2 @c This is part of the Quagga Manual.
3 @c @value{COPYRIGHT_STR}
5 @c Copyright @copyright{} 2015 Hewlett Packard Enterprise Development LP
6 @c See file quagga.texi for copying conditions.
10 @acronym{BGP} stands for a Border Gateway Protocol. The lastest BGP version
11 is 4. It is referred as BGP-4. BGP-4 is one of the Exterior Gateway
12 Protocols and de-fact standard of Inter Domain routing protocol.
13 BGP-4 is described in @cite{RFC1771, A Border Gateway Protocol
16 Many extensions have been added to @cite{RFC1771}. @cite{RFC2858,
17 Multiprotocol Extensions for BGP-4} provides multiprotocol support to
27 * BGP Address Family::
29 * BGP Communities Attribute::
30 * BGP Extended Communities Attribute::
31 * Displaying BGP routes::
32 * Capability Negotiation::
35 * How to set up a 6-Bone connection::
36 * Dump BGP packets and table::
37 * BGP Configuration Examples::
43 Default configuration file of @command{bgpd} is @file{bgpd.conf}.
44 @command{bgpd} searches the current directory first then
45 @value{INSTALL_PREFIX_ETC}/bgpd.conf. All of bgpd's command must be
46 configured in @file{bgpd.conf}.
48 @command{bgpd} specific invocation options are described below. Common
49 options may also be specified (@pxref{Common Invocation Options}).
53 @itemx --bgp_port=@var{PORT}
54 Set the bgp protocol's port number.
58 When program terminates, retain BGP routes added by zebra.
62 Specify a specific IP address for bgpd to listen on, rather than its
63 default of INADDR_ANY / IN6ADDR_ANY. This can be useful to constrain bgpd
64 to an internal address, or to run multiple bgpd processes on one host.
71 First of all you must configure BGP router with @command{router bgp}
72 command. To configure BGP router, you need AS number. AS number is an
73 identification of autonomous system. BGP protocol uses the AS number
74 for detecting whether the BGP connection is internal one or external one.
76 @deffn Command {router bgp @var{asn}} {}
77 Enable a BGP protocol process with the specified @var{asn}. After
78 this statement you can input any @code{BGP Commands}. You can not
79 create different BGP process under different @var{asn} without
80 specifying @code{multiple-instance} (@pxref{Multiple instance}).
83 @deffn Command {no router bgp @var{asn}} {}
84 Destroy a BGP protocol process with the specified @var{asn}.
87 @deffn {BGP} {bgp router-id @var{A.B.C.D}} {}
88 This command specifies the router-ID. If @command{bgpd} connects to @command{zebra} it gets
89 interface and address information. In that case default router ID value
90 is selected as the largest IP Address of the interfaces. When
91 @code{router zebra} is not enabled @command{bgpd} can't get interface information
92 so @code{router-id} is set to 0.0.0.0. So please set router-id by hand.
97 * BGP decision process::
98 * BGP route flap dampening::
102 @subsection BGP distance
104 @deffn {BGP} {distance bgp <1-255> <1-255> <1-255>} {}
105 This command change distance value of BGP. Each argument is distance
106 value for external routes, internal routes and local routes.
109 @deffn {BGP} {distance <1-255> @var{A.B.C.D/M}} {}
110 @deffnx {BGP} {distance <1-255> @var{A.B.C.D/M} @var{word}} {}
111 This command set distance value to
114 @node BGP decision process
115 @subsection BGP decision process
117 The decision process Quagga BGP uses to select routes is as follows:
120 @item 1. Weight check
121 prefer higher local weight routes to lower routes.
123 @item 2. Local preference check
124 prefer higher local preference routes to lower.
126 @item 3. Local route check
127 Prefer local routes (statics, aggregates, redistributed) to received routes.
129 @item 4. AS path length check
130 Prefer shortest hop-count AS_PATHs.
132 @item 5. Origin check
133 Prefer the lowest origin type route. That is, prefer IGP origin routes to
134 EGP, to Incomplete routes.
137 Where routes with a MED were received from the same AS,
138 prefer the route with the lowest MED. @xref{BGP MED}.
140 @item 7. External check
141 Prefer the route received from an external, eBGP peer
142 over routes received from other types of peers.
144 @item 8. IGP cost check
145 Prefer the route with the lower IGP cost.
147 @item 9. Multi-path check
148 If multi-pathing is enabled, then check whether
149 the routes not yet distinguished in preference may be considered equal. If
150 @ref{bgp bestpath as-path multipath-relax} is set, all such routes are
151 considered equal, otherwise routes received via iBGP with identical AS_PATHs
152 or routes received from eBGP neighbours in the same AS are considered equal.
154 @item 10 Already-selected external check
156 Where both routes were received from eBGP peers, then prefer the route which
157 is already selected. Note that this check is not applied if @ref{bgp
158 bestpath compare-routerid} is configured. This check can prevent some cases
161 @item 11. Router-ID check
162 Prefer the route with the lowest @w{router-ID}. If the
163 route has an @w{ORIGINATOR_ID} attribute, through iBGP reflection, then that
164 router ID is used, otherwise the @w{router-ID} of the peer the route was
165 received from is used.
167 @item 12. Cluster-List length check
168 The route with the shortest cluster-list
169 length is used. The cluster-list reflects the iBGP reflection path the
172 @item 13. Peer address
173 Prefer the route received from the peer with the higher
174 transport layer address, as a last-resort tie-breaker.
178 @deffn {BGP} {bgp bestpath as-path confed} {}
179 This command specifies that the length of confederation path sets and
180 sequences should should be taken into account during the BGP best path
184 @deffn {BGP} {bgp bestpath as-path multipath-relax} {}
185 @anchor{bgp bestpath as-path multipath-relax}
186 This command specifies that BGP decision process should consider paths
187 of equal AS_PATH length candidates for multipath computation. Without
188 the knob, the entire AS_PATH must match for multipath computation.
191 @deffn {BGP} {bgp bestpath compare-routerid} {}
192 @anchor{bgp bestpath compare-routerid}
194 Ensure that when comparing routes where both are equal on most metrics,
195 including local-pref, AS_PATH length, IGP cost, MED, that the tie is broken
198 If this option is enabled, then the already-selected check, where
199 already selected eBGP routes are preferred, is skipped.
201 If a route has an @w{ORIGINATOR_ID} attribute because it has been reflected,
202 that @w{ORIGINATOR_ID} will be used. Otherwise, the router-ID of the peer the
203 route was received from will be used.
205 The advantage of this is that the route-selection (at this point) will be
206 more deterministic. The disadvantage is that a few or even one lowest-ID
207 router may attract all trafic to otherwise-equal paths because of this
208 check. It may increase the possibility of MED or IGP oscillation, unless
209 other measures were taken to avoid these. The exact behaviour will be
210 sensitive to the iBGP and reflection topology.
215 @node BGP route flap dampening
216 @subsection BGP route flap dampening
218 @deffn {BGP} {bgp dampening @var{<1-45>} @var{<1-20000>} @var{<1-20000>} @var{<1-255>}} {}
219 This command enables BGP route-flap dampening and specifies dampening parameters.
222 @item @asis{half-life}
223 Half-life time for the penalty
224 @item @asis{reuse-threshold}
225 Value to start reusing a route
226 @item @asis{suppress-threshold}
227 Value to start suppressing a route
228 @item @asis{max-suppress}
229 Maximum duration to suppress a stable route
232 The route-flap damping algorithm is compatible with @cite{RFC2439}. The use of this command
233 is not recommended nowadays, see @uref{http://www.ripe.net/ripe/docs/ripe-378,,RIPE-378}.
239 The BGP MED (Multi_Exit_Discriminator) attribute has properties which can
240 cause subtle convergence problems in BGP. These properties and problems
241 have proven to be hard to understand, at least historically, and may still
242 not be widely understood. The following attempts to collect together and
243 present what is known about MED, to help operators and Quagga users in
244 designing and configuring their networks.
246 The BGP @acronym{MED, Multi_Exit_Discriminator} attribute is intended to
247 allow one AS to indicate its preferences for its ingress points to another
248 AS. The MED attribute will not be propagated on to another AS by the
249 receiving AS - it is `non-transitive' in the BGP sense.
251 E.g., if AS X and AS Y have 2 different BGP peering points, then AS X
252 might set a MED of 100 on routes advertised at one and a MED of 200 at the
253 other. When AS Y selects between otherwise equal routes to or via
254 AS X, AS Y should prefer to take the path via the lower MED peering of 100 with
255 AS X. Setting the MED allows an AS to influence the routing taken to it
256 within another, neighbouring AS.
258 In this use of MED it is not really meaningful to compare the MED value on
259 routes where the next AS on the paths differs. E.g., if AS Y also had a
260 route for some destination via AS Z in addition to the routes from AS X, and
261 AS Z had also set a MED, it wouldn't make sense for AS Y to compare AS Z's
262 MED values to those of AS X. The MED values have been set by different
263 administrators, with different frames of reference.
265 The default behaviour of BGP therefore is to not compare MED values across
266 routes received from different neighbouring ASes. In Quagga this is done by
267 comparing the neighbouring, left-most AS in the received AS_PATHs of the
268 routes and only comparing MED if those are the same.
270 @c TeXInfo uses the old, non-UTF-8 capable, pdftex, and so
271 @c doesn't render TeX the unicode precedes character correctly in PDF, etc.
272 @c Using a TeX code on the other hand doesn't work for non-TeX outputs
273 @c (plaintext, e.g.). So, use an output-conditional macro.
287 Unfortunately, this behaviour of MED, of sometimes being compared across
288 routes and sometimes not, depending on the properties of those other routes,
289 means MED can cause the order of preference over all the routes to be
290 undefined. That is, given routes A, B, and C, if A is preferred to B, and B
291 is preferred to C, then a well-defined order should mean the preference is
292 transitive (in the sense of orders @footnote{For some set of objects to have
293 an order, there @emph{must} be some binary ordering relation that is defined
294 for @emph{every} combination of those objects, and that relation @emph{must}
295 be transitive. I.e.@:, if the relation operator is @mprec{}, and if
296 a @mprec{} b and b @mprec{} c then that relation must carry over
297 and it @emph{must} be that a @mprec{} c for the objects to have an
298 order. The ordering relation may allow for equality, i.e.
299 a @mprec{} b and b @mprec{} a may both be true amd imply that
300 a and b are equal in the order and not distinguished by it, in
301 which case the set has a partial order. Otherwise, if there is an order,
302 all the objects have a distinct place in the order and the set has a total
303 order.}) and that A would be preferred to C.
305 However, when MED is involved this need not be the case. With MED it is
306 possible that C is actually preferred over A. So A is preferred to B, B is
307 preferred to C, but C is preferred to A. This can be true even where BGP
308 defines a deterministic ``most preferred'' route out of the full set of
309 A,B,C. With MED, for any given set of routes there may be a
310 deterministically preferred route, but there need not be any way to arrange
311 them into any order of preference. With unmodified MED, the order of
312 preference of routes literally becomes undefined.
314 That MED can induce non-transitive preferences over routes can cause issues.
315 Firstly, it may be perceived to cause routing table churn locally at
316 speakers; secondly, and more seriously, it may cause routing instability in
317 iBGP topologies, where sets of speakers continually oscillate between
320 The first issue arises from how speakers often implement routing decisions.
321 Though BGP defines a selection process that will deterministically select
322 the same route as best at any given speaker, even with MED, that process
323 requires evaluating all routes together. For performance and ease of
324 implementation reasons, many implementations evaluate route preferences in a
325 pair-wise fashion instead. Given there is no well-defined order when MED is
326 involved, the best route that will be chosen becomes subject to
327 implementation details, such as the order the routes are stored in. That
328 may be (locally) non-deterministic, e.g.@: it may be the order the routes
331 This indeterminism may be considered undesirable, though it need not cause
332 problems. It may mean additional routing churn is perceived, as sometimes
333 more updates may be produced than at other times in reaction to some event .
335 This first issue can be fixed with a more deterministic route selection that
336 ensures routes are ordered by the neighbouring AS during selection.
337 @xref{bgp deterministic-med}. This may reduce the number of updates as
338 routes are received, and may in some cases reduce routing churn. Though, it
339 could equally deterministically produce the largest possible set of updates
340 in response to the most common sequence of received updates.
342 A deterministic order of evaluation tends to imply an additional overhead of
343 sorting over any set of n routes to a destination. The implementation of
344 deterministic MED in Quagga scales significantly worse than most sorting
345 algorithms at present, with the number of paths to a given destination.
346 That number is often low enough to not cause any issues, but where there are
347 many paths, the deterministic comparison may quickly become increasingly
348 expensive in terms of CPU.
350 Deterministic local evaluation can @emph{not} fix the second, more major,
351 issue of MED however. Which is that the non-transitive preference of routes
352 MED can cause may lead to routing instability or oscillation across multiple
353 speakers in iBGP topologies. This can occur with full-mesh iBGP, but is
354 particularly problematic in non-full-mesh iBGP topologies that further
355 reduce the routing information known to each speaker. This has primarily
356 been documented with iBGP route-reflection topologies. However, any
357 route-hiding technologies potentially could also exacerbate oscillation with
360 This second issue occurs where speakers each have only a subset of routes,
361 and there are cycles in the preferences between different combinations of
362 routes - as the undefined order of preference of MED allows - and the routes
363 are distributed in a way that causes the BGP speakers to 'chase' those
364 cycles. This can occur even if all speakers use a deterministic order of
365 evaluation in route selection.
367 E.g., speaker 4 in AS A might receive a route from speaker 2 in AS X, and
368 from speaker 3 in AS Y; while speaker 5 in AS A might receive that route
369 from speaker 1 in AS Y. AS Y might set a MED of 200 at speaker 1, and 100
370 at speaker 3. I.e, using ASN:ID:MED to label the speakers:
375 X:2------|--A:4-------A:5--|-Y:1:200
381 Assuming all other metrics are equal (AS_PATH, ORIGIN, 0 IGP costs), then
382 based on the RFC4271 decision process speaker 4 will choose X:2 over
383 Y:3:100, based on the lower ID of 2. Speaker 4 advertises X:2 to speaker 5.
384 Speaker 5 will continue to prefer Y:1:200 based on the ID, and advertise
385 this to speaker 4. Speaker 4 will now have the full set of routes, and the
386 Y:1:200 it receives from 5 will beat X:2, but when speaker 4 compares
387 Y:1:200 to Y:3:100 the MED check now becomes active as the ASes match, and
388 now Y:3:100 is preferred. Speaker 4 therefore now advertises Y:3:100 to 5,
389 which will also agrees that Y:3:100 is preferred to Y:1:200, and so
390 withdraws the latter route from 4. Speaker 4 now has only X:2 and Y:3:100,
391 and X:2 beats Y:3:100, and so speaker 4 implicitly updates its route to
392 speaker 5 to X:2. Speaker 5 sees that Y:1:200 beats X:2 based on the ID,
393 and advertises Y:1:200 to speaker 4, and the cycle continues.
395 The root cause is the lack of a clear order of preference caused by how MED
396 sometimes is and sometimes is not compared, leading to this cycle in the
397 preferences between the routes:
401 /---> X:2 ---beats---> Y:3:100 --\
404 \---beats--- Y:1:200 <---beats---/
408 This particular type of oscillation in full-mesh iBGP topologies can be
409 avoided by speakers preferring already selected, external routes rather than
410 choosing to update to new a route based on a post-MED metric (e.g.
411 router-ID), at the cost of a non-deterministic selection process. Quagga
412 implements this, as do many other implementations, so long as it is not
413 overridden by setting @ref{bgp bestpath compare-routerid}, and see also
414 @ref{BGP decision process}, .
416 However, more complex and insidious cycles of oscillation are possible with
417 iBGP route-reflection, which are not so easily avoided. These have been
418 documented in various places. See, e.g., @cite{McPherson, D. and Gill, V.
419 and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation
420 Condition", IETF RFC3345}, and @cite{Flavel, A. and M. Roughan, "Stable
421 and flexible iBGP", ACM SIGCOMM 2009}, and @cite{Griffin, T. and G. Wilfong,
422 "On the correctness of IBGP configuration", ACM SIGCOMM 2002} for concrete
423 examples and further references.
425 There is as of this writing @emph{no} known way to use MED for its original
426 purpose; @emph{and} reduce routing information in iBGP topologies;
427 @emph{and} be sure to avoid the instability problems of MED due the
428 non-transitive routing preferences it can induce; in general on arbitrary
431 There may be iBGP topology specific ways to reduce the instability risks,
432 even while using MED, e.g.@: by constraining the reflection topology and by
433 tuning IGP costs between route-reflector clusters, see RFC3345 for details.
434 In the near future, the Add-Path extension to BGP may also solve MED
435 oscillation while still allowing MED to be used as intended, by distributing
436 "best-paths per neighbour AS". This would be at the cost of distributing at
437 least as many routes to all speakers as a full-mesh iBGP would, if not more,
438 while also imposing similar CPU overheads as the "Deterministic MED" feature
439 at each Add-Path reflector.
441 More generally, the instability problems that MED can introduce on more
442 complex, non-full-mesh, iBGP topologies may be avoided either by:
447 Setting @ref{bgp always-compare-med}, however this allows MED to be compared
448 across values set by different neighbour ASes, which may not produce
449 coherent desirable results, of itself.
452 Effectively ignoring MED by setting MED to the same value (e.g.@: 0) using
453 @ref{routemap set metric} on all received routes, in combination with
454 setting @ref{bgp always-compare-med} on all speakers. This is the simplest
455 and most performant way to avoid MED oscillation issues, where an AS is happy
456 not to allow neighbours to inject this problematic metric.
460 As MED is evaluated after the AS_PATH length check, another possible use for
461 MED is for intra-AS steering of routes with equal AS_PATH length, as an
462 extension of the last case above. As MED is evaluated before IGP metric,
463 this can allow cold-potato routing to be implemented to send traffic to
464 preferred hand-offs with neighbours, rather than the closest hand-off
465 according to the IGP metric.
467 Note that even if action is taken to address the MED non-transitivity
468 issues, other oscillations may still be possible. E.g., on IGP cost if
469 iBGP and IGP topologies are at cross-purposes with each other - see the
470 Flavel and Roughan paper above for an example. Hence the guideline that the
471 iBGP topology should follow the IGP topology.
473 @deffn {BGP} {bgp deterministic-med} {}
474 @anchor{bgp deterministic-med}
476 Carry out route-selection in way that produces deterministic answers
477 locally, even in the face of MED and the lack of a well-defined order of
478 preference it can induce on routes. Without this option the preferred route
479 with MED may be determined largely by the order that routes were received
482 Setting this option will have a performance cost that may be noticeable when
483 there are many routes for each destination. Currently in Quagga it is
484 implemented in a way that scales poorly as the number of routes per
485 destination increases.
487 The default is that this option is not set.
490 Note that there are other sources of indeterminism in the route selection
491 process, specifically, the preference for older and already selected routes
492 from eBGP peers, @xref{BGP decision process}.
494 @deffn {BGP} {bgp always-compare-med} {}
495 @anchor{bgp always-compare-med}
497 Always compare the MED on routes, even when they were received from
498 different neighbouring ASes. Setting this option makes the order of
499 preference of routes more defined, and should eliminate MED induced
502 If using this option, it may also be desirable to use @ref{routemap set
503 metric} to set MED to 0 on routes received from external neighbours.
505 This option can be used, together with @ref{routemap set metric} to use MED
506 as an intra-AS metric to steer equal-length AS_PATH routes to, e.g., desired
517 * Route Aggregation::
518 * Redistribute to BGP::
522 @subsection BGP route
524 @deffn {BGP} {network @var{A.B.C.D/M}} {}
525 This command adds the announcement network.
532 This configuration example says that network 10.0.0.0/8 will be
533 announced to all neighbors. Some vendors' routers don't advertise
534 routes if they aren't present in their IGP routing tables; @code{bgpd}
535 doesn't care about IGP routes when announcing its routes.
538 @deffn {BGP} {no network @var{A.B.C.D/M}} {}
541 @node Route Aggregation
542 @subsection Route Aggregation
544 @deffn {BGP} {aggregate-address @var{A.B.C.D/M}} {}
545 This command specifies an aggregate address.
548 @deffn {BGP} {aggregate-address @var{A.B.C.D/M} as-set} {}
549 This command specifies an aggregate address. Resulting routes include
553 @deffn {BGP} {aggregate-address @var{A.B.C.D/M} summary-only} {}
554 This command specifies an aggregate address. Aggreated routes will
558 @deffn {BGP} {no aggregate-address @var{A.B.C.D/M}} {}
561 @node Redistribute to BGP
562 @subsection Redistribute to BGP
564 @deffn {BGP} {redistribute kernel} {}
565 Redistribute kernel route to BGP process.
568 @deffn {BGP} {redistribute static} {}
569 Redistribute static route to BGP process.
572 @deffn {BGP} {redistribute connected} {}
573 Redistribute connected route to BGP process.
576 @deffn {BGP} {redistribute rip} {}
577 Redistribute RIP route to BGP process.
580 @deffn {BGP} {redistribute ospf} {}
581 Redistribute OSPF route to BGP process.
584 @deffn {BGP} {update-delay @var{max-delay}} {}
585 @deffnx {BGP} {update-delay @var{max-delay} @var{establish-wait}} {}
586 This feature is used to enable read-only mode on BGP process restart or when
587 BGP process is cleared using 'clear ip bgp *'. When applicable, read-only mode
588 would begin as soon as the first peer reaches Established status and a timer
589 for max-delay seconds is started.
591 During this mode BGP doesn't run any best-path or generate any updates to its
592 peers. This mode continues until:
593 1. All the configured peers, except the shutdown peers, have sent explicit EOR
594 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
595 Established is considered an implicit-EOR.
596 If the establish-wait optional value is given, then BGP will wait for
597 peers to reach established from the begining of the update-delay till the
598 establish-wait period is over, i.e. the minimum set of established peers for
599 which EOR is expected would be peers established during the establish-wait
600 window, not necessarily all the configured neighbors.
601 2. max-delay period is over.
602 On hitting any of the above two conditions, BGP resumes the decision process
603 and generates updates to its peers.
605 Default max-delay is 0, i.e. the feature is off by default.
608 @deffn {BGP} {table-map @var{route-map-name}} {}
609 This feature is used to apply a route-map on route updates from BGP to Zebra.
610 All the applicable match operations are allowed, such as match on prefix,
611 next-hop, communities, etc. Set operations for this attach-point are limited
612 to metric and next-hop only. Any operation of this feature does not affect
615 Supported for ipv4 and ipv6 address families. It works on multi-paths as well,
616 however, metric setting is based on the best-path only.
624 * BGP Peer commands::
629 @subsection Defining Peer
631 @deffn {BGP} {neighbor @var{peer} remote-as @var{asn}} {}
632 Creates a new neighbor whose remote-as is @var{asn}. @var{peer}
633 can be an IPv4 address or an IPv6 address.
637 neighbor 10.0.0.1 remote-as 2
640 In this case my router, in AS-1, is trying to peer with AS-2 at
643 This command must be the first command used when configuring a neighbor.
644 If the remote-as is not specified, @command{bgpd} will complain like this:
646 can't find neighbor 10.0.0.1
650 @node BGP Peer commands
651 @subsection BGP Peer commands
653 In a @code{router bgp} clause there are neighbor specific configurations
656 @deffn {BGP} {neighbor @var{peer} shutdown} {}
657 @deffnx {BGP} {no neighbor @var{peer} shutdown} {}
658 Shutdown the peer. We can delete the neighbor's configuration by
659 @code{no neighbor @var{peer} remote-as @var{as-number}} but all
660 configuration of the neighbor will be deleted. When you want to
661 preserve the configuration, but want to drop the BGP peer, use this
665 @deffn {BGP} {neighbor @var{peer} ebgp-multihop} {}
666 @deffnx {BGP} {no neighbor @var{peer} ebgp-multihop} {}
669 @deffn {BGP} {neighbor @var{peer} description ...} {}
670 @deffnx {BGP} {no neighbor @var{peer} description ...} {}
671 Set description of the peer.
674 @deffn {BGP} {neighbor @var{peer} version @var{version}} {}
675 Set up the neighbor's BGP version. @var{version} can be @var{4},
676 @var{4+} or @var{4-}. BGP version @var{4} is the default value used for
677 BGP peering. BGP version @var{4+} means that the neighbor supports
678 Multiprotocol Extensions for BGP-4. BGP version @var{4-} is similar but
679 the neighbor speaks the old Internet-Draft revision 00's Multiprotocol
680 Extensions for BGP-4. Some routing software is still using this
684 @deffn {BGP} {neighbor @var{peer} interface @var{ifname}} {}
685 @deffnx {BGP} {no neighbor @var{peer} interface @var{ifname}} {}
686 When you connect to a BGP peer over an IPv6 link-local address, you
687 have to specify the @var{ifname} of the interface used for the
688 connection. To specify IPv4 session addresses, see the
689 @code{neighbor @var{peer} update-source} command below.
691 This command is deprecated and may be removed in a future release. Its
692 use should be avoided.
695 @deffn {BGP} {neighbor @var{peer} next-hop-self [all]} {}
696 @deffnx {BGP} {no neighbor @var{peer} next-hop-self [all]} {}
697 This command specifies an announced route's nexthop as being equivalent
698 to the address of the bgp router if it is learned via eBGP.
699 If the optional keyword @code{all} is specified the modifiation is done
700 also for routes learned via iBGP.
703 @deffn {BGP} {neighbor @var{peer} update-source @var{<ifname|address>}} {}
704 @deffnx {BGP} {no neighbor @var{peer} update-source} {}
705 Specify the IPv4 source address to use for the @acronym{BGP} session to this
706 neighbour, may be specified as either an IPv4 address directly or
707 as an interface name (in which case the @command{zebra} daemon MUST be running
708 in order for @command{bgpd} to be able to retrieve interface state).
712 neighbor foo update-source 192.168.0.1
713 neighbor bar update-source lo0
718 @deffn {BGP} {neighbor @var{peer} default-originate} {}
719 @deffnx {BGP} {no neighbor @var{peer} default-originate} {}
720 @command{bgpd}'s default is to not announce the default route (0.0.0.0/0) even it
721 is in routing table. When you want to announce default routes to the
722 peer, use this command.
725 @deffn {BGP} {neighbor @var{peer} port @var{port}} {}
726 @deffnx {BGP} {neighbor @var{peer} port @var{port}} {}
729 @deffn {BGP} {neighbor @var{peer} send-community} {}
730 @deffnx {BGP} {neighbor @var{peer} send-community} {}
733 @deffn {BGP} {neighbor @var{peer} weight @var{weight}} {}
734 @deffnx {BGP} {no neighbor @var{peer} weight @var{weight}} {}
735 This command specifies a default @var{weight} value for the neighbor's
739 @deffn {BGP} {neighbor @var{peer} maximum-prefix @var{number}} {}
740 @deffnx {BGP} {no neighbor @var{peer} maximum-prefix @var{number}} {}
743 @deffn {BGP} {neighbor @var{peer} local-as @var{as-number}} {}
744 @deffnx {BGP} {neighbor @var{peer} local-as @var{as-number} no-prepend} {}
745 @deffnx {BGP} {neighbor @var{peer} local-as @var{as-number} no-prepend replace-as} {}
746 @deffnx {BGP} {no neighbor @var{peer} local-as} {}
747 Specify an alternate AS for this BGP process when interacting with the
748 specified peer. With no modifiers, the specified local-as is prepended to
749 the received AS_PATH when receiving routing updates from the peer, and
750 prepended to the outgoing AS_PATH (after the process local AS) when
751 transmitting local routes to the peer.
753 If the no-prepend attribute is specified, then the supplied local-as is not
754 prepended to the received AS_PATH.
756 If the replace-as attribute is specified, then only the supplied local-as is
757 prepended to the AS_PATH when transmitting local-route updates to this peer.
759 Note that replace-as can only be specified if no-prepend is.
761 This command is only allowed for eBGP peers.
764 @deffn {BGP} {neighbor @var{peer} ttl-security hops @var{number}} {}
765 @deffnx {BGP} {no neighbor @var{peer} ttl-security hops @var{number}} {}
766 This command enforces Generalized TTL Security Mechanism (GTSM), as
767 specified in RFC 5082. With this command, only neighbors that are the
768 specified number of hops away will be allowed to become neighbors. This
769 command is mututally exclusive with @command{ebgp-multihop}.
773 @subsection Peer filtering
775 @deffn {BGP} {neighbor @var{peer} distribute-list @var{name} [in|out]} {}
776 This command specifies a distribute-list for the peer. @var{direct} is
777 @samp{in} or @samp{out}.
780 @deffn {BGP command} {neighbor @var{peer} prefix-list @var{name} [in|out]} {}
783 @deffn {BGP command} {neighbor @var{peer} filter-list @var{name} [in|out]} {}
786 @deffn {BGP} {neighbor @var{peer} route-map @var{name} [in|out]} {}
787 Apply a route-map on the neighbor. @var{direct} must be @code{in} or
791 @deffn {BGP} {bgp route-reflector allow-outbound-policy} {}
792 By default, attribute modification via route-map policy out is not reflected
793 on reflected routes. This option allows the modifications to be reflected as
794 well. Once enabled, it affects all reflected routes.
797 @c -----------------------------------------------------------------------
799 @section BGP Peer Group
801 @deffn {BGP} {neighbor @var{word} peer-group} {}
802 This command defines a new peer group.
805 @deffn {BGP} {neighbor @var{peer} peer-group @var{word}} {}
806 This command bind specific peer to peer group @var{word}.
809 @node BGP Address Family
810 @section BGP Address Family
812 Multiprotocol BGP enables BGP to carry routing information for multiple
813 Network Layer protocols. BGP supports multiple Address Family
814 Identifier (AFI), namely IPv4 and IPv6. Support is also provided for
815 multiple sets of per-AFI information via Subsequent Address Family
816 Identifiers (SAFI). In addition to unicast information, VPN information
817 @cite{RFC4364} and @cite{RFC4659}, and Encapsulation information
818 @cite{RFC5512} is supported.
820 @deffn {Command} {show ip bgp vpnv4 all} {}
821 @deffnx {Command} {show ipv6 bgp vpn all} {}
822 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
825 @deffn {Command} {show ip bgp encap all} {}
826 @deffnx {Command} {show ipv6 bgp encap all} {}
827 Print active IPV4 or IPV6 routes advertised via the Encapsulation SAFI.
830 @deffn {Command} {show bgp ipv4 encap summary} {}
831 @deffnx {Command} {show bgp ipv4 vpn summary} {}
832 @deffnx {Command} {show bgp ipv6 encap summary} {}
833 @deffnx {Command} {show bgp ipv6 vpn summary} {}
834 Print a summary of neighbor connections for the specified AFI/SAFI combination.
837 @c -----------------------------------------------------------------------
838 @node Autonomous System
839 @section Autonomous System
841 The @acronym{AS,Autonomous System} number is one of the essential
842 element of BGP. BGP is a distance vector routing protocol, and the
843 AS-Path framework provides distance vector metric and loop detection to
844 BGP. @cite{RFC1930, Guidelines for creation, selection, and
845 registration of an Autonomous System (AS)} provides some background on
846 the concepts of an AS.
848 The AS number is a two octet value, ranging in value from 1 to 65535.
849 The AS numbers 64512 through 65535 are defined as private AS numbers.
850 Private AS numbers must not to be advertised in the global Internet.
853 * AS Path Regular Expression::
854 * Display BGP Routes by AS Path::
855 * AS Path Access List::
856 * Using AS Path in Route Map::
857 * Private AS Numbers::
860 @node AS Path Regular Expression
861 @subsection AS Path Regular Expression
863 AS path regular expression can be used for displaying BGP routes and
864 AS path access list. AS path regular expression is based on
865 @code{POSIX 1003.2} regular expressions. Following description is
866 just a subset of @code{POSIX} regular expression. User can use full
867 @code{POSIX} regular expression. Adding to that special character '_'
868 is added for AS path regular expression.
872 Matches any single character.
874 Matches 0 or more occurrences of pattern.
876 Matches 1 or more occurrences of pattern.
878 Match 0 or 1 occurrences of pattern.
880 Matches the beginning of the line.
882 Matches the end of the line.
884 Character @code{_} has special meanings in AS path regular expression.
885 It matches to space and comma , and AS set delimiter @{ and @} and AS
886 confederation delimiter @code{(} and @code{)}. And it also matches to
887 the beginning of the line and the end of the line. So @code{_} can be
888 used for AS value boundaries match. @code{show ip bgp regexp _7675_}
889 matches to all of BGP routes which as AS number include @var{7675}.
892 @node Display BGP Routes by AS Path
893 @subsection Display BGP Routes by AS Path
895 To show BGP routes which has specific AS path information @code{show
896 ip bgp} command can be used.
898 @deffn Command {show ip bgp regexp @var{line}} {}
899 This commands display BGP routes that matches AS path regular
900 expression @var{line}.
903 @node AS Path Access List
904 @subsection AS Path Access List
906 AS path access list is user defined AS path.
908 @deffn {Command} {ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
909 This command defines a new AS path access list.
912 @deffn {Command} {no ip as-path access-list @var{word}} {}
913 @deffnx {Command} {no ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
916 @node Using AS Path in Route Map
917 @subsection Using AS Path in Route Map
919 @deffn {Route Map} {match as-path @var{word}} {}
922 @deffn {Route Map} {set as-path prepend @var{as-path}} {}
923 Prepend the given string of AS numbers to the AS_PATH.
926 @deffn {Route Map} {set as-path prepend last-as @var{num}} {}
927 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
930 @node Private AS Numbers
931 @subsection Private AS Numbers
933 @c -----------------------------------------------------------------------
934 @node BGP Communities Attribute
935 @section BGP Communities Attribute
937 BGP communities attribute is widely used for implementing policy
938 routing. Network operators can manipulate BGP communities attribute
939 based on their network policy. BGP communities attribute is defined
940 in @cite{RFC1997, BGP Communities Attribute} and
941 @cite{RFC1998, An Application of the BGP Community Attribute
942 in Multi-home Routing}. It is an optional transitive attribute,
943 therefore local policy can travel through different autonomous system.
945 Communities attribute is a set of communities values. Each
946 communities value is 4 octet long. The following format is used to
947 define communities value.
951 This format represents 4 octet communities value. @code{AS} is high
952 order 2 octet in digit format. @code{VAL} is low order 2 octet in
953 digit format. This format is useful to define AS oriented policy
954 value. For example, @code{7675:80} can be used when AS 7675 wants to
955 pass local policy value 80 to neighboring peer.
957 @code{internet} represents well-known communities value 0.
959 @code{no-export} represents well-known communities value @code{NO_EXPORT}@*
960 @r{(0xFFFFFF01)}. All routes carry this value must not be advertised
961 to outside a BGP confederation boundary. If neighboring BGP peer is
962 part of BGP confederation, the peer is considered as inside a BGP
963 confederation boundary, so the route will be announced to the peer.
965 @code{no-advertise} represents well-known communities value
966 @code{NO_ADVERTISE}@*@r{(0xFFFFFF02)}. All routes carry this value
967 must not be advertise to other BGP peers.
969 @code{local-AS} represents well-known communities value
970 @code{NO_EXPORT_SUBCONFED} @r{(0xFFFFFF03)}. All routes carry this
971 value must not be advertised to external BGP peers. Even if the
972 neighboring router is part of confederation, it is considered as
973 external BGP peer, so the route will not be announced to the peer.
976 When BGP communities attribute is received, duplicated communities
977 value in the communities attribute is ignored and each communities
978 values are sorted in numerical order.
981 * BGP Community Lists::
982 * Numbered BGP Community Lists::
983 * BGP Community in Route Map::
984 * Display BGP Routes by Community::
985 * Using BGP Communities Attribute::
988 @node BGP Community Lists
989 @subsection BGP Community Lists
991 BGP community list is a user defined BGP communites attribute list.
992 BGP community list can be used for matching or manipulating BGP
993 communities attribute in updates.
995 There are two types of community list. One is standard community
996 list and another is expanded community list. Standard community list
997 defines communities attribute. Expanded community list defines
998 communities attribute string with regular expression. Standard
999 community list is compiled into binary format when user define it.
1000 Standard community list will be directly compared to BGP communities
1001 attribute in BGP updates. Therefore the comparison is faster than
1002 expanded community list.
1004 @deffn Command {ip community-list standard @var{name} @{permit|deny@} @var{community}} {}
1005 This command defines a new standard community list. @var{community}
1006 is communities value. The @var{community} is compiled into community
1007 structure. We can define multiple community list under same name. In
1008 that case match will happen user defined order. Once the
1009 community list matches to communities attribute in BGP updates it
1010 return permit or deny by the community list definition. When there is
1011 no matched entry, deny will be returned. When @var{community} is
1012 empty it matches to any routes.
1015 @deffn Command {ip community-list expanded @var{name} @{permit|deny@} @var{line}} {}
1016 This command defines a new expanded community list. @var{line} is a
1017 string expression of communities attribute. @var{line} can include
1018 regular expression to match communities attribute in BGP updates.
1021 @deffn Command {no ip community-list @var{name}} {}
1022 @deffnx Command {no ip community-list standard @var{name}} {}
1023 @deffnx Command {no ip community-list expanded @var{name}} {}
1024 These commands delete community lists specified by @var{name}. All of
1025 community lists shares a single name space. So community lists can be
1026 removed simpley specifying community lists name.
1029 @deffn {Command} {show ip community-list} {}
1030 @deffnx {Command} {show ip community-list @var{name}} {}
1031 This command display current community list information. When
1032 @var{name} is specified the specified community list's information is
1036 # show ip community-list
1037 Named Community standard list CLIST
1038 permit 7675:80 7675:100 no-export
1040 Named Community expanded list EXPAND
1043 # show ip community-list CLIST
1044 Named Community standard list CLIST
1045 permit 7675:80 7675:100 no-export
1050 @node Numbered BGP Community Lists
1051 @subsection Numbered BGP Community Lists
1053 When number is used for BGP community list name, the number has
1054 special meanings. Community list number in the range from 1 and 99 is
1055 standard community list. Community list number in the range from 100
1056 to 199 is expanded community list. These community lists are called
1057 as numbered community lists. On the other hand normal community lists
1058 is called as named community lists.
1060 @deffn Command {ip community-list <1-99> @{permit|deny@} @var{community}} {}
1061 This command defines a new community list. <1-99> is standard
1062 community list number. Community list name within this range defines
1063 standard community list. When @var{community} is empty it matches to
1067 @deffn Command {ip community-list <100-199> @{permit|deny@} @var{community}} {}
1068 This command defines a new community list. <100-199> is expanded
1069 community list number. Community list name within this range defines
1070 expanded community list.
1073 @deffn Command {ip community-list @var{name} @{permit|deny@} @var{community}} {}
1074 When community list type is not specifed, the community list type is
1075 automatically detected. If @var{community} can be compiled into
1076 communities attribute, the community list is defined as a standard
1077 community list. Otherwise it is defined as an expanded community
1078 list. This feature is left for backward compability. Use of this
1079 feature is not recommended.
1082 @node BGP Community in Route Map
1083 @subsection BGP Community in Route Map
1085 In Route Map (@pxref{Route Map}), we can match or set BGP
1086 communities attribute. Using this feature network operator can
1087 implement their network policy based on BGP communities attribute.
1089 Following commands can be used in Route Map.
1091 @deffn {Route Map} {match community @var{word}} {}
1092 @deffnx {Route Map} {match community @var{word} exact-match} {}
1093 This command perform match to BGP updates using community list
1094 @var{word}. When the one of BGP communities value match to the one of
1095 communities value in community list, it is match. When
1096 @code{exact-match} keyword is spcified, match happen only when BGP
1097 updates have completely same communities value specified in the
1101 @deffn {Route Map} {set community none} {}
1102 @deffnx {Route Map} {set community @var{community}} {}
1103 @deffnx {Route Map} {set community @var{community} additive} {}
1104 This command manipulate communities value in BGP updates. When
1105 @code{none} is specified as communities value, it removes entire
1106 communities attribute from BGP updates. When @var{community} is not
1107 @code{none}, specified communities value is set to BGP updates. If
1108 BGP updates already has BGP communities value, the existing BGP
1109 communities value is replaced with specified @var{community} value.
1110 When @code{additive} keyword is specified, @var{community} is appended
1111 to the existing communities value.
1114 @deffn {Route Map} {set comm-list @var{word} delete} {}
1115 This command remove communities value from BGP communities attribute.
1116 The @var{word} is community list name. When BGP route's communities
1117 value matches to the community list @var{word}, the communities value
1118 is removed. When all of communities value is removed eventually, the
1119 BGP update's communities attribute is completely removed.
1122 @node Display BGP Routes by Community
1123 @subsection Display BGP Routes by Community
1125 To show BGP routes which has specific BGP communities attribute,
1126 @code{show ip bgp} command can be used. The @var{community} value and
1127 community list can be used for @code{show ip bgp} command.
1129 @deffn Command {show ip bgp community} {}
1130 @deffnx Command {show ip bgp community @var{community}} {}
1131 @deffnx Command {show ip bgp community @var{community} exact-match} {}
1132 @code{show ip bgp community} displays BGP routes which has communities
1133 attribute. When @var{community} is specified, BGP routes that matches
1134 @var{community} value is displayed. For this command, @code{internet}
1135 keyword can't be used for @var{community} value. When
1136 @code{exact-match} is specified, it display only routes that have an
1140 @deffn Command {show ip bgp community-list @var{word}} {}
1141 @deffnx Command {show ip bgp community-list @var{word} exact-match} {}
1142 This commands display BGP routes that matches community list
1143 @var{word}. When @code{exact-match} is specified, display only routes
1144 that have an exact match.
1147 @node Using BGP Communities Attribute
1148 @subsection Using BGP Communities Attribute
1150 Following configuration is the most typical usage of BGP communities
1151 attribute. AS 7675 provides upstream Internet connection to AS 100.
1152 When following configuration exists in AS 7675, AS 100 networks
1153 operator can set local preference in AS 7675 network by setting BGP
1154 communities attribute to the updates.
1158 neighbor 192.168.0.1 remote-as 100
1159 neighbor 192.168.0.1 route-map RMAP in
1161 ip community-list 70 permit 7675:70
1162 ip community-list 70 deny
1163 ip community-list 80 permit 7675:80
1164 ip community-list 80 deny
1165 ip community-list 90 permit 7675:90
1166 ip community-list 90 deny
1168 route-map RMAP permit 10
1170 set local-preference 70
1172 route-map RMAP permit 20
1174 set local-preference 80
1176 route-map RMAP permit 30
1178 set local-preference 90
1181 Following configuration announce 10.0.0.0/8 from AS 100 to AS 7675.
1182 The route has communities value 7675:80 so when above configuration
1183 exists in AS 7675, announced route's local preference will be set to
1189 neighbor 192.168.0.2 remote-as 7675
1190 neighbor 192.168.0.2 route-map RMAP out
1192 ip prefix-list PLIST permit 10.0.0.0/8
1194 route-map RMAP permit 10
1195 match ip address prefix-list PLIST
1196 set community 7675:80
1199 Following configuration is an example of BGP route filtering using
1200 communities attribute. This configuration only permit BGP routes
1201 which has BGP communities value 0:80 or 0:90. Network operator can
1202 put special internal communities value at BGP border router, then
1203 limit the BGP routes announcement into the internal network.
1207 neighbor 192.168.0.1 remote-as 100
1208 neighbor 192.168.0.1 route-map RMAP in
1210 ip community-list 1 permit 0:80 0:90
1212 route-map RMAP permit in
1216 Following exmaple filter BGP routes which has communities value 1:1.
1217 When there is no match community-list returns deny. To avoid
1218 filtering all of routes, we need to define permit any at last.
1222 neighbor 192.168.0.1 remote-as 100
1223 neighbor 192.168.0.1 route-map RMAP in
1225 ip community-list standard FILTER deny 1:1
1226 ip community-list standard FILTER permit
1228 route-map RMAP permit 10
1229 match community FILTER
1232 Communities value keyword @code{internet} has special meanings in
1233 standard community lists. In below example @code{internet} act as
1234 match any. It matches all of BGP routes even if the route does not
1235 have communities attribute at all. So community list @code{INTERNET}
1236 is same as above example's @code{FILTER}.
1239 ip community-list standard INTERNET deny 1:1
1240 ip community-list standard INTERNET permit internet
1243 Following configuration is an example of communities value deletion.
1244 With this configuration communities value 100:1 and 100:2 is removed
1245 from BGP updates. For communities value deletion, only @code{permit}
1246 community-list is used. @code{deny} community-list is ignored.
1250 neighbor 192.168.0.1 remote-as 100
1251 neighbor 192.168.0.1 route-map RMAP in
1253 ip community-list standard DEL permit 100:1 100:2
1255 route-map RMAP permit 10
1256 set comm-list DEL delete
1259 @c -----------------------------------------------------------------------
1260 @node BGP Extended Communities Attribute
1261 @section BGP Extended Communities Attribute
1263 BGP extended communities attribute is introduced with MPLS VPN/BGP
1264 technology. MPLS VPN/BGP expands capability of network infrastructure
1265 to provide VPN functionality. At the same time it requires a new
1266 framework for policy routing. With BGP Extended Communities Attribute
1267 we can use Route Target or Site of Origin for implementing network
1268 policy for MPLS VPN/BGP.
1270 BGP Extended Communities Attribute is similar to BGP Communities
1271 Attribute. It is an optional transitive attribute. BGP Extended
1272 Communities Attribute can carry multiple Extended Community value.
1273 Each Extended Community value is eight octet length.
1275 BGP Extended Communities Attribute provides an extended range
1276 compared with BGP Communities Attribute. Adding to that there is a
1277 type field in each value to provides community space structure.
1279 There are two format to define Extended Community value. One is AS
1280 based format the other is IP address based format.
1284 This is a format to define AS based Extended Community value.
1285 @code{AS} part is 2 octets Global Administrator subfield in Extended
1286 Community value. @code{VAL} part is 4 octets Local Administrator
1287 subfield. @code{7675:100} represents AS 7675 policy value 100.
1288 @item IP-Address:VAL
1289 This is a format to define IP address based Extended Community value.
1290 @code{IP-Address} part is 4 octets Global Administrator subfield.
1291 @code{VAL} part is 2 octets Local Administrator subfield.
1292 @code{10.0.0.1:100} represents
1296 * BGP Extended Community Lists::
1297 * BGP Extended Communities in Route Map::
1300 @node BGP Extended Community Lists
1301 @subsection BGP Extended Community Lists
1303 Expanded Community Lists is a user defined BGP Expanded Community
1306 @deffn Command {ip extcommunity-list standard @var{name} @{permit|deny@} @var{extcommunity}} {}
1307 This command defines a new standard extcommunity-list.
1308 @var{extcommunity} is extended communities value. The
1309 @var{extcommunity} is compiled into extended community structure. We
1310 can define multiple extcommunity-list under same name. In that case
1311 match will happen user defined order. Once the extcommunity-list
1312 matches to extended communities attribute in BGP updates it return
1313 permit or deny based upon the extcommunity-list definition. When
1314 there is no matched entry, deny will be returned. When
1315 @var{extcommunity} is empty it matches to any routes.
1318 @deffn Command {ip extcommunity-list expanded @var{name} @{permit|deny@} @var{line}} {}
1319 This command defines a new expanded extcommunity-list. @var{line} is
1320 a string expression of extended communities attribute. @var{line} can
1321 include regular expression to match extended communities attribute in
1325 @deffn Command {no ip extcommunity-list @var{name}} {}
1326 @deffnx Command {no ip extcommunity-list standard @var{name}} {}
1327 @deffnx Command {no ip extcommunity-list expanded @var{name}} {}
1328 These commands delete extended community lists specified by
1329 @var{name}. All of extended community lists shares a single name
1330 space. So extended community lists can be removed simpley specifying
1334 @deffn {Command} {show ip extcommunity-list} {}
1335 @deffnx {Command} {show ip extcommunity-list @var{name}} {}
1336 This command display current extcommunity-list information. When
1337 @var{name} is specified the community list's information is shown.
1340 # show ip extcommunity-list
1344 @node BGP Extended Communities in Route Map
1345 @subsection BGP Extended Communities in Route Map
1347 @deffn {Route Map} {match extcommunity @var{word}} {}
1350 @deffn {Route Map} {set extcommunity rt @var{extcommunity}} {}
1351 This command set Route Target value.
1354 @deffn {Route Map} {set extcommunity soo @var{extcommunity}} {}
1355 This command set Site of Origin value.
1358 @c -----------------------------------------------------------------------
1359 @node Displaying BGP routes
1360 @section Displaying BGP Routes
1364 * More Show IP BGP::
1368 @subsection Show IP BGP
1370 @deffn {Command} {show ip bgp} {}
1371 @deffnx {Command} {show ip bgp @var{A.B.C.D}} {}
1372 @deffnx {Command} {show ip bgp @var{X:X::X:X}} {}
1373 This command displays BGP routes. When no route is specified it
1374 display all of IPv4 BGP routes.
1378 BGP table version is 0, local router ID is 10.1.1.1
1379 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
1380 Origin codes: i - IGP, e - EGP, ? - incomplete
1382 Network Next Hop Metric LocPrf Weight Path
1383 *> 1.1.1.1/32 0.0.0.0 0 32768 i
1385 Total number of prefixes 1
1388 @node More Show IP BGP
1389 @subsection More Show IP BGP
1391 @deffn {Command} {show ip bgp regexp @var{line}} {}
1392 This command display BGP routes using AS path regular expression (@pxref{Display BGP Routes by AS Path}).
1395 @deffn Command {show ip bgp community @var{community}} {}
1396 @deffnx Command {show ip bgp community @var{community} exact-match} {}
1397 This command display BGP routes using @var{community} (@pxref{Display
1398 BGP Routes by Community}).
1401 @deffn Command {show ip bgp community-list @var{word}} {}
1402 @deffnx Command {show ip bgp community-list @var{word} exact-match} {}
1403 This command display BGP routes using community list (@pxref{Display
1404 BGP Routes by Community}).
1407 @deffn {Command} {show ip bgp summary} {}
1410 @deffn {Command} {show ip bgp neighbor [@var{peer}]} {}
1413 @deffn {Command} {clear ip bgp @var{peer}} {}
1414 Clear peers which have addresses of X.X.X.X
1417 @deffn {Command} {clear ip bgp @var{peer} soft in} {}
1418 Clear peer using soft reconfiguration.
1421 @deffn {Command} {show ip bgp dampened-paths} {}
1422 Display paths suppressed due to dampening
1425 @deffn {Command} {show ip bgp flap-statistics} {}
1426 Display flap statistics of routes
1429 @deffn {Command} {show debug} {}
1432 @deffn {Command} {debug event} {}
1435 @deffn {Command} {debug update} {}
1438 @deffn {Command} {debug keepalive} {}
1441 @deffn {Command} {no debug event} {}
1444 @deffn {Command} {no debug update} {}
1447 @deffn {Command} {no debug keepalive} {}
1450 @node Capability Negotiation
1451 @section Capability Negotiation
1453 When adding IPv6 routing information exchange feature to BGP. There
1454 were some proposals. @acronym{IETF,Internet Engineering Task Force}
1455 @acronym{IDR, Inter Domain Routing} @acronym{WG, Working group} adopted
1456 a proposal called Multiprotocol Extension for BGP. The specification
1457 is described in @cite{RFC2283}. The protocol does not define new protocols.
1458 It defines new attributes to existing BGP. When it is used exchanging
1459 IPv6 routing information it is called BGP-4+. When it is used for
1460 exchanging multicast routing information it is called MBGP.
1462 @command{bgpd} supports Multiprotocol Extension for BGP. So if remote
1463 peer supports the protocol, @command{bgpd} can exchange IPv6 and/or
1464 multicast routing information.
1466 Traditional BGP did not have the feature to detect remote peer's
1467 capabilities, e.g. whether it can handle prefix types other than IPv4
1468 unicast routes. This was a big problem using Multiprotocol Extension
1469 for BGP to operational network. @cite{RFC2842, Capabilities
1470 Advertisement with BGP-4} adopted a feature called Capability
1471 Negotiation. @command{bgpd} use this Capability Negotiation to detect
1472 the remote peer's capabilities. If the peer is only configured as IPv4
1473 unicast neighbor, @command{bgpd} does not send these Capability
1474 Negotiation packets (at least not unless other optional BGP features
1475 require capability negotation).
1477 By default, Quagga will bring up peering with minimal common capability
1478 for the both sides. For example, local router has unicast and
1479 multicast capabilitie and remote router has unicast capability. In
1480 this case, the local router will establish the connection with unicast
1481 only capability. When there are no common capabilities, Quagga sends
1482 Unsupported Capability error and then resets the connection.
1484 If you want to completely match capabilities with remote peer. Please
1485 use @command{strict-capability-match} command.
1487 @deffn {BGP} {neighbor @var{peer} strict-capability-match} {}
1488 @deffnx {BGP} {no neighbor @var{peer} strict-capability-match} {}
1489 Strictly compares remote capabilities and local capabilities. If capabilities
1490 are different, send Unsupported Capability error then reset connection.
1493 You may want to disable sending Capability Negotiation OPEN message
1494 optional parameter to the peer when remote peer does not implement
1495 Capability Negotiation. Please use @command{dont-capability-negotiate}
1496 command to disable the feature.
1498 @deffn {BGP} {neighbor @var{peer} dont-capability-negotiate} {}
1499 @deffnx {BGP} {no neighbor @var{peer} dont-capability-negotiate} {}
1500 Suppress sending Capability Negotiation as OPEN message optional
1501 parameter to the peer. This command only affects the peer is configured
1502 other than IPv4 unicast configuration.
1505 When remote peer does not have capability negotiation feature, remote
1506 peer will not send any capabilities at all. In that case, bgp
1507 configures the peer with configured capabilities.
1509 You may prefer locally configured capabilities more than the negotiated
1510 capabilities even though remote peer sends capabilities. If the peer
1511 is configured by @command{override-capability}, @command{bgpd} ignores
1512 received capabilities then override negotiated capabilities with
1515 @deffn {BGP} {neighbor @var{peer} override-capability} {}
1516 @deffnx {BGP} {no neighbor @var{peer} override-capability} {}
1517 Override the result of Capability Negotiation with local configuration.
1518 Ignore remote peer's capability value.
1521 @node Route Reflector
1522 @section Route Reflector
1524 @deffn {BGP} {bgp cluster-id @var{a.b.c.d}} {}
1527 @deffn {BGP} {neighbor @var{peer} route-reflector-client} {}
1528 @deffnx {BGP} {no neighbor @var{peer} route-reflector-client} {}
1532 @section Route Server
1534 At an Internet Exchange point, many ISPs are connected to each other by
1535 external BGP peering. Normally these external BGP connection are done by
1536 @samp{full mesh} method. As with internal BGP full mesh formation,
1537 this method has a scaling problem.
1539 This scaling problem is well known. Route Server is a method to resolve
1540 the problem. Each ISP's BGP router only peers to Route Server. Route
1541 Server serves as BGP information exchange to other BGP routers. By
1542 applying this method, numbers of BGP connections is reduced from
1543 O(n*(n-1)/2) to O(n).
1545 Unlike normal BGP router, Route Server must have several routing tables
1546 for managing different routing policies for each BGP speaker. We call the
1547 routing tables as different @code{view}s. @command{bgpd} can work as
1548 normal BGP router or Route Server or both at the same time.
1551 * Multiple instance::
1552 * BGP instance and view::
1554 * Viewing the view::
1557 @node Multiple instance
1558 @subsection Multiple instance
1560 To enable multiple view function of @code{bgpd}, you must turn on
1561 multiple instance feature beforehand.
1563 @deffn {Command} {bgp multiple-instance} {}
1564 Enable BGP multiple instance feature. After this feature is enabled,
1565 you can make multiple BGP instances or multiple BGP views.
1568 @deffn {Command} {no bgp multiple-instance} {}
1569 Disable BGP multiple instance feature. You can not disable this feature
1570 when BGP multiple instances or views exist.
1573 When you want to make configuration more Cisco like one,
1575 @deffn {Command} {bgp config-type cisco} {}
1576 Cisco compatible BGP configuration output.
1579 When bgp config-type cisco is specified,
1581 ``no synchronization'' is displayed.
1582 ``no auto-summary'' is displayed.
1584 ``network'' and ``aggregate-address'' argument is displayed as
1587 Quagga: network 10.0.0.0/8
1588 Cisco: network 10.0.0.0
1590 Quagga: aggregate-address 192.168.0.0/24
1591 Cisco: aggregate-address 192.168.0.0 255.255.255.0
1593 Community attribute handling is also different. If there is no
1594 configuration is specified community attribute and extended community
1595 attribute are sent to neighbor. When user manually disable the
1596 feature community attribute is not sent to the neighbor. In case of
1597 @command{bgp config-type cisco} is specified, community attribute is not
1598 sent to the neighbor by default. To send community attribute user has
1599 to specify @command{neighbor A.B.C.D send-community} command.
1604 neighbor 10.0.0.1 remote-as 1
1605 no neighbor 10.0.0.1 send-community
1608 neighbor 10.0.0.1 remote-as 1
1609 neighbor 10.0.0.1 send-community
1613 @deffn {Command} {bgp config-type zebra} {}
1614 Quagga style BGP configuration. This is default.
1617 @node BGP instance and view
1618 @subsection BGP instance and view
1620 BGP instance is a normal BGP process. The result of route selection
1621 goes to the kernel routing table. You can setup different AS at the
1622 same time when BGP multiple instance feature is enabled.
1624 @deffn {Command} {router bgp @var{as-number}} {}
1625 Make a new BGP instance. You can use arbitrary word for the @var{name}.
1630 bgp multiple-instance
1633 neighbor 10.0.0.1 remote-as 2
1634 neighbor 10.0.0.2 remote-as 3
1637 neighbor 10.0.0.3 remote-as 4
1638 neighbor 10.0.0.4 remote-as 5
1642 BGP view is almost same as normal BGP process. The result of
1643 route selection does not go to the kernel routing table. BGP view is
1644 only for exchanging BGP routing information.
1646 @deffn {Command} {router bgp @var{as-number} view @var{name}} {}
1647 Make a new BGP view. You can use arbitrary word for the @var{name}. This
1648 view's route selection result does not go to the kernel routing table.
1651 With this command, you can setup Route Server like below.
1655 bgp multiple-instance
1658 neighbor 10.0.0.1 remote-as 2
1659 neighbor 10.0.0.2 remote-as 3
1662 neighbor 10.0.0.3 remote-as 4
1663 neighbor 10.0.0.4 remote-as 5
1667 @node Routing policy
1668 @subsection Routing policy
1670 You can set different routing policy for a peer. For example, you can
1671 set different filter for a peer.
1675 bgp multiple-instance
1678 neighbor 10.0.0.1 remote-as 2
1679 neighbor 10.0.0.1 distribute-list 1 in
1682 neighbor 10.0.0.1 remote-as 2
1683 neighbor 10.0.0.1 distribute-list 2 in
1687 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view
1688 2. When the update is inserted into view 1, distribute-list 1 is
1689 applied. On the other hand, when the update is inserted into view 2,
1690 distribute-list 2 is applied.
1692 @node Viewing the view
1693 @subsection Viewing the view
1695 To display routing table of BGP view, you must specify view name.
1697 @deffn {Command} {show ip bgp view @var{name}} {}
1698 Display routing table of BGP view @var{name}.
1701 @node How to set up a 6-Bone connection
1702 @section How to set up a 6-Bone connection
1710 ! Actually there is no need to configure zebra
1716 ! This means that routes go through zebra and into the kernel.
1720 ! MP-BGP configuration
1723 bgp router-id 10.0.0.1
1724 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as @var{as-number}
1727 network 3ffe:506::/32
1728 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
1729 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
1730 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as @var{as-number}
1731 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
1734 ipv6 access-list all permit any
1736 ! Set output nexthop address.
1738 route-map set-nexthop permit 10
1739 match ipv6 address all
1740 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
1741 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
1743 ! logfile FILENAME is obsolete. Please use log file FILENAME
1750 @node Dump BGP packets and table
1751 @section Dump BGP packets and table
1753 @deffn Command {dump bgp all @var{path} [@var{interval}]} {}
1754 @deffnx Command {dump bgp all-et @var{path} [@var{interval}]} {}
1755 @deffnx Command {no dump bgp all [@var{path}] [@var{interval}]} {}
1756 Dump all BGP packet and events to @var{path} file.
1757 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1758 The path @var{path} can be set with date and time formatting (strftime).
1759 The type ‘all-et’ enables support for Extended Timestamp Header (@pxref{Packet Binary Dump Format}).
1760 (@pxref{Packet Binary Dump Format})
1763 @deffn Command {dump bgp updates @var{path} [@var{interval}]} {}
1764 @deffnx Command {dump bgp updates-et @var{path} [@var{interval}]} {}
1765 @deffnx Command {no dump bgp updates [@var{path}] [@var{interval}]} {}
1766 Dump only BGP updates messages to @var{path} file.
1767 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1768 The path @var{path} can be set with date and time formatting (strftime).
1769 The type ‘updates-et’ enables support for Extended Timestamp Header (@pxref{Packet Binary Dump Format}).
1772 @deffn Command {dump bgp routes-mrt @var{path}} {}
1773 @deffnx Command {dump bgp routes-mrt @var{path} @var{interval}} {}
1774 @deffnx Command {no dump bgp route-mrt [@var{path}] [@var{interval}]} {}
1775 Dump whole BGP routing table to @var{path}. This is heavy process.
1776 The path @var{path} can be set with date and time formatting (strftime).
1777 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1780 Note: the interval variable can also be set using hours and minutes: 04h20m00.
1783 @node BGP Configuration Examples
1784 @section BGP Configuration Examples
1786 Example of a session to an upstream, advertising only one prefix to it.
1790 bgp router-id 10.236.87.1
1791 network 10.236.87.0/24
1792 neighbor upstream peer-group
1793 neighbor upstream remote-as 64515
1794 neighbor upstream capability dynamic
1795 neighbor upstream prefix-list pl-allowed-adv out
1796 neighbor 10.1.1.1 peer-group upstream
1797 neighbor 10.1.1.1 description ACME ISP
1799 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
1800 ip prefix-list pl-allowed-adv seq 10 deny any
1804 A more complex example. With upstream, peer and customer sessions.
1805 Advertising global prefixes and NO_EXPORT prefixes and providing
1806 actions for customer routes based on community values. Extensive use of
1807 route-maps and the 'call' feature to support selective advertising of
1808 prefixes. This example is intended as guidance only, it has NOT been
1809 tested and almost certainly containts silly mistakes, if not serious
1814 bgp router-id 10.236.87.1
1815 network 10.123.456.0/24
1816 network 10.123.456.128/25 route-map rm-no-export
1817 neighbor upstream capability dynamic
1818 neighbor upstream route-map rm-upstream-out out
1819 neighbor cust capability dynamic
1820 neighbor cust route-map rm-cust-in in
1821 neighbor cust route-map rm-cust-out out
1822 neighbor cust send-community both
1823 neighbor peer capability dynamic
1824 neighbor peer route-map rm-peer-in in
1825 neighbor peer route-map rm-peer-out out
1826 neighbor peer send-community both
1827 neighbor 10.1.1.1 remote-as 64515
1828 neighbor 10.1.1.1 peer-group upstream
1829 neighbor 10.2.1.1 remote-as 64516
1830 neighbor 10.2.1.1 peer-group upstream
1831 neighbor 10.3.1.1 remote-as 64517
1832 neighbor 10.3.1.1 peer-group cust-default
1833 neighbor 10.3.1.1 description customer1
1834 neighbor 10.3.1.1 prefix-list pl-cust1-network in
1835 neighbor 10.4.1.1 remote-as 64518
1836 neighbor 10.4.1.1 peer-group cust
1837 neighbor 10.4.1.1 prefix-list pl-cust2-network in
1838 neighbor 10.4.1.1 description customer2
1839 neighbor 10.5.1.1 remote-as 64519
1840 neighbor 10.5.1.1 peer-group peer
1841 neighbor 10.5.1.1 prefix-list pl-peer1-network in
1842 neighbor 10.5.1.1 description peer AS 1
1843 neighbor 10.6.1.1 remote-as 64520
1844 neighbor 10.6.1.1 peer-group peer
1845 neighbor 10.6.1.1 prefix-list pl-peer2-network in
1846 neighbor 10.6.1.1 description peer AS 2
1848 ip prefix-list pl-default permit 0.0.0.0/0
1850 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
1851 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
1853 ip prefix-list pl-cust1-network permit 10.3.1.0/24
1854 ip prefix-list pl-cust1-network permit 10.3.2.0/24
1856 ip prefix-list pl-cust2-network permit 10.4.1.0/24
1858 ip prefix-list pl-peer1-network permit 10.5.1.0/24
1859 ip prefix-list pl-peer1-network permit 10.5.2.0/24
1860 ip prefix-list pl-peer1-network permit 192.168.0.0/24
1862 ip prefix-list pl-peer2-network permit 10.6.1.0/24
1863 ip prefix-list pl-peer2-network permit 10.6.2.0/24
1864 ip prefix-list pl-peer2-network permit 192.168.1.0/24
1865 ip prefix-list pl-peer2-network permit 192.168.2.0/24
1866 ip prefix-list pl-peer2-network permit 172.16.1/24
1868 ip as-path access-list asp-own-as permit ^$
1869 ip as-path access-list asp-own-as permit _64512_
1871 ! #################################################################
1872 ! Match communities we provide actions for, on routes receives from
1873 ! customers. Communities values of <our-ASN>:X, with X, have actions:
1875 ! 100 - blackhole the prefix
1876 ! 200 - set no_export
1877 ! 300 - advertise only to other customers
1878 ! 400 - advertise only to upstreams
1879 ! 500 - set no_export when advertising to upstreams
1880 ! 2X00 - set local_preference to X00
1882 ! blackhole the prefix of the route
1883 ip community-list standard cm-blackhole permit 64512:100
1885 ! set no-export community before advertising
1886 ip community-list standard cm-set-no-export permit 64512:200
1888 ! advertise only to other customers
1889 ip community-list standard cm-cust-only permit 64512:300
1891 ! advertise only to upstreams
1892 ip community-list standard cm-upstream-only permit 64512:400
1894 ! advertise to upstreams with no-export
1895 ip community-list standard cm-upstream-noexport permit 64512:500
1897 ! set local-pref to least significant 3 digits of the community
1898 ip community-list standard cm-prefmod-100 permit 64512:2100
1899 ip community-list standard cm-prefmod-200 permit 64512:2200
1900 ip community-list standard cm-prefmod-300 permit 64512:2300
1901 ip community-list standard cm-prefmod-400 permit 64512:2400
1902 ip community-list expanded cme-prefmod-range permit 64512:2...
1904 ! Informational communities
1906 ! 3000 - learned from upstream
1907 ! 3100 - learned from customer
1908 ! 3200 - learned from peer
1910 ip community-list standard cm-learnt-upstream permit 64512:3000
1911 ip community-list standard cm-learnt-cust permit 64512:3100
1912 ip community-list standard cm-learnt-peer permit 64512:3200
1914 ! ###################################################################
1915 ! Utility route-maps
1917 ! These utility route-maps generally should not used to permit/deny
1918 ! routes, i.e. they do not have meaning as filters, and hence probably
1919 ! should be used with 'on-match next'. These all finish with an empty
1920 ! permit entry so as not interfere with processing in the caller.
1922 route-map rm-no-export permit 10
1923 set community additive no-export
1924 route-map rm-no-export permit 20
1926 route-map rm-blackhole permit 10
1927 description blackhole, up-pref and ensure it cant escape this AS
1928 set ip next-hop 127.0.0.1
1929 set local-preference 10
1930 set community additive no-export
1931 route-map rm-blackhole permit 20
1933 ! Set local-pref as requested
1934 route-map rm-prefmod permit 10
1935 match community cm-prefmod-100
1936 set local-preference 100
1937 route-map rm-prefmod permit 20
1938 match community cm-prefmod-200
1939 set local-preference 200
1940 route-map rm-prefmod permit 30
1941 match community cm-prefmod-300
1942 set local-preference 300
1943 route-map rm-prefmod permit 40
1944 match community cm-prefmod-400
1945 set local-preference 400
1946 route-map rm-prefmod permit 50
1948 ! Community actions to take on receipt of route.
1949 route-map rm-community-in permit 10
1950 description check for blackholing, no point continuing if it matches.
1951 match community cm-blackhole
1953 route-map rm-community-in permit 20
1954 match community cm-set-no-export
1957 route-map rm-community-in permit 30
1958 match community cme-prefmod-range
1960 route-map rm-community-in permit 40
1962 ! #####################################################################
1963 ! Community actions to take when advertising a route.
1964 ! These are filtering route-maps,
1966 ! Deny customer routes to upstream with cust-only set.
1967 route-map rm-community-filt-to-upstream deny 10
1968 match community cm-learnt-cust
1969 match community cm-cust-only
1970 route-map rm-community-filt-to-upstream permit 20
1972 ! Deny customer routes to other customers with upstream-only set.
1973 route-map rm-community-filt-to-cust deny 10
1974 match community cm-learnt-cust
1975 match community cm-upstream-only
1976 route-map rm-community-filt-to-cust permit 20
1978 ! ###################################################################
1979 ! The top-level route-maps applied to sessions. Further entries could
1980 ! be added obviously..
1983 route-map rm-cust-in permit 10
1984 call rm-community-in
1986 route-map rm-cust-in permit 20
1987 set community additive 64512:3100
1988 route-map rm-cust-in permit 30
1990 route-map rm-cust-out permit 10
1991 call rm-community-filt-to-cust
1993 route-map rm-cust-out permit 20
1995 ! Upstream transit ASes
1996 route-map rm-upstream-out permit 10
1997 description filter customer prefixes which are marked cust-only
1998 call rm-community-filt-to-upstream
2000 route-map rm-upstream-out permit 20
2001 description only customer routes are provided to upstreams/peers
2002 match community cm-learnt-cust
2005 ! outbound policy is same as for upstream
2006 route-map rm-peer-out permit 10
2007 call rm-upstream-out
2009 route-map rm-peer-in permit 10
2010 set community additive 64512:3200