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 @c No longer need the precedes character definition
308 However, when MED is involved this need not be the case. With MED it is
309 possible that C is actually preferred over A. So A is preferred to B, B is
310 preferred to C, but C is preferred to A. This can be true even where BGP
311 defines a deterministic ``most preferred'' route out of the full set of
312 A,B,C. With MED, for any given set of routes there may be a
313 deterministically preferred route, but there need not be any way to arrange
314 them into any order of preference. With unmodified MED, the order of
315 preference of routes literally becomes undefined.
317 That MED can induce non-transitive preferences over routes can cause issues.
318 Firstly, it may be perceived to cause routing table churn locally at
319 speakers; secondly, and more seriously, it may cause routing instability in
320 iBGP topologies, where sets of speakers continually oscillate between
323 The first issue arises from how speakers often implement routing decisions.
324 Though BGP defines a selection process that will deterministically select
325 the same route as best at any given speaker, even with MED, that process
326 requires evaluating all routes together. For performance and ease of
327 implementation reasons, many implementations evaluate route preferences in a
328 pair-wise fashion instead. Given there is no well-defined order when MED is
329 involved, the best route that will be chosen becomes subject to
330 implementation details, such as the order the routes are stored in. That
331 may be (locally) non-deterministic, e.g.@: it may be the order the routes
334 This indeterminism may be considered undesirable, though it need not cause
335 problems. It may mean additional routing churn is perceived, as sometimes
336 more updates may be produced than at other times in reaction to some event .
338 This first issue can be fixed with a more deterministic route selection that
339 ensures routes are ordered by the neighbouring AS during selection.
340 @xref{bgp deterministic-med}. This may reduce the number of updates as
341 routes are received, and may in some cases reduce routing churn. Though, it
342 could equally deterministically produce the largest possible set of updates
343 in response to the most common sequence of received updates.
345 A deterministic order of evaluation tends to imply an additional overhead of
346 sorting over any set of n routes to a destination. The implementation of
347 deterministic MED in Quagga scales significantly worse than most sorting
348 algorithms at present, with the number of paths to a given destination.
349 That number is often low enough to not cause any issues, but where there are
350 many paths, the deterministic comparison may quickly become increasingly
351 expensive in terms of CPU.
353 Deterministic local evaluation can @emph{not} fix the second, more major,
354 issue of MED however. Which is that the non-transitive preference of routes
355 MED can cause may lead to routing instability or oscillation across multiple
356 speakers in iBGP topologies. This can occur with full-mesh iBGP, but is
357 particularly problematic in non-full-mesh iBGP topologies that further
358 reduce the routing information known to each speaker. This has primarily
359 been documented with iBGP route-reflection topologies. However, any
360 route-hiding technologies potentially could also exacerbate oscillation with
363 This second issue occurs where speakers each have only a subset of routes,
364 and there are cycles in the preferences between different combinations of
365 routes - as the undefined order of preference of MED allows - and the routes
366 are distributed in a way that causes the BGP speakers to 'chase' those
367 cycles. This can occur even if all speakers use a deterministic order of
368 evaluation in route selection.
370 E.g., speaker 4 in AS A might receive a route from speaker 2 in AS X, and
371 from speaker 3 in AS Y; while speaker 5 in AS A might receive that route
372 from speaker 1 in AS Y. AS Y might set a MED of 200 at speaker 1, and 100
373 at speaker 3. I.e, using ASN:ID:MED to label the speakers:
378 X:2------|--A:4-------A:5--|-Y:1:200
384 Assuming all other metrics are equal (AS_PATH, ORIGIN, 0 IGP costs), then
385 based on the RFC4271 decision process speaker 4 will choose X:2 over
386 Y:3:100, based on the lower ID of 2. Speaker 4 advertises X:2 to speaker 5.
387 Speaker 5 will continue to prefer Y:1:200 based on the ID, and advertise
388 this to speaker 4. Speaker 4 will now have the full set of routes, and the
389 Y:1:200 it receives from 5 will beat X:2, but when speaker 4 compares
390 Y:1:200 to Y:3:100 the MED check now becomes active as the ASes match, and
391 now Y:3:100 is preferred. Speaker 4 therefore now advertises Y:3:100 to 5,
392 which will also agrees that Y:3:100 is preferred to Y:1:200, and so
393 withdraws the latter route from 4. Speaker 4 now has only X:2 and Y:3:100,
394 and X:2 beats Y:3:100, and so speaker 4 implicitly updates its route to
395 speaker 5 to X:2. Speaker 5 sees that Y:1:200 beats X:2 based on the ID,
396 and advertises Y:1:200 to speaker 4, and the cycle continues.
398 The root cause is the lack of a clear order of preference caused by how MED
399 sometimes is and sometimes is not compared, leading to this cycle in the
400 preferences between the routes:
404 /---> X:2 ---beats---> Y:3:100 --\
407 \---beats--- Y:1:200 <---beats---/
411 This particular type of oscillation in full-mesh iBGP topologies can be
412 avoided by speakers preferring already selected, external routes rather than
413 choosing to update to new a route based on a post-MED metric (e.g.
414 router-ID), at the cost of a non-deterministic selection process. Quagga
415 implements this, as do many other implementations, so long as it is not
416 overridden by setting @ref{bgp bestpath compare-routerid}, and see also
417 @ref{BGP decision process}, .
419 However, more complex and insidious cycles of oscillation are possible with
420 iBGP route-reflection, which are not so easily avoided. These have been
421 documented in various places. See, e.g., @cite{McPherson, D. and Gill, V.
422 and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation
423 Condition", IETF RFC3345}, and @cite{Flavel, A. and M. Roughan, "Stable
424 and flexible iBGP", ACM SIGCOMM 2009}, and @cite{Griffin, T. and G. Wilfong,
425 "On the correctness of IBGP configuration", ACM SIGCOMM 2002} for concrete
426 examples and further references.
428 There is as of this writing @emph{no} known way to use MED for its original
429 purpose; @emph{and} reduce routing information in iBGP topologies;
430 @emph{and} be sure to avoid the instability problems of MED due the
431 non-transitive routing preferences it can induce; in general on arbitrary
434 There may be iBGP topology specific ways to reduce the instability risks,
435 even while using MED, e.g.@: by constraining the reflection topology and by
436 tuning IGP costs between route-reflector clusters, see RFC3345 for details.
437 In the near future, the Add-Path extension to BGP may also solve MED
438 oscillation while still allowing MED to be used as intended, by distributing
439 "best-paths per neighbour AS". This would be at the cost of distributing at
440 least as many routes to all speakers as a full-mesh iBGP would, if not more,
441 while also imposing similar CPU overheads as the "Deterministic MED" feature
442 at each Add-Path reflector.
444 More generally, the instability problems that MED can introduce on more
445 complex, non-full-mesh, iBGP topologies may be avoided either by:
450 Setting @ref{bgp always-compare-med}, however this allows MED to be compared
451 across values set by different neighbour ASes, which may not produce
452 coherent desirable results, of itself.
455 Effectively ignoring MED by setting MED to the same value (e.g.@: 0) using
456 @ref{routemap set metric} on all received routes, in combination with
457 setting @ref{bgp always-compare-med} on all speakers. This is the simplest
458 and most performant way to avoid MED oscillation issues, where an AS is happy
459 not to allow neighbours to inject this problematic metric.
463 As MED is evaluated after the AS_PATH length check, another possible use for
464 MED is for intra-AS steering of routes with equal AS_PATH length, as an
465 extension of the last case above. As MED is evaluated before IGP metric,
466 this can allow cold-potato routing to be implemented to send traffic to
467 preferred hand-offs with neighbours, rather than the closest hand-off
468 according to the IGP metric.
470 Note that even if action is taken to address the MED non-transitivity
471 issues, other oscillations may still be possible. E.g., on IGP cost if
472 iBGP and IGP topologies are at cross-purposes with each other - see the
473 Flavel and Roughan paper above for an example. Hence the guideline that the
474 iBGP topology should follow the IGP topology.
476 @deffn {BGP} {bgp deterministic-med} {}
477 @anchor{bgp deterministic-med}
479 Carry out route-selection in way that produces deterministic answers
480 locally, even in the face of MED and the lack of a well-defined order of
481 preference it can induce on routes. Without this option the preferred route
482 with MED may be determined largely by the order that routes were received
485 Setting this option will have a performance cost that may be noticeable when
486 there are many routes for each destination. Currently in Quagga it is
487 implemented in a way that scales poorly as the number of routes per
488 destination increases.
490 The default is that this option is not set.
493 Note that there are other sources of indeterminism in the route selection
494 process, specifically, the preference for older and already selected routes
495 from eBGP peers, @xref{BGP decision process}.
497 @deffn {BGP} {bgp always-compare-med} {}
498 @anchor{bgp always-compare-med}
500 Always compare the MED on routes, even when they were received from
501 different neighbouring ASes. Setting this option makes the order of
502 preference of routes more defined, and should eliminate MED induced
505 If using this option, it may also be desirable to use @ref{routemap set
506 metric} to set MED to 0 on routes received from external neighbours.
508 This option can be used, together with @ref{routemap set metric} to use MED
509 as an intra-AS metric to steer equal-length AS_PATH routes to, e.g., desired
520 * Route Aggregation::
521 * Redistribute to BGP::
525 @subsection BGP route
527 @deffn {BGP} {network @var{A.B.C.D/M}} {}
528 This command adds the announcement network.
535 This configuration example says that network 10.0.0.0/8 will be
536 announced to all neighbors. Some vendors' routers don't advertise
537 routes if they aren't present in their IGP routing tables; @code{bgpd}
538 doesn't care about IGP routes when announcing its routes.
541 @deffn {BGP} {no network @var{A.B.C.D/M}} {}
544 @node Route Aggregation
545 @subsection Route Aggregation
547 @deffn {BGP} {aggregate-address @var{A.B.C.D/M}} {}
548 This command specifies an aggregate address.
551 @deffn {BGP} {aggregate-address @var{A.B.C.D/M} as-set} {}
552 This command specifies an aggregate address. Resulting routes include
556 @deffn {BGP} {aggregate-address @var{A.B.C.D/M} summary-only} {}
557 This command specifies an aggregate address. Aggreated routes will
561 @deffn {BGP} {no aggregate-address @var{A.B.C.D/M}} {}
564 @node Redistribute to BGP
565 @subsection Redistribute to BGP
567 @deffn {BGP} {redistribute kernel} {}
568 Redistribute kernel route to BGP process.
571 @deffn {BGP} {redistribute static} {}
572 Redistribute static route to BGP process.
575 @deffn {BGP} {redistribute connected} {}
576 Redistribute connected route to BGP process.
579 @deffn {BGP} {redistribute rip} {}
580 Redistribute RIP route to BGP process.
583 @deffn {BGP} {redistribute ospf} {}
584 Redistribute OSPF route to BGP process.
587 @deffn {BGP} {update-delay @var{max-delay}} {}
588 @deffnx {BGP} {update-delay @var{max-delay} @var{establish-wait}} {}
589 This feature is used to enable read-only mode on BGP process restart or when
590 BGP process is cleared using 'clear ip bgp *'. When applicable, read-only mode
591 would begin as soon as the first peer reaches Established status and a timer
592 for max-delay seconds is started.
594 During this mode BGP doesn't run any best-path or generate any updates to its
595 peers. This mode continues until:
596 1. All the configured peers, except the shutdown peers, have sent explicit EOR
597 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
598 Established is considered an implicit-EOR.
599 If the establish-wait optional value is given, then BGP will wait for
600 peers to reach established from the begining of the update-delay till the
601 establish-wait period is over, i.e. the minimum set of established peers for
602 which EOR is expected would be peers established during the establish-wait
603 window, not necessarily all the configured neighbors.
604 2. max-delay period is over.
605 On hitting any of the above two conditions, BGP resumes the decision process
606 and generates updates to its peers.
608 Default max-delay is 0, i.e. the feature is off by default.
611 @deffn {BGP} {table-map @var{route-map-name}} {}
612 This feature is used to apply a route-map on route updates from BGP to Zebra.
613 All the applicable match operations are allowed, such as match on prefix,
614 next-hop, communities, etc. Set operations for this attach-point are limited
615 to metric and next-hop only. Any operation of this feature does not affect
618 Supported for ipv4 and ipv6 address families. It works on multi-paths as well,
619 however, metric setting is based on the best-path only.
627 * BGP Peer commands::
632 @subsection Defining Peer
634 @deffn {BGP} {neighbor @var{peer} remote-as @var{asn}} {}
635 Creates a new neighbor whose remote-as is @var{asn}. @var{peer}
636 can be an IPv4 address or an IPv6 address.
640 neighbor 10.0.0.1 remote-as 2
643 In this case my router, in AS-1, is trying to peer with AS-2 at
646 This command must be the first command used when configuring a neighbor.
647 If the remote-as is not specified, @command{bgpd} will complain like this:
649 can't find neighbor 10.0.0.1
653 @node BGP Peer commands
654 @subsection BGP Peer commands
656 In a @code{router bgp} clause there are neighbor specific configurations
659 @deffn {BGP} {neighbor @var{peer} shutdown} {}
660 @deffnx {BGP} {no neighbor @var{peer} shutdown} {}
661 Shutdown the peer. We can delete the neighbor's configuration by
662 @code{no neighbor @var{peer} remote-as @var{as-number}} but all
663 configuration of the neighbor will be deleted. When you want to
664 preserve the configuration, but want to drop the BGP peer, use this
668 @deffn {BGP} {neighbor @var{peer} ebgp-multihop} {}
669 @deffnx {BGP} {no neighbor @var{peer} ebgp-multihop} {}
672 @deffn {BGP} {neighbor @var{peer} description ...} {}
673 @deffnx {BGP} {no neighbor @var{peer} description ...} {}
674 Set description of the peer.
677 @deffn {BGP} {neighbor @var{peer} version @var{version}} {}
678 Set up the neighbor's BGP version. @var{version} can be @var{4},
679 @var{4+} or @var{4-}. BGP version @var{4} is the default value used for
680 BGP peering. BGP version @var{4+} means that the neighbor supports
681 Multiprotocol Extensions for BGP-4. BGP version @var{4-} is similar but
682 the neighbor speaks the old Internet-Draft revision 00's Multiprotocol
683 Extensions for BGP-4. Some routing software is still using this
687 @deffn {BGP} {neighbor @var{peer} interface @var{ifname}} {}
688 @deffnx {BGP} {no neighbor @var{peer} interface @var{ifname}} {}
689 When you connect to a BGP peer over an IPv6 link-local address, you
690 have to specify the @var{ifname} of the interface used for the
691 connection. To specify IPv4 session addresses, see the
692 @code{neighbor @var{peer} update-source} command below.
694 This command is deprecated and may be removed in a future release. Its
695 use should be avoided.
698 @deffn {BGP} {neighbor @var{peer} next-hop-self [all]} {}
699 @deffnx {BGP} {no neighbor @var{peer} next-hop-self [all]} {}
700 This command specifies an announced route's nexthop as being equivalent
701 to the address of the bgp router if it is learned via eBGP.
702 If the optional keyword @code{all} is specified the modifiation is done
703 also for routes learned via iBGP.
706 @deffn {BGP} {neighbor @var{peer} update-source @var{<ifname|address>}} {}
707 @deffnx {BGP} {no neighbor @var{peer} update-source} {}
708 Specify the IPv4 source address to use for the @acronym{BGP} session to this
709 neighbour, may be specified as either an IPv4 address directly or
710 as an interface name (in which case the @command{zebra} daemon MUST be running
711 in order for @command{bgpd} to be able to retrieve interface state).
715 neighbor foo update-source 192.168.0.1
716 neighbor bar update-source lo0
721 @deffn {BGP} {neighbor @var{peer} default-originate} {}
722 @deffnx {BGP} {no neighbor @var{peer} default-originate} {}
723 @command{bgpd}'s default is to not announce the default route (0.0.0.0/0) even it
724 is in routing table. When you want to announce default routes to the
725 peer, use this command.
728 @deffn {BGP} {neighbor @var{peer} port @var{port}} {}
729 @deffnx {BGP} {neighbor @var{peer} port @var{port}} {}
732 @deffn {BGP} {neighbor @var{peer} send-community} {}
733 @deffnx {BGP} {neighbor @var{peer} send-community} {}
736 @deffn {BGP} {neighbor @var{peer} weight @var{weight}} {}
737 @deffnx {BGP} {no neighbor @var{peer} weight @var{weight}} {}
738 This command specifies a default @var{weight} value for the neighbor's
742 @deffn {BGP} {neighbor @var{peer} maximum-prefix @var{number}} {}
743 @deffnx {BGP} {no neighbor @var{peer} maximum-prefix @var{number}} {}
746 @deffn {BGP} {neighbor @var{peer} local-as @var{as-number}} {}
747 @deffnx {BGP} {neighbor @var{peer} local-as @var{as-number} no-prepend} {}
748 @deffnx {BGP} {neighbor @var{peer} local-as @var{as-number} no-prepend replace-as} {}
749 @deffnx {BGP} {no neighbor @var{peer} local-as} {}
750 Specify an alternate AS for this BGP process when interacting with the
751 specified peer. With no modifiers, the specified local-as is prepended to
752 the received AS_PATH when receiving routing updates from the peer, and
753 prepended to the outgoing AS_PATH (after the process local AS) when
754 transmitting local routes to the peer.
756 If the no-prepend attribute is specified, then the supplied local-as is not
757 prepended to the received AS_PATH.
759 If the replace-as attribute is specified, then only the supplied local-as is
760 prepended to the AS_PATH when transmitting local-route updates to this peer.
762 Note that replace-as can only be specified if no-prepend is.
764 This command is only allowed for eBGP peers.
767 @deffn {BGP} {neighbor @var{peer} ttl-security hops @var{number}} {}
768 @deffnx {BGP} {no neighbor @var{peer} ttl-security hops @var{number}} {}
769 This command enforces Generalized TTL Security Mechanism (GTSM), as
770 specified in RFC 5082. With this command, only neighbors that are the
771 specified number of hops away will be allowed to become neighbors. This
772 command is mututally exclusive with @command{ebgp-multihop}.
776 @subsection Peer filtering
778 @deffn {BGP} {neighbor @var{peer} distribute-list @var{name} [in|out]} {}
779 This command specifies a distribute-list for the peer. @var{direct} is
780 @samp{in} or @samp{out}.
783 @deffn {BGP command} {neighbor @var{peer} prefix-list @var{name} [in|out]} {}
786 @deffn {BGP command} {neighbor @var{peer} filter-list @var{name} [in|out]} {}
789 @deffn {BGP} {neighbor @var{peer} route-map @var{name} [in|out]} {}
790 Apply a route-map on the neighbor. @var{direct} must be @code{in} or
794 @deffn {BGP} {bgp route-reflector allow-outbound-policy} {}
795 By default, attribute modification via route-map policy out is not reflected
796 on reflected routes. This option allows the modifications to be reflected as
797 well. Once enabled, it affects all reflected routes.
800 @c -----------------------------------------------------------------------
802 @section BGP Peer Group
804 @deffn {BGP} {neighbor @var{word} peer-group} {}
805 This command defines a new peer group.
808 @deffn {BGP} {neighbor @var{peer} peer-group @var{word}} {}
809 This command bind specific peer to peer group @var{word}.
812 @node BGP Address Family
813 @section BGP Address Family
815 Multiprotocol BGP enables BGP to carry routing information for multiple
816 Network Layer protocols. BGP supports multiple Address Family
817 Identifier (AFI), namely IPv4 and IPv6. Support is also provided for
818 multiple sets of per-AFI information via Subsequent Address Family
819 Identifiers (SAFI). In addition to unicast information, VPN information
820 @cite{RFC4364} and @cite{RFC4659}, and Encapsulation information
821 @cite{RFC5512} is supported.
823 @deffn {Command} {show ip bgp vpnv4 all} {}
824 @deffnx {Command} {show ipv6 bgp vpn all} {}
825 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
828 @deffn {Command} {show ip bgp encap all} {}
829 @deffnx {Command} {show ipv6 bgp encap all} {}
830 Print active IPV4 or IPV6 routes advertised via the Encapsulation SAFI.
833 @deffn {Command} {show bgp ipv4 encap summary} {}
834 @deffnx {Command} {show bgp ipv4 vpn summary} {}
835 @deffnx {Command} {show bgp ipv6 encap summary} {}
836 @deffnx {Command} {show bgp ipv6 vpn summary} {}
837 Print a summary of neighbor connections for the specified AFI/SAFI combination.
840 @c -----------------------------------------------------------------------
841 @node Autonomous System
842 @section Autonomous System
844 The @acronym{AS,Autonomous System} number is one of the essential
845 element of BGP. BGP is a distance vector routing protocol, and the
846 AS-Path framework provides distance vector metric and loop detection to
847 BGP. @cite{RFC1930, Guidelines for creation, selection, and
848 registration of an Autonomous System (AS)} provides some background on
849 the concepts of an AS.
851 The AS number is a two octet value, ranging in value from 1 to 65535.
852 The AS numbers 64512 through 65535 are defined as private AS numbers.
853 Private AS numbers must not to be advertised in the global Internet.
856 * AS Path Regular Expression::
857 * Display BGP Routes by AS Path::
858 * AS Path Access List::
859 * Using AS Path in Route Map::
860 * Private AS Numbers::
863 @node AS Path Regular Expression
864 @subsection AS Path Regular Expression
866 AS path regular expression can be used for displaying BGP routes and
867 AS path access list. AS path regular expression is based on
868 @code{POSIX 1003.2} regular expressions. Following description is
869 just a subset of @code{POSIX} regular expression. User can use full
870 @code{POSIX} regular expression. Adding to that special character '_'
871 is added for AS path regular expression.
875 Matches any single character.
877 Matches 0 or more occurrences of pattern.
879 Matches 1 or more occurrences of pattern.
881 Match 0 or 1 occurrences of pattern.
883 Matches the beginning of the line.
885 Matches the end of the line.
887 Character @code{_} has special meanings in AS path regular expression.
888 It matches to space and comma , and AS set delimiter @{ and @} and AS
889 confederation delimiter @code{(} and @code{)}. And it also matches to
890 the beginning of the line and the end of the line. So @code{_} can be
891 used for AS value boundaries match. @code{show ip bgp regexp _7675_}
892 matches to all of BGP routes which as AS number include @var{7675}.
895 @node Display BGP Routes by AS Path
896 @subsection Display BGP Routes by AS Path
898 To show BGP routes which has specific AS path information @code{show
899 ip bgp} command can be used.
901 @deffn Command {show ip bgp regexp @var{line}} {}
902 This commands display BGP routes that matches AS path regular
903 expression @var{line}.
906 @node AS Path Access List
907 @subsection AS Path Access List
909 AS path access list is user defined AS path.
911 @deffn {Command} {ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
912 This command defines a new AS path access list.
915 @deffn {Command} {no ip as-path access-list @var{word}} {}
916 @deffnx {Command} {no ip as-path access-list @var{word} @{permit|deny@} @var{line}} {}
919 @node Using AS Path in Route Map
920 @subsection Using AS Path in Route Map
922 @deffn {Route Map} {match as-path @var{word}} {}
925 @deffn {Route Map} {set as-path prepend @var{as-path}} {}
926 Prepend the given string of AS numbers to the AS_PATH.
929 @deffn {Route Map} {set as-path prepend last-as @var{num}} {}
930 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
933 @node Private AS Numbers
934 @subsection Private AS Numbers
936 @c -----------------------------------------------------------------------
937 @node BGP Communities Attribute
938 @section BGP Communities Attribute
940 BGP communities attribute is widely used for implementing policy
941 routing. Network operators can manipulate BGP communities attribute
942 based on their network policy. BGP communities attribute is defined
943 in @cite{RFC1997, BGP Communities Attribute} and
944 @cite{RFC1998, An Application of the BGP Community Attribute
945 in Multi-home Routing}. It is an optional transitive attribute,
946 therefore local policy can travel through different autonomous system.
948 Communities attribute is a set of communities values. Each
949 communities value is 4 octet long. The following format is used to
950 define communities value.
954 This format represents 4 octet communities value. @code{AS} is high
955 order 2 octet in digit format. @code{VAL} is low order 2 octet in
956 digit format. This format is useful to define AS oriented policy
957 value. For example, @code{7675:80} can be used when AS 7675 wants to
958 pass local policy value 80 to neighboring peer.
960 @code{internet} represents well-known communities value 0.
962 @code{no-export} represents well-known communities value @code{NO_EXPORT}@*
963 @r{(0xFFFFFF01)}. All routes carry this value must not be advertised
964 to outside a BGP confederation boundary. If neighboring BGP peer is
965 part of BGP confederation, the peer is considered as inside a BGP
966 confederation boundary, so the route will be announced to the peer.
968 @code{no-advertise} represents well-known communities value
969 @code{NO_ADVERTISE}@*@r{(0xFFFFFF02)}. All routes carry this value
970 must not be advertise to other BGP peers.
972 @code{local-AS} represents well-known communities value
973 @code{NO_EXPORT_SUBCONFED} @r{(0xFFFFFF03)}. All routes carry this
974 value must not be advertised to external BGP peers. Even if the
975 neighboring router is part of confederation, it is considered as
976 external BGP peer, so the route will not be announced to the peer.
979 When BGP communities attribute is received, duplicated communities
980 value in the communities attribute is ignored and each communities
981 values are sorted in numerical order.
984 * BGP Community Lists::
985 * Numbered BGP Community Lists::
986 * BGP Community in Route Map::
987 * Display BGP Routes by Community::
988 * Using BGP Communities Attribute::
991 @node BGP Community Lists
992 @subsection BGP Community Lists
994 BGP community list is a user defined BGP communites attribute list.
995 BGP community list can be used for matching or manipulating BGP
996 communities attribute in updates.
998 There are two types of community list. One is standard community
999 list and another is expanded community list. Standard community list
1000 defines communities attribute. Expanded community list defines
1001 communities attribute string with regular expression. Standard
1002 community list is compiled into binary format when user define it.
1003 Standard community list will be directly compared to BGP communities
1004 attribute in BGP updates. Therefore the comparison is faster than
1005 expanded community list.
1007 @deffn Command {ip community-list standard @var{name} @{permit|deny@} @var{community}} {}
1008 This command defines a new standard community list. @var{community}
1009 is communities value. The @var{community} is compiled into community
1010 structure. We can define multiple community list under same name. In
1011 that case match will happen user defined order. Once the
1012 community list matches to communities attribute in BGP updates it
1013 return permit or deny by the community list definition. When there is
1014 no matched entry, deny will be returned. When @var{community} is
1015 empty it matches to any routes.
1018 @deffn Command {ip community-list expanded @var{name} @{permit|deny@} @var{line}} {}
1019 This command defines a new expanded community list. @var{line} is a
1020 string expression of communities attribute. @var{line} can include
1021 regular expression to match communities attribute in BGP updates.
1024 @deffn Command {no ip community-list @var{name}} {}
1025 @deffnx Command {no ip community-list standard @var{name}} {}
1026 @deffnx Command {no ip community-list expanded @var{name}} {}
1027 These commands delete community lists specified by @var{name}. All of
1028 community lists shares a single name space. So community lists can be
1029 removed simpley specifying community lists name.
1032 @deffn {Command} {show ip community-list} {}
1033 @deffnx {Command} {show ip community-list @var{name}} {}
1034 This command display current community list information. When
1035 @var{name} is specified the specified community list's information is
1039 # show ip community-list
1040 Named Community standard list CLIST
1041 permit 7675:80 7675:100 no-export
1043 Named Community expanded list EXPAND
1046 # show ip community-list CLIST
1047 Named Community standard list CLIST
1048 permit 7675:80 7675:100 no-export
1053 @node Numbered BGP Community Lists
1054 @subsection Numbered BGP Community Lists
1056 When number is used for BGP community list name, the number has
1057 special meanings. Community list number in the range from 1 and 99 is
1058 standard community list. Community list number in the range from 100
1059 to 199 is expanded community list. These community lists are called
1060 as numbered community lists. On the other hand normal community lists
1061 is called as named community lists.
1063 @deffn Command {ip community-list <1-99> @{permit|deny@} @var{community}} {}
1064 This command defines a new community list. <1-99> is standard
1065 community list number. Community list name within this range defines
1066 standard community list. When @var{community} is empty it matches to
1070 @deffn Command {ip community-list <100-199> @{permit|deny@} @var{community}} {}
1071 This command defines a new community list. <100-199> is expanded
1072 community list number. Community list name within this range defines
1073 expanded community list.
1076 @deffn Command {ip community-list @var{name} @{permit|deny@} @var{community}} {}
1077 When community list type is not specifed, the community list type is
1078 automatically detected. If @var{community} can be compiled into
1079 communities attribute, the community list is defined as a standard
1080 community list. Otherwise it is defined as an expanded community
1081 list. This feature is left for backward compability. Use of this
1082 feature is not recommended.
1085 @node BGP Community in Route Map
1086 @subsection BGP Community in Route Map
1088 In Route Map (@pxref{Route Map}), we can match or set BGP
1089 communities attribute. Using this feature network operator can
1090 implement their network policy based on BGP communities attribute.
1092 Following commands can be used in Route Map.
1094 @deffn {Route Map} {match community @var{word}} {}
1095 @deffnx {Route Map} {match community @var{word} exact-match} {}
1096 This command perform match to BGP updates using community list
1097 @var{word}. When the one of BGP communities value match to the one of
1098 communities value in community list, it is match. When
1099 @code{exact-match} keyword is spcified, match happen only when BGP
1100 updates have completely same communities value specified in the
1104 @deffn {Route Map} {set community none} {}
1105 @deffnx {Route Map} {set community @var{community}} {}
1106 @deffnx {Route Map} {set community @var{community} additive} {}
1107 This command manipulate communities value in BGP updates. When
1108 @code{none} is specified as communities value, it removes entire
1109 communities attribute from BGP updates. When @var{community} is not
1110 @code{none}, specified communities value is set to BGP updates. If
1111 BGP updates already has BGP communities value, the existing BGP
1112 communities value is replaced with specified @var{community} value.
1113 When @code{additive} keyword is specified, @var{community} is appended
1114 to the existing communities value.
1117 @deffn {Route Map} {set comm-list @var{word} delete} {}
1118 This command remove communities value from BGP communities attribute.
1119 The @var{word} is community list name. When BGP route's communities
1120 value matches to the community list @var{word}, the communities value
1121 is removed. When all of communities value is removed eventually, the
1122 BGP update's communities attribute is completely removed.
1125 @node Display BGP Routes by Community
1126 @subsection Display BGP Routes by Community
1128 To show BGP routes which has specific BGP communities attribute,
1129 @code{show ip bgp} command can be used. The @var{community} value and
1130 community list can be used for @code{show ip bgp} command.
1132 @deffn Command {show ip bgp community} {}
1133 @deffnx Command {show ip bgp community @var{community}} {}
1134 @deffnx Command {show ip bgp community @var{community} exact-match} {}
1135 @code{show ip bgp community} displays BGP routes which has communities
1136 attribute. When @var{community} is specified, BGP routes that matches
1137 @var{community} value is displayed. For this command, @code{internet}
1138 keyword can't be used for @var{community} value. When
1139 @code{exact-match} is specified, it display only routes that have an
1143 @deffn Command {show ip bgp community-list @var{word}} {}
1144 @deffnx Command {show ip bgp community-list @var{word} exact-match} {}
1145 This commands display BGP routes that matches community list
1146 @var{word}. When @code{exact-match} is specified, display only routes
1147 that have an exact match.
1150 @node Using BGP Communities Attribute
1151 @subsection Using BGP Communities Attribute
1153 Following configuration is the most typical usage of BGP communities
1154 attribute. AS 7675 provides upstream Internet connection to AS 100.
1155 When following configuration exists in AS 7675, AS 100 networks
1156 operator can set local preference in AS 7675 network by setting BGP
1157 communities attribute to the updates.
1161 neighbor 192.168.0.1 remote-as 100
1162 neighbor 192.168.0.1 route-map RMAP in
1164 ip community-list 70 permit 7675:70
1165 ip community-list 70 deny
1166 ip community-list 80 permit 7675:80
1167 ip community-list 80 deny
1168 ip community-list 90 permit 7675:90
1169 ip community-list 90 deny
1171 route-map RMAP permit 10
1173 set local-preference 70
1175 route-map RMAP permit 20
1177 set local-preference 80
1179 route-map RMAP permit 30
1181 set local-preference 90
1184 Following configuration announce 10.0.0.0/8 from AS 100 to AS 7675.
1185 The route has communities value 7675:80 so when above configuration
1186 exists in AS 7675, announced route's local preference will be set to
1192 neighbor 192.168.0.2 remote-as 7675
1193 neighbor 192.168.0.2 route-map RMAP out
1195 ip prefix-list PLIST permit 10.0.0.0/8
1197 route-map RMAP permit 10
1198 match ip address prefix-list PLIST
1199 set community 7675:80
1202 Following configuration is an example of BGP route filtering using
1203 communities attribute. This configuration only permit BGP routes
1204 which has BGP communities value 0:80 or 0:90. Network operator can
1205 put special internal communities value at BGP border router, then
1206 limit the BGP routes announcement into the internal network.
1210 neighbor 192.168.0.1 remote-as 100
1211 neighbor 192.168.0.1 route-map RMAP in
1213 ip community-list 1 permit 0:80 0:90
1215 route-map RMAP permit in
1219 Following exmaple filter BGP routes which has communities value 1:1.
1220 When there is no match community-list returns deny. To avoid
1221 filtering all of routes, we need to define permit any at last.
1225 neighbor 192.168.0.1 remote-as 100
1226 neighbor 192.168.0.1 route-map RMAP in
1228 ip community-list standard FILTER deny 1:1
1229 ip community-list standard FILTER permit
1231 route-map RMAP permit 10
1232 match community FILTER
1235 Communities value keyword @code{internet} has special meanings in
1236 standard community lists. In below example @code{internet} act as
1237 match any. It matches all of BGP routes even if the route does not
1238 have communities attribute at all. So community list @code{INTERNET}
1239 is same as above example's @code{FILTER}.
1242 ip community-list standard INTERNET deny 1:1
1243 ip community-list standard INTERNET permit internet
1246 Following configuration is an example of communities value deletion.
1247 With this configuration communities value 100:1 and 100:2 is removed
1248 from BGP updates. For communities value deletion, only @code{permit}
1249 community-list is used. @code{deny} community-list is ignored.
1253 neighbor 192.168.0.1 remote-as 100
1254 neighbor 192.168.0.1 route-map RMAP in
1256 ip community-list standard DEL permit 100:1 100:2
1258 route-map RMAP permit 10
1259 set comm-list DEL delete
1262 @c -----------------------------------------------------------------------
1263 @node BGP Extended Communities Attribute
1264 @section BGP Extended Communities Attribute
1266 BGP extended communities attribute is introduced with MPLS VPN/BGP
1267 technology. MPLS VPN/BGP expands capability of network infrastructure
1268 to provide VPN functionality. At the same time it requires a new
1269 framework for policy routing. With BGP Extended Communities Attribute
1270 we can use Route Target or Site of Origin for implementing network
1271 policy for MPLS VPN/BGP.
1273 BGP Extended Communities Attribute is similar to BGP Communities
1274 Attribute. It is an optional transitive attribute. BGP Extended
1275 Communities Attribute can carry multiple Extended Community value.
1276 Each Extended Community value is eight octet length.
1278 BGP Extended Communities Attribute provides an extended range
1279 compared with BGP Communities Attribute. Adding to that there is a
1280 type field in each value to provides community space structure.
1282 There are two format to define Extended Community value. One is AS
1283 based format the other is IP address based format.
1287 This is a format to define AS based Extended Community value.
1288 @code{AS} part is 2 octets Global Administrator subfield in Extended
1289 Community value. @code{VAL} part is 4 octets Local Administrator
1290 subfield. @code{7675:100} represents AS 7675 policy value 100.
1291 @item IP-Address:VAL
1292 This is a format to define IP address based Extended Community value.
1293 @code{IP-Address} part is 4 octets Global Administrator subfield.
1294 @code{VAL} part is 2 octets Local Administrator subfield.
1295 @code{10.0.0.1:100} represents
1299 * BGP Extended Community Lists::
1300 * BGP Extended Communities in Route Map::
1303 @node BGP Extended Community Lists
1304 @subsection BGP Extended Community Lists
1306 Expanded Community Lists is a user defined BGP Expanded Community
1309 @deffn Command {ip extcommunity-list standard @var{name} @{permit|deny@} @var{extcommunity}} {}
1310 This command defines a new standard extcommunity-list.
1311 @var{extcommunity} is extended communities value. The
1312 @var{extcommunity} is compiled into extended community structure. We
1313 can define multiple extcommunity-list under same name. In that case
1314 match will happen user defined order. Once the extcommunity-list
1315 matches to extended communities attribute in BGP updates it return
1316 permit or deny based upon the extcommunity-list definition. When
1317 there is no matched entry, deny will be returned. When
1318 @var{extcommunity} is empty it matches to any routes.
1321 @deffn Command {ip extcommunity-list expanded @var{name} @{permit|deny@} @var{line}} {}
1322 This command defines a new expanded extcommunity-list. @var{line} is
1323 a string expression of extended communities attribute. @var{line} can
1324 include regular expression to match extended communities attribute in
1328 @deffn Command {no ip extcommunity-list @var{name}} {}
1329 @deffnx Command {no ip extcommunity-list standard @var{name}} {}
1330 @deffnx Command {no ip extcommunity-list expanded @var{name}} {}
1331 These commands delete extended community lists specified by
1332 @var{name}. All of extended community lists shares a single name
1333 space. So extended community lists can be removed simpley specifying
1337 @deffn {Command} {show ip extcommunity-list} {}
1338 @deffnx {Command} {show ip extcommunity-list @var{name}} {}
1339 This command display current extcommunity-list information. When
1340 @var{name} is specified the community list's information is shown.
1343 # show ip extcommunity-list
1347 @node BGP Extended Communities in Route Map
1348 @subsection BGP Extended Communities in Route Map
1350 @deffn {Route Map} {match extcommunity @var{word}} {}
1353 @deffn {Route Map} {set extcommunity rt @var{extcommunity}} {}
1354 This command set Route Target value.
1357 @deffn {Route Map} {set extcommunity soo @var{extcommunity}} {}
1358 This command set Site of Origin value.
1361 @c -----------------------------------------------------------------------
1362 @node Displaying BGP routes
1363 @section Displaying BGP Routes
1367 * More Show IP BGP::
1371 @subsection Show IP BGP
1373 @deffn {Command} {show ip bgp} {}
1374 @deffnx {Command} {show ip bgp @var{A.B.C.D}} {}
1375 @deffnx {Command} {show ip bgp @var{X:X::X:X}} {}
1376 This command displays BGP routes. When no route is specified it
1377 display all of IPv4 BGP routes.
1381 BGP table version is 0, local router ID is 10.1.1.1
1382 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
1383 Origin codes: i - IGP, e - EGP, ? - incomplete
1385 Network Next Hop Metric LocPrf Weight Path
1386 *> 1.1.1.1/32 0.0.0.0 0 32768 i
1388 Total number of prefixes 1
1391 @node More Show IP BGP
1392 @subsection More Show IP BGP
1394 @deffn {Command} {show ip bgp regexp @var{line}} {}
1395 This command display BGP routes using AS path regular expression (@pxref{Display BGP Routes by AS Path}).
1398 @deffn Command {show ip bgp community @var{community}} {}
1399 @deffnx Command {show ip bgp community @var{community} exact-match} {}
1400 This command display BGP routes using @var{community} (@pxref{Display
1401 BGP Routes by Community}).
1404 @deffn Command {show ip bgp community-list @var{word}} {}
1405 @deffnx Command {show ip bgp community-list @var{word} exact-match} {}
1406 This command display BGP routes using community list (@pxref{Display
1407 BGP Routes by Community}).
1410 @deffn {Command} {show ip bgp summary} {}
1413 @deffn {Command} {show ip bgp neighbor [@var{peer}]} {}
1416 @deffn {Command} {clear ip bgp @var{peer}} {}
1417 Clear peers which have addresses of X.X.X.X
1420 @deffn {Command} {clear ip bgp @var{peer} soft in} {}
1421 Clear peer using soft reconfiguration.
1424 @deffn {Command} {show ip bgp dampened-paths} {}
1425 Display paths suppressed due to dampening
1428 @deffn {Command} {show ip bgp flap-statistics} {}
1429 Display flap statistics of routes
1432 @deffn {Command} {show debug} {}
1435 @deffn {Command} {debug event} {}
1438 @deffn {Command} {debug update} {}
1441 @deffn {Command} {debug keepalive} {}
1444 @deffn {Command} {no debug event} {}
1447 @deffn {Command} {no debug update} {}
1450 @deffn {Command} {no debug keepalive} {}
1453 @node Capability Negotiation
1454 @section Capability Negotiation
1456 When adding IPv6 routing information exchange feature to BGP. There
1457 were some proposals. @acronym{IETF,Internet Engineering Task Force}
1458 @acronym{IDR, Inter Domain Routing} @acronym{WG, Working group} adopted
1459 a proposal called Multiprotocol Extension for BGP. The specification
1460 is described in @cite{RFC2283}. The protocol does not define new protocols.
1461 It defines new attributes to existing BGP. When it is used exchanging
1462 IPv6 routing information it is called BGP-4+. When it is used for
1463 exchanging multicast routing information it is called MBGP.
1465 @command{bgpd} supports Multiprotocol Extension for BGP. So if remote
1466 peer supports the protocol, @command{bgpd} can exchange IPv6 and/or
1467 multicast routing information.
1469 Traditional BGP did not have the feature to detect remote peer's
1470 capabilities, e.g. whether it can handle prefix types other than IPv4
1471 unicast routes. This was a big problem using Multiprotocol Extension
1472 for BGP to operational network. @cite{RFC2842, Capabilities
1473 Advertisement with BGP-4} adopted a feature called Capability
1474 Negotiation. @command{bgpd} use this Capability Negotiation to detect
1475 the remote peer's capabilities. If the peer is only configured as IPv4
1476 unicast neighbor, @command{bgpd} does not send these Capability
1477 Negotiation packets (at least not unless other optional BGP features
1478 require capability negotation).
1480 By default, Quagga will bring up peering with minimal common capability
1481 for the both sides. For example, local router has unicast and
1482 multicast capabilitie and remote router has unicast capability. In
1483 this case, the local router will establish the connection with unicast
1484 only capability. When there are no common capabilities, Quagga sends
1485 Unsupported Capability error and then resets the connection.
1487 If you want to completely match capabilities with remote peer. Please
1488 use @command{strict-capability-match} command.
1490 @deffn {BGP} {neighbor @var{peer} strict-capability-match} {}
1491 @deffnx {BGP} {no neighbor @var{peer} strict-capability-match} {}
1492 Strictly compares remote capabilities and local capabilities. If capabilities
1493 are different, send Unsupported Capability error then reset connection.
1496 You may want to disable sending Capability Negotiation OPEN message
1497 optional parameter to the peer when remote peer does not implement
1498 Capability Negotiation. Please use @command{dont-capability-negotiate}
1499 command to disable the feature.
1501 @deffn {BGP} {neighbor @var{peer} dont-capability-negotiate} {}
1502 @deffnx {BGP} {no neighbor @var{peer} dont-capability-negotiate} {}
1503 Suppress sending Capability Negotiation as OPEN message optional
1504 parameter to the peer. This command only affects the peer is configured
1505 other than IPv4 unicast configuration.
1508 When remote peer does not have capability negotiation feature, remote
1509 peer will not send any capabilities at all. In that case, bgp
1510 configures the peer with configured capabilities.
1512 You may prefer locally configured capabilities more than the negotiated
1513 capabilities even though remote peer sends capabilities. If the peer
1514 is configured by @command{override-capability}, @command{bgpd} ignores
1515 received capabilities then override negotiated capabilities with
1518 @deffn {BGP} {neighbor @var{peer} override-capability} {}
1519 @deffnx {BGP} {no neighbor @var{peer} override-capability} {}
1520 Override the result of Capability Negotiation with local configuration.
1521 Ignore remote peer's capability value.
1524 @node Route Reflector
1525 @section Route Reflector
1527 @deffn {BGP} {bgp cluster-id @var{a.b.c.d}} {}
1530 @deffn {BGP} {neighbor @var{peer} route-reflector-client} {}
1531 @deffnx {BGP} {no neighbor @var{peer} route-reflector-client} {}
1535 @section Route Server
1537 At an Internet Exchange point, many ISPs are connected to each other by
1538 external BGP peering. Normally these external BGP connection are done by
1539 @samp{full mesh} method. As with internal BGP full mesh formation,
1540 this method has a scaling problem.
1542 This scaling problem is well known. Route Server is a method to resolve
1543 the problem. Each ISP's BGP router only peers to Route Server. Route
1544 Server serves as BGP information exchange to other BGP routers. By
1545 applying this method, numbers of BGP connections is reduced from
1546 O(n*(n-1)/2) to O(n).
1548 Unlike normal BGP router, Route Server must have several routing tables
1549 for managing different routing policies for each BGP speaker. We call the
1550 routing tables as different @code{view}s. @command{bgpd} can work as
1551 normal BGP router or Route Server or both at the same time.
1554 * Multiple instance::
1555 * BGP instance and view::
1557 * Viewing the view::
1560 @node Multiple instance
1561 @subsection Multiple instance
1563 To enable multiple view function of @code{bgpd}, you must turn on
1564 multiple instance feature beforehand.
1566 @deffn {Command} {bgp multiple-instance} {}
1567 Enable BGP multiple instance feature. After this feature is enabled,
1568 you can make multiple BGP instances or multiple BGP views.
1571 @deffn {Command} {no bgp multiple-instance} {}
1572 Disable BGP multiple instance feature. You can not disable this feature
1573 when BGP multiple instances or views exist.
1576 When you want to make configuration more Cisco like one,
1578 @deffn {Command} {bgp config-type cisco} {}
1579 Cisco compatible BGP configuration output.
1582 When bgp config-type cisco is specified,
1584 ``no synchronization'' is displayed.
1585 ``no auto-summary'' is displayed.
1587 ``network'' and ``aggregate-address'' argument is displayed as
1590 Quagga: network 10.0.0.0/8
1591 Cisco: network 10.0.0.0
1593 Quagga: aggregate-address 192.168.0.0/24
1594 Cisco: aggregate-address 192.168.0.0 255.255.255.0
1596 Community attribute handling is also different. If there is no
1597 configuration is specified community attribute and extended community
1598 attribute are sent to neighbor. When user manually disable the
1599 feature community attribute is not sent to the neighbor. In case of
1600 @command{bgp config-type cisco} is specified, community attribute is not
1601 sent to the neighbor by default. To send community attribute user has
1602 to specify @command{neighbor A.B.C.D send-community} command.
1607 neighbor 10.0.0.1 remote-as 1
1608 no neighbor 10.0.0.1 send-community
1611 neighbor 10.0.0.1 remote-as 1
1612 neighbor 10.0.0.1 send-community
1616 @deffn {Command} {bgp config-type zebra} {}
1617 Quagga style BGP configuration. This is default.
1620 @node BGP instance and view
1621 @subsection BGP instance and view
1623 BGP instance is a normal BGP process. The result of route selection
1624 goes to the kernel routing table. You can setup different AS at the
1625 same time when BGP multiple instance feature is enabled.
1627 @deffn {Command} {router bgp @var{as-number}} {}
1628 Make a new BGP instance. You can use arbitrary word for the @var{name}.
1633 bgp multiple-instance
1636 neighbor 10.0.0.1 remote-as 2
1637 neighbor 10.0.0.2 remote-as 3
1640 neighbor 10.0.0.3 remote-as 4
1641 neighbor 10.0.0.4 remote-as 5
1645 BGP view is almost same as normal BGP process. The result of
1646 route selection does not go to the kernel routing table. BGP view is
1647 only for exchanging BGP routing information.
1649 @deffn {Command} {router bgp @var{as-number} view @var{name}} {}
1650 Make a new BGP view. You can use arbitrary word for the @var{name}. This
1651 view's route selection result does not go to the kernel routing table.
1654 With this command, you can setup Route Server like below.
1658 bgp multiple-instance
1661 neighbor 10.0.0.1 remote-as 2
1662 neighbor 10.0.0.2 remote-as 3
1665 neighbor 10.0.0.3 remote-as 4
1666 neighbor 10.0.0.4 remote-as 5
1670 @node Routing policy
1671 @subsection Routing policy
1673 You can set different routing policy for a peer. For example, you can
1674 set different filter for a peer.
1678 bgp multiple-instance
1681 neighbor 10.0.0.1 remote-as 2
1682 neighbor 10.0.0.1 distribute-list 1 in
1685 neighbor 10.0.0.1 remote-as 2
1686 neighbor 10.0.0.1 distribute-list 2 in
1690 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view
1691 2. When the update is inserted into view 1, distribute-list 1 is
1692 applied. On the other hand, when the update is inserted into view 2,
1693 distribute-list 2 is applied.
1695 @node Viewing the view
1696 @subsection Viewing the view
1698 To display routing table of BGP view, you must specify view name.
1700 @deffn {Command} {show ip bgp view @var{name}} {}
1701 Display routing table of BGP view @var{name}.
1704 @node How to set up a 6-Bone connection
1705 @section How to set up a 6-Bone connection
1713 ! Actually there is no need to configure zebra
1719 ! This means that routes go through zebra and into the kernel.
1723 ! MP-BGP configuration
1726 bgp router-id 10.0.0.1
1727 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as @var{as-number}
1730 network 3ffe:506::/32
1731 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
1732 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
1733 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as @var{as-number}
1734 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
1737 ipv6 access-list all permit any
1739 ! Set output nexthop address.
1741 route-map set-nexthop permit 10
1742 match ipv6 address all
1743 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
1744 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
1746 ! logfile FILENAME is obsolete. Please use log file FILENAME
1753 @node Dump BGP packets and table
1754 @section Dump BGP packets and table
1756 @deffn Command {dump bgp all @var{path} [@var{interval}]} {}
1757 @deffnx Command {dump bgp all-et @var{path} [@var{interval}]} {}
1758 @deffnx Command {no dump bgp all [@var{path}] [@var{interval}]} {}
1759 Dump all BGP packet and events to @var{path} file.
1760 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1761 The path @var{path} can be set with date and time formatting (strftime).
1762 The type ‘all-et’ enables support for Extended Timestamp Header (@pxref{Packet Binary Dump Format}).
1763 (@pxref{Packet Binary Dump Format})
1766 @deffn Command {dump bgp updates @var{path} [@var{interval}]} {}
1767 @deffnx Command {dump bgp updates-et @var{path} [@var{interval}]} {}
1768 @deffnx Command {no dump bgp updates [@var{path}] [@var{interval}]} {}
1769 Dump only BGP updates messages to @var{path} file.
1770 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1771 The path @var{path} can be set with date and time formatting (strftime).
1772 The type ‘updates-et’ enables support for Extended Timestamp Header (@pxref{Packet Binary Dump Format}).
1775 @deffn Command {dump bgp routes-mrt @var{path}} {}
1776 @deffnx Command {dump bgp routes-mrt @var{path} @var{interval}} {}
1777 @deffnx Command {no dump bgp route-mrt [@var{path}] [@var{interval}]} {}
1778 Dump whole BGP routing table to @var{path}. This is heavy process.
1779 The path @var{path} can be set with date and time formatting (strftime).
1780 If @var{interval} is set, a new file will be created for echo @var{interval} of seconds.
1783 Note: the interval variable can also be set using hours and minutes: 04h20m00.
1786 @node BGP Configuration Examples
1787 @section BGP Configuration Examples
1789 Example of a session to an upstream, advertising only one prefix to it.
1793 bgp router-id 10.236.87.1
1794 network 10.236.87.0/24
1795 neighbor upstream peer-group
1796 neighbor upstream remote-as 64515
1797 neighbor upstream capability dynamic
1798 neighbor upstream prefix-list pl-allowed-adv out
1799 neighbor 10.1.1.1 peer-group upstream
1800 neighbor 10.1.1.1 description ACME ISP
1802 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
1803 ip prefix-list pl-allowed-adv seq 10 deny any
1807 A more complex example. With upstream, peer and customer sessions.
1808 Advertising global prefixes and NO_EXPORT prefixes and providing
1809 actions for customer routes based on community values. Extensive use of
1810 route-maps and the 'call' feature to support selective advertising of
1811 prefixes. This example is intended as guidance only, it has NOT been
1812 tested and almost certainly containts silly mistakes, if not serious
1817 bgp router-id 10.236.87.1
1818 network 10.123.456.0/24
1819 network 10.123.456.128/25 route-map rm-no-export
1820 neighbor upstream capability dynamic
1821 neighbor upstream route-map rm-upstream-out out
1822 neighbor cust capability dynamic
1823 neighbor cust route-map rm-cust-in in
1824 neighbor cust route-map rm-cust-out out
1825 neighbor cust send-community both
1826 neighbor peer capability dynamic
1827 neighbor peer route-map rm-peer-in in
1828 neighbor peer route-map rm-peer-out out
1829 neighbor peer send-community both
1830 neighbor 10.1.1.1 remote-as 64515
1831 neighbor 10.1.1.1 peer-group upstream
1832 neighbor 10.2.1.1 remote-as 64516
1833 neighbor 10.2.1.1 peer-group upstream
1834 neighbor 10.3.1.1 remote-as 64517
1835 neighbor 10.3.1.1 peer-group cust-default
1836 neighbor 10.3.1.1 description customer1
1837 neighbor 10.3.1.1 prefix-list pl-cust1-network in
1838 neighbor 10.4.1.1 remote-as 64518
1839 neighbor 10.4.1.1 peer-group cust
1840 neighbor 10.4.1.1 prefix-list pl-cust2-network in
1841 neighbor 10.4.1.1 description customer2
1842 neighbor 10.5.1.1 remote-as 64519
1843 neighbor 10.5.1.1 peer-group peer
1844 neighbor 10.5.1.1 prefix-list pl-peer1-network in
1845 neighbor 10.5.1.1 description peer AS 1
1846 neighbor 10.6.1.1 remote-as 64520
1847 neighbor 10.6.1.1 peer-group peer
1848 neighbor 10.6.1.1 prefix-list pl-peer2-network in
1849 neighbor 10.6.1.1 description peer AS 2
1851 ip prefix-list pl-default permit 0.0.0.0/0
1853 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
1854 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
1856 ip prefix-list pl-cust1-network permit 10.3.1.0/24
1857 ip prefix-list pl-cust1-network permit 10.3.2.0/24
1859 ip prefix-list pl-cust2-network permit 10.4.1.0/24
1861 ip prefix-list pl-peer1-network permit 10.5.1.0/24
1862 ip prefix-list pl-peer1-network permit 10.5.2.0/24
1863 ip prefix-list pl-peer1-network permit 192.168.0.0/24
1865 ip prefix-list pl-peer2-network permit 10.6.1.0/24
1866 ip prefix-list pl-peer2-network permit 10.6.2.0/24
1867 ip prefix-list pl-peer2-network permit 192.168.1.0/24
1868 ip prefix-list pl-peer2-network permit 192.168.2.0/24
1869 ip prefix-list pl-peer2-network permit 172.16.1/24
1871 ip as-path access-list asp-own-as permit ^$
1872 ip as-path access-list asp-own-as permit _64512_
1874 ! #################################################################
1875 ! Match communities we provide actions for, on routes receives from
1876 ! customers. Communities values of <our-ASN>:X, with X, have actions:
1878 ! 100 - blackhole the prefix
1879 ! 200 - set no_export
1880 ! 300 - advertise only to other customers
1881 ! 400 - advertise only to upstreams
1882 ! 500 - set no_export when advertising to upstreams
1883 ! 2X00 - set local_preference to X00
1885 ! blackhole the prefix of the route
1886 ip community-list standard cm-blackhole permit 64512:100
1888 ! set no-export community before advertising
1889 ip community-list standard cm-set-no-export permit 64512:200
1891 ! advertise only to other customers
1892 ip community-list standard cm-cust-only permit 64512:300
1894 ! advertise only to upstreams
1895 ip community-list standard cm-upstream-only permit 64512:400
1897 ! advertise to upstreams with no-export
1898 ip community-list standard cm-upstream-noexport permit 64512:500
1900 ! set local-pref to least significant 3 digits of the community
1901 ip community-list standard cm-prefmod-100 permit 64512:2100
1902 ip community-list standard cm-prefmod-200 permit 64512:2200
1903 ip community-list standard cm-prefmod-300 permit 64512:2300
1904 ip community-list standard cm-prefmod-400 permit 64512:2400
1905 ip community-list expanded cme-prefmod-range permit 64512:2...
1907 ! Informational communities
1909 ! 3000 - learned from upstream
1910 ! 3100 - learned from customer
1911 ! 3200 - learned from peer
1913 ip community-list standard cm-learnt-upstream permit 64512:3000
1914 ip community-list standard cm-learnt-cust permit 64512:3100
1915 ip community-list standard cm-learnt-peer permit 64512:3200
1917 ! ###################################################################
1918 ! Utility route-maps
1920 ! These utility route-maps generally should not used to permit/deny
1921 ! routes, i.e. they do not have meaning as filters, and hence probably
1922 ! should be used with 'on-match next'. These all finish with an empty
1923 ! permit entry so as not interfere with processing in the caller.
1925 route-map rm-no-export permit 10
1926 set community additive no-export
1927 route-map rm-no-export permit 20
1929 route-map rm-blackhole permit 10
1930 description blackhole, up-pref and ensure it cant escape this AS
1931 set ip next-hop 127.0.0.1
1932 set local-preference 10
1933 set community additive no-export
1934 route-map rm-blackhole permit 20
1936 ! Set local-pref as requested
1937 route-map rm-prefmod permit 10
1938 match community cm-prefmod-100
1939 set local-preference 100
1940 route-map rm-prefmod permit 20
1941 match community cm-prefmod-200
1942 set local-preference 200
1943 route-map rm-prefmod permit 30
1944 match community cm-prefmod-300
1945 set local-preference 300
1946 route-map rm-prefmod permit 40
1947 match community cm-prefmod-400
1948 set local-preference 400
1949 route-map rm-prefmod permit 50
1951 ! Community actions to take on receipt of route.
1952 route-map rm-community-in permit 10
1953 description check for blackholing, no point continuing if it matches.
1954 match community cm-blackhole
1956 route-map rm-community-in permit 20
1957 match community cm-set-no-export
1960 route-map rm-community-in permit 30
1961 match community cme-prefmod-range
1963 route-map rm-community-in permit 40
1965 ! #####################################################################
1966 ! Community actions to take when advertising a route.
1967 ! These are filtering route-maps,
1969 ! Deny customer routes to upstream with cust-only set.
1970 route-map rm-community-filt-to-upstream deny 10
1971 match community cm-learnt-cust
1972 match community cm-cust-only
1973 route-map rm-community-filt-to-upstream permit 20
1975 ! Deny customer routes to other customers with upstream-only set.
1976 route-map rm-community-filt-to-cust deny 10
1977 match community cm-learnt-cust
1978 match community cm-upstream-only
1979 route-map rm-community-filt-to-cust permit 20
1981 ! ###################################################################
1982 ! The top-level route-maps applied to sessions. Further entries could
1983 ! be added obviously..
1986 route-map rm-cust-in permit 10
1987 call rm-community-in
1989 route-map rm-cust-in permit 20
1990 set community additive 64512:3100
1991 route-map rm-cust-in permit 30
1993 route-map rm-cust-out permit 10
1994 call rm-community-filt-to-cust
1996 route-map rm-cust-out permit 20
1998 ! Upstream transit ASes
1999 route-map rm-upstream-out permit 10
2000 description filter customer prefixes which are marked cust-only
2001 call rm-community-filt-to-upstream
2003 route-map rm-upstream-out permit 20
2004 description only customer routes are provided to upstreams/peers
2005 match community cm-learnt-cust
2008 ! outbound policy is same as for upstream
2009 route-map rm-peer-out permit 10
2010 call rm-upstream-out
2012 route-map rm-peer-in permit 10
2013 set community additive 64512:3200