2 @c This is part of the Frr Manual.
3 @c @value{COPYRIGHT_STR}
5 @c Copyright @copyright{} 2015 Hewlett Packard Enterprise Development LP
6 @c See file frr.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 Frr 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 Frr 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 Frr 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 Frr 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. Frr
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 Frr 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} {redistribute vpn} {}
585 Redistribute VNC routes to BGP process.
588 @deffn {BGP} {update-delay @var{max-delay}} {}
589 @deffnx {BGP} {update-delay @var{max-delay} @var{establish-wait}} {}
590 This feature is used to enable read-only mode on BGP process restart or when
591 BGP process is cleared using 'clear ip bgp *'. When applicable, read-only mode
592 would begin as soon as the first peer reaches Established status and a timer
593 for max-delay seconds is started.
595 During this mode BGP doesn't run any best-path or generate any updates to its
596 peers. This mode continues until:
597 1. All the configured peers, except the shutdown peers, have sent explicit EOR
598 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
599 Established is considered an implicit-EOR.
600 If the establish-wait optional value is given, then BGP will wait for
601 peers to reach established from the begining of the update-delay till the
602 establish-wait period is over, i.e. the minimum set of established peers for
603 which EOR is expected would be peers established during the establish-wait
604 window, not necessarily all the configured neighbors.
605 2. max-delay period is over.
606 On hitting any of the above two conditions, BGP resumes the decision process
607 and generates updates to its peers.
609 Default max-delay is 0, i.e. the feature is off by default.
612 @deffn {BGP} {table-map @var{route-map-name}} {}
613 This feature is used to apply a route-map on route updates from BGP to Zebra.
614 All the applicable match operations are allowed, such as match on prefix,
615 next-hop, communities, etc. Set operations for this attach-point are limited
616 to metric and next-hop only. Any operation of this feature does not affect
619 Supported for ipv4 and ipv6 address families. It works on multi-paths as well,
620 however, metric setting is based on the best-path only.
628 * BGP Peer commands::
633 @subsection Defining Peer
635 @deffn {BGP} {neighbor @var{peer} remote-as @var{asn}} {}
636 Creates a new neighbor whose remote-as is @var{asn}. @var{peer}
637 can be an IPv4 address or an IPv6 address.
641 neighbor 10.0.0.1 remote-as 2
644 In this case my router, in AS-1, is trying to peer with AS-2 at
647 This command must be the first command used when configuring a neighbor.
648 If the remote-as is not specified, @command{bgpd} will complain like this:
650 can't find neighbor 10.0.0.1
654 @node BGP Peer commands
655 @subsection BGP Peer commands
657 In a @code{router bgp} clause there are neighbor specific configurations
660 @deffn {BGP} {neighbor @var{peer} shutdown} {}
661 @deffnx {BGP} {no neighbor @var{peer} shutdown} {}
662 Shutdown the peer. We can delete the neighbor's configuration by
663 @code{no neighbor @var{peer} remote-as @var{as-number}} but all
664 configuration of the neighbor will be deleted. When you want to
665 preserve the configuration, but want to drop the BGP peer, use this
669 @deffn {BGP} {neighbor @var{peer} ebgp-multihop} {}
670 @deffnx {BGP} {no neighbor @var{peer} ebgp-multihop} {}
673 @deffn {BGP} {neighbor @var{peer} description ...} {}
674 @deffnx {BGP} {no neighbor @var{peer} description ...} {}
675 Set description of the peer.
678 @deffn {BGP} {neighbor @var{peer} version @var{version}} {}
679 Set up the neighbor's BGP version. @var{version} can be @var{4},
680 @var{4+} or @var{4-}. BGP version @var{4} is the default value used for
681 BGP peering. BGP version @var{4+} means that the neighbor supports
682 Multiprotocol Extensions for BGP-4. BGP version @var{4-} is similar but
683 the neighbor speaks the old Internet-Draft revision 00's Multiprotocol
684 Extensions for BGP-4. Some routing software is still using this
688 @deffn {BGP} {neighbor @var{peer} interface @var{ifname}} {}
689 @deffnx {BGP} {no neighbor @var{peer} interface @var{ifname}} {}
690 When you connect to a BGP peer over an IPv6 link-local address, you
691 have to specify the @var{ifname} of the interface used for the
692 connection. To specify IPv4 session addresses, see the
693 @code{neighbor @var{peer} update-source} command below.
695 This command is deprecated and may be removed in a future release. Its
696 use should be avoided.
699 @deffn {BGP} {neighbor @var{peer} next-hop-self [all]} {}
700 @deffnx {BGP} {no neighbor @var{peer} next-hop-self [all]} {}
701 This command specifies an announced route's nexthop as being equivalent
702 to the address of the bgp router if it is learned via eBGP.
703 If the optional keyword @code{all} is specified the modifiation is done
704 also for routes learned via iBGP.
707 @deffn {BGP} {neighbor @var{peer} update-source @var{<ifname|address>}} {}
708 @deffnx {BGP} {no neighbor @var{peer} update-source} {}
709 Specify the IPv4 source address to use for the @acronym{BGP} session to this
710 neighbour, may be specified as either an IPv4 address directly or
711 as an interface name (in which case the @command{zebra} daemon MUST be running
712 in order for @command{bgpd} to be able to retrieve interface state).
716 neighbor foo update-source 192.168.0.1
717 neighbor bar update-source lo0
722 @deffn {BGP} {neighbor @var{peer} default-originate} {}
723 @deffnx {BGP} {no neighbor @var{peer} default-originate} {}
724 @command{bgpd}'s default is to not announce the default route (0.0.0.0/0) even it
725 is in routing table. When you want to announce default routes to the
726 peer, use this command.
729 @deffn {BGP} {neighbor @var{peer} port @var{port}} {}
730 @deffnx {BGP} {neighbor @var{peer} port @var{port}} {}
733 @deffn {BGP} {neighbor @var{peer} send-community} {}
734 @deffnx {BGP} {neighbor @var{peer} send-community} {}
737 @deffn {BGP} {neighbor @var{peer} weight @var{weight}} {}
738 @deffnx {BGP} {no neighbor @var{peer} weight @var{weight}} {}
739 This command specifies a default @var{weight} value for the neighbor's
743 @deffn {BGP} {neighbor @var{peer} maximum-prefix @var{number}} {}
744 @deffnx {BGP} {no neighbor @var{peer} maximum-prefix @var{number}} {}
747 @deffn {BGP} {neighbor @var{peer} local-as @var{as-number}} {}
748 @deffnx {BGP} {neighbor @var{peer} local-as @var{as-number} no-prepend} {}
749 @deffnx {BGP} {neighbor @var{peer} local-as @var{as-number} no-prepend replace-as} {}
750 @deffnx {BGP} {no neighbor @var{peer} local-as} {}
751 Specify an alternate AS for this BGP process when interacting with the
752 specified peer. With no modifiers, the specified local-as is prepended to
753 the received AS_PATH when receiving routing updates from the peer, and
754 prepended to the outgoing AS_PATH (after the process local AS) when
755 transmitting local routes to the peer.
757 If the no-prepend attribute is specified, then the supplied local-as is not
758 prepended to the received AS_PATH.
760 If the replace-as attribute is specified, then only the supplied local-as is
761 prepended to the AS_PATH when transmitting local-route updates to this peer.
763 Note that replace-as can only be specified if no-prepend is.
765 This command is only allowed for eBGP peers.
768 @deffn {BGP} {neighbor @var{peer} ttl-security hops @var{number}} {}
769 @deffnx {BGP} {no neighbor @var{peer} ttl-security hops @var{number}} {}
770 This command enforces Generalized TTL Security Mechanism (GTSM), as
771 specified in RFC 5082. With this command, only neighbors that are the
772 specified number of hops away will be allowed to become neighbors. This
773 command is mututally exclusive with @command{ebgp-multihop}.
777 @subsection Peer filtering
779 @deffn {BGP} {neighbor @var{peer} distribute-list @var{name} [in|out]} {}
780 This command specifies a distribute-list for the peer. @var{direct} is
781 @samp{in} or @samp{out}.
784 @deffn {BGP command} {neighbor @var{peer} prefix-list @var{name} [in|out]} {}
787 @deffn {BGP command} {neighbor @var{peer} filter-list @var{name} [in|out]} {}
790 @deffn {BGP} {neighbor @var{peer} route-map @var{name} [in|out]} {}
791 Apply a route-map on the neighbor. @var{direct} must be @code{in} or
795 @deffn {BGP} {bgp route-reflector allow-outbound-policy} {}
796 By default, attribute modification via route-map policy out is not reflected
797 on reflected routes. This option allows the modifications to be reflected as
798 well. Once enabled, it affects all reflected routes.
801 @c -----------------------------------------------------------------------
803 @section BGP Peer Group
805 @deffn {BGP} {neighbor @var{word} peer-group} {}
806 This command defines a new peer group.
809 @deffn {BGP} {neighbor @var{peer} peer-group @var{word}} {}
810 This command bind specific peer to peer group @var{word}.
813 @node BGP Address Family
814 @section BGP Address Family
816 Multiprotocol BGP enables BGP to carry routing information for multiple
817 Network Layer protocols. BGP supports multiple Address Family
818 Identifier (AFI), namely IPv4 and IPv6. Support is also provided for
819 multiple sets of per-AFI information via Subsequent Address Family
820 Identifiers (SAFI). In addition to unicast information, VPN information
821 @cite{RFC4364} and @cite{RFC4659}, and Encapsulation information
822 @cite{RFC5512} is supported.
824 @deffn {Command} {show ip bgp vpnv4 all} {}
825 @deffnx {Command} {show ipv6 bgp vpn all} {}
826 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
829 @deffn {Command} {show ip bgp encap all} {}
830 @deffnx {Command} {show ipv6 bgp encap all} {}
831 Print active IPV4 or IPV6 routes advertised via the Encapsulation SAFI.
834 @deffn {Command} {show bgp ipv4 encap summary} {}
835 @deffnx {Command} {show bgp ipv4 vpn summary} {}
836 @deffnx {Command} {show bgp ipv6 encap summary} {}
837 @deffnx {Command} {show bgp ipv6 vpn summary} {}
838 Print a summary of neighbor connections for the specified AFI/SAFI combination.
841 @c -----------------------------------------------------------------------
842 @node Autonomous System
843 @section Autonomous System
845 The @acronym{AS,Autonomous System} number is one of the essential
846 element of BGP. BGP is a distance vector routing protocol, and the
847 AS-Path framework provides distance vector metric and loop detection to
848 BGP. @cite{RFC1930, Guidelines for creation, selection, and
849 registration of an Autonomous System (AS)} provides some background on
850 the concepts of an AS.
852 The AS number is a two octet value, ranging in value from 1 to 65535.
853 The AS numbers 64512 through 65535 are defined as private AS numbers.
854 Private AS numbers must not to be advertised in the global Internet.
857 * AS Path Regular Expression::
858 * Display BGP Routes by AS Path::
859 * AS Path Access List::
860 * Using AS Path in Route Map::
861 * Private AS Numbers::
864 @node AS Path Regular Expression
865 @subsection AS Path Regular Expression
867 AS path regular expression can be used for displaying BGP routes and
868 AS path access list. AS path regular expression is based on
869 @code{POSIX 1003.2} regular expressions. Following description is
870 just a subset of @code{POSIX} regular expression. User can use full
871 @code{POSIX} regular expression. Adding to that special character '_'
872 is added for AS path regular expression.
876 Matches any single character.
878 Matches 0 or more occurrences of pattern.
880 Matches 1 or more occurrences of pattern.
882 Match 0 or 1 occurrences of pattern.
884 Matches the beginning of the line.
886 Matches the end of the line.
888 Character @code{_} has special meanings in AS path regular expression.
889 It matches to space and comma , and AS set delimiter @{ and @} and AS
890 confederation delimiter @code{(} and @code{)}. And it also matches to
891 the beginning of the line and the end of the line. So @code{_} can be
892 used for AS value boundaries match. @code{show ip bgp regexp _7675_}
893 matches to all of BGP routes which as AS number include @var{7675}.
896 @node Display BGP Routes by AS Path
897 @subsection Display BGP Routes by AS Path
899 To show BGP routes which has specific AS path information @code{show
900 ip bgp} command can be used.
902 @deffn Command {show ip bgp regexp @var{line}} {}
903 This commands display BGP routes that matches AS path regular
904 expression @var{line}.
907 @node AS Path Access List
908 @subsection AS Path Access List
910 AS path access list is user defined AS path.
912 @deffn {Command} {ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
913 This command defines a new AS path access list.
916 @deffn {Command} {no ip as-path access-list @var{word}} {}
917 @deffnx {Command} {no ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
920 @node Using AS Path in Route Map
921 @subsection Using AS Path in Route Map
923 @deffn {Route Map} {match as-path @var{word}} {}
926 @deffn {Route Map} {set as-path prepend @var{as-path}} {}
927 Prepend the given string of AS numbers to the AS_PATH.
930 @deffn {Route Map} {set as-path prepend last-as @var{num}} {}
931 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
934 @node Private AS Numbers
935 @subsection Private AS Numbers
937 @c -----------------------------------------------------------------------
938 @node BGP Communities Attribute
939 @section BGP Communities Attribute
941 BGP communities attribute is widely used for implementing policy
942 routing. Network operators can manipulate BGP communities attribute
943 based on their network policy. BGP communities attribute is defined
944 in @cite{RFC1997, BGP Communities Attribute} and
945 @cite{RFC1998, An Application of the BGP Community Attribute
946 in Multi-home Routing}. It is an optional transitive attribute,
947 therefore local policy can travel through different autonomous system.
949 Communities attribute is a set of communities values. Each
950 communities value is 4 octet long. The following format is used to
951 define communities value.
955 This format represents 4 octet communities value. @code{AS} is high
956 order 2 octet in digit format. @code{VAL} is low order 2 octet in
957 digit format. This format is useful to define AS oriented policy
958 value. For example, @code{7675:80} can be used when AS 7675 wants to
959 pass local policy value 80 to neighboring peer.
961 @code{internet} represents well-known communities value 0.
963 @code{no-export} represents well-known communities value @code{NO_EXPORT}@*
964 @r{(0xFFFFFF01)}. All routes carry this value must not be advertised
965 to outside a BGP confederation boundary. If neighboring BGP peer is
966 part of BGP confederation, the peer is considered as inside a BGP
967 confederation boundary, so the route will be announced to the peer.
969 @code{no-advertise} represents well-known communities value
970 @code{NO_ADVERTISE}@*@r{(0xFFFFFF02)}. All routes carry this value
971 must not be advertise to other BGP peers.
973 @code{local-AS} represents well-known communities value
974 @code{NO_EXPORT_SUBCONFED} @r{(0xFFFFFF03)}. All routes carry this
975 value must not be advertised to external BGP peers. Even if the
976 neighboring router is part of confederation, it is considered as
977 external BGP peer, so the route will not be announced to the peer.
980 When BGP communities attribute is received, duplicated communities
981 value in the communities attribute is ignored and each communities
982 values are sorted in numerical order.
985 * BGP Community Lists::
986 * Numbered BGP Community Lists::
987 * BGP Community in Route Map::
988 * Display BGP Routes by Community::
989 * Using BGP Communities Attribute::
992 @node BGP Community Lists
993 @subsection BGP Community Lists
995 BGP community list is a user defined BGP communites attribute list.
996 BGP community list can be used for matching or manipulating BGP
997 communities attribute in updates.
999 There are two types of community list. One is standard community
1000 list and another is expanded community list. Standard community list
1001 defines communities attribute. Expanded community list defines
1002 communities attribute string with regular expression. Standard
1003 community list is compiled into binary format when user define it.
1004 Standard community list will be directly compared to BGP communities
1005 attribute in BGP updates. Therefore the comparison is faster than
1006 expanded community list.
1008 @deffn Command {ip community-list standard @var{name} @{permit|deny@} @var{community}} {}
1009 This command defines a new standard community list. @var{community}
1010 is communities value. The @var{community} is compiled into community
1011 structure. We can define multiple community list under same name. In
1012 that case match will happen user defined order. Once the
1013 community list matches to communities attribute in BGP updates it
1014 return permit or deny by the community list definition. When there is
1015 no matched entry, deny will be returned. When @var{community} is
1016 empty it matches to any routes.
1019 @deffn Command {ip community-list expanded @var{name} @{permit|deny@} @var{line}} {}
1020 This command defines a new expanded community list. @var{line} is a
1021 string expression of communities attribute. @var{line} can include
1022 regular expression to match communities attribute in BGP updates.
1025 @deffn Command {no ip community-list @var{name}} {}
1026 @deffnx Command {no ip community-list standard @var{name}} {}
1027 @deffnx Command {no ip community-list expanded @var{name}} {}
1028 These commands delete community lists specified by @var{name}. All of
1029 community lists shares a single name space. So community lists can be
1030 removed simpley specifying community lists name.
1033 @deffn {Command} {show ip community-list} {}
1034 @deffnx {Command} {show ip community-list @var{name}} {}
1035 This command display current community list information. When
1036 @var{name} is specified the specified community list's information is
1040 # show ip community-list
1041 Named Community standard list CLIST
1042 permit 7675:80 7675:100 no-export
1044 Named Community expanded list EXPAND
1047 # show ip community-list CLIST
1048 Named Community standard list CLIST
1049 permit 7675:80 7675:100 no-export
1054 @node Numbered BGP Community Lists
1055 @subsection Numbered BGP Community Lists
1057 When number is used for BGP community list name, the number has
1058 special meanings. Community list number in the range from 1 and 99 is
1059 standard community list. Community list number in the range from 100
1060 to 199 is expanded community list. These community lists are called
1061 as numbered community lists. On the other hand normal community lists
1062 is called as named community lists.
1064 @deffn Command {ip community-list <1-99> @{permit|deny@} @var{community}} {}
1065 This command defines a new community list. <1-99> is standard
1066 community list number. Community list name within this range defines
1067 standard community list. When @var{community} is empty it matches to
1071 @deffn Command {ip community-list <100-199> @{permit|deny@} @var{community}} {}
1072 This command defines a new community list. <100-199> is expanded
1073 community list number. Community list name within this range defines
1074 expanded community list.
1077 @deffn Command {ip community-list @var{name} @{permit|deny@} @var{community}} {}
1078 When community list type is not specifed, the community list type is
1079 automatically detected. If @var{community} can be compiled into
1080 communities attribute, the community list is defined as a standard
1081 community list. Otherwise it is defined as an expanded community
1082 list. This feature is left for backward compability. Use of this
1083 feature is not recommended.
1086 @node BGP Community in Route Map
1087 @subsection BGP Community in Route Map
1089 In Route Map (@pxref{Route Map}), we can match or set BGP
1090 communities attribute. Using this feature network operator can
1091 implement their network policy based on BGP communities attribute.
1093 Following commands can be used in Route Map.
1095 @deffn {Route Map} {match community @var{word}} {}
1096 @deffnx {Route Map} {match community @var{word} exact-match} {}
1097 This command perform match to BGP updates using community list
1098 @var{word}. When the one of BGP communities value match to the one of
1099 communities value in community list, it is match. When
1100 @code{exact-match} keyword is spcified, match happen only when BGP
1101 updates have completely same communities value specified in the
1105 @deffn {Route Map} {set community none} {}
1106 @deffnx {Route Map} {set community @var{community}} {}
1107 @deffnx {Route Map} {set community @var{community} additive} {}
1108 This command manipulate communities value in BGP updates. When
1109 @code{none} is specified as communities value, it removes entire
1110 communities attribute from BGP updates. When @var{community} is not
1111 @code{none}, specified communities value is set to BGP updates. If
1112 BGP updates already has BGP communities value, the existing BGP
1113 communities value is replaced with specified @var{community} value.
1114 When @code{additive} keyword is specified, @var{community} is appended
1115 to the existing communities value.
1118 @deffn {Route Map} {set comm-list @var{word} delete} {}
1119 This command remove communities value from BGP communities attribute.
1120 The @var{word} is community list name. When BGP route's communities
1121 value matches to the community list @var{word}, the communities value
1122 is removed. When all of communities value is removed eventually, the
1123 BGP update's communities attribute is completely removed.
1126 @node Display BGP Routes by Community
1127 @subsection Display BGP Routes by Community
1129 To show BGP routes which has specific BGP communities attribute,
1130 @code{show ip bgp} command can be used. The @var{community} value and
1131 community list can be used for @code{show ip bgp} command.
1133 @deffn Command {show ip bgp community} {}
1134 @deffnx Command {show ip bgp community @var{community}} {}
1135 @deffnx Command {show ip bgp community @var{community} exact-match} {}
1136 @code{show ip bgp community} displays BGP routes which has communities
1137 attribute. When @var{community} is specified, BGP routes that matches
1138 @var{community} value is displayed. For this command, @code{internet}
1139 keyword can't be used for @var{community} value. When
1140 @code{exact-match} is specified, it display only routes that have an
1144 @deffn Command {show ip bgp community-list @var{word}} {}
1145 @deffnx Command {show ip bgp community-list @var{word} exact-match} {}
1146 This commands display BGP routes that matches community list
1147 @var{word}. When @code{exact-match} is specified, display only routes
1148 that have an exact match.
1151 @node Using BGP Communities Attribute
1152 @subsection Using BGP Communities Attribute
1154 Following configuration is the most typical usage of BGP communities
1155 attribute. AS 7675 provides upstream Internet connection to AS 100.
1156 When following configuration exists in AS 7675, AS 100 networks
1157 operator can set local preference in AS 7675 network by setting BGP
1158 communities attribute to the updates.
1162 neighbor 192.168.0.1 remote-as 100
1163 neighbor 192.168.0.1 route-map RMAP in
1165 ip community-list 70 permit 7675:70
1166 ip community-list 70 deny
1167 ip community-list 80 permit 7675:80
1168 ip community-list 80 deny
1169 ip community-list 90 permit 7675:90
1170 ip community-list 90 deny
1172 route-map RMAP permit 10
1174 set local-preference 70
1176 route-map RMAP permit 20
1178 set local-preference 80
1180 route-map RMAP permit 30
1182 set local-preference 90
1185 Following configuration announce 10.0.0.0/8 from AS 100 to AS 7675.
1186 The route has communities value 7675:80 so when above configuration
1187 exists in AS 7675, announced route's local preference will be set to
1193 neighbor 192.168.0.2 remote-as 7675
1194 neighbor 192.168.0.2 route-map RMAP out
1196 ip prefix-list PLIST permit 10.0.0.0/8
1198 route-map RMAP permit 10
1199 match ip address prefix-list PLIST
1200 set community 7675:80
1203 Following configuration is an example of BGP route filtering using
1204 communities attribute. This configuration only permit BGP routes
1205 which has BGP communities value 0:80 or 0:90. Network operator can
1206 put special internal communities value at BGP border router, then
1207 limit the BGP routes announcement into the internal network.
1211 neighbor 192.168.0.1 remote-as 100
1212 neighbor 192.168.0.1 route-map RMAP in
1214 ip community-list 1 permit 0:80 0:90
1216 route-map RMAP permit in
1220 Following exmaple filter BGP routes which has communities value 1:1.
1221 When there is no match community-list returns deny. To avoid
1222 filtering all of routes, we need to define permit any at last.
1226 neighbor 192.168.0.1 remote-as 100
1227 neighbor 192.168.0.1 route-map RMAP in
1229 ip community-list standard FILTER deny 1:1
1230 ip community-list standard FILTER permit
1232 route-map RMAP permit 10
1233 match community FILTER
1236 Communities value keyword @code{internet} has special meanings in
1237 standard community lists. In below example @code{internet} act as
1238 match any. It matches all of BGP routes even if the route does not
1239 have communities attribute at all. So community list @code{INTERNET}
1240 is same as above example's @code{FILTER}.
1243 ip community-list standard INTERNET deny 1:1
1244 ip community-list standard INTERNET permit internet
1247 Following configuration is an example of communities value deletion.
1248 With this configuration communities value 100:1 and 100:2 is removed
1249 from BGP updates. For communities value deletion, only @code{permit}
1250 community-list is used. @code{deny} community-list is ignored.
1254 neighbor 192.168.0.1 remote-as 100
1255 neighbor 192.168.0.1 route-map RMAP in
1257 ip community-list standard DEL permit 100:1 100:2
1259 route-map RMAP permit 10
1260 set comm-list DEL delete
1263 @c -----------------------------------------------------------------------
1264 @node BGP Extended Communities Attribute
1265 @section BGP Extended Communities Attribute
1267 BGP extended communities attribute is introduced with MPLS VPN/BGP
1268 technology. MPLS VPN/BGP expands capability of network infrastructure
1269 to provide VPN functionality. At the same time it requires a new
1270 framework for policy routing. With BGP Extended Communities Attribute
1271 we can use Route Target or Site of Origin for implementing network
1272 policy for MPLS VPN/BGP.
1274 BGP Extended Communities Attribute is similar to BGP Communities
1275 Attribute. It is an optional transitive attribute. BGP Extended
1276 Communities Attribute can carry multiple Extended Community value.
1277 Each Extended Community value is eight octet length.
1279 BGP Extended Communities Attribute provides an extended range
1280 compared with BGP Communities Attribute. Adding to that there is a
1281 type field in each value to provides community space structure.
1283 There are two format to define Extended Community value. One is AS
1284 based format the other is IP address based format.
1288 This is a format to define AS based Extended Community value.
1289 @code{AS} part is 2 octets Global Administrator subfield in Extended
1290 Community value. @code{VAL} part is 4 octets Local Administrator
1291 subfield. @code{7675:100} represents AS 7675 policy value 100.
1292 @item IP-Address:VAL
1293 This is a format to define IP address based Extended Community value.
1294 @code{IP-Address} part is 4 octets Global Administrator subfield.
1295 @code{VAL} part is 2 octets Local Administrator subfield.
1296 @code{10.0.0.1:100} represents
1300 * BGP Extended Community Lists::
1301 * BGP Extended Communities in Route Map::
1304 @node BGP Extended Community Lists
1305 @subsection BGP Extended Community Lists
1307 Expanded Community Lists is a user defined BGP Expanded Community
1310 @deffn Command {ip extcommunity-list standard @var{name} @{permit|deny@} @var{extcommunity}} {}
1311 This command defines a new standard extcommunity-list.
1312 @var{extcommunity} is extended communities value. The
1313 @var{extcommunity} is compiled into extended community structure. We
1314 can define multiple extcommunity-list under same name. In that case
1315 match will happen user defined order. Once the extcommunity-list
1316 matches to extended communities attribute in BGP updates it return
1317 permit or deny based upon the extcommunity-list definition. When
1318 there is no matched entry, deny will be returned. When
1319 @var{extcommunity} is empty it matches to any routes.
1322 @deffn Command {ip extcommunity-list expanded @var{name} @{permit|deny@} @var{line}} {}
1323 This command defines a new expanded extcommunity-list. @var{line} is
1324 a string expression of extended communities attribute. @var{line} can
1325 include regular expression to match extended communities attribute in
1329 @deffn Command {no ip extcommunity-list @var{name}} {}
1330 @deffnx Command {no ip extcommunity-list standard @var{name}} {}
1331 @deffnx Command {no ip extcommunity-list expanded @var{name}} {}
1332 These commands delete extended community lists specified by
1333 @var{name}. All of extended community lists shares a single name
1334 space. So extended community lists can be removed simpley specifying
1338 @deffn {Command} {show ip extcommunity-list} {}
1339 @deffnx {Command} {show ip extcommunity-list @var{name}} {}
1340 This command display current extcommunity-list information. When
1341 @var{name} is specified the community list's information is shown.
1344 # show ip extcommunity-list
1348 @node BGP Extended Communities in Route Map
1349 @subsection BGP Extended Communities in Route Map
1351 @deffn {Route Map} {match extcommunity @var{word}} {}
1354 @deffn {Route Map} {set extcommunity rt @var{extcommunity}} {}
1355 This command set Route Target value.
1358 @deffn {Route Map} {set extcommunity soo @var{extcommunity}} {}
1359 This command set Site of Origin value.
1362 @c -----------------------------------------------------------------------
1363 @node Displaying BGP routes
1364 @section Displaying BGP Routes
1368 * More Show IP BGP::
1372 @subsection Show IP BGP
1374 @deffn {Command} {show ip bgp} {}
1375 @deffnx {Command} {show ip bgp @var{A.B.C.D}} {}
1376 @deffnx {Command} {show ip bgp @var{X:X::X:X}} {}
1377 This command displays BGP routes. When no route is specified it
1378 display all of IPv4 BGP routes.
1382 BGP table version is 0, local router ID is 10.1.1.1
1383 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
1384 Origin codes: i - IGP, e - EGP, ? - incomplete
1386 Network Next Hop Metric LocPrf Weight Path
1387 *> 1.1.1.1/32 0.0.0.0 0 32768 i
1389 Total number of prefixes 1
1392 @node More Show IP BGP
1393 @subsection More Show IP BGP
1395 @deffn {Command} {show ip bgp regexp @var{line}} {}
1396 This command display BGP routes using AS path regular expression (@pxref{Display BGP Routes by AS Path}).
1399 @deffn Command {show ip bgp community @var{community}} {}
1400 @deffnx Command {show ip bgp community @var{community} exact-match} {}
1401 This command display BGP routes using @var{community} (@pxref{Display
1402 BGP Routes by Community}).
1405 @deffn Command {show ip bgp community-list @var{word}} {}
1406 @deffnx Command {show ip bgp community-list @var{word} exact-match} {}
1407 This command display BGP routes using community list (@pxref{Display
1408 BGP Routes by Community}).
1411 @deffn {Command} {show ip bgp summary} {}
1414 @deffn {Command} {show ip bgp neighbor [@var{peer}]} {}
1417 @deffn {Command} {clear ip bgp @var{peer}} {}
1418 Clear peers which have addresses of X.X.X.X
1421 @deffn {Command} {clear ip bgp @var{peer} soft in} {}
1422 Clear peer using soft reconfiguration.
1425 @deffn {Command} {show ip bgp dampened-paths} {}
1426 Display paths suppressed due to dampening
1429 @deffn {Command} {show ip bgp flap-statistics} {}
1430 Display flap statistics of routes
1433 @deffn {Command} {show debug} {}
1436 @deffn {Command} {debug event} {}
1439 @deffn {Command} {debug update} {}
1442 @deffn {Command} {debug keepalive} {}
1445 @deffn {Command} {no debug event} {}
1448 @deffn {Command} {no debug update} {}
1451 @deffn {Command} {no debug keepalive} {}
1454 @node Capability Negotiation
1455 @section Capability Negotiation
1457 When adding IPv6 routing information exchange feature to BGP. There
1458 were some proposals. @acronym{IETF,Internet Engineering Task Force}
1459 @acronym{IDR, Inter Domain Routing} @acronym{WG, Working group} adopted
1460 a proposal called Multiprotocol Extension for BGP. The specification
1461 is described in @cite{RFC2283}. The protocol does not define new protocols.
1462 It defines new attributes to existing BGP. When it is used exchanging
1463 IPv6 routing information it is called BGP-4+. When it is used for
1464 exchanging multicast routing information it is called MBGP.
1466 @command{bgpd} supports Multiprotocol Extension for BGP. So if remote
1467 peer supports the protocol, @command{bgpd} can exchange IPv6 and/or
1468 multicast routing information.
1470 Traditional BGP did not have the feature to detect remote peer's
1471 capabilities, e.g. whether it can handle prefix types other than IPv4
1472 unicast routes. This was a big problem using Multiprotocol Extension
1473 for BGP to operational network. @cite{RFC2842, Capabilities
1474 Advertisement with BGP-4} adopted a feature called Capability
1475 Negotiation. @command{bgpd} use this Capability Negotiation to detect
1476 the remote peer's capabilities. If the peer is only configured as IPv4
1477 unicast neighbor, @command{bgpd} does not send these Capability
1478 Negotiation packets (at least not unless other optional BGP features
1479 require capability negotation).
1481 By default, Frr will bring up peering with minimal common capability
1482 for the both sides. For example, local router has unicast and
1483 multicast capabilitie and remote router has unicast capability. In
1484 this case, the local router will establish the connection with unicast
1485 only capability. When there are no common capabilities, Frr sends
1486 Unsupported Capability error and then resets the connection.
1488 If you want to completely match capabilities with remote peer. Please
1489 use @command{strict-capability-match} command.
1491 @deffn {BGP} {neighbor @var{peer} strict-capability-match} {}
1492 @deffnx {BGP} {no neighbor @var{peer} strict-capability-match} {}
1493 Strictly compares remote capabilities and local capabilities. If capabilities
1494 are different, send Unsupported Capability error then reset connection.
1497 You may want to disable sending Capability Negotiation OPEN message
1498 optional parameter to the peer when remote peer does not implement
1499 Capability Negotiation. Please use @command{dont-capability-negotiate}
1500 command to disable the feature.
1502 @deffn {BGP} {neighbor @var{peer} dont-capability-negotiate} {}
1503 @deffnx {BGP} {no neighbor @var{peer} dont-capability-negotiate} {}
1504 Suppress sending Capability Negotiation as OPEN message optional
1505 parameter to the peer. This command only affects the peer is configured
1506 other than IPv4 unicast configuration.
1509 When remote peer does not have capability negotiation feature, remote
1510 peer will not send any capabilities at all. In that case, bgp
1511 configures the peer with configured capabilities.
1513 You may prefer locally configured capabilities more than the negotiated
1514 capabilities even though remote peer sends capabilities. If the peer
1515 is configured by @command{override-capability}, @command{bgpd} ignores
1516 received capabilities then override negotiated capabilities with
1519 @deffn {BGP} {neighbor @var{peer} override-capability} {}
1520 @deffnx {BGP} {no neighbor @var{peer} override-capability} {}
1521 Override the result of Capability Negotiation with local configuration.
1522 Ignore remote peer's capability value.
1525 @node Route Reflector
1526 @section Route Reflector
1528 @deffn {BGP} {bgp cluster-id @var{a.b.c.d}} {}
1531 @deffn {BGP} {neighbor @var{peer} route-reflector-client} {}
1532 @deffnx {BGP} {no neighbor @var{peer} route-reflector-client} {}
1536 @section Route Server
1538 At an Internet Exchange point, many ISPs are connected to each other by
1539 external BGP peering. Normally these external BGP connection are done by
1540 @samp{full mesh} method. As with internal BGP full mesh formation,
1541 this method has a scaling problem.
1543 This scaling problem is well known. Route Server is a method to resolve
1544 the problem. Each ISP's BGP router only peers to Route Server. Route
1545 Server serves as BGP information exchange to other BGP routers. By
1546 applying this method, numbers of BGP connections is reduced from
1547 O(n*(n-1)/2) to O(n).
1549 Unlike normal BGP router, Route Server must have several routing tables
1550 for managing different routing policies for each BGP speaker. We call the
1551 routing tables as different @code{view}s. @command{bgpd} can work as
1552 normal BGP router or Route Server or both at the same time.
1555 * Multiple instance::
1556 * BGP instance and view::
1558 * Viewing the view::
1561 @node Multiple instance
1562 @subsection Multiple instance
1564 To enable multiple view function of @code{bgpd}, you must turn on
1565 multiple instance feature beforehand.
1567 @deffn {Command} {bgp multiple-instance} {}
1568 Enable BGP multiple instance feature. After this feature is enabled,
1569 you can make multiple BGP instances or multiple BGP views.
1572 @deffn {Command} {no bgp multiple-instance} {}
1573 Disable BGP multiple instance feature. You can not disable this feature
1574 when BGP multiple instances or views exist.
1577 When you want to make configuration more Cisco like one,
1579 @deffn {Command} {bgp config-type cisco} {}
1580 Cisco compatible BGP configuration output.
1583 When bgp config-type cisco is specified,
1585 ``no synchronization'' is displayed.
1586 ``no auto-summary'' is displayed.
1588 ``network'' and ``aggregate-address'' argument is displayed as
1591 Frr: network 10.0.0.0/8
1592 Cisco: network 10.0.0.0
1594 Frr: aggregate-address 192.168.0.0/24
1595 Cisco: aggregate-address 192.168.0.0 255.255.255.0
1597 Community attribute handling is also different. If there is no
1598 configuration is specified community attribute and extended community
1599 attribute are sent to neighbor. When user manually disable the
1600 feature community attribute is not sent to the neighbor. In case of
1601 @command{bgp config-type cisco} is specified, community attribute is not
1602 sent to the neighbor by default. To send community attribute user has
1603 to specify @command{neighbor A.B.C.D send-community} command.
1608 neighbor 10.0.0.1 remote-as 1
1609 no neighbor 10.0.0.1 send-community
1612 neighbor 10.0.0.1 remote-as 1
1613 neighbor 10.0.0.1 send-community
1617 @deffn {Command} {bgp config-type zebra} {}
1618 Frr style BGP configuration. This is default.
1621 @node BGP instance and view
1622 @subsection BGP instance and view
1624 BGP instance is a normal BGP process. The result of route selection
1625 goes to the kernel routing table. You can setup different AS at the
1626 same time when BGP multiple instance feature is enabled.
1628 @deffn {Command} {router bgp @var{as-number}} {}
1629 Make a new BGP instance. You can use arbitrary word for the @var{name}.
1634 bgp multiple-instance
1637 neighbor 10.0.0.1 remote-as 2
1638 neighbor 10.0.0.2 remote-as 3
1641 neighbor 10.0.0.3 remote-as 4
1642 neighbor 10.0.0.4 remote-as 5
1646 BGP view is almost same as normal BGP process. The result of
1647 route selection does not go to the kernel routing table. BGP view is
1648 only for exchanging BGP routing information.
1650 @deffn {Command} {router bgp @var{as-number} view @var{name}} {}
1651 Make a new BGP view. You can use arbitrary word for the @var{name}. This
1652 view's route selection result does not go to the kernel routing table.
1655 With this command, you can setup Route Server like below.
1659 bgp multiple-instance
1662 neighbor 10.0.0.1 remote-as 2
1663 neighbor 10.0.0.2 remote-as 3
1666 neighbor 10.0.0.3 remote-as 4
1667 neighbor 10.0.0.4 remote-as 5
1671 @node Routing policy
1672 @subsection Routing policy
1674 You can set different routing policy for a peer. For example, you can
1675 set different filter for a peer.
1679 bgp multiple-instance
1682 neighbor 10.0.0.1 remote-as 2
1683 neighbor 10.0.0.1 distribute-list 1 in
1686 neighbor 10.0.0.1 remote-as 2
1687 neighbor 10.0.0.1 distribute-list 2 in
1691 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view
1692 2. When the update is inserted into view 1, distribute-list 1 is
1693 applied. On the other hand, when the update is inserted into view 2,
1694 distribute-list 2 is applied.
1696 @node Viewing the view
1697 @subsection Viewing the view
1699 To display routing table of BGP view, you must specify view name.
1701 @deffn {Command} {show ip bgp view @var{name}} {}
1702 Display routing table of BGP view @var{name}.
1705 @node How to set up a 6-Bone connection
1706 @section How to set up a 6-Bone connection
1714 ! Actually there is no need to configure zebra
1720 ! This means that routes go through zebra and into the kernel.
1724 ! MP-BGP configuration
1727 bgp router-id 10.0.0.1
1728 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as @var{as-number}
1731 network 3ffe:506::/32
1732 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
1733 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
1734 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as @var{as-number}
1735 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
1738 ipv6 access-list all permit any
1740 ! Set output nexthop address.
1742 route-map set-nexthop permit 10
1743 match ipv6 address all
1744 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
1745 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
1747 ! logfile FILENAME is obsolete. Please use log file FILENAME
1754 @node Dump BGP packets and table
1755 @section Dump BGP packets and table
1757 @deffn Command {dump bgp all @var{path} [@var{interval}]} {}
1758 @deffnx Command {dump bgp all-et @var{path} [@var{interval}]} {}
1759 @deffnx Command {no dump bgp all [@var{path}] [@var{interval}]} {}
1760 Dump all BGP packet and events to @var{path} file.
1761 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1762 The path @var{path} can be set with date and time formatting (strftime).
1763 The type ‘all-et’ enables support for Extended Timestamp Header (@pxref{Packet Binary Dump Format}).
1764 (@pxref{Packet Binary Dump Format})
1767 @deffn Command {dump bgp updates @var{path} [@var{interval}]} {}
1768 @deffnx Command {dump bgp updates-et @var{path} [@var{interval}]} {}
1769 @deffnx Command {no dump bgp updates [@var{path}] [@var{interval}]} {}
1770 Dump only BGP updates messages to @var{path} file.
1771 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1772 The path @var{path} can be set with date and time formatting (strftime).
1773 The type ‘updates-et’ enables support for Extended Timestamp Header (@pxref{Packet Binary Dump Format}).
1776 @deffn Command {dump bgp routes-mrt @var{path}} {}
1777 @deffnx Command {dump bgp routes-mrt @var{path} @var{interval}} {}
1778 @deffnx Command {no dump bgp route-mrt [@var{path}] [@var{interval}]} {}
1779 Dump whole BGP routing table to @var{path}. This is heavy process.
1780 The path @var{path} can be set with date and time formatting (strftime).
1781 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1784 Note: the interval variable can also be set using hours and minutes: 04h20m00.
1787 @node BGP Configuration Examples
1788 @section BGP Configuration Examples
1790 Example of a session to an upstream, advertising only one prefix to it.
1794 bgp router-id 10.236.87.1
1795 network 10.236.87.0/24
1796 neighbor upstream peer-group
1797 neighbor upstream remote-as 64515
1798 neighbor upstream capability dynamic
1799 neighbor upstream prefix-list pl-allowed-adv out
1800 neighbor 10.1.1.1 peer-group upstream
1801 neighbor 10.1.1.1 description ACME ISP
1803 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
1804 ip prefix-list pl-allowed-adv seq 10 deny any
1808 A more complex example. With upstream, peer and customer sessions.
1809 Advertising global prefixes and NO_EXPORT prefixes and providing
1810 actions for customer routes based on community values. Extensive use of
1811 route-maps and the 'call' feature to support selective advertising of
1812 prefixes. This example is intended as guidance only, it has NOT been
1813 tested and almost certainly containts silly mistakes, if not serious
1818 bgp router-id 10.236.87.1
1819 network 10.123.456.0/24
1820 network 10.123.456.128/25 route-map rm-no-export
1821 neighbor upstream capability dynamic
1822 neighbor upstream route-map rm-upstream-out out
1823 neighbor cust capability dynamic
1824 neighbor cust route-map rm-cust-in in
1825 neighbor cust route-map rm-cust-out out
1826 neighbor cust send-community both
1827 neighbor peer capability dynamic
1828 neighbor peer route-map rm-peer-in in
1829 neighbor peer route-map rm-peer-out out
1830 neighbor peer send-community both
1831 neighbor 10.1.1.1 remote-as 64515
1832 neighbor 10.1.1.1 peer-group upstream
1833 neighbor 10.2.1.1 remote-as 64516
1834 neighbor 10.2.1.1 peer-group upstream
1835 neighbor 10.3.1.1 remote-as 64517
1836 neighbor 10.3.1.1 peer-group cust-default
1837 neighbor 10.3.1.1 description customer1
1838 neighbor 10.3.1.1 prefix-list pl-cust1-network in
1839 neighbor 10.4.1.1 remote-as 64518
1840 neighbor 10.4.1.1 peer-group cust
1841 neighbor 10.4.1.1 prefix-list pl-cust2-network in
1842 neighbor 10.4.1.1 description customer2
1843 neighbor 10.5.1.1 remote-as 64519
1844 neighbor 10.5.1.1 peer-group peer
1845 neighbor 10.5.1.1 prefix-list pl-peer1-network in
1846 neighbor 10.5.1.1 description peer AS 1
1847 neighbor 10.6.1.1 remote-as 64520
1848 neighbor 10.6.1.1 peer-group peer
1849 neighbor 10.6.1.1 prefix-list pl-peer2-network in
1850 neighbor 10.6.1.1 description peer AS 2
1852 ip prefix-list pl-default permit 0.0.0.0/0
1854 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
1855 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
1857 ip prefix-list pl-cust1-network permit 10.3.1.0/24
1858 ip prefix-list pl-cust1-network permit 10.3.2.0/24
1860 ip prefix-list pl-cust2-network permit 10.4.1.0/24
1862 ip prefix-list pl-peer1-network permit 10.5.1.0/24
1863 ip prefix-list pl-peer1-network permit 10.5.2.0/24
1864 ip prefix-list pl-peer1-network permit 192.168.0.0/24
1866 ip prefix-list pl-peer2-network permit 10.6.1.0/24
1867 ip prefix-list pl-peer2-network permit 10.6.2.0/24
1868 ip prefix-list pl-peer2-network permit 192.168.1.0/24
1869 ip prefix-list pl-peer2-network permit 192.168.2.0/24
1870 ip prefix-list pl-peer2-network permit 172.16.1/24
1872 ip as-path access-list asp-own-as permit ^$
1873 ip as-path access-list asp-own-as permit _64512_
1875 ! #################################################################
1876 ! Match communities we provide actions for, on routes receives from
1877 ! customers. Communities values of <our-ASN>:X, with X, have actions:
1879 ! 100 - blackhole the prefix
1880 ! 200 - set no_export
1881 ! 300 - advertise only to other customers
1882 ! 400 - advertise only to upstreams
1883 ! 500 - set no_export when advertising to upstreams
1884 ! 2X00 - set local_preference to X00
1886 ! blackhole the prefix of the route
1887 ip community-list standard cm-blackhole permit 64512:100
1889 ! set no-export community before advertising
1890 ip community-list standard cm-set-no-export permit 64512:200
1892 ! advertise only to other customers
1893 ip community-list standard cm-cust-only permit 64512:300
1895 ! advertise only to upstreams
1896 ip community-list standard cm-upstream-only permit 64512:400
1898 ! advertise to upstreams with no-export
1899 ip community-list standard cm-upstream-noexport permit 64512:500
1901 ! set local-pref to least significant 3 digits of the community
1902 ip community-list standard cm-prefmod-100 permit 64512:2100
1903 ip community-list standard cm-prefmod-200 permit 64512:2200
1904 ip community-list standard cm-prefmod-300 permit 64512:2300
1905 ip community-list standard cm-prefmod-400 permit 64512:2400
1906 ip community-list expanded cme-prefmod-range permit 64512:2...
1908 ! Informational communities
1910 ! 3000 - learned from upstream
1911 ! 3100 - learned from customer
1912 ! 3200 - learned from peer
1914 ip community-list standard cm-learnt-upstream permit 64512:3000
1915 ip community-list standard cm-learnt-cust permit 64512:3100
1916 ip community-list standard cm-learnt-peer permit 64512:3200
1918 ! ###################################################################
1919 ! Utility route-maps
1921 ! These utility route-maps generally should not used to permit/deny
1922 ! routes, i.e. they do not have meaning as filters, and hence probably
1923 ! should be used with 'on-match next'. These all finish with an empty
1924 ! permit entry so as not interfere with processing in the caller.
1926 route-map rm-no-export permit 10
1927 set community additive no-export
1928 route-map rm-no-export permit 20
1930 route-map rm-blackhole permit 10
1931 description blackhole, up-pref and ensure it cant escape this AS
1932 set ip next-hop 127.0.0.1
1933 set local-preference 10
1934 set community additive no-export
1935 route-map rm-blackhole permit 20
1937 ! Set local-pref as requested
1938 route-map rm-prefmod permit 10
1939 match community cm-prefmod-100
1940 set local-preference 100
1941 route-map rm-prefmod permit 20
1942 match community cm-prefmod-200
1943 set local-preference 200
1944 route-map rm-prefmod permit 30
1945 match community cm-prefmod-300
1946 set local-preference 300
1947 route-map rm-prefmod permit 40
1948 match community cm-prefmod-400
1949 set local-preference 400
1950 route-map rm-prefmod permit 50
1952 ! Community actions to take on receipt of route.
1953 route-map rm-community-in permit 10
1954 description check for blackholing, no point continuing if it matches.
1955 match community cm-blackhole
1957 route-map rm-community-in permit 20
1958 match community cm-set-no-export
1961 route-map rm-community-in permit 30
1962 match community cme-prefmod-range
1964 route-map rm-community-in permit 40
1966 ! #####################################################################
1967 ! Community actions to take when advertising a route.
1968 ! These are filtering route-maps,
1970 ! Deny customer routes to upstream with cust-only set.
1971 route-map rm-community-filt-to-upstream deny 10
1972 match community cm-learnt-cust
1973 match community cm-cust-only
1974 route-map rm-community-filt-to-upstream permit 20
1976 ! Deny customer routes to other customers with upstream-only set.
1977 route-map rm-community-filt-to-cust deny 10
1978 match community cm-learnt-cust
1979 match community cm-upstream-only
1980 route-map rm-community-filt-to-cust permit 20
1982 ! ###################################################################
1983 ! The top-level route-maps applied to sessions. Further entries could
1984 ! be added obviously..
1987 route-map rm-cust-in permit 10
1988 call rm-community-in
1990 route-map rm-cust-in permit 20
1991 set community additive 64512:3100
1992 route-map rm-cust-in permit 30
1994 route-map rm-cust-out permit 10
1995 call rm-community-filt-to-cust
1997 route-map rm-cust-out permit 20
1999 ! Upstream transit ASes
2000 route-map rm-upstream-out permit 10
2001 description filter customer prefixes which are marked cust-only
2002 call rm-community-filt-to-upstream
2004 route-map rm-upstream-out permit 20
2005 description only customer routes are provided to upstreams/peers
2006 match community cm-learnt-cust
2009 ! outbound policy is same as for upstream
2010 route-map rm-peer-out permit 10
2011 call rm-upstream-out
2013 route-map rm-peer-in permit 10
2014 set community additive 64512:3200