for a packet according to its
3851
parameters. Setting of these rules is outside the scope of BIRD's work (on
3852
Linux, you can use the <tt/ip/ command), but you can create several routing
3853
tables in BIRD, connect them to the kernel ones, use filters to control which
3854
routes appear in which tables and also you can employ the Pipe protocol for
3855
exporting a selected subset of one table to another one.
3856

    
3857
<sect1>Configuration
3858
<label id="pipe-config">
3859

    
3860
<p>Essentially, the Pipe protocol is just a channel connected to a table on both
3861
sides. Therefore, the configuration block for <cf/protocol pipe/ shall directly
3862
include standard channel config options; see the example below.
3863

    
3864
<p><descrip>
3865
	<tag><label id="pipe-peer-table">peer table <m/table/</tag>
3866
	Defines secondary routing table to connect to. The primary one is
3867
	selected by the <cf/table/ keyword.
3868
</descrip>
3869

    
3870
<sect1>Attributes
3871
<label id="pipe-attr">
3872

    
3873
<p>The Pipe protocol doesn't define any route attributes.
3874

    
3875
<sect1>Example
3876
<label id="pipe-exam">
3877

    
3878
<p>Let's consider a router which serves as a boundary router of two different
3879
autonomous systems, each of them connected to a subset of interfaces of the
3880
router, having its own exterior connectivity and wishing to use the other AS as
3881
a backup connectivity in case of outage of its own exterior line.
3882

    
3883
<p>Probably the simplest solution to this situation is to use two routing tables
3884
(we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
3885
packets having arrived from interfaces belonging to the first AS will be routed
3886
according to <cf/as1/ and similarly for the second AS. Thus we have split our
3887
router to two logical routers, each one acting on its own routing table, having
3888
its own routing protocols on its own interfaces. In order to use the other AS's
3889
routes for backup purposes, we can pass the routes between the tables through a
3890
Pipe protocol while decreasing their preferences and correcting their BGP paths
3891
to reflect the AS boundary crossing.
3892

    
3893
<code>
3894
ipv4 table as1;				# Define the tables
3895
ipv4 table as2;
3896

    
3897
protocol kernel kern1 {			# Synchronize them with the kernel
3898
	ipv4 { table as1; export all; };
3899
	kernel table 1;
3900
}
3901

    
3902
protocol kernel kern2 {
3903
	ipv4 { table as2; export all; };
3904
	kernel table 2;
3905
}
3906

    
3907
protocol bgp bgp1 {			# The outside connections
3908
	ipv4 { table as1; import all; export all; };
3909
	local as 1;
3910
	neighbor 192.168.0.1 as 1001;
3911
}
3912

    
3913
protocol bgp bgp2 {
3914
	ipv4 { table as2; import all; export all; };
3915
	local as 2;
3916
	neighbor 10.0.0.1 as 1002;
3917
}
3918

    
3919
protocol pipe {				# The Pipe
3920
	table as1;
3921
	peer table as2;
3922
	export filter {
3923
		if net ~ [ 1.0.0.0/8+] then {	# Only AS1 networks
3924
			if preference>10 then preference = preference-10;
3925
			if source=RTS_BGP then bgp_path.prepend(1);
3926
			accept;
3927
		}
3928
		reject;
3929
	};
3930
	import filter {
3931
		if net ~ [ 2.0.0.0/8+] then {	# Only AS2 networks
3932
			if preference>10 then preference = preference-10;
3933
			if source=RTS_BGP then bgp_path.prepend(2);
3934
			accept;
3935
		}
3936
		reject;
3937
	};
3938
}
3939
</code>
3940

    
3941

    
3942
<sect>RAdv
3943
<label id="radv">
3944

    
3945
<sect1>Introduction
3946
<label id="radv-intro">
3947

    
3948
<p>The RAdv protocol is an implementation of Router Advertisements, which are
3949
used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
3950
time intervals or as an answer to a request) advertisement packets to connected
3951
networks. These packets contain basic information about a local network (e.g. a
3952
list of network prefixes), which allows network hosts to autoconfigure network
3953
addresses and choose a default route. BIRD implements router behavior as defined
3954
in <rfc id="4861">, router preferences and specific routes (<rfc id="4191">),
3955
and DNS extensions (<rfc id="6106">).
3956

    
3957
<p>The RAdv protocols supports just IPv6 channel.
3958

    
3959
<sect1>Configuration
3960
<label id="radv-config">
3961

    
3962
<p>There are several classes of definitions in RAdv configuration -- interface
3963
definitions, prefix definitions and DNS definitions:
3964

    
3965
<descrip>
3966
	<tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3967
	Interface definitions specify a set of interfaces on which the
3968
	protocol is activated and contain interface specific options.
3969
	See <ref id="proto-iface" name="interface"> common options for
3970
	detailed description.
3971

    
3972
	<tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
3973
	Prefix definitions allow to modify a list of advertised prefixes. By
3974
	default, the advertised prefixes are the same as the network prefixes
3975
	assigned to the interface. For each network prefix, the matching prefix
3976
	definition is found and its options are used. If no matching prefix
3977
	definition is found, the prefix is used with default options.
3978

    
3979
	Prefix definitions can be either global or interface-specific. The
3980
	second ones are part of interface options. The prefix definition
3981
	matching is done in the first-match style, when interface-specific
3982
	definitions are processed before global definitions. As expected, the
3983
	prefix definition is matching if the network prefix is a subnet of the
3984
	prefix in prefix definition.
3985

    
3986
	<tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
3987
	RDNSS definitions allow to specify a list of advertised recursive DNS
3988
	servers together with their options. As options are seldom necessary,
3989
	there is also a short variant <cf>rdnss <m/address/</cf> that just
3990
	specifies one DNS server. Multiple definitions are cumulative. RDNSS
3991
	definitions may also be interface-specific when used inside interface
3992
	options. By default, interface uses both global and interface-specific
3993
	options, but that can be changed by <cf/rdnss local/ option.
3994

    
3995
	<tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
3996
	DNSSL definitions allow to specify a list of advertised DNS search
3997
	domains together with their options. Like <cf/rdnss/ above, multiple
3998
	definitions are cumulative, they can be used also as interface-specific
3999
	options and there is a short variant <cf>dnssl <m/domain/</cf> that just
4000
	specifies one DNS search domain.
4001

    
4002
	<tag><label id="radv-trigger">trigger <m/prefix/</tag>
4003
	RAdv protocol could be configured to change its behavior based on
4004
	availability of routes. When this option is used, the protocol waits in
4005
	suppressed state until a <it/trigger route/ (for the specified network)
4006
	is exported to the protocol, the protocol also returns to suppressed
4007
	state if the <it/trigger route/ disappears. Note that route export
4008
	depends on specified export filter, as usual. This option could be used,
4009
	e.g., for handling failover in multihoming scenarios.
4010

    
4011
	During suppressed state, router advertisements are generated, but with
4012
	some fields zeroed. Exact behavior depends on which fields are zeroed,
4013
	this can be configured by <cf/sensitive/ option for appropriate
4014
	fields. By default, just <cf/default lifetime/ (also called <cf/router
4015
	lifetime/) is zeroed, which means hosts cannot use the router as a
4016
	default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
4017
	also be configured as <cf/sensitive/ for a prefix, which would cause
4018
	autoconfigured IPs to be deprecated or even removed.
4019

    
4020
	<tag><label id="radv-propagate-routes">propagate routes <m/switch/</tag>
4021
	This option controls propagation of more specific routes, as defined in
4022
	<rfc id="4191">. If enabled, all routes exported to the RAdv protocol,
4023
	with the exception of the trigger prefix, are added to advertisments as
4024
	additional options. The lifetime and preference of advertised routes can
4025
	be set individually by <cf/ra_lifetime/ and <cf/ra_preference/ route
4026
	attributes, or per interface by <cf/route lifetime/ and
4027
	<cf/route preference/ options. Default: disabled.
4028

    
4029
	Note that the RFC discourages from sending more than 17 routes and
4030
	recommends the routes to be configured manually.
4031
</descrip>
4032

    
4033
<p>Interface specific options:
4034

    
4035
<descrip>
4036
	<tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
4037
	Unsolicited router advertisements are sent in irregular time intervals.
4038
	This option specifies the maximum length of these intervals, in seconds.
4039
	Valid values are 4-1800. Default: 600
4040

    
4041
	<tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
4042
	This option specifies the minimum length of that intervals, in seconds.
4043
	Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
4044
	about 1/3 * <cf/max ra interval/.
4045

    
4046
	<tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
4047
	The minimum delay between two consecutive router advertisements, in
4048
	seconds. Default: 3
4049

    
4050
	<tag><label id="radv-iface-managed">managed <m/switch/</tag>
4051
	This option specifies whether hosts should use DHCPv6 for IP address
4052
	configuration. Default: no
4053

    
4054
	<tag><label id="radv-iface-other-config">other config <m/switch/</tag>
4055
	This option specifies whether hosts should use DHCPv6 to receive other
4056
	configuration information. Default: no
4057

    
4058
	<tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
4059
	This option specifies which value of MTU should be used by hosts. 0
4060
	means unspecified. Default: 0
4061

    
4062
	<tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
4063
	This option specifies the time (in milliseconds) how long hosts should
4064
	assume a neighbor is reachable (from the last confirmation). Maximum is
4065
	3600000, 0 means unspecified. Default 0.
4066

    
4067
	<tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
4068
	This option specifies the time (in milliseconds) how long hosts should
4069
	wait before retransmitting Neighbor Solicitation messages. 0 means
4070
	unspecified. Default 0.
4071

    
4072
	<tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
4073
	This option specifies which value of Hop Limit should be used by
4074
	hosts. Valid values are 0-255, 0 means unspecified. Default: 64
4075

    
4076
	<tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
4077
	This option specifies the time (in seconds) how long (since the receipt
4078
	of RA) hosts may use the router as a default router. 0 means do not use
4079
	as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
4080
	Default: 3 * <cf/max ra	interval/, <cf/sensitive/ yes.
4081

    
4082
	<tag><label id="radv-iface-default-preference">default preference low|medium|high</tag>
4083
	This option specifies the Default Router Preference value to advertise
4084
	to hosts. Default: medium.
4085

    
4086
	<tag><label id="radv-iface-route-lifetime">route lifetime <m/expr/ [sensitive <m/switch/]</tag>
4087
	This option specifies the default value of advertised lifetime for
4088
	specific routes; i.e., the time (in seconds) for how long (since the
4089
	receipt of RA) hosts should consider these routes valid. A special value
4090
	0xffffffff represents infinity. The lifetime can be overriden on a per
4091
	route basis by the <ref id="rta-ra-lifetime" name="ra_lifetime"> route
4092
	attribute. Default: 3 * <cf/max ra interval/, <cf/sensitive/ no.
4093

    
4094
	For the <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
4095
	If <cf/sensitive/ is enabled, even the routes with the <cf/ra_lifetime/
4096
	attribute become sensitive to the trigger.
4097

    
4098
	<tag><label id="radv-iface-route-preference">route preference low|medium|high</tag>
4099
	This option specifies the default value of advertised route preference
4100
	for specific routes. The value can be overriden on a per route basis by
4101
	the <ref id="rta-ra-preference" name="ra_preference"> route attribute.
4102
	Default: medium.
4103

    
4104
	<tag><label id="radv-prefix-linger-time">prefix linger time <m/expr/</tag>
4105
	When a prefix or a route disappears, it is advertised for some time with
4106
	zero lifetime, to inform clients it is no longer valid. This option
4107
	specifies the time (in seconds) for how long prefixes are advertised
4108
	that way. Default: 3 * <cf/max ra interval/.
4109

    
4110
	<tag><label id="radv-route-linger-time">route linger time <m/expr/</tag>
4111
	When a prefix or a route disappears, it is advertised for some time with
4112
	zero lifetime, to inform clients it is no longer valid. This option
4113
	specifies the time (in seconds) for how long routes are advertised
4114
	that way. Default: 3 * <cf/max ra interval/.
4115

    
4116
	<tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
4117
	Use only local (interface-specific) RDNSS definitions for this
4118
	interface. Otherwise, both global and local definitions are used. Could
4119
	also be used to disable RDNSS for given interface if no local definitons
4120
	are specified. Default: no.
4121

    
4122
	<tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
4123
	Use only local DNSSL definitions for this interface. See <cf/rdnss local/
4124
	option above. Default: no.
4125
</descrip>
4126

    
4127
<p>Prefix specific options
4128

    
4129
<descrip>
4130
	<tag><label id="radv-prefix-skip">skip <m/switch/</tag>
4131
	This option allows to specify that given prefix should not be
4132
	advertised. This is useful for making exceptions from a default policy
4133
	of advertising all prefixes. Note that for withdrawing an already
4134
	advertised prefix it is more useful to advertise it with zero valid
4135
	lifetime. Default: no
4136

    
4137
	<tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
4138
	This option specifies whether hosts may use the advertised prefix for
4139
	onlink determination. Default: yes
4140

    
4141
	<tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
4142
	This option specifies whether hosts may use the advertised prefix for
4143
	stateless autoconfiguration. Default: yes
4144

    
4145
	<tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
4146
	This option specifies the time (in seconds) how long (after the
4147
	receipt of RA) the prefix information is valid, i.e., autoconfigured
4148
	IP addresses can be assigned and hosts with that IP addresses are
4149
	considered directly reachable. 0 means the prefix is no longer
4150
	valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
4151
	Default: 86400 (1 day), <cf/sensitive/ no.
4152

    
4153
	<tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
4154
	This option specifies the time (in seconds) how long (after the
4155
	receipt of RA) IP addresses generated from the prefix using stateless
4156
	autoconfiguration remain preferred. For <cf/sensitive/ option,
4157
	see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
4158
	<cf/sensitive/ no.
4159
</descrip>
4160

    
4161
<p>RDNSS specific options:
4162

    
4163
<descrip>
4164
	<tag><label id="radv-rdnss-ns">ns <m/address/</tag>
4165
	This option specifies one recursive DNS server. Can be used multiple
4166
	times for multiple servers. It is mandatory to have at least one
4167
	<cf/ns/ option in <cf/rdnss/ definition.
4168

    
4169
	<tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
4170
	This option specifies the time how long the RDNSS information may be
4171
	used by clients after the receipt of RA. It is expressed either in
4172
	seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
4173
	interval/. Note that RDNSS information is also invalidated when
4174
	<cf/default lifetime/ expires. 0 means these addresses are no longer
4175
	valid DNS servers. Default: 3 * <cf/max ra interval/.
4176
</descrip>
4177

    
4178
<p>DNSSL specific options:
4179

    
4180
<descrip>
4181
	<tag><label id="radv-dnssl-domain">domain <m/address/</tag>
4182
	This option specifies one DNS search domain. Can be used multiple times
4183
	for multiple domains. It is mandatory to have at least one <cf/domain/
4184
	option in <cf/dnssl/ definition.
4185

    
4186
	<tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
4187
	This option specifies the time how long the DNSSL information may be
4188
	used by clients after the receipt of RA. Details are the same as for
4189
	RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
4190
</descrip>
4191

    
4192
<sect1>Attributes
4193
<label id="radv-attr">
4194

    
4195
<p>RAdv defines two route attributes:
4196

    
4197
<descrip>
4198
	<tag><label id="rta-ra-preference">enum ra_preference</tag>
4199
	The preference of the route. The value can be <it/RA_PREF_LOW/,
4200
	<it/RA_PREF_MEDIUM/ or <it/RA_PREF_HIGH/. If the attribute is not set,
4201
	the <ref id="radv-iface-route-preference" name="route preference">
4202
	option is used.
4203

    
4204
	<tag><label id="rta-ra-lifetime">int ra_lifetime</tag>
4205
	The advertised lifetime of the route, in seconds. The special value of
4206
	0xffffffff represents infinity. If the attribute is not set, the
4207
	<ref id="radv-iface-route-lifetime" name="route lifetime">
4208
	option is used.
4209
</descrip>
4210

    
4211
<sect1>Example
4212
<label id="radv-exam">
4213

    
4214
<p><code>
4215
ipv6 table radv_routes;			# Manually configured routes go here
4216

    
4217
protocol static {
4218
	ipv6 { table radv_routes; };
4219

    
4220
	route 2001:0DB8:4000::/48 unreachable;
4221
	route 2001:0DB8:4010::/48 unreachable;
4222

    
4223
	route 2001:0DB8:4020::/48 unreachable {
4224
		ra_preference = RA_PREF_HIGH;
4225
		ra_lifetime = 3600;
4226
	};
4227
}
4228

    
4229
protocol radv {
4230
	propagate routes yes;		# Propagate the routes from the radv_routes table
4231
	ipv6 { table radv_routes; export all; };
4232

    
4233
	interface "eth2" {
4234
		max ra interval 5;	# Fast failover with more routers
4235
		managed yes;		# Using DHCPv6 on eth2
4236
		prefix ::/0 {
4237
			autonomous off;	# So do not autoconfigure any IP
4238
		};
4239
	};
4240

    
4241
	interface "eth*";		# No need for any other options
4242

    
4243
	prefix 2001:0DB8:1234::/48 {
4244
		preferred lifetime 0;	# Deprecated address range
4245
	};
4246

    
4247
	prefix 2001:0DB8:2000::/48 {
4248
		autonomous off;		# Do not autoconfigure
4249
	};
4250

    
4251
	rdnss 2001:0DB8:1234::10;	# Short form of RDNSS
4252

    
4253
	rdnss {
4254
		lifetime mult 10;
4255
		ns 2001:0DB8:1234::11;
4256
		ns 2001:0DB8:1234::12;
4257
	};
4258

    
4259
	dnssl {
4260
		lifetime 3600;
4261
		domain "abc.com";
4262
		domain "xyz.com";
4263
	};
4264
}
4265
</code>
4266

    
4267

    
4268
<sect>RIP
4269
<label id="rip">
4270

    
4271
<sect1>Introduction
4272
<label id="rip-intro">
4273

    
4274
<p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
4275
where each router broadcasts (to all its neighbors) distances to all networks it
4276
can reach. When a router hears distance to another network, it increments it and
4277
broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
4278
network goes unreachable, routers keep telling each other that its distance is
4279
the original distance plus 1 (actually, plus interface metric, which is usually
4280
one). After some time, the distance reaches infinity (that's 15 in RIP) and all
4281
routers know that network is unreachable. RIP tries to minimize situations where
4282
counting to infinity is necessary, because it is slow. Due to infinity being 16,
4283
you can't use RIP on networks where maximal distance is higher than 15
4284
hosts.
4285

    
4286
<p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
4287
id="2080">), and RIP cryptographic authentication (<rfc id="4822">).
4288

    
4289
<p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
4290
convergence, big network load and inability to handle larger networks makes it
4291
pretty much obsolete. It is still usable on very small networks.
4292

    
4293
<sect1>Configuration
4294
<label id="rip-config">
4295

    
4296
<p>RIP configuration consists mainly of common protocol options and interface
4297
definitions, most RIP options are interface specific. RIPng (RIP for IPv6)
4298
protocol instance can be configured by using <cf/rip ng/ instead of just
4299
<cf/rip/ as a protocol type.
4300

    
4301
<p>RIP needs one IPv4 channel. RIPng needs one IPv6 channel. If no channel is
4302
configured, appropriate channel is defined with default parameters.
4303

    
4304
<code>
4305
protocol rip [ng] [&lt;name&gt;] {
4306
	infinity &lt;number&gt;;
4307
	ecmp &lt;switch&gt; [limit &lt;number&gt;];
4308
	interface &lt;interface pattern&gt; {
4309
		metric &lt;number&gt;;
4310
		mode multicast|broadcast;
4311
		passive &lt;switch&gt;;
4312
		address &lt;ip&gt;;
4313
		port &lt;number&gt;;
4314
		version 1|2;
4315
		split horizon &lt;switch&gt;;
4316
		poison reverse &lt;switch&gt;;
4317
		check zero &lt;switch&gt;;
4318
		update time &lt;number&gt;;
4319
		timeout time &lt;number&gt;;
4320
		garbage time &lt;number&gt;;
4321
		ecmp weight &lt;number&gt;;
4322
		ttl security &lt;switch&gt;; | tx only;
4323
		tx class|dscp &lt;number&gt;;
4324
		tx priority &lt;number&gt;;
4325
		rx buffer &lt;number&gt;;
4326
		tx length &lt;number&gt;;
4327
		check link &lt;switch&gt;;
4328
		authentication none|plaintext|cryptographic;
4329
		password "&lt;text&gt;";
4330
		password "&lt;text&gt;" {
4331
			id &lt;num&gt;;
4332
			generate from "&lt;date&gt;";
4333
			generate to "&lt;date&gt;";
4334
			accept from "&lt;date&gt;";
4335
			accept to "&lt;date&gt;";
4336
			from "&lt;date&gt;";
4337
			to "&lt;date&gt;";
4338
			algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
4339
		};
4340
	};
4341
}
4342
</code>
4343

    
4344
<descrip>
4345
	<tag><label id="rip-infinity">infinity <M>number</M></tag>
4346
	Selects the distance of infinity. Bigger values will make
4347
	protocol convergence even slower. The default value is 16.
4348

    
4349
	<tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
4350
	This option specifies whether RIP is allowed to generate ECMP
4351
	(equal-cost multipath) routes. Such routes are used when there are
4352
	several directions to the destination, each with the same (computed)
4353
	cost. This option also allows to specify a limit on maximum number of
4354
	nexthops in one route. By default, ECMP is enabled if supported by
4355
	Kernel. Default value of the limit is 16.
4356

    
4357
	<tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
4358
	Interface definitions specify a set of interfaces on which the
4359
	protocol is activated and contain interface specific options.
4360
	See <ref id="proto-iface" name="interface"> common options for
4361
	detailed description.
4362
</descrip>
4363

    
4364
<p>Interface specific options:
4365

    
4366
<descrip>
4367
	<tag><label id="rip-iface-metric">metric <m/num/</tag>
4368
	This option specifies the metric of the interface. When a route is
4369
	received from the interface, its metric is increased by this value
4370
	before further processing. Valid values are 1-255, but values higher
4371
	than infinity has no further meaning. Default: 1.
4372

    
4373
	<tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
4374
	This option selects the mode for RIP to use on the interface. The
4375
	default is multicast mode for RIPv2 and broadcast mode for RIPv1.
4376
	RIPng always uses the multicast mode.
4377

    
4378
	<tag><label id="rip-iface-passive">passive <m/switch/</tag>
4379
	Passive interfaces receive routing updates but do not transmit any
4380
	messages. Default: no.
4381

    
4382
	<tag><label id="rip-iface-address">address <m/ip/</tag>
4383
	This option specifies a destination address used for multicast or
4384
	broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
4385
	(ff02::9) multicast address, or an appropriate broadcast address in the
4386
	broadcast mode.
4387

    
4388
	<tag><label id="rip-iface-port">port <m/number/</tag>
4389
	This option selects an UDP port to operate on, the default is the
4390
	official RIP (520) or RIPng (521) port.
4391

    
4392
	<tag><label id="rip-iface-version">version 1|2</tag>
4393
	This option selects the version of RIP used on the interface. For RIPv1,
4394
	automatic subnet aggregation is not implemented, only classful network
4395
	routes and host routes are propagated. Note that BIRD allows RIPv1 to be
4396
	configured with features that are defined for RIPv2 only, like
4397
	authentication or using multicast sockets. The default is RIPv2 for IPv4
4398
	RIP, the option is not supported for RIPng, as no further versions are
4399
	defined.
4400

    
4401
	<tag><label id="rip-iface-version-only">version only <m/switch/</tag>
4402
	Regardless of RIP version configured for the interface, BIRD accepts
4403
	incoming packets of any RIP version. This option restrict accepted
4404
	packets to the configured version. Default: no.
4405

    
4406
	<tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
4407
	Split horizon is a scheme for preventing routing loops. When split
4408
	horizon is active, routes are not regularly propagated back to the
4409
	interface from which they were received. They are either not propagated
4410
	back at all (plain split horizon) or propagated back with an infinity
4411
	metric (split horizon with poisoned reverse). Therefore, other routers
4412
	on the interface will not consider the router as a part of an
4413
	independent path to the destination of the route. Default: yes.
4414

    
4415
	<tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
4416
	When split horizon is active, this option specifies whether the poisoned
4417
	reverse variant (propagating routes back with an infinity metric) is
4418
	used. The poisoned reverse has some advantages in faster convergence,
4419
	but uses more network traffic. Default: yes.
4420

    
4421
	<tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
4422
	Received RIPv1 packets with non-zero values in reserved fields should
4423
	be discarded. This option specifies whether the check is performed or
4424
	such packets are just processed as usual. Default: yes.
4425

    
4426
	<tag><label id="rip-iface-update-time">update time <m/number/</tag>
4427
	Specifies the number of seconds between periodic updates. A lower number
4428
	will mean faster convergence but bigger network load. Default: 30.
4429

    
4430
	<tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
4431
	Specifies the time interval (in seconds) between the last received route
4432
	announcement and the route expiration. After that, the network is
4433
	considered unreachable, but still is propagated with infinity distance.
4434
	Default: 180.
4435

    
4436
	<tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
4437
	Specifies the time interval (in seconds) between the route expiration
4438
	and the removal of the unreachable network entry. The garbage interval,
4439
	when a route with infinity metric is propagated, is used for both
4440
	internal (after expiration) and external (after withdrawal) routes.
4441
	Default: 120.
4442

    
4443
	<tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
4444
	When ECMP (multipath) routes are allowed, this value specifies a
4445
	relative weight used for nexthops going through the iface. Valid
4446
	values are 1-256. Default value is 1.
4447

    
4448
	<tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
4449
	Selects authentication method to be used. <cf/none/ means that packets
4450
	are not authenticated at all, <cf/plaintext/ means that a plaintext
4451
	password is embedded into each packet, and <cf/cryptographic/ means that
4452
	packets are authenticated using some cryptographic hash function
4453
	selected by option <cf/algorithm/ for each key. The default
4454
	cryptographic algorithm for RIP keys is Keyed-MD5. If you set
4455
	authentication to not-none, it is a good idea to add <cf>password</cf>
4456
	section. Default: none.
4457

    
4458
	<tag><label id="rip-iface-pass">password "<m/text/"</tag>
4459
	Specifies a password used for authentication. See <ref id="proto-pass"
4460
	name="password"> common option for detailed description.
4461

    
4462
	<tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
4463
	TTL security is a feature that protects routing protocols from remote
4464
	spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
4465
	destined to neighbors. Because TTL is decremented when packets are
4466
	forwarded, it is non-trivial to spoof packets with TTL 255 from remote
4467
	locations.
4468

    
4469
	If this option is enabled, the router will send RIP packets with TTL 255
4470
	and drop received packets with TTL less than 255. If this option si set
4471
	to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
4472
	for received packets. Such setting does not offer protection, but offers
4473
	compatibility with neighbors regardless of whether they use ttl
4474
	security.
4475

    
4476
	For RIPng, TTL security is a standard behavior (required by <rfc
4477
	id="2080">) and therefore default value is yes. For IPv4 RIP, default
4478
	value is no.
4479

    
4480
	<tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
4481
	These options specify the ToS/DiffServ/Traffic class/Priority of the
4482
	outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
4483
	option for detailed description.
4484

    
4485
	<tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
4486
	This option specifies the size of buffers used for packet processing.
4487
	The buffer size should be bigger than maximal size of received packets.
4488
	The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
4489

    
4490
	<tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
4491
	This option specifies the maximum length of generated RIP packets. To
4492
	avoid IP fragmentation, it should not exceed the interface MTU value.
4493
	The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
4494

    
4495
	<tag><label id="rip-iface-check-link">check link <m/switch/</tag>
4496
	If set, the hardware link state (as reported by OS) is taken into
4497
	consideration. When the link disappears (e.g. an ethernet cable is
4498
	unplugged), neighbors are immediately considered unreachable and all
4499
	routes received from them are withdrawn. It is possible that some
4500
	hardware drivers or platforms do not implement this feature.
4501
	Default: yes.
4502
</descrip>
4503

    
4504
<sect1>Attributes
4505
<label id="rip-attr">
4506

    
4507
<p>RIP defines two route attributes:
4508

    
4509
<descrip>
4510
	<tag><label id="rta-rip-metric">int rip_metric</tag>
4511
	RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
4512
	from different RIP instances are available and all of them have the same
4513
	preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
4514
	non-RIP route is exported to RIP, the default metric is 1.
4515

    
4516
	<tag><label id="rta-rip-tag">int rip_tag</tag>
4517
	RIP route tag: a 16-bit number which can be used to carry additional
4518
	information with the route (for example, an originating AS number in
4519
	case of external routes). When a non-RIP route is exported to RIP, the
4520
	default tag is 0.
4521
</descrip>
4522

    
4523
<sect1>Example
4524
<label id="rip-exam">
4525

    
4526
<p><code>
4527
protocol rip {
4528
	ipv4 {
4529
		import all;
4530
		export all;
4531
	};
4532
	interface "eth*" {
4533
		metric 2;
4534
		port 1520;
4535
		mode multicast;
4536
		update time 12;
4537
		timeout time 60;
4538
		authentication cryptographic;
4539
		password "secret" { algorithm hmac sha256; };
4540
	};
4541
}
4542
</code>
4543

    
4544

    
4545
<sect>RPKI
4546
<label id="rpki">
4547

    
4548
<sect1>Introduction
4549

    
4550
<p>The Resource Public Key Infrastructure (RPKI) is mechanism for origin
4551
validation of BGP routes (RFC 6480). BIRD supports only so-called RPKI-based
4552
origin validation. There is implemented RPKI to Router (RPKI-RTR) protocol (RFC
4553
6810). It uses some of the RPKI data to allow a router to verify that the
4554
autonomous system announcing an IP address prefix is in fact authorized to do
4555
so. This is not crypto checked so can be violated. But it should prevent the
4556
vast majority of accidental hijackings on the Internet today, e.g. the famous
4557
Pakastani accidental announcement of YouTube's address space.
4558

    
4559
<p>The RPKI-RTR protocol receives and maintains a set of ROAs from a cache
4560
server (also called validator). You can validate routes (RFC 6483) using
4561
function <cf/roa_check()/ in filter and set it as import filter at the BGP
4562
protocol. BIRD should re-validate all of affected routes after RPKI update by
4563
RFC 6811, but we don't support it yet! You can use a BIRD's client command
4564
<cf>reload in <m/bgp_protocol_name/</cf> for manual call of revalidation of all
4565
routes.
4566

    
4567
<sect1>Supported transports
4568
<p>
4569
<itemize>
4570
        <item>Unprotected transport over TCP uses a port 323. The cache server
4571
        and BIRD router should be on the same trusted and controlled network
4572
        for security reasons.
4573
        <item>SSHv2 encrypted transport connection uses the normal SSH port
4574
        22.
4575
</itemize>
4576

    
4577
<sect1>Configuration
4578

    
4579
<p>We currently support just one cache server per protocol. However you can
4580
define more RPKI protocols generally.
4581

    
4582
<code>
4583
protocol rpki [&lt;name&gt;] {
4584
        roa4 { table &lt;tab&gt;; };
4585
        roa6 { table &lt;tab&gt;; };
4586
        remote &lt;ip&gt; | "&lt;domain&gt;" [port &lt;num&gt;];
4587
        port &lt;num&gt;;
4588
        refresh [keep] &lt;num&gt;;
4589
        retry [keep] &lt;num&gt;;
4590
        expire [keep] &lt;num&gt;;
4591
        transport tcp;
4592
        transport ssh {
4593
                bird private key "&lt;/path/to/id_rsa&gt;";
4594
                remote public key "&lt;/path/to/known_host&gt;";
4595
                user "&lt;name&gt;";
4596
        };
4597
}
4598
</code>
4599

    
4600
<p>Alse note that you have to specify the ROA channel. If you want to import
4601
only IPv4 prefixes you have to specify only roa4 channel. Similarly with IPv6
4602
prefixes only. If you want to fetch both IPv4 and even IPv6 ROAs you have to
4603
specify both channels.
4604

    
4605
<sect2>RPKI protocol options
4606
<p>
4607
<descrip>
4608
        <tag>remote <m/ip/ | "<m/hostname/" [port <m/num/]</tag> Specifies
4609
        a destination address of the cache server.  Can be specified by an IP
4610
        address or by full domain name string.  Only one cache can be specified
4611
        per protocol. This option is required.
4612

    
4613
        <tag>port <m/num/</tag> Specifies the port number. The default port
4614
        number is 323 for transport without any encryption and 22 for transport
4615
        with SSH encryption.
4616

    
4617
        <tag>refresh [keep] <m/num/</tag> Time period in seconds. Tells how
4618
        long to wait before next attempting to poll the cache using a Serial
4619
        Query or a Reset Query packet. Must be lower than 86400 seconds (one
4620
        day). Too low value can caused a false positive detection of
4621
        network connection problems.  A keyword <cf/keep/ suppresses updating
4622
        this value by a cache server.
4623
        Default: 3600 seconds
4624

    
4625
        <tag>retry [keep] <m/num/</tag> Time period in seconds between a failed
4626
        Serial/Reset Query and a next attempt.  Maximum allowed value is 7200
4627
        seconds (two hours). Too low value can caused a false positive
4628
        detection of network connection problems.  A keyword <cf/keep/
4629
        suppresses updating this value by a cache server.
4630
        Default: 600 seconds
4631

    
4632
        <tag>expire [keep] <m/num/</tag> Time period in seconds. Received
4633
        records are deleted if the client was unable to successfully refresh
4634
        data for this time period.  Must be in range from 600 seconds (ten
4635
        minutes) to 172800 seconds (two days).  A keyword <cf/keep/
4636
        suppresses updating this value by a cache server.
4637
        Default: 7200 seconds
4638

    
4639
        <tag>transport tcp</tag> Unprotected transport over TCP. It's a default
4640
        transport. Should be used only on secure private networks.
4641
        Default: tcp
4642

    
4643
        <tag>transport ssh { <m/SSH transport options.../ }</tag> It enables a
4644
        SSHv2 transport encryption. Cannot be combined with a TCP transport.
4645
        Default: off
4646
</descrip>
4647

    
4648
<sect3>SSH transport options
4649
<p>
4650
<descrip>
4651
	<tag>bird private key "<m>/path/to/id_rsa</m>"</tag>
4652
	A path to the BIRD's private SSH key for authentication.
4653
	It can be a <cf><m>id_rsa</m></cf> file.
4654

    
4655
	<tag>remote public key "<m>/path/to/known_host</m>"</tag>
4656
	A path to the cache's public SSH key for verification identity
4657
	of the cache server. It could be a path to <cf><m>known_host</m></cf> file.
4658

    
4659
	<tag>user "<m/name/"</tag>
4660
	A SSH user name for authentication. This option is a required.
4661
</descrip>
4662

    
4663
<sect1>Examples
4664
<sect2>BGP origin validation
4665
<p>Policy: Don't import <cf/ROA_INVALID/ routes.
4666
<code>
4667
roa4 table r4;
4668
roa6 table r6;
4669

    
4670
protocol rpki {
4671
	debug all;
4672

    
4673
	roa4 { table r4; };
4674
	roa6 { table r6; };
4675

    
4676
	# Please, do not use rpki-validator.realmv6.org in production
4677
	remote "rpki-validator.realmv6.org" port 8282;
4678

    
4679
	retry keep 5;
4680
	refresh keep 30;
4681
	expire 600;
4682
}
4683

    
4684
filter peer_in_v4 {
4685
	if (roa_check(r4, net, bgp_path.last) = ROA_INVALID) then
4686
	{
4687
		print "Ignore invalid ROA ", net, " for ASN ", bgp_path.last;
4688
		reject;
4689
	}
4690
	accept;
4691
}
4692

    
4693
protocol bgp {
4694
	debug all;
4695
	local as 65000;
4696
	neighbor 192.168.2.1 as 65001;
4697
	ipv4 {
4698
		import filter peer_in_v4;
4699
		export none;
4700
	};
4701
}
4702
</code>
4703

    
4704
<sect2>SSHv2 transport encryption
4705
<p>
4706
<code>
4707
roa4 table r4;
4708
roa6 table r6;
4709

    
4710
protocol rpki {
4711
	debug all;
4712

    
4713
	roa4 { table r4; };
4714
	roa6 { table r6; };
4715

    
4716
	remote 127.0.0.1 port 2345;
4717
	transport ssh {
4718
		bird private key "/home/birdgeek/.ssh/id_rsa";
4719
		remote public key "/home/birdgeek/.ssh/known_hosts";
4720
		user "birdgeek";
4721
	};
4722

    
4723
	# Default interval values
4724
}
4725
</code>
4726

    
4727

    
4728
<sect>Static
4729
<label id="static">
4730

    
4731
<p>The Static protocol doesn't communicate with other routers in the network,
4732
but instead it allows you to define routes manually. This is often used for
4733
specifying how to forward packets to parts of the network which don't use
4734
dynamic routing at all and also for defining sink routes (i.e., those telling to
4735
return packets as undeliverable if they are in your IP block, you don't have any
4736
specific destination for them and you don't want to send them out through the
4737
default route to prevent routing loops).
4738

    
4739
<p>There are three classes of definitions in Static protocol configuration --
4740
global options, static route definitions, and per-route options. Usually, the
4741
definition of the protocol contains mainly a list of static routes.
4742
Static routes have no specific attributes.
4743

    
4744
<p>Global options:
4745

    
4746
<descrip>
4747
	<tag><label id="static-check-link">check link <m/switch/</tag>
4748
	If set, hardware link states of network interfaces are taken into
4749
	consideration.  When link disappears (e.g. ethernet cable is unplugged),
4750
	static routes directing to that interface are removed. It is possible
4751
	that some hardware drivers or platforms do not implement this feature.
4752
	Default: off.
4753

    
4754
	<tag><label id="static-igp-table">igp table <m/name/</tag>
4755
	Specifies a table that is used for route table lookups of recursive
4756
	routes. Default: the same table as the protocol is connected to.
4757
</descrip>
4758

    
4759
<p>Route definitions (each may also contain a block of per-route options):
4760

    
4761
<sect1>Regular routes; MPLS switching rules
4762

    
4763
<p>There exist several types of routes; keep in mind that <m/prefix/ syntax is
4764
<ref id="type-prefix" name="dependent on network type">.
4765

    
4766
<descrip>
4767
	<tag>route <m/prefix/ via <m/ip/|<m/"interface"/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4768
	Next hop routes may bear one or more <ref id="route-next-hop" name="next hops">.
4769
	Every next hop is preceded by <cf/via/ and configured as shown.
4770

    
4771
	<tag>route <m/prefix/ recursive <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4772
	Recursive nexthop resolves the given IP in the configured IGP table and
4773
	uses that route's next hop. The MPLS stacks are concatenated; on top is
4774
	the IGP's nexthop stack and on bottom is this route's stack.
4775

    
4776
	<tag>route <m/prefix/ blackhole|unreachable|prohibit</tag>
4777
	Special routes specifying to silently drop the packet, return it as
4778
	unreachable or return it as administratively prohibited. First two
4779
	targets are also known as <cf/drop/ and <cf/reject/.
4780
</descrip>
4781

    
4782
<p>When the particular destination is not available (the interface is down or
4783
the next hop of the route is not a neighbor at the moment), Static just
4784
uninstalls the route from the table it is connected to and adds it again as soon
4785
as the destination becomes adjacent again.
4786

    
4787
<sect1>Route Origin Authorization
4788

    
4789
<p>The ROA config is just <cf>route <m/prefix/ max <m/int/ as <m/int/</cf> with no nexthop.
4790

    
4791
<sect1>Flowspec
4792
<label id="flowspec-network-type">
4793

    
4794
<p>The flow specification are rules for routers and firewalls for filtering
4795
purpose. It is described by <rfc id="5575">. There are 3 types of arguments:
4796
<m/inet4/ or <m/inet6/ prefixes, bitmasks matching expressions and numbers
4797
matching expressions.
4798

    
4799
Bitmasks matching is written using <m/value/<cf>/</cf><m/mask/ or
4800
<cf/!/<m/value/<cf>/</cf><m/mask/ pairs. It means that <cf/(/<m/data/ <cf/&/
4801
<m/mask/<cf/)/ is or is not equal to <m/value/.
4802

    
4803
Numbers matching is a matching sequence of numbers and ranges separeted by a
4804
commas (<cf/,/) (e.g. <cf/10,20,30/). Ranges can be written using double dots
4805
<cf/../ notation (e.g. <cf/80..90,120..124/). An alternative notation are
4806
sequence of one or more pairs of relational operators and values separated by
4807
logical operators <cf/&&/ or <cf/||/. Allowed relational operators are <cf/=/,
4808
<cf/!=/, <cf/</, <cf/<=/, <cf/>/, <cf/>=/, <cf/true/ and <cf/false/.
4809

    
4810
<sect2>IPv4 Flowspec
4811

    
4812
<p><descrip>
4813
	<tag><label id="flow-dst">dst <m/inet4/</tag>
4814
	Set a matching destination prefix (e.g. <cf>dst 192.168.0.0/16</cf>).
4815
	Only this option is mandatory in IPv4 Flowspec.
4816

    
4817
	<tag><label id="flow-src">src <m/inet4/</tag>
4818
	Set a matching source prefix (e.g. <cf>src 10.0.0.0/8</cf>).
4819

    
4820
	<tag><label id="flow-proto">proto <m/numbers-match/</tag>
4821
	Set a matching IP protocol numbers (e.g.  <cf/proto 6/).
4822

    
4823
	<tag><label id="flow-port">port <m/numbers-match/</tag>
4824
	Set a matching source or destination TCP/UDP port numbers (e.g.
4825
	<cf>port 1..1023,1194,3306</cf>).
4826

    
4827
	<tag><label id="flow-dport">dport <m/numbers-match/</tag>
4828
	Set a mating destination port numbers (e.g. <cf>dport 49151</cf>).
4829

    
4830
	<tag><label id="flow-sport">sport <m/numbers-match/</tag>
4831
	Set a matching source port numbers (e.g. <cf>sport = 0</cf>).
4832

    
4833
	<tag><label id="flow-icmp-type">icmp type <m/numbers-match/</tag>
4834
	Set a matching type field number of an ICMP packet (e.g. <cf>icmp type
4835
	3</cf>)
4836

    
4837
	<tag><label id="flow-icmp-code">icmp code <m/numbers-match/</tag>
4838
	Set a matching code field number of an ICMP packet (e.g. <cf>icmp code
4839
	1</cf>)
4840

    
4841
	<tag><label id="flow-tcp-flags">tcp flags <m/bitmask-match/</tag>
4842
	Set a matching bitmask for TCP header flags (aka control bits) (e.g.
4843
	<cf>tcp flags 0x03/0x0f;</cf>). The maximum length of mask is 12 bits
4844
	(0xfff).
4845

    
4846
	<tag><label id="flow-length">length <m/numbers-match/</tag>
4847
	Set a matching packet length (e.g. <cf>length > 1500;</cf>)
4848

    
4849
	<tag><label id="flow-dscp">dscp <m/numbers-match/</tag>
4850
	Set a matching DiffServ Code Point number (e.g. <cf>length > 1500;</cf>).
4851

    
4852
	<tag><label id="flow-fragment">fragment <m/fragmentation-type/</tag>
4853
	Set a matching type of packet fragmentation. Allowed fragmentation
4854
	types are <cf/dont_fragment/, <cf/is_fragment/, <cf/first_fragment/,
4855
	<cf/last_fragment/ (e.g. <cf>fragment is_fragment &&
4856
	!dont_fragment</cf>).
4857
</descrip>
4858

    
4859
<p><code>
4860
protocol static {
4861
	flow4;
4862

    
4863
	route flow4 {
4864
		dst 10.0.0.0/8;
4865
		port > 24 && < 30 || 40..50,60..70,80 && >= 90;
4866
		tcp flags 0x03/0x0f;
4867
		length > 1024;
4868
		dscp = 63;
4869
		fragment dont_fragment, is_fragment || !first_fragment;
4870
	};
4871
}
4872
</code>
4873

    
4874
<sect2>Differences for IPv6 Flowspec
4875

    
4876
<p>Flowspec IPv6 are same as Flowspec IPv4 with a few exceptions.
4877
<itemize>
4878
	<item>Prefixes <m/inet6/ can be specified not only with prefix length,
4879
	but with prefix <cf/offset/ <m/num/ too (e.g.
4880
	<cf>::1234:5678:9800:0000/101 offset 64</cf>). Offset means to don't
4881
	care of <m/num/ first bits.
4882
	<item>IPv6 Flowspec hasn't mandatory any flowspec component.
4883
	<item>In IPv6 packets, there is a matching the last next header value
4884
	for a matching IP protocol number (e.g. <cf>next header 6</cf>).
4885
	<item>It is not possible to set <cf>dont_fragment</cf> as a type of
4886
	packet fragmentation.
4887
</itemize>
4888

    
4889
<p><descrip>
4890
	<tag><label id="flow6-dst">dst <m/inet6/ [offset <m/num/]</tag>
4891
	Set a matching destination IPv6 prefix (e.g. <cf>dst
4892
	::1c77:3769:27ad:a11a/128 offset 64</cf>).
4893

    
4894
	<tag><label id="flow6-src">src <m/inet6/ [offset <m/num/]</tag>
4895
	Set a matching source IPv6 prefix (e.g. <cf>src fe80::/64</cf>).
4896

    
4897
	<tag><label id="flow6-next-header">next header <m/numbers-match/</tag>
4898
	Set a matching IP protocol numbers (e.g. <cf>next header != 6</cf>).
4899

    
4900
	<tag><label id="flow6-label">label <m/bitmask-match/</tag>
4901
	Set a 20-bit bitmask for matching Flow Label field in IPv6 packets
4902
	(e.g. <cf>label 0x8e5/0x8e5</cf>).
4903
</descrip>
4904

    
4905
<p><code>
4906
protocol static {
4907
	flow6 { table myflow6; };
4908

    
4909
	route flow6 {
4910
		dst fec0:1122:3344:5566:7788:99aa:bbcc:ddee/128;
4911
		src 0000:0000:0000:0001:1234:5678:9800:0000/101 offset 63;
4912
		next header = 23;
4913
		sport > 24 && < 30 || = 40 || 50,60,70..80;
4914
		dport = 50;
4915
		tcp flags 0x03/0x0f, !0/0xff || 0x33/0x33;
4916
		fragment !is_fragment || !first_fragment;
4917
		label 0xaaaa/0xaaaa && 0x33/0x33;
4918
	};
4919
}
4920
</code>
4921

    
4922
<sect1>Per-route options
4923
<p>
4924
<descrip>
4925
	<tag><label id="static-route-bfd">bfd <m/switch/</tag>
4926
	The Static protocol could use BFD protocol for next hop liveness
4927
	detection. If enabled, a BFD session to the route next hop is created
4928
	and the static route is BFD-controlled -- the static route is announced
4929
	only if the next hop liveness is confirmed by BFD. If the BFD session
4930
	fails, the static route is removed. Note that this is a bit different
4931
	compared to other protocols, which may use BFD as an advisory mechanism
4932
	for fast failure detection but ignores it if a BFD session is not even
4933
	established.
4934

    
4935
	This option can be used for static routes with a direct next hop, or
4936
	also for for individual next hops in a static multipath route (see
4937
	above). Note that BFD protocol also has to be configured, see
4938
	<ref id="bfd" name="BFD"> section for details. Default value is no.
4939

    
4940
	<tag><label id="static-route-filter"><m/filter expression/</tag>
4941
	This is a special option that allows filter expressions to be configured
4942
	on per-route basis. Can be used multiple times. These expressions are
4943
	evaluated when the route is originated, similarly to the import filter
4944
	of the static protocol. This is especially useful for configuring route
4945
	attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
4946
	exported to the OSPF protocol.
4947
</descrip>
4948

    
4949
<sect1>Example static config
4950

    
4951
<p><code>
4952
protocol static {
4953
	ipv4 { table testable; };	# Connect to a non-default routing table
4954
	check link;			# Advertise routes only if link is up
4955
	route 0.0.0.0/0 via 198.51.100.130; # Default route
4956
	route 10.0.0.0/8		# Multipath route
4957
		via 198.51.100.10 weight 2
4958
		via 198.51.100.20 bfd	# BFD-controlled next hop
4959
		via 192.0.2.1;
4960
	route 203.0.113.0/24 unreachable; # Sink route
4961
	route 10.2.0.0/24 via "arc0";	# Secondary network
4962
	route 192.168.10.0/24 via 198.51.100.100 {
4963
		ospf_metric1 = 20;	# Set extended attribute
4964
	}
4965
	route 192.168.10.0/24 via 198.51.100.100 {
4966
		ospf_metric2 = 100;	# Set extended attribute
4967
		ospf_tag = 2;		# Set extended attribute
4968
		bfd;			# BFD-controlled route
4969
	}
4970
}
4971
</code>
4972

    
4973

    
4974
<chapt>Conclusions
4975
<label id="conclusion">
4976

    
4977
<sect>Future work
4978
<label id="future-work">
4979

    
4980
<p>Although BIRD supports all the commonly used routing protocols, there are
4981
still some features which would surely deserve to be implemented in future
4982
versions of BIRD:
4983

    
4984
<itemize>
4985
<item>Opaque LSA's
4986
<item>Route aggregation and flap dampening
4987
<item>Multicast routing protocols
4988
<item>Ports to other systems
4989
</itemize>
4990

    
4991

    
4992
<sect>Getting more help
4993
<label id="help">
4994

    
4995
<p>If you use BIRD, you're welcome to join the bird-users mailing list
4996
(<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
4997
where you can share your experiences with the other users and consult
4998
your problems with the authors. To subscribe to the list, visit
4999
<HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
5000
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
5001

    
5002
<p>BIRD is a relatively young system and it probably contains some bugs. You can
5003
report any problems to the bird-users list and the authors will be glad to solve
5004
them, but before you do so, please make sure you have read the available
5005
documentation and that you are running the latest version (available at
5006
<HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
5007
(Of course, a patch which fixes the bug is always welcome as an attachment.)
5008

    
5009
<p>If you want to understand what is going inside, Internet standards are a good
5010
and interesting reading. You can get them from
5011
<HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
5012
nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
5013
name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
5014

    
5015
<p><it/Good luck!/
5016

    
5017
</book>
5018

    
5019
<!--
5020
LocalWords:  GPL IPv GateD BGPv RIPv OSPFv Linux sgml html dvi sgmltools Pavel
5021
LocalWords:  linuxdoc dtd descrip config conf syslog stderr auth ospf bgp Mbps
5022
LocalWords:  router's eval expr num birdc ctl UNIX if's enums bool int ip GCC
5023
LocalWords:  len ipaddress pxlen netmask enum bgppath bgpmask clist gw md eth
5024
LocalWords:  RTS printn quitbird iBGP AS'es eBGP RFC multiprotocol IGP Machek
5025
LocalWords:  EGP misconfigurations keepalive pref aggr aggregator BIRD's RTC
5026
LocalWords:  OS'es AS's multicast nolisten misconfigured UID blackhole MRTD MTU
5027
LocalWords:  uninstalls ethernets IP binutils ANYCAST anycast dest RTD ICMP rfc
5028
LocalWords:  compat multicasts nonbroadcast pointopoint loopback sym stats
5029
LocalWords:  Perl SIGHUP dd mm yy HH MM SS EXT IA UNICAST multihop Discriminator txt
5030
LocalWords:  proto wildcard Ondrej Filip
5031
-->