7 :abbr:`BGP` stands for Border Gateway Protocol. The latest BGP version is 4.
8 BGP-4 is one of the Exterior Gateway Protocols and the de facto standard
9 interdomain routing protocol. BGP-4 is described in :rfc:`1771` and updated by
10 :rfc:`4271`. :rfc:`2858` adds multiprotocol support to BGP-4.
17 The default configuration file of *bgpd* is :file:`bgpd.conf`. *bgpd* searches
18 the current directory first, followed by |INSTALL_PREFIX_ETC|/bgpd.conf. All of
19 *bgpd*'s commands must be configured in :file:`bgpd.conf` when the integrated
20 config is not being used.
22 *bgpd* specific invocation options are described below. Common options may also
23 be specified (:ref:`common-invocation-options`).
27 .. option:: -p, --bgp_port <port>
29 Set the bgp protocol's port number. When port number is 0, that means do not
32 .. option:: -l, --listenon
34 Specify a specific IP address for bgpd to listen on, rather than its default
35 of ``0.0.0.0`` / ``::``. This can be useful to constrain bgpd to an internal
36 address, or to run multiple bgpd processes on one host.
38 .. _bgp-basic-concepts:
43 .. _bgp-autonomous-systems:
50 An AS is a connected group of one or more IP prefixes run by one or more
51 network operators which has a SINGLE and CLEARLY DEFINED routing policy.
53 Each AS has an identifying number associated with it called an :abbr:`ASN
54 (Autonomous System Number)`. This is a two octet value ranging in value from 1
55 to 65535. The AS numbers 64512 through 65535 are defined as private AS numbers.
56 Private AS numbers must not be advertised on the global Internet.
58 The :abbr:`ASN (Autonomous System Number)` is one of the essential elements of
59 BGP. BGP is a distance vector routing protocol, and the AS-Path framework
60 provides distance vector metric and loop detection to BGP.
62 .. seealso:: :rfc:`1930`
64 .. _bgp-address-families:
69 Multiprotocol extensions enable BGP to carry routing information for multiple
70 network layer protocols. BGP supports an Address Family Identifier (AFI) for
71 IPv4 and IPv6. Support is also provided for multiple sets of per-AFI
72 information via the BGP Subsequent Address Family Identifier (SAFI). FRR
73 supports SAFIs for unicast information, labeled information (:rfc:`3107` and
74 :rfc:`8277`), and Layer 3 VPN information (:rfc:`4364` and :rfc:`4659`).
76 .. _bgp-route-selection:
81 The route selection process used by FRR's BGP implementation uses the following
82 decision criterion, starting at the top of the list and going towards the
83 bottom until one of the factors can be used.
87 Prefer higher local weight routes to lower routes.
89 2. **Local preference check**
91 Prefer higher local preference routes to lower.
93 3. **Local route check**
95 Prefer local routes (statics, aggregates, redistributed) to received routes.
97 4. **AS path length check**
99 Prefer shortest hop-count AS_PATHs.
103 Prefer the lowest origin type route. That is, prefer IGP origin routes to
104 EGP, to Incomplete routes.
108 Where routes with a MED were received from the same AS, prefer the route
109 with the lowest MED. :ref:`bgp-med`.
111 7. **External check**
113 Prefer the route received from an external, eBGP peer over routes received
114 from other types of peers.
116 8. **IGP cost check**
118 Prefer the route with the lower IGP cost.
120 9. **Multi-path check**
122 If multi-pathing is enabled, then check whether the routes not yet
123 distinguished in preference may be considered equal. If
124 :clicmd:`bgp bestpath as-path multipath-relax` is set, all such routes are
125 considered equal, otherwise routes received via iBGP with identical AS_PATHs
126 or routes received from eBGP neighbours in the same AS are considered equal.
128 10. **Already-selected external check**
130 Where both routes were received from eBGP peers, then prefer the route
131 which is already selected. Note that this check is not applied if
132 :clicmd:`bgp bestpath compare-routerid` is configured. This check can
133 prevent some cases of oscillation.
135 11. **Router-ID check**
137 Prefer the route with the lowest `router-ID`. If the route has an
138 `ORIGINATOR_ID` attribute, through iBGP reflection, then that router ID is
139 used, otherwise the `router-ID` of the peer the route was received from is
142 12. **Cluster-List length check**
144 The route with the shortest cluster-list length is used. The cluster-list
145 reflects the iBGP reflection path the route has taken.
149 Prefer the route received from the peer with the higher transport layer
150 address, as a last-resort tie-breaker.
152 .. _bgp-capability-negotiation:
154 Capability Negotiation
155 ----------------------
157 When adding IPv6 routing information exchange feature to BGP. There were some
158 proposals. :abbr:`IETF (Internet Engineering Task Force)`
159 :abbr:`IDR (Inter Domain Routing)` adopted a proposal called Multiprotocol
160 Extension for BGP. The specification is described in :rfc:`2283`. The protocol
161 does not define new protocols. It defines new attributes to existing BGP. When
162 it is used exchanging IPv6 routing information it is called BGP-4+. When it is
163 used for exchanging multicast routing information it is called MBGP.
165 *bgpd* supports Multiprotocol Extension for BGP. So if a remote peer supports
166 the protocol, *bgpd* can exchange IPv6 and/or multicast routing information.
168 Traditional BGP did not have the feature to detect a remote peer's
169 capabilities, e.g. whether it can handle prefix types other than IPv4 unicast
170 routes. This was a big problem using Multiprotocol Extension for BGP in an
171 operational network. :rfc:`2842` adopted a feature called Capability
172 Negotiation. *bgpd* use this Capability Negotiation to detect the remote peer's
173 capabilities. If a peer is only configured as an IPv4 unicast neighbor, *bgpd*
174 does not send these Capability Negotiation packets (at least not unless other
175 optional BGP features require capability negotiation).
177 By default, FRR will bring up peering with minimal common capability for the
178 both sides. For example, if the local router has unicast and multicast
179 capabilities and the remote router only has unicast capability the local router
180 will establish the connection with unicast only capability. When there are no
181 common capabilities, FRR sends Unsupported Capability error and then resets the
184 .. _bgp-router-configuration:
186 BGP Router Configuration
187 ========================
192 First of all you must configure BGP router with the :clicmd:`router bgp ASN`
193 command. The AS number is an identifier for the autonomous system. The BGP
194 protocol uses the AS number for detecting whether the BGP connection is
195 internal or external.
197 .. index:: router bgp ASN
198 .. clicmd:: router bgp ASN
200 Enable a BGP protocol process with the specified ASN. After
201 this statement you can input any `BGP Commands`.
203 .. index:: no router bgp ASN
204 .. clicmd:: no router bgp ASN
206 Destroy a BGP protocol process with the specified ASN.
208 .. index:: bgp router-id A.B.C.D
209 .. clicmd:: bgp router-id A.B.C.D
211 This command specifies the router-ID. If *bgpd* connects to *zebra* it gets
212 interface and address information. In that case default router ID value is
213 selected as the largest IP Address of the interfaces. When `router zebra` is
214 not enabled *bgpd* can't get interface information so `router-id` is set to
215 0.0.0.0. So please set router-id by hand.
218 .. _bgp-multiple-autonomous-systems:
220 Multiple Autonomous Systems
221 ---------------------------
223 FRR's BGP implementation is capable of running multiple autonomous systems at
224 once. Each configured AS corresponds to a :ref:`zebra-vrf`. In the past, to get
225 the same functionality the network administrator had to run a new *bgpd*
226 process; using VRFs allows multiple autonomous systems to be handled in a
229 When using multiple autonomous systems, all router config blocks after the
230 first one must specify a VRF to be the target of BGP's route selection. This
231 VRF must be unique within respect to all other VRFs being used for the same
232 purpose, i.e. two different autonomous systems cannot use the same VRF.
233 However, the same AS can be used with different VRFs.
237 The separated nature of VRFs makes it possible to peer a single *bgpd*
238 process to itself, on one machine. Note that this can be done fully within
239 BGP without a corresponding VRF in the kernel or Zebra, which enables some
240 practical use cases such as :ref:`route reflectors <bgp-route-reflector>`
243 Configuration of additional autonomous systems, or of a router that targets a
244 specific VRF, is accomplished with the following command:
246 .. index:: router bgp ASN vrf VRFNAME
247 .. clicmd:: router bgp ASN vrf VRFNAME
249 ``VRFNAME`` is matched against VRFs configured in the kernel. When ``vrf
250 VRFNAME`` is not specified, the BGP protocol process belongs to the default
253 An example configuration with multiple autonomous systems might look like this:
258 neighbor 10.0.0.1 remote-as 20
259 neighbor 10.0.0.2 remote-as 30
261 router bgp 2 vrf blue
262 neighbor 10.0.0.3 remote-as 40
263 neighbor 10.0.0.4 remote-as 50
266 neighbor 10.0.0.5 remote-as 60
267 neighbor 10.0.0.6 remote-as 70
270 In the past this feature done differently and the following commands were
271 required to enable the functionality. They are now deprecated.
274 This command is deprecated and may be safely removed from the config.
276 .. index:: bgp multiple-instance
277 .. clicmd:: bgp multiple-instance
279 Enable BGP multiple instance feature. Because this is now the default
280 configuration this command will not be displayed in the running
284 This command is deprecated and may be safely removed from the config.
286 .. index:: no bgp multiple-instance
287 .. clicmd:: no bgp multiple-instance
289 In previous versions of FRR, this command disabled the BGP multiple instance
290 feature. This functionality is automatically turned on when BGP multiple
291 instances or views exist so this command no longer does anything.
293 .. seealso:: :ref:`bgp-vrf-route-leaking`
294 .. seealso:: :ref:`zebra-vrf`
302 In addition to supporting multiple autonomous systems, FRR's BGP implementation
303 also supports *views*.
305 BGP views are almost the same as normal BGP processes, except that routes
306 selected by BGP are not installed into the kernel routing table. Each BGP view
307 provides an independent set of routing information which is only distributed
308 via BGP. Multiple views can be supported, and BGP view information is always
309 independent from other routing protocols and Zebra/kernel routes. BGP views use
310 the core instance (i.e., default VRF) for communication with peers.
312 .. index:: router bgp AS-NUMBER view NAME
313 .. clicmd:: router bgp AS-NUMBER view NAME
315 Make a new BGP view. You can use an arbitrary word for the ``NAME``. Routes
316 selected by the view are not installed into the kernel routing table.
318 With this command, you can setup Route Server like below.
324 neighbor 10.0.0.1 remote-as 2
325 neighbor 10.0.0.2 remote-as 3
328 neighbor 10.0.0.3 remote-as 4
329 neighbor 10.0.0.4 remote-as 5
331 .. index:: show [ip] bgp view NAME
332 .. clicmd:: show [ip] bgp view NAME
334 Display the routing table of BGP view ``NAME``.
340 .. index:: bgp bestpath as-path confed
341 .. clicmd:: bgp bestpath as-path confed
343 This command specifies that the length of confederation path sets and
344 sequences should should be taken into account during the BGP best path
347 .. index:: bgp bestpath as-path multipath-relax
348 .. clicmd:: bgp bestpath as-path multipath-relax
350 This command specifies that BGP decision process should consider paths
351 of equal AS_PATH length candidates for multipath computation. Without
352 the knob, the entire AS_PATH must match for multipath computation.
354 .. clicmd:: bgp bestpath compare-routerid
356 Ensure that when comparing routes where both are equal on most metrics,
357 including local-pref, AS_PATH length, IGP cost, MED, that the tie is broken
360 If this option is enabled, then the already-selected check, where
361 already selected eBGP routes are preferred, is skipped.
363 If a route has an `ORIGINATOR_ID` attribute because it has been reflected,
364 that `ORIGINATOR_ID` will be used. Otherwise, the router-ID of the peer the
365 route was received from will be used.
367 The advantage of this is that the route-selection (at this point) will be
368 more deterministic. The disadvantage is that a few or even one lowest-ID
369 router may attract all traffic to otherwise-equal paths because of this
370 check. It may increase the possibility of MED or IGP oscillation, unless
371 other measures were taken to avoid these. The exact behaviour will be
372 sensitive to the iBGP and reflection topology.
376 Administrative Distance Metrics
377 -------------------------------
379 .. index:: distance bgp (1-255) (1-255) (1-255)
380 .. clicmd:: distance bgp (1-255) (1-255) (1-255)
382 This command change distance value of BGP. The arguments are the distance
383 values for for external routes, internal routes and local routes
386 .. index:: distance (1-255) A.B.C.D/M
387 .. clicmd:: distance (1-255) A.B.C.D/M
389 .. index:: distance (1-255) A.B.C.D/M WORD
390 .. clicmd:: distance (1-255) A.B.C.D/M WORD
392 Sets the administrative distance for a particular route.
394 .. _bgp-route-flap-dampening:
399 .. clicmd:: bgp dampening (1-45) (1-20000) (1-20000) (1-255)
401 This command enables BGP route-flap dampening and specifies dampening parameters.
404 Half-life time for the penalty
407 Value to start reusing a route
410 Value to start suppressing a route
413 Maximum duration to suppress a stable route
415 The route-flap damping algorithm is compatible with :rfc:`2439`. The use of
416 this command is not recommended nowadays.
419 https://www.ripe.net/publications/docs/ripe-378
423 Multi-Exit Discriminator
424 ------------------------
426 The BGP :abbr:`MED (Multi-Exit Discriminator)` attribute has properties which
427 can cause subtle convergence problems in BGP. These properties and problems
428 have proven to be hard to understand, at least historically, and may still not
429 be widely understood. The following attempts to collect together and present
430 what is known about MED, to help operators and FRR users in designing and
431 configuring their networks.
433 The BGP :abbr:`MED` attribute is intended to allow one AS to indicate its
434 preferences for its ingress points to another AS. The MED attribute will not be
435 propagated on to another AS by the receiving AS - it is 'non-transitive' in the
438 E.g., if AS X and AS Y have 2 different BGP peering points, then AS X might set
439 a MED of 100 on routes advertised at one and a MED of 200 at the other. When AS
440 Y selects between otherwise equal routes to or via AS X, AS Y should prefer to
441 take the path via the lower MED peering of 100 with AS X. Setting the MED
442 allows an AS to influence the routing taken to it within another, neighbouring
445 In this use of MED it is not really meaningful to compare the MED value on
446 routes where the next AS on the paths differs. E.g., if AS Y also had a route
447 for some destination via AS Z in addition to the routes from AS X, and AS Z had
448 also set a MED, it wouldn't make sense for AS Y to compare AS Z's MED values to
449 those of AS X. The MED values have been set by different administrators, with
450 different frames of reference.
452 The default behaviour of BGP therefore is to not compare MED values across
453 routes received from different neighbouring ASes. In FRR this is done by
454 comparing the neighbouring, left-most AS in the received AS_PATHs of the routes
455 and only comparing MED if those are the same.
457 Unfortunately, this behaviour of MED, of sometimes being compared across routes
458 and sometimes not, depending on the properties of those other routes, means MED
459 can cause the order of preference over all the routes to be undefined. That is,
460 given routes A, B, and C, if A is preferred to B, and B is preferred to C, then
461 a well-defined order should mean the preference is transitive (in the sense of
462 orders [#med-transitivity-rant]_) and that A would be preferred to C.
464 However, when MED is involved this need not be the case. With MED it is
465 possible that C is actually preferred over A. So A is preferred to B, B is
466 preferred to C, but C is preferred to A. This can be true even where BGP
467 defines a deterministic 'most preferred' route out of the full set of A,B,C.
468 With MED, for any given set of routes there may be a deterministically
469 preferred route, but there need not be any way to arrange them into any order
470 of preference. With unmodified MED, the order of preference of routes literally
473 That MED can induce non-transitive preferences over routes can cause issues.
474 Firstly, it may be perceived to cause routing table churn locally at speakers;
475 secondly, and more seriously, it may cause routing instability in iBGP
476 topologies, where sets of speakers continually oscillate between different
479 The first issue arises from how speakers often implement routing decisions.
480 Though BGP defines a selection process that will deterministically select the
481 same route as best at any given speaker, even with MED, that process requires
482 evaluating all routes together. For performance and ease of implementation
483 reasons, many implementations evaluate route preferences in a pair-wise fashion
484 instead. Given there is no well-defined order when MED is involved, the best
485 route that will be chosen becomes subject to implementation details, such as
486 the order the routes are stored in. That may be (locally) non-deterministic,
487 e.g.: it may be the order the routes were received in.
489 This indeterminism may be considered undesirable, though it need not cause
490 problems. It may mean additional routing churn is perceived, as sometimes more
491 updates may be produced than at other times in reaction to some event .
493 This first issue can be fixed with a more deterministic route selection that
494 ensures routes are ordered by the neighbouring AS during selection.
495 :clicmd:`bgp deterministic-med`. This may reduce the number of updates as routes
496 are received, and may in some cases reduce routing churn. Though, it could
497 equally deterministically produce the largest possible set of updates in
498 response to the most common sequence of received updates.
500 A deterministic order of evaluation tends to imply an additional overhead of
501 sorting over any set of n routes to a destination. The implementation of
502 deterministic MED in FRR scales significantly worse than most sorting
503 algorithms at present, with the number of paths to a given destination. That
504 number is often low enough to not cause any issues, but where there are many
505 paths, the deterministic comparison may quickly become increasingly expensive
508 Deterministic local evaluation can *not* fix the second, more major, issue of
509 MED however. Which is that the non-transitive preference of routes MED can
510 cause may lead to routing instability or oscillation across multiple speakers
511 in iBGP topologies. This can occur with full-mesh iBGP, but is particularly
512 problematic in non-full-mesh iBGP topologies that further reduce the routing
513 information known to each speaker. This has primarily been documented with iBGP
514 route-reflection topologies. However, any route-hiding technologies potentially
515 could also exacerbate oscillation with MED.
517 This second issue occurs where speakers each have only a subset of routes, and
518 there are cycles in the preferences between different combinations of routes -
519 as the undefined order of preference of MED allows - and the routes are
520 distributed in a way that causes the BGP speakers to 'chase' those cycles. This
521 can occur even if all speakers use a deterministic order of evaluation in route
524 E.g., speaker 4 in AS A might receive a route from speaker 2 in AS X, and from
525 speaker 3 in AS Y; while speaker 5 in AS A might receive that route from
526 speaker 1 in AS Y. AS Y might set a MED of 200 at speaker 1, and 100 at speaker
527 3. I.e, using ASN:ID:MED to label the speakers:
533 X:2------|--A:4-------A:5--|-Y:1:200
539 Assuming all other metrics are equal (AS_PATH, ORIGIN, 0 IGP costs), then based
540 on the RFC4271 decision process speaker 4 will choose X:2 over Y:3:100, based
541 on the lower ID of 2. Speaker 4 advertises X:2 to speaker 5. Speaker 5 will
542 continue to prefer Y:1:200 based on the ID, and advertise this to speaker 4.
543 Speaker 4 will now have the full set of routes, and the Y:1:200 it receives
544 from 5 will beat X:2, but when speaker 4 compares Y:1:200 to Y:3:100 the MED
545 check now becomes active as the ASes match, and now Y:3:100 is preferred.
546 Speaker 4 therefore now advertises Y:3:100 to 5, which will also agrees that
547 Y:3:100 is preferred to Y:1:200, and so withdraws the latter route from 4.
548 Speaker 4 now has only X:2 and Y:3:100, and X:2 beats Y:3:100, and so speaker 4
549 implicitly updates its route to speaker 5 to X:2. Speaker 5 sees that Y:1:200
550 beats X:2 based on the ID, and advertises Y:1:200 to speaker 4, and the cycle
553 The root cause is the lack of a clear order of preference caused by how MED
554 sometimes is and sometimes is not compared, leading to this cycle in the
555 preferences between the routes:
560 /---> X:2 ---beats---> Y:3:100 --\\
563 \\---beats--- Y:1:200 <---beats---/
567 This particular type of oscillation in full-mesh iBGP topologies can be
568 avoided by speakers preferring already selected, external routes rather than
569 choosing to update to new a route based on a post-MED metric (e.g. router-ID),
570 at the cost of a non-deterministic selection process. FRR implements this, as
571 do many other implementations, so long as it is not overridden by setting
572 :clicmd:`bgp bestpath compare-routerid`, and see also
573 :ref:`bgp-route-selection`.
575 However, more complex and insidious cycles of oscillation are possible with
576 iBGP route-reflection, which are not so easily avoided. These have been
577 documented in various places. See, e.g.:
579 - [bgp-route-osci-cond]_
580 - [stable-flexible-ibgp]_
581 - [ibgp-correctness]_
583 for concrete examples and further references.
585 There is as of this writing *no* known way to use MED for its original purpose;
586 *and* reduce routing information in iBGP topologies; *and* be sure to avoid the
587 instability problems of MED due the non-transitive routing preferences it can
588 induce; in general on arbitrary networks.
590 There may be iBGP topology specific ways to reduce the instability risks, even
591 while using MED, e.g.: by constraining the reflection topology and by tuning
592 IGP costs between route-reflector clusters, see :rfc:`3345` for details. In the
593 near future, the Add-Path extension to BGP may also solve MED oscillation while
594 still allowing MED to be used as intended, by distributing "best-paths per
595 neighbour AS". This would be at the cost of distributing at least as many
596 routes to all speakers as a full-mesh iBGP would, if not more, while also
597 imposing similar CPU overheads as the "Deterministic MED" feature at each
600 More generally, the instability problems that MED can introduce on more
601 complex, non-full-mesh, iBGP topologies may be avoided either by:
603 - Setting :clicmd:`bgp always-compare-med`, however this allows MED to be compared
604 across values set by different neighbour ASes, which may not produce
605 coherent desirable results, of itself.
606 - Effectively ignoring MED by setting MED to the same value (e.g.: 0) using
607 :clicmd:`set metric METRIC` on all received routes, in combination with
608 setting :clicmd:`bgp always-compare-med` on all speakers. This is the simplest
609 and most performant way to avoid MED oscillation issues, where an AS is happy
610 not to allow neighbours to inject this problematic metric.
612 As MED is evaluated after the AS_PATH length check, another possible use for
613 MED is for intra-AS steering of routes with equal AS_PATH length, as an
614 extension of the last case above. As MED is evaluated before IGP metric, this
615 can allow cold-potato routing to be implemented to send traffic to preferred
616 hand-offs with neighbours, rather than the closest hand-off according to the
619 Note that even if action is taken to address the MED non-transitivity issues,
620 other oscillations may still be possible. E.g., on IGP cost if iBGP and IGP
621 topologies are at cross-purposes with each other - see the Flavel and Roughan
622 paper above for an example. Hence the guideline that the iBGP topology should
623 follow the IGP topology.
625 .. index:: bgp deterministic-med
626 .. clicmd:: bgp deterministic-med
628 Carry out route-selection in way that produces deterministic answers
629 locally, even in the face of MED and the lack of a well-defined order of
630 preference it can induce on routes. Without this option the preferred route
631 with MED may be determined largely by the order that routes were received
634 Setting this option will have a performance cost that may be noticeable when
635 there are many routes for each destination. Currently in FRR it is
636 implemented in a way that scales poorly as the number of routes per
637 destination increases.
639 The default is that this option is not set.
641 Note that there are other sources of indeterminism in the route selection
642 process, specifically, the preference for older and already selected routes
643 from eBGP peers, :ref:`bgp-route-selection`.
645 .. index:: bgp always-compare-med
646 .. clicmd:: bgp always-compare-med
648 Always compare the MED on routes, even when they were received from
649 different neighbouring ASes. Setting this option makes the order of
650 preference of routes more defined, and should eliminate MED induced
653 If using this option, it may also be desirable to use
654 :clicmd:`set metric METRIC` to set MED to 0 on routes received from external
657 This option can be used, together with :clicmd:`set metric METRIC` to use
658 MED as an intra-AS metric to steer equal-length AS_PATH routes to, e.g.,
666 .. index:: network A.B.C.D/M
667 .. clicmd:: network A.B.C.D/M
669 This command adds the announcement network.
674 address-family ipv4 unicast
678 This configuration example says that network 10.0.0.0/8 will be
679 announced to all neighbors. Some vendors' routers don't advertise
680 routes if they aren't present in their IGP routing tables; `bgpd`
681 doesn't care about IGP routes when announcing its routes.
683 .. index:: no network A.B.C.D/M
684 .. clicmd:: no network A.B.C.D/M
686 .. _bgp-route-aggregation:
691 .. index:: aggregate-address A.B.C.D/M
692 .. clicmd:: aggregate-address A.B.C.D/M
694 This command specifies an aggregate address.
696 .. index:: aggregate-address A.B.C.D/M as-set
697 .. clicmd:: aggregate-address A.B.C.D/M as-set
699 This command specifies an aggregate address. Resulting routes include
702 .. index:: aggregate-address A.B.C.D/M summary-only
703 .. clicmd:: aggregate-address A.B.C.D/M summary-only
705 This command specifies an aggregate address. Aggregated routes will
708 .. index:: no aggregate-address A.B.C.D/M
709 .. clicmd:: no aggregate-address A.B.C.D/M
711 .. _bgp-redistribute-to-bgp:
716 .. index:: redistribute kernel
717 .. clicmd:: redistribute kernel
719 Redistribute kernel route to BGP process.
721 .. index:: redistribute static
722 .. clicmd:: redistribute static
724 Redistribute static route to BGP process.
726 .. index:: redistribute connected
727 .. clicmd:: redistribute connected
729 Redistribute connected route to BGP process.
731 .. index:: redistribute rip
732 .. clicmd:: redistribute rip
734 Redistribute RIP route to BGP process.
736 .. index:: redistribute ospf
737 .. clicmd:: redistribute ospf
739 Redistribute OSPF route to BGP process.
741 .. index:: redistribute vpn
742 .. clicmd:: redistribute vpn
744 Redistribute VNC routes to BGP process.
746 .. index:: update-delay MAX-DELAY
747 .. clicmd:: update-delay MAX-DELAY
749 .. index:: update-delay MAX-DELAY ESTABLISH-WAIT
750 .. clicmd:: update-delay MAX-DELAY ESTABLISH-WAIT
752 This feature is used to enable read-only mode on BGP process restart or when
753 BGP process is cleared using 'clear ip bgp \*'. When applicable, read-only
754 mode would begin as soon as the first peer reaches Established status and a
755 timer for max-delay seconds is started.
757 During this mode BGP doesn't run any best-path or generate any updates to its
758 peers. This mode continues until:
760 1. All the configured peers, except the shutdown peers, have sent explicit EOR
761 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
762 Established is considered an implicit-EOR.
763 If the establish-wait optional value is given, then BGP will wait for
764 peers to reach established from the beginning of the update-delay till the
765 establish-wait period is over, i.e. the minimum set of established peers for
766 which EOR is expected would be peers established during the establish-wait
767 window, not necessarily all the configured neighbors.
768 2. max-delay period is over.
770 On hitting any of the above two conditions, BGP resumes the decision process
771 and generates updates to its peers.
773 Default max-delay is 0, i.e. the feature is off by default.
775 .. index:: table-map ROUTE-MAP-NAME
776 .. clicmd:: table-map ROUTE-MAP-NAME
778 This feature is used to apply a route-map on route updates from BGP to
779 Zebra. All the applicable match operations are allowed, such as match on
780 prefix, next-hop, communities, etc. Set operations for this attach-point are
781 limited to metric and next-hop only. Any operation of this feature does not
782 affect BGPs internal RIB.
784 Supported for ipv4 and ipv6 address families. It works on multi-paths as
785 well, however, metric setting is based on the best-path only.
792 .. _bgp-defining-peers:
797 .. index:: neighbor PEER remote-as ASN
798 .. clicmd:: neighbor PEER remote-as ASN
800 Creates a new neighbor whose remote-as is ASN. PEER can be an IPv4 address
801 or an IPv6 address or an interface to use for the connection.
806 neighbor 10.0.0.1 remote-as 2
808 In this case my router, in AS-1, is trying to peer with AS-2 at 10.0.0.1.
810 This command must be the first command used when configuring a neighbor. If
811 the remote-as is not specified, *bgpd* will complain like this: ::
813 can't find neighbor 10.0.0.1
815 .. index:: neighbor PEER remote-as internal
816 .. clicmd:: neighbor PEER remote-as internal
818 Create a peer as you would when you specify an ASN, except that if the
819 peers ASN is different than mine as specified under the :clicmd:`router bgp ASN`
820 command the connection will be denied.
822 .. index:: neighbor PEER remote-as external
823 .. clicmd:: neighbor PEER remote-as external
825 Create a peer as you would when you specify an ASN, except that if the
826 peers ASN is the same as mine as specified under the :clicmd:`router bgp ASN`
827 command the connection will be denied.
829 .. _bgp-configuring-peers:
834 .. index:: [no] neighbor PEER shutdown
835 .. clicmd:: [no] neighbor PEER shutdown
837 Shutdown the peer. We can delete the neighbor's configuration by
838 ``no neighbor PEER remote-as ASN`` but all configuration of the neighbor
839 will be deleted. When you want to preserve the configuration, but want to
840 drop the BGP peer, use this syntax.
842 .. index:: [no] neighbor PEER disable-connected-check
843 .. clicmd:: [no] neighbor PEER disable-connected-check
845 Allow peerings between directly connected eBGP peers using loopback
848 .. index:: [no] neighbor PEER ebgp-multihop
849 .. clicmd:: [no] neighbor PEER ebgp-multihop
851 .. index:: [no] neighbor PEER description ...
852 .. clicmd:: [no] neighbor PEER description ...
854 Set description of the peer.
856 .. index:: [no] neighbor PEER version VERSION
857 .. clicmd:: [no] neighbor PEER version VERSION
859 Set up the neighbor's BGP version. `version` can be `4`, `4+` or `4-`. BGP
860 version `4` is the default value used for BGP peering. BGP version `4+`
861 means that the neighbor supports Multiprotocol Extensions for BGP-4. BGP
862 version `4-` is similar but the neighbor speaks the old Internet-Draft
863 revision 00's Multiprotocol Extensions for BGP-4. Some routing software is
864 still using this version.
866 .. index:: [no] neighbor PEER interface IFNAME
867 .. clicmd:: [no] neighbor PEER interface IFNAME
869 When you connect to a BGP peer over an IPv6 link-local address, you have to
870 specify the IFNAME of the interface used for the connection. To specify
871 IPv4 session addresses, see the ``neighbor PEER update-source`` command
874 This command is deprecated and may be removed in a future release. Its use
877 .. index:: [no] neighbor PEER next-hop-self [all]
878 .. clicmd:: [no] neighbor PEER next-hop-self [all]
880 This command specifies an announced route's nexthop as being equivalent to
881 the address of the bgp router if it is learned via eBGP. If the optional
882 keyword `all` is specified the modification is done also for routes learned
885 .. index:: [no] neighbor PEER update-source <IFNAME|ADDRESS>
886 .. clicmd:: [no] neighbor PEER update-source <IFNAME|ADDRESS>
888 Specify the IPv4 source address to use for the :abbr:`BGP` session to this
889 neighbour, may be specified as either an IPv4 address directly or as an
890 interface name (in which case the *zebra* daemon MUST be running in order
891 for *bgpd* to be able to retrieve interface state).
896 neighbor foo update-source 192.168.0.1
897 neighbor bar update-source lo0
900 .. index:: [no] neighbor PEER default-originate
901 .. clicmd:: [no] neighbor PEER default-originate
903 *bgpd*'s default is to not announce the default route (0.0.0.0/0) even if it
904 is in routing table. When you want to announce default routes to the peer,
907 .. index:: neighbor PEER port PORT
908 .. clicmd:: neighbor PEER port PORT
910 .. index:: neighbor PEER send-community
911 .. clicmd:: neighbor PEER send-community
913 .. index:: [no] neighbor PEER weight WEIGHT
914 .. clicmd:: [no] neighbor PEER weight WEIGHT
916 This command specifies a default `weight` value for the neighbor's routes.
918 .. index:: [no] neighbor PEER maximum-prefix NUMBER
919 .. clicmd:: [no] neighbor PEER maximum-prefix NUMBER
921 .. index:: [no] neighbor PEER local-as AS-NUMBER no-prepend
922 .. clicmd:: [no] neighbor PEER local-as AS-NUMBER no-prepend
924 .. index:: [no] neighbor PEER local-as AS-NUMBER no-prepend replace-as
925 .. clicmd:: [no] neighbor PEER local-as AS-NUMBER no-prepend replace-as
927 .. index:: [no] neighbor PEER local-as AS-NUMBER
928 .. clicmd:: [no] neighbor PEER local-as AS-NUMBER
930 Specify an alternate AS for this BGP process when interacting with the
931 specified peer. With no modifiers, the specified local-as is prepended to
932 the received AS_PATH when receiving routing updates from the peer, and
933 prepended to the outgoing AS_PATH (after the process local AS) when
934 transmitting local routes to the peer.
936 If the no-prepend attribute is specified, then the supplied local-as is not
937 prepended to the received AS_PATH.
939 If the replace-as attribute is specified, then only the supplied local-as is
940 prepended to the AS_PATH when transmitting local-route updates to this peer.
942 Note that replace-as can only be specified if no-prepend is.
944 This command is only allowed for eBGP peers.
946 .. index:: [no] neighbor PEER ttl-security hops NUMBER
947 .. clicmd:: [no] neighbor PEER ttl-security hops NUMBER
949 This command enforces Generalized TTL Security Mechanism (GTSM), as
950 specified in RFC 5082. With this command, only neighbors that are the
951 specified number of hops away will be allowed to become neighbors. This
952 command is mutually exclusive with *ebgp-multihop*.
954 .. index:: [no] neighbor PEER capability extended-nexthop
955 .. clicmd:: [no] neighbor PEER capability extended-nexthop
957 Allow bgp to negotiate the extended-nexthop capability with it's peer.
958 If you are peering over a v6 LL address then this capability is turned
959 on automatically. If you are peering over a v6 Global Address then
960 turning on this command will allow BGP to install v4 routes with
961 v6 nexthops if you do not have v4 configured on interfaces.
963 .. index:: [no] bgp fast-external-failover
964 .. clicmd:: [no] bgp fast-external-failover
966 This command causes bgp to not take down ebgp peers immediately
967 when a link flaps. `bgp fast-external-failover` is the default
968 and will not be displayed as part of a `show run`. The no form
969 of the command turns off this ability.
971 .. _bgp-peer-filtering:
976 .. index:: neighbor PEER distribute-list NAME [in|out]
977 .. clicmd:: neighbor PEER distribute-list NAME [in|out]
979 This command specifies a distribute-list for the peer. `direct` is
982 .. index:: neighbor PEER prefix-list NAME [in|out]
983 .. clicmd:: neighbor PEER prefix-list NAME [in|out]
985 .. index:: neighbor PEER filter-list NAME [in|out]
986 .. clicmd:: neighbor PEER filter-list NAME [in|out]
988 .. index:: neighbor PEER route-map NAME [in|out]
989 .. clicmd:: neighbor PEER route-map NAME [in|out]
991 Apply a route-map on the neighbor. `direct` must be `in` or `out`.
993 .. index:: bgp route-reflector allow-outbound-policy
994 .. clicmd:: bgp route-reflector allow-outbound-policy
996 By default, attribute modification via route-map policy out is not reflected
997 on reflected routes. This option allows the modifications to be reflected as
998 well. Once enabled, it affects all reflected routes.
1005 Peer groups are used to help improve scaling by generating the same
1006 update information to all members of a peer group. Note that this means
1007 that the routes generated by a member of a peer group will be sent back
1008 to that originating peer with the originator identifier attribute set to
1009 indicated the originating peer. All peers not associated with a
1010 specific peer group are treated as belonging to a default peer group,
1011 and will share updates.
1013 .. index:: neighbor WORD peer-group
1014 .. clicmd:: neighbor WORD peer-group
1016 This command defines a new peer group.
1018 .. index:: neighbor PEER peer-group WORD
1019 .. clicmd:: neighbor PEER peer-group WORD
1021 This command bind specific peer to peer group WORD.
1023 .. index:: neighbor PEER solo
1024 .. clicmd:: neighbor PEER solo
1026 This command is used to indicate that routes advertised by the peer
1027 should not be reflected back to the peer. This command only is only
1028 meaningful when there is a single peer defined in the peer-group.
1030 Capability Negotiation
1031 ^^^^^^^^^^^^^^^^^^^^^^
1033 .. index:: neighbor PEER strict-capability-match
1034 .. clicmd:: neighbor PEER strict-capability-match
1036 .. index:: no neighbor PEER strict-capability-match
1037 .. clicmd:: no neighbor PEER strict-capability-match
1039 Strictly compares remote capabilities and local capabilities. If
1040 capabilities are different, send Unsupported Capability error then reset
1043 You may want to disable sending Capability Negotiation OPEN message optional
1044 parameter to the peer when remote peer does not implement Capability
1045 Negotiation. Please use *dont-capability-negotiate* command to disable the
1048 .. index:: neighbor PEER dont-capability-negotiate
1049 .. clicmd:: neighbor PEER dont-capability-negotiate
1051 .. index:: no neighbor PEER dont-capability-negotiate
1052 .. clicmd:: no neighbor PEER dont-capability-negotiate
1054 Suppress sending Capability Negotiation as OPEN message optional parameter
1055 to the peer. This command only affects the peer is configured other than
1056 IPv4 unicast configuration.
1058 When remote peer does not have capability negotiation feature, remote peer
1059 will not send any capabilities at all. In that case, bgp configures the peer
1060 with configured capabilities.
1062 You may prefer locally configured capabilities more than the negotiated
1063 capabilities even though remote peer sends capabilities. If the peer is
1064 configured by *override-capability*, *bgpd* ignores received capabilities
1065 then override negotiated capabilities with configured values.
1067 .. index:: neighbor PEER override-capability
1068 .. clicmd:: neighbor PEER override-capability
1070 .. index:: no neighbor PEER override-capability
1071 .. clicmd:: no neighbor PEER override-capability
1073 Override the result of Capability Negotiation with local configuration.
1074 Ignore remote peer's capability value.
1076 .. _bgp-as-path-access-lists:
1078 AS Path Access Lists
1079 --------------------
1081 AS path access list is user defined AS path.
1083 .. index:: ip as-path access-list WORD permit|deny LINE
1084 .. clicmd:: ip as-path access-list WORD permit|deny LINE
1086 This command defines a new AS path access list.
1088 .. index:: no ip as-path access-list WORD
1089 .. clicmd:: no ip as-path access-list WORD
1091 .. index:: no ip as-path access-list WORD permit|deny LINE
1092 .. clicmd:: no ip as-path access-list WORD permit|deny LINE
1094 .. _bgp-using-as-path-in-route-map:
1096 Using AS Path in Route Map
1097 --------------------------
1099 .. index:: match as-path WORD
1100 .. clicmd:: match as-path WORD
1103 .. index:: set as-path prepend AS-PATH
1104 .. clicmd:: set as-path prepend AS-PATH
1106 Prepend the given string of AS numbers to the AS_PATH.
1108 .. index:: set as-path prepend last-as NUM
1109 .. clicmd:: set as-path prepend last-as NUM
1111 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
1113 .. _bgp-communities-attribute:
1115 Communities Attribute
1116 ---------------------
1118 The BGP communities attribute is widely used for implementing policy routing.
1119 Network operators can manipulate BGP communities attribute based on their
1120 network policy. BGP communities attribute is defined in :rfc:`1997` and
1121 :rfc:`1998`. It is an optional transitive attribute, therefore local policy can
1122 travel through different autonomous system.
1124 The communities attribute is a set of communities values. Each community value
1125 is 4 octet long. The following format is used to define the community value.
1128 This format represents 4 octet communities value. ``AS`` is high order 2
1129 octet in digit format. ``VAL`` is low order 2 octet in digit format. This
1130 format is useful to define AS oriented policy value. For example,
1131 ``7675:80`` can be used when AS 7675 wants to pass local policy value 80 to
1135 ``internet`` represents well-known communities value 0.
1137 ``graceful-shutdown``
1138 ``graceful-shutdown`` represents well-known communities value
1139 ``GRACEFUL_SHUTDOWN`` ``0xFFFF0000`` ``65535:0``. :rfc:`8326` implements
1140 the purpose Graceful BGP Session Shutdown to reduce the amount of
1141 lost traffic when taking BGP sessions down for maintainance. The use
1142 of the community needs to be supported from your peers side to
1143 actually have any effect.
1146 ``accept-own`` represents well-known communities value ``ACCEPT_OWN``
1147 ``0xFFFF0001`` ``65535:1``. :rfc:`7611` implements a way to signal
1148 to a router to accept routes with a local nexthop address. This
1149 can be the case when doing policing and having traffic having a
1150 nexthop located in another VRF but still local interface to the
1151 router. It is recommended to read the RFC for full details.
1153 ``route-filter-translated-v4``
1154 ``route-filter-translated-v4`` represents well-known communities value
1155 ``ROUTE_FILTER_TRANSLATED_v4`` ``0xFFFF0002`` ``65535:2``.
1158 ``route-filter-v4`` represents well-known communities value
1159 ``ROUTE_FILTER_v4`` ``0xFFFF0003`` ``65535:3``.
1161 ``route-filter-translated-v6``
1162 ``route-filter-translated-v6`` represents well-known communities value
1163 ``ROUTE_FILTER_TRANSLATED_v6`` ``0xFFFF0004`` ``65535:4``.
1166 ``route-filter-v6`` represents well-known communities value
1167 ``ROUTE_FILTER_v6`` ``0xFFFF0005`` ``65535:5``.
1170 ``llgr-stale`` represents well-known communities value ``LLGR_STALE``
1171 ``0xFFFF0006`` ``65535:6``.
1172 Assigned and intented only for use with routers supporting the
1173 Long-lived Graceful Restart Capability as described in
1174 :rfc:`draft-uttaro-idr-bgp-persistence`.
1175 Routers recieving routes with this community may (depending on
1176 implementation) choose allow to reject or modify routes on the
1177 presence or absence of this community.
1180 ``no-llgr`` represents well-known communities value ``NO_LLGR``
1181 ``0xFFFF0007`` ``65535:7``.
1182 Assigned and intented only for use with routers supporting the
1183 Long-lived Graceful Restart Capability as described in
1184 :rfc:`draft-uttaro-idr-bgp-persistence`.
1185 Routers recieving routes with this community may (depending on
1186 implementation) choose allow to reject or modify routes on the
1187 presence or absence of this community.
1189 ``accept-own-nexthop``
1190 ``accept-own-nexthop`` represents well-known communities value
1191 ``accept-own-nexthop`` ``0xFFFF0008`` ``65535:8``.
1192 :rfc:`draft-agrewal-idr-accept-own-nexthop` describes
1193 how to tag and label VPN routes to be able to send traffic between VRFs
1194 via an internal layer 2 domain on the same PE device. Refer to
1195 :rfc:`draft-agrewal-idr-accept-own-nexthop` for full details.
1198 ``blackhole`` represents well-known communities value ``BLACKHOLE``
1199 ``0xFFFF029A`` ``65535:666``. :rfc:`7999` documents sending prefixes to
1200 EBGP peers and upstream for the purpose of blackholing traffic.
1201 Prefixes tagged with the this community should normally not be
1202 re-advertised from neighbors of the originating network. It is
1203 recommended upon receiving prefixes tagged with this community to
1204 add ``NO_EXPORT`` and ``NO_ADVERTISE``.
1207 ``no-export`` represents well-known communities value ``NO_EXPORT``
1208 ``0xFFFFFF01``. All routes carry this value must not be advertised to
1209 outside a BGP confederation boundary. If neighboring BGP peer is part of BGP
1210 confederation, the peer is considered as inside a BGP confederation
1211 boundary, so the route will be announced to the peer.
1214 ``no-advertise`` represents well-known communities value ``NO_ADVERTISE``
1215 ``0xFFFFFF02``. All routes carry this value must not be advertise to other
1219 ``local-AS`` represents well-known communities value ``NO_EXPORT_SUBCONFED``
1220 ``0xFFFFFF03``. All routes carry this value must not be advertised to
1221 external BGP peers. Even if the neighboring router is part of confederation,
1222 it is considered as external BGP peer, so the route will not be announced to
1226 ``no-peer`` represents well-known communities value ``NOPEER``
1227 ``0xFFFFFF04`` ``65535:65284``. :rfc:`3765` is used to communicate to
1228 another network how the originating network want the prefix propagated.
1230 When the communities attribute is received duplicate community values in the
1231 attribute are ignored and value is sorted in numerical order.
1233 .. _bgp-community-lists:
1237 Community lists are user defined lists of community attribute values. These
1238 lists can be used for matching or manipulating the communities attribute in
1241 There are two types of community list:
1244 This type accepts an explicit value for the atttribute.
1247 This type accepts a regular expression. Because the regex must be
1248 interpreted on each use expanded community lists are slower than standard
1251 .. index:: ip community-list standard NAME permit|deny COMMUNITY
1252 .. clicmd:: ip community-list standard NAME permit|deny COMMUNITY
1254 This command defines a new standard community list. ``COMMUNITY`` is
1255 communities value. The ``COMMUNITY`` is compiled into community structure.
1256 We can define multiple community list under same name. In that case match
1257 will happen user defined order. Once the community list matches to
1258 communities attribute in BGP updates it return permit or deny by the
1259 community list definition. When there is no matched entry, deny will be
1260 returned. When ``COMMUNITY`` is empty it matches to any routes.
1262 .. index:: ip community-list expanded NAME permit|deny COMMUNITY
1263 .. clicmd:: ip community-list expanded NAME permit|deny COMMUNITY
1265 This command defines a new expanded community list. ``COMMUNITY`` is a
1266 string expression of communities attribute. ``COMMUNITY`` can be a regular
1267 expression (:ref:`bgp-regular-expressions`) to match the communities
1268 attribute in BGP updates.
1271 It is recommended to use the more explicit versions of this command.
1273 .. index:: ip community-list NAME permit|deny COMMUNITY
1274 .. clicmd:: ip community-list NAME permit|deny COMMUNITY
1276 When the community list type is not specified, the community list type is
1277 automatically detected. If ``COMMUNITY`` can be compiled into communities
1278 attribute, the community list is defined as a standard community list.
1279 Otherwise it is defined as an expanded community list. This feature is left
1280 for backward compatibility. Use of this feature is not recommended.
1283 .. index:: no ip community-list [standard|expanded] NAME
1284 .. clicmd:: no ip community-list [standard|expanded] NAME
1286 Deletes the community list specified by ``NAME``. All community lists share
1287 the same namespace, so it's not necessary to specify ``standard`` or
1288 ``expanded``; these modifiers are purely aesthetic.
1290 .. index:: show ip community-list [NAME]
1291 .. clicmd:: show ip community-list [NAME]
1293 Displays community list information. When ``NAME`` is specified the
1294 specified community list's information is shown.
1298 # show ip community-list
1299 Named Community standard list CLIST
1300 permit 7675:80 7675:100 no-export
1302 Named Community expanded list EXPAND
1305 # show ip community-list CLIST
1306 Named Community standard list CLIST
1307 permit 7675:80 7675:100 no-export
1311 .. _bgp-numbered-community-lists:
1313 Numbered Community Lists
1314 ^^^^^^^^^^^^^^^^^^^^^^^^
1316 When number is used for BGP community list name, the number has
1317 special meanings. Community list number in the range from 1 and 99 is
1318 standard community list. Community list number in the range from 100
1319 to 199 is expanded community list. These community lists are called
1320 as numbered community lists. On the other hand normal community lists
1321 is called as named community lists.
1323 .. index:: ip community-list (1-99) permit|deny COMMUNITY
1324 .. clicmd:: ip community-list (1-99) permit|deny COMMUNITY
1326 This command defines a new community list. The argument to (1-99) defines
1327 the list identifier.
1329 .. index:: ip community-list (100-199) permit|deny COMMUNITY
1330 .. clicmd:: ip community-list (100-199) permit|deny COMMUNITY
1332 This command defines a new expanded community list. The argument to
1333 (100-199) defines the list identifier.
1335 .. _bgp-using-communities-in-route-map:
1337 Using Communities in Route Maps
1338 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1340 In :ref:`route-map` we can match on or set the BGP communities attribute. Using
1341 this feature network operator can implement their network policy based on BGP
1342 communities attribute.
1344 The ollowing commands can be used in route maps:
1346 .. index:: match community WORD exact-match [exact-match]
1347 .. clicmd:: match community WORD exact-match [exact-match]
1349 This command perform match to BGP updates using community list WORD. When
1350 the one of BGP communities value match to the one of communities value in
1351 community list, it is match. When `exact-match` keyword is specified, match
1352 happen only when BGP updates have completely same communities value
1353 specified in the community list.
1355 .. index:: set community <none|COMMUNITY> additive
1356 .. clicmd:: set community <none|COMMUNITY> additive
1358 This command sets the community value in BGP updates. If the attribute is
1359 already configured, the newly provided value replaces the old one unless the
1360 ``additive`` keyword is specified, in which case the new value is appended
1361 to the existing value.
1363 If ``none`` is specified as the community value, the communities attribute
1366 .. index:: set comm-list WORD delete
1367 .. clicmd:: set comm-list WORD delete
1369 This command remove communities value from BGP communities attribute. The
1370 ``word`` is community list name. When BGP route's communities value matches
1371 to the community list ``word``, the communities value is removed. When all
1372 of communities value is removed eventually, the BGP update's communities
1373 attribute is completely removed.
1375 .. _bgp-communities-example:
1377 Example Configuration
1378 ^^^^^^^^^^^^^^^^^^^^^
1380 The following configuration is exemplary of the most typical usage of BGP
1381 communities attribute. In the example, AS 7675 provides an upstream Internet
1382 connection to AS 100. When the following configuration exists in AS 7675, the
1383 network operator of AS 100 can set local preference in AS 7675 network by
1384 setting BGP communities attribute to the updates.
1389 neighbor 192.168.0.1 remote-as 100
1390 address-family ipv4 unicast
1391 neighbor 192.168.0.1 route-map RMAP in
1394 ip community-list 70 permit 7675:70
1395 ip community-list 70 deny
1396 ip community-list 80 permit 7675:80
1397 ip community-list 80 deny
1398 ip community-list 90 permit 7675:90
1399 ip community-list 90 deny
1401 route-map RMAP permit 10
1403 set local-preference 70
1405 route-map RMAP permit 20
1407 set local-preference 80
1409 route-map RMAP permit 30
1411 set local-preference 90
1414 The following configuration announces ``10.0.0.0/8`` from AS 100 to AS 7675.
1415 The route has communities value ``7675:80`` so when above configuration exists
1416 in AS 7675, the announced routes' local preference value will be set to 80.
1422 neighbor 192.168.0.2 remote-as 7675
1423 address-family ipv4 unicast
1424 neighbor 192.168.0.2 route-map RMAP out
1427 ip prefix-list PLIST permit 10.0.0.0/8
1429 route-map RMAP permit 10
1430 match ip address prefix-list PLIST
1431 set community 7675:80
1434 The following configuration is an example of BGP route filtering using
1435 communities attribute. This configuration only permit BGP routes which has BGP
1436 communities value ``0:80`` or ``0:90``. The network operator can set special
1437 internal communities value at BGP border router, then limit the BGP route
1438 announcements into the internal network.
1443 neighbor 192.168.0.1 remote-as 100
1444 address-family ipv4 unicast
1445 neighbor 192.168.0.1 route-map RMAP in
1448 ip community-list 1 permit 0:80 0:90
1450 route-map RMAP permit in
1454 The following example filters BGP routes which have a community value of
1455 ``1:1``. When there is no match community-list returns ``deny``. To avoid
1456 filtering all routes, a ``permit`` line is set at the end of the
1462 neighbor 192.168.0.1 remote-as 100
1463 address-family ipv4 unicast
1464 neighbor 192.168.0.1 route-map RMAP in
1467 ip community-list standard FILTER deny 1:1
1468 ip community-list standard FILTER permit
1470 route-map RMAP permit 10
1471 match community FILTER
1474 The communities value keyword ``internet`` has special meanings in standard
1475 community lists. In the below example ``internet`` matches all BGP routes even
1476 if the route does not have communities attribute at all. So community list
1477 ``INTERNET`` is the same as ``FILTER`` in the previous example.
1481 ip community-list standard INTERNET deny 1:1
1482 ip community-list standard INTERNET permit internet
1485 The following configuration is an example of communities value deletion. With
1486 this configuration the community values ``100:1`` and ``100:2`` are removed
1487 from BGP updates. For communities value deletion, only ``permit``
1488 community-list is used. ``deny`` community-list is ignored.
1493 neighbor 192.168.0.1 remote-as 100
1494 address-family ipv4 unicast
1495 neighbor 192.168.0.1 route-map RMAP in
1498 ip community-list standard DEL permit 100:1 100:2
1500 route-map RMAP permit 10
1501 set comm-list DEL delete
1504 .. _bgp-extended-communities-attribute:
1506 Extended Communities Attribute
1507 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1509 BGP extended communities attribute is introduced with MPLS VPN/BGP technology.
1510 MPLS VPN/BGP expands capability of network infrastructure to provide VPN
1511 functionality. At the same time it requires a new framework for policy routing.
1512 With BGP Extended Communities Attribute we can use Route Target or Site of
1513 Origin for implementing network policy for MPLS VPN/BGP.
1515 BGP Extended Communities Attribute is similar to BGP Communities Attribute. It
1516 is an optional transitive attribute. BGP Extended Communities Attribute can
1517 carry multiple Extended Community value. Each Extended Community value is
1520 BGP Extended Communities Attribute provides an extended range compared with BGP
1521 Communities Attribute. Adding to that there is a type field in each value to
1522 provides community space structure.
1524 There are two format to define Extended Community value. One is AS based format
1525 the other is IP address based format.
1528 This is a format to define AS based Extended Community value. ``AS`` part
1529 is 2 octets Global Administrator subfield in Extended Community value.
1530 ``VAL`` part is 4 octets Local Administrator subfield. ``7675:100``
1531 represents AS 7675 policy value 100.
1534 This is a format to define IP address based Extended Community value.
1535 ``IP-Address`` part is 4 octets Global Administrator subfield. ``VAL`` part
1536 is 2 octets Local Administrator subfield.
1538 .. _bgp-extended-community-lists:
1540 Extended Community Lists
1541 ^^^^^^^^^^^^^^^^^^^^^^^^
1543 .. index:: ip extcommunity-list standard NAME permit|deny EXTCOMMUNITY
1544 .. clicmd:: ip extcommunity-list standard NAME permit|deny EXTCOMMUNITY
1546 This command defines a new standard extcommunity-list. `extcommunity` is
1547 extended communities value. The `extcommunity` is compiled into extended
1548 community structure. We can define multiple extcommunity-list under same
1549 name. In that case match will happen user defined order. Once the
1550 extcommunity-list matches to extended communities attribute in BGP updates
1551 it return permit or deny based upon the extcommunity-list definition. When
1552 there is no matched entry, deny will be returned. When `extcommunity` is
1553 empty it matches to any routes.
1555 .. index:: ip extcommunity-list expanded NAME permit|deny LINE
1556 .. clicmd:: ip extcommunity-list expanded NAME permit|deny LINE
1558 This command defines a new expanded extcommunity-list. `line` is a string
1559 expression of extended communities attribute. `line` can be a regular
1560 expression (:ref:`bgp-regular-expressions`) to match an extended communities
1561 attribute in BGP updates.
1563 .. index:: no ip extcommunity-list NAME
1564 .. clicmd:: no ip extcommunity-list NAME
1566 .. index:: no ip extcommunity-list standard NAME
1567 .. clicmd:: no ip extcommunity-list standard NAME
1569 .. index:: no ip extcommunity-list expanded NAME
1570 .. clicmd:: no ip extcommunity-list expanded NAME
1572 These commands delete extended community lists specified by `name`. All of
1573 extended community lists shares a single name space. So extended community
1574 lists can be removed simply specifying the name.
1576 .. index:: show ip extcommunity-list
1577 .. clicmd:: show ip extcommunity-list
1579 .. index:: show ip extcommunity-list NAME
1580 .. clicmd:: show ip extcommunity-list NAME
1582 This command displays current extcommunity-list information. When `name` is
1583 specified the community list's information is shown.::
1585 # show ip extcommunity-list
1588 .. _bgp-extended-communities-in-route-map:
1590 BGP Extended Communities in Route Map
1591 """""""""""""""""""""""""""""""""""""
1593 .. index:: match extcommunity WORD
1594 .. clicmd:: match extcommunity WORD
1596 .. index:: set extcommunity rt EXTCOMMUNITY
1597 .. clicmd:: set extcommunity rt EXTCOMMUNITY
1599 This command set Route Target value.
1601 .. index:: set extcommunity soo EXTCOMMUNITY
1602 .. clicmd:: set extcommunity soo EXTCOMMUNITY
1604 This command set Site of Origin value.
1606 .. _bgp-large-communities-attribute:
1608 Large Communities Attribute
1609 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
1611 The BGP Large Communities attribute was introduced in Feb 2017 with
1614 The BGP Large Communities Attribute is similar to the BGP Communities Attribute
1615 except that it has 3 components instead of two and each of which are 4 octets
1616 in length. Large Communities bring additional functionality and convenience
1617 over traditional communities, specifically the fact that the ``GLOBAL`` part
1618 below is now 4 octets wide allowing seamless use in networks using 4-byte ASNs.
1620 ``GLOBAL:LOCAL1:LOCAL2``
1621 This is the format to define Large Community values. Referencing :rfc:`8195`
1622 the values are commonly referred to as follows:
1624 - The ``GLOBAL`` part is a 4 octet Global Administrator field, commonly used
1625 as the operators AS number.
1626 - The ``LOCAL1`` part is a 4 octet Local Data Part 1 subfield referred to as
1628 - The ``LOCAL2`` part is a 4 octet Local Data Part 2 field and referred to
1629 as the parameter subfield.
1631 As an example, ``65551:1:10`` represents AS 65551 function 1 and parameter
1632 10. The referenced RFC above gives some guidelines on recommended usage.
1634 .. _bgp-large-community-lists:
1636 Large Community Lists
1637 """""""""""""""""""""
1639 Two types of large community lists are supported, namely `standard` and
1642 .. index:: ip large-community-list standard NAME permit|deny LARGE-COMMUNITY
1643 .. clicmd:: ip large-community-list standard NAME permit|deny LARGE-COMMUNITY
1645 This command defines a new standard large-community-list. `large-community`
1646 is the Large Community value. We can add multiple large communities under
1647 same name. In that case the match will happen in the user defined order.
1648 Once the large-community-list matches the Large Communities attribute in BGP
1649 updates it will return permit or deny based upon the large-community-list
1650 definition. When there is no matched entry, a deny will be returned. When
1651 `large-community` is empty it matches any routes.
1653 .. index:: ip large-community-list expanded NAME permit|deny LINE
1654 .. clicmd:: ip large-community-list expanded NAME permit|deny LINE
1656 This command defines a new expanded large-community-list. Where `line` is a
1657 string matching expression, it will be compared to the entire Large
1658 Communities attribute as a string, with each large-community in order from
1659 lowest to highest. `line` can also be a regular expression which matches
1660 this Large Community attribute.
1662 .. index:: no ip large-community-list NAME
1663 .. clicmd:: no ip large-community-list NAME
1665 .. index:: no ip large-community-list standard NAME
1666 .. clicmd:: no ip large-community-list standard NAME
1668 .. index:: no ip large-community-list expanded NAME
1669 .. clicmd:: no ip large-community-list expanded NAME
1671 These commands delete Large Community lists specified by `name`. All Large
1672 Community lists share a single namespace. This means Large Community lists
1673 can be removed by simply specifying the name.
1675 .. index:: show ip large-community-list
1676 .. clicmd:: show ip large-community-list
1678 .. index:: show ip large-community-list NAME
1679 .. clicmd:: show ip large-community-list NAME
1681 This command display current large-community-list information. When
1682 `name` is specified the community list information is shown.
1684 .. index:: show ip bgp large-community-info
1685 .. clicmd:: show ip bgp large-community-info
1687 This command displays the current large communities in use.
1689 .. _bgp-large-communities-in-route-map:
1691 Large Communities in Route Map
1692 """"""""""""""""""""""""""""""
1694 .. index:: match large-community LINE
1695 .. clicmd:: match large-community LINE
1697 Where `line` can be a simple string to match, or a regular expression. It
1698 is very important to note that this match occurs on the entire
1699 large-community string as a whole, where each large-community is ordered
1700 from lowest to highest.
1702 .. index:: set large-community LARGE-COMMUNITY
1703 .. clicmd:: set large-community LARGE-COMMUNITY
1705 .. index:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
1706 .. clicmd:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
1708 .. index:: set large-community LARGE-COMMUNITY additive
1709 .. clicmd:: set large-community LARGE-COMMUNITY additive
1711 These commands are used for setting large-community values. The first
1712 command will overwrite any large-communities currently present.
1713 The second specifies two large-communities, which overwrites the current
1714 large-community list. The third will add a large-community value without
1715 overwriting other values. Multiple large-community values can be specified.
1723 *bgpd* supports :abbr:`L3VPN (Layer 3 Virtual Private Networks)` :abbr:`VRFs
1724 (Virtual Routing and Forwarding)` for IPv4 :rfc:`4364` and IPv6 :rfc:`4659`.
1725 L3VPN routes, and their associated VRF MPLS labels, can be distributed to VPN
1726 SAFI neighbors in the *default*, i.e., non VRF, BGP instance. VRF MPLS labels
1727 are reached using *core* MPLS labels which are distributed using LDP or BGP
1728 labeled unicast. *bgpd* also supports inter-VRF route leaking.
1731 .. _bgp-vrf-route-leaking:
1736 BGP routes may be leaked (i.e. copied) between a unicast VRF RIB and the VPN
1737 SAFI RIB of the default VRF for use in MPLS-based L3VPNs. Unicast routes may
1738 also be leaked between any VRFs (including the unicast RIB of the default BGP
1739 instanced). A shortcut syntax is also available for specifying leaking from one
1740 VRF to another VRF using the default instance's VPN RIB as the intemediary. A
1741 common application of the VRF-VRF feature is to connect a customer's private
1742 routing domain to a provider's VPN service. Leaking is configured from the
1743 point of view of an individual VRF: ``import`` refers to routes leaked from VPN
1744 to a unicast VRF, whereas ``export`` refers to routes leaked from a unicast VRF
1750 Routes exported from a unicast VRF to the VPN RIB must be augmented by two
1753 - an :abbr:`RD (Route Distinguisher)`
1754 - an :abbr:`RTLIST (Route-target List)`
1756 Configuration for these exported routes must, at a minimum, specify these two
1759 Routes imported from the VPN RIB to a unicast VRF are selected according to
1760 their RTLISTs. Routes whose RTLIST contains at least one route-target in
1761 common with the configured import RTLIST are leaked. Configuration for these
1762 imported routes must specify an RTLIST to be matched.
1764 The RD, which carries no semantic value, is intended to make the route unique
1765 in the VPN RIB among all routes of its prefix that originate from all the
1766 customers and sites that are attached to the provider's VPN service.
1767 Accordingly, each site of each customer is typically assigned an RD that is
1768 unique across the entire provider network.
1770 The RTLIST is a set of route-target extended community values whose purpose is
1771 to specify route-leaking policy. Typically, a customer is assigned a single
1772 route-target value for import and export to be used at all customer sites. This
1773 configuration specifies a simple topology wherein a customer has a single
1774 routing domain which is shared across all its sites. More complex routing
1775 topologies are possible through use of additional route-targets to augment the
1776 leaking of sets of routes in various ways.
1778 When using the shortcut syntax for vrf-to-vrf leaking, the RD and RT are
1781 General configuration
1782 ^^^^^^^^^^^^^^^^^^^^^
1784 Configuration of route leaking between a unicast VRF RIB and the VPN SAFI RIB
1785 of the default VRF is accomplished via commands in the context of a VRF
1788 .. index:: rd vpn export AS:NN|IP:nn
1789 .. clicmd:: rd vpn export AS:NN|IP:nn
1791 Specifies the route distinguisher to be added to a route exported from the
1792 current unicast VRF to VPN.
1794 .. index:: no rd vpn export [AS:NN|IP:nn]
1795 .. clicmd:: no rd vpn export [AS:NN|IP:nn]
1797 Deletes any previously-configured export route distinguisher.
1799 .. index:: rt vpn import|export|both RTLIST...
1800 .. clicmd:: rt vpn import|export|both RTLIST...
1802 Specifies the route-target list to be attached to a route (export) or the
1803 route-target list to match against (import) when exporting/importing between
1804 the current unicast VRF and VPN.
1806 The RTLIST is a space-separated list of route-targets, which are BGP
1807 extended community values as described in
1808 :ref:`bgp-extended-communities-attribute`.
1810 .. index:: no rt vpn import|export|both [RTLIST...]
1811 .. clicmd:: no rt vpn import|export|both [RTLIST...]
1813 Deletes any previously-configured import or export route-target list.
1815 .. index:: label vpn export (0..1048575)|auto
1816 .. clicmd:: label vpn export (0..1048575)|auto
1818 Specifies an optional MPLS label to be attached to a route exported from the
1819 current unicast VRF to VPN. If label is specified as ``auto``, the label
1820 value is automatically assigned from a pool maintained by the zebra
1821 daemon. If zebra is not running, automatic label assignment will not
1822 complete, which will block corresponding route export.
1824 .. index:: no label vpn export [(0..1048575)|auto]
1825 .. clicmd:: no label vpn export [(0..1048575)|auto]
1827 Deletes any previously-configured export label.
1829 .. index:: nexthop vpn export A.B.C.D|X:X::X:X
1830 .. clicmd:: nexthop vpn export A.B.C.D|X:X::X:X
1832 Specifies an optional nexthop value to be assigned to a route exported from
1833 the current unicast VRF to VPN. If left unspecified, the nexthop will be set
1834 to 0.0.0.0 or 0:0::0:0 (self).
1836 .. index:: no nexthop vpn export [A.B.C.D|X:X::X:X]
1837 .. clicmd:: no nexthop vpn export [A.B.C.D|X:X::X:X]
1839 Deletes any previously-configured export nexthop.
1841 .. index:: route-map vpn import|export MAP
1842 .. clicmd:: route-map vpn import|export MAP
1844 Specifies an optional route-map to be applied to routes imported or exported
1845 between the current unicast VRF and VPN.
1847 .. index:: no route-map vpn import|export [MAP]
1848 .. clicmd:: no route-map vpn import|export [MAP]
1850 Deletes any previously-configured import or export route-map.
1852 .. index:: import|export vpn
1853 .. clicmd:: import|export vpn
1855 Enables import or export of routes between the current unicast VRF and VPN.
1857 .. index:: no import|export vpn
1858 .. clicmd:: no import|export vpn
1860 Disables import or export of routes between the current unicast VRF and VPN.
1862 .. index:: import vrf VRFNAME
1863 .. clicmd:: import vrf VRFNAME
1865 Shortcut syntax for specifying automatic leaking from vrf VRFNAME to
1866 the current VRF using the VPN RIB as intermediary. The RD and RT
1867 are auto derived and should not be specified explicitly for either the
1868 source or destination VRF's.
1870 This shortcut syntax mode is not compatible with the explicit
1871 `import vpn` and `export vpn` statements for the two VRF's involved.
1872 The CLI will disallow attempts to configure incompatible leaking
1875 .. index:: no import vrf VRFNAME
1876 .. clicmd:: no import vrf VRFNAME
1878 Disables automatic leaking from vrf VRFNAME to the current VRF using
1879 the VPN RIB as intermediary.
1882 .. _bgp-cisco-compatibility:
1887 FRR has commands that change some configuration syntax and default behavior to
1888 behave more closely to Cisco conventions. These are deprecated and will be
1889 removed in a future version of FRR.
1892 Please transition to using the FRR specific syntax for your configuration.
1894 .. index:: bgp config-type cisco
1895 .. clicmd:: bgp config-type cisco
1897 Cisco compatible BGP configuration output.
1899 When this configuration line is specified:
1901 - ``no synchronization`` is displayed. This command does nothing and is for
1902 display purposes only.
1903 - ``no auto-summary`` is displayed.
1904 - The ``network`` and ``aggregate-address`` arguments are displayed as:
1910 FRR: network 10.0.0.0/8
1911 Cisco: network 10.0.0.0
1913 FRR: aggregate-address 192.168.0.0/24
1914 Cisco: aggregate-address 192.168.0.0 255.255.255.0
1916 Community attribute handling is also different. If no configuration is
1917 specified community attribute and extended community attribute are sent to
1918 the neighbor. If a user manually disables the feature, the community
1919 attribute is not sent to the neighbor. When ``bgp config-type cisco`` is
1920 specified, the community attribute is not sent to the neighbor by default.
1921 To send the community attribute user has to specify
1922 :clicmd:`neighbor A.B.C.D send-community` like so:
1928 neighbor 10.0.0.1 remote-as 1
1929 address-family ipv4 unicast
1930 no neighbor 10.0.0.1 send-community
1934 neighbor 10.0.0.1 remote-as 1
1935 address-family ipv4 unicast
1936 neighbor 10.0.0.1 send-community
1941 Please transition to using the FRR specific syntax for your configuration.
1943 .. index:: bgp config-type zebra
1944 .. clicmd:: bgp config-type zebra
1946 FRR style BGP configuration. This is the default.
1953 .. index:: show debug
1954 .. clicmd:: show debug
1956 Show all enabled debugs.
1958 .. index:: [no] debug bgp neighbor-events
1959 .. clicmd:: [no] debug bgp neighbor-events
1961 Enable or disable debugging for neighbor events. This provides general
1962 information on BGP events such as peer connection / disconnection, session
1963 establishment / teardown, and capability negotiation.
1965 .. index:: [no] debug bgp updates
1966 .. clicmd:: [no] debug bgp updates
1968 Enable or disable debugging for BGP updates. This provides information on
1969 BGP UPDATE messages transmitted and received between local and remote
1972 .. index:: [no] debug bgp keepalives
1973 .. clicmd:: [no] debug bgp keepalives
1975 Enable or disable debugging for BGP keepalives. This provides information on
1976 BGP KEEPALIVE messages transmitted and received between local and remote
1979 .. index:: [no] debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
1980 .. clicmd:: [no] debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
1982 Enable or disable debugging for bestpath selection on the specified prefix.
1984 .. index:: [no] debug bgp nht
1985 .. clicmd:: [no] debug bgp nht
1987 Enable or disable debugging of BGP nexthop tracking.
1989 .. index:: [no] debug bgp update-groups
1990 .. clicmd:: [no] debug bgp update-groups
1992 Enable or disable debugging of dynamic update groups. This provides general
1993 information on group creation, deletion, join and prune events.
1995 .. index:: [no] debug bgp zebra
1996 .. clicmd:: [no] debug bgp zebra
1998 Enable or disable debugging of communications between *bgpd* and *zebra*.
2000 Dumping Messages and Routing Tables
2001 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2003 .. index:: dump bgp all PATH [INTERVAL]
2004 .. clicmd:: dump bgp all PATH [INTERVAL]
2006 .. index:: dump bgp all-et PATH [INTERVAL]
2007 .. clicmd:: dump bgp all-et PATH [INTERVAL]
2009 .. index:: no dump bgp all [PATH] [INTERVAL]
2010 .. clicmd:: no dump bgp all [PATH] [INTERVAL]
2012 Dump all BGP packet and events to `path` file.
2013 If `interval` is set, a new file will be created for echo `interval` of
2014 seconds. The path `path` can be set with date and time formatting
2015 (strftime). The type ‘all-et’ enables support for Extended Timestamp Header
2016 (:ref:`packet-binary-dump-format`).
2018 .. index:: dump bgp updates PATH [INTERVAL]
2019 .. clicmd:: dump bgp updates PATH [INTERVAL]
2021 .. index:: dump bgp updates-et PATH [INTERVAL]
2022 .. clicmd:: dump bgp updates-et PATH [INTERVAL]
2024 .. index:: no dump bgp updates [PATH] [INTERVAL]
2025 .. clicmd:: no dump bgp updates [PATH] [INTERVAL]
2027 Dump only BGP updates messages to `path` file.
2028 If `interval` is set, a new file will be created for echo `interval` of
2029 seconds. The path `path` can be set with date and time formatting
2030 (strftime). The type ‘updates-et’ enables support for Extended Timestamp
2031 Header (:ref:`packet-binary-dump-format`).
2033 .. index:: dump bgp routes-mrt PATH
2034 .. clicmd:: dump bgp routes-mrt PATH
2036 .. index:: dump bgp routes-mrt PATH INTERVAL
2037 .. clicmd:: dump bgp routes-mrt PATH INTERVAL
2039 .. index:: no dump bgp route-mrt [PATH] [INTERVAL]
2040 .. clicmd:: no dump bgp route-mrt [PATH] [INTERVAL]
2042 Dump whole BGP routing table to `path`. This is heavy process. The path
2043 `path` can be set with date and time formatting (strftime). If `interval` is
2044 set, a new file will be created for echo `interval` of seconds.
2046 Note: the interval variable can also be set using hours and minutes: 04h20m00.
2049 .. _bgp-other-commands:
2054 .. index:: clear bgp ipv4|ipv6 \*
2055 .. clicmd:: clear bgp ipv4|ipv6 \*
2057 Clear all address family peers.
2059 .. index:: clear bgp ipv4|ipv6 PEER
2060 .. clicmd:: clear bgp ipv4|ipv6 PEER
2062 Clear peers which have addresses of X.X.X.X
2064 .. index:: clear bgp ipv4|ipv6 PEER soft in
2065 .. clicmd:: clear bgp ipv4|ipv6 PEER soft in
2067 Clear peer using soft reconfiguration.
2070 .. _bgp-displaying-bgp-information:
2072 Displaying BGP Information
2073 ==========================
2075 The following four commands display the IPv6 and IPv4 routing tables, depending
2076 on whether or not the ``ip`` keyword is used.
2077 Actually, :clicmd:`show ip bgp` command was used on older `Quagga` routing
2078 daemon project, while :clicmd:`show bgp` command is the new format. The choice
2079 has been done to keep old format with IPv4 routing table, while new format
2080 displays IPv6 routing table.
2082 .. index:: show ip bgp
2083 .. clicmd:: show ip bgp
2085 .. index:: show ip bgp A.B.C.D
2086 .. clicmd:: show ip bgp A.B.C.D
2089 .. clicmd:: show bgp
2091 .. index:: show bgp X:X::X:X
2092 .. clicmd:: show bgp X:X::X:X
2094 These commands display BGP routes. When no route is specified, the default
2095 is to display all BGP routes.
2099 BGP table version is 0, local router ID is 10.1.1.1
2100 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
2101 Origin codes: i - IGP, e - EGP, ? - incomplete
2103 Network Next Hop Metric LocPrf Weight Path
2104 \*> 1.1.1.1/32 0.0.0.0 0 32768 i
2106 Total number of prefixes 1
2108 Some other commands provide additional options for filtering the output.
2110 .. index:: show [ip] bgp regexp LINE
2111 .. clicmd:: show [ip] bgp regexp LINE
2113 This command displays BGP routes using AS path regular expression
2114 (:ref:`bgp-regular-expressions`).
2116 .. index:: show [ip] bgp summary
2117 .. clicmd:: show [ip] bgp summary
2119 Show a bgp peer summary for the specified address family.
2121 The old command structure :clicmd:`show ip bgp` may be removed in the future
2122 and should no longer be used. In order to reach the other BGP routing tables
2123 other than the IPv6 routing table given by :clicmd:`show bgp`, the new command
2124 structure is extended with :clicmd:`show bgp [afi] [safi]`.
2126 .. index:: show bgp [afi] [safi]
2127 .. clicmd:: show bgp [afi] [safi]
2129 .. index:: show bgp <ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast>
2130 .. clicmd:: show bgp <ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast>
2132 These commands display BGP routes for the specific routing table indicated by
2133 the selected afi and the selected safi. If no afi and no safi value is given,
2134 the command falls back to the default IPv6 routing table
2136 .. index:: show bgp [afi] [safi] summary
2137 .. clicmd:: show bgp [afi] [safi] summary
2139 Show a bgp peer summary for the specified address family, and subsequent
2142 .. index:: show bgp [afi] [safi] neighbor [PEER]
2143 .. clicmd:: show bgp [afi] [safi] neighbor [PEER]
2145 This command shows information on a specific BGP peer of the relevant
2146 afi and safi selected.
2148 .. index:: show bgp [afi] [safi] dampening dampened-paths
2149 .. clicmd:: show bgp [afi] [safi] dampening dampened-paths
2151 Display paths suppressed due to dampening of the selected afi and safi
2154 .. index:: show bgp [afi] [safi] dampening flap-statistics
2155 .. clicmd:: show bgp [afi] [safi] dampening flap-statistics
2157 Display flap statistics of routes of the selected afi and safi selected.
2159 .. _bgp-display-routes-by-community:
2161 Displaying Routes by Community Attribute
2162 ----------------------------------------
2164 The following commands allow displaying routes based on their community
2167 .. index:: show [ip] bgp <ipv4|ipv6> community
2168 .. clicmd:: show [ip] bgp <ipv4|ipv6> community
2170 .. index:: show [ip] bgp <ipv4|ipv6> community COMMUNITY
2171 .. clicmd:: show [ip] bgp <ipv4|ipv6> community COMMUNITY
2173 .. index:: show [ip] bgp <ipv4|ipv6> community COMMUNITY exact-match
2174 .. clicmd:: show [ip] bgp <ipv4|ipv6> community COMMUNITY exact-match
2176 These commands display BGP routes which have the community attribute.
2177 attribute. When ``COMMUNITY`` is specified, BGP routes that match that
2178 community are displayed. When `exact-match` is specified, it display only
2179 routes that have an exact match.
2181 .. index:: show [ip] bgp <ipv4|ipv6> community-list WORD
2182 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD
2184 .. index:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match
2185 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match
2187 These commands display BGP routes for the address family specified that
2188 match the specified community list. When `exact-match` is specified, it
2189 displays only routes that have an exact match.
2191 .. _bgp-display-routes-by-as-path:
2193 Displaying Routes by AS Path
2194 ----------------------------
2196 .. index:: show bgp ipv4|ipv6 regexp LINE
2197 .. clicmd:: show bgp ipv4|ipv6 regexp LINE
2199 This commands displays BGP routes that matches a regular
2200 expression `line` (:ref:`bgp-regular-expressions`).
2202 .. index:: show [ip] bgp ipv4 vpn
2203 .. clicmd:: show [ip] bgp ipv4 vpn
2205 .. index:: show [ip] bgp ipv6 vpn
2206 .. clicmd:: show [ip] bgp ipv6 vpn
2208 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
2210 .. index:: show bgp ipv4 vpn summary
2211 .. clicmd:: show bgp ipv4 vpn summary
2213 .. index:: show bgp ipv6 vpn summary
2214 .. clicmd:: show bgp ipv6 vpn summary
2216 Print a summary of neighbor connections for the specified AFI/SAFI combination.
2219 .. _bgp-route-reflector:
2224 .. note:: This documentation is woefully incomplete.
2226 .. index:: bgp cluster-id A.B.C.D
2227 .. clicmd:: bgp cluster-id A.B.C.D
2229 .. index:: neighbor PEER route-reflector-client
2230 .. clicmd:: neighbor PEER route-reflector-client
2232 .. index:: no neighbor PEER route-reflector-client
2233 .. clicmd:: no neighbor PEER route-reflector-client
2241 You can set different routing policy for a peer. For example, you can set
2242 different filter for a peer.
2246 bgp multiple-instance
2249 neighbor 10.0.0.1 remote-as 2
2250 address-family ipv4 unicast
2251 neighbor 10.0.0.1 distribute-list 1 in
2255 neighbor 10.0.0.1 remote-as 2
2256 address-family ipv4 unicast
2257 neighbor 10.0.0.1 distribute-list 2 in
2260 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view 2.
2261 When the update is inserted into view 1, distribute-list 1 is applied. On the
2262 other hand, when the update is inserted into view 2, distribute-list 2 is
2266 .. _bgp-regular-expressions:
2268 BGP Regular Expressions
2269 =======================
2271 BGP regular expressions are based on :t:`POSIX 1003.2` regular expressions. The
2272 following description is just a quick subset of the POSIX regular expressions.
2276 Matches any single character.
2279 Matches 0 or more occurrences of pattern.
2282 Matches 1 or more occurrences of pattern.
2285 Match 0 or 1 occurrences of pattern.
2288 Matches the beginning of the line.
2291 Matches the end of the line.
2294 The ``_`` character has special meanings in BGP regular expressions. It
2295 matches to space and comma , and AS set delimiter ``{`` and ``}`` and AS
2296 confederation delimiter ``(`` and ``)``. And it also matches to the
2297 beginning of the line and the end of the line. So ``_`` can be used for AS
2298 value boundaries match. This character technically evaluates to
2302 .. _bgp-configuration-examples:
2304 Miscellaneous Configuration Examples
2305 ====================================
2307 Example of a session to an upstream, advertising only one prefix to it.
2312 bgp router-id 10.236.87.1
2313 neighbor upstream peer-group
2314 neighbor upstream remote-as 64515
2315 neighbor upstream capability dynamic
2316 neighbor 10.1.1.1 peer-group upstream
2317 neighbor 10.1.1.1 description ACME ISP
2319 address-family ipv4 unicast
2320 network 10.236.87.0/24
2321 neighbor upstream prefix-list pl-allowed-adv out
2324 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
2325 ip prefix-list pl-allowed-adv seq 10 deny any
2327 A more complex example including upstream, peer and customer sessions
2328 advertising global prefixes and NO_EXPORT prefixes and providing actions for
2329 customer routes based on community values. Extensive use is made of route-maps
2330 and the 'call' feature to support selective advertising of prefixes. This
2331 example is intended as guidance only, it has NOT been tested and almost
2332 certainly contains silly mistakes, if not serious flaws.
2337 bgp router-id 10.236.87.1
2338 neighbor upstream capability dynamic
2339 neighbor cust capability dynamic
2340 neighbor peer capability dynamic
2341 neighbor 10.1.1.1 remote-as 64515
2342 neighbor 10.1.1.1 peer-group upstream
2343 neighbor 10.2.1.1 remote-as 64516
2344 neighbor 10.2.1.1 peer-group upstream
2345 neighbor 10.3.1.1 remote-as 64517
2346 neighbor 10.3.1.1 peer-group cust-default
2347 neighbor 10.3.1.1 description customer1
2348 neighbor 10.4.1.1 remote-as 64518
2349 neighbor 10.4.1.1 peer-group cust
2350 neighbor 10.4.1.1 description customer2
2351 neighbor 10.5.1.1 remote-as 64519
2352 neighbor 10.5.1.1 peer-group peer
2353 neighbor 10.5.1.1 description peer AS 1
2354 neighbor 10.6.1.1 remote-as 64520
2355 neighbor 10.6.1.1 peer-group peer
2356 neighbor 10.6.1.1 description peer AS 2
2358 address-family ipv4 unicast
2359 network 10.123.456.0/24
2360 network 10.123.456.128/25 route-map rm-no-export
2361 neighbor upstream route-map rm-upstream-out out
2362 neighbor cust route-map rm-cust-in in
2363 neighbor cust route-map rm-cust-out out
2364 neighbor cust send-community both
2365 neighbor peer route-map rm-peer-in in
2366 neighbor peer route-map rm-peer-out out
2367 neighbor peer send-community both
2368 neighbor 10.3.1.1 prefix-list pl-cust1-network in
2369 neighbor 10.4.1.1 prefix-list pl-cust2-network in
2370 neighbor 10.5.1.1 prefix-list pl-peer1-network in
2371 neighbor 10.6.1.1 prefix-list pl-peer2-network in
2374 ip prefix-list pl-default permit 0.0.0.0/0
2376 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
2377 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
2379 ip prefix-list pl-cust1-network permit 10.3.1.0/24
2380 ip prefix-list pl-cust1-network permit 10.3.2.0/24
2382 ip prefix-list pl-cust2-network permit 10.4.1.0/24
2384 ip prefix-list pl-peer1-network permit 10.5.1.0/24
2385 ip prefix-list pl-peer1-network permit 10.5.2.0/24
2386 ip prefix-list pl-peer1-network permit 192.168.0.0/24
2388 ip prefix-list pl-peer2-network permit 10.6.1.0/24
2389 ip prefix-list pl-peer2-network permit 10.6.2.0/24
2390 ip prefix-list pl-peer2-network permit 192.168.1.0/24
2391 ip prefix-list pl-peer2-network permit 192.168.2.0/24
2392 ip prefix-list pl-peer2-network permit 172.16.1/24
2394 ip as-path access-list asp-own-as permit ^$
2395 ip as-path access-list asp-own-as permit _64512_
2397 ! #################################################################
2398 ! Match communities we provide actions for, on routes receives from
2399 ! customers. Communities values of <our-ASN>:X, with X, have actions:
2401 ! 100 - blackhole the prefix
2402 ! 200 - set no_export
2403 ! 300 - advertise only to other customers
2404 ! 400 - advertise only to upstreams
2405 ! 500 - set no_export when advertising to upstreams
2406 ! 2X00 - set local_preference to X00
2408 ! blackhole the prefix of the route
2409 ip community-list standard cm-blackhole permit 64512:100
2411 ! set no-export community before advertising
2412 ip community-list standard cm-set-no-export permit 64512:200
2414 ! advertise only to other customers
2415 ip community-list standard cm-cust-only permit 64512:300
2417 ! advertise only to upstreams
2418 ip community-list standard cm-upstream-only permit 64512:400
2420 ! advertise to upstreams with no-export
2421 ip community-list standard cm-upstream-noexport permit 64512:500
2423 ! set local-pref to least significant 3 digits of the community
2424 ip community-list standard cm-prefmod-100 permit 64512:2100
2425 ip community-list standard cm-prefmod-200 permit 64512:2200
2426 ip community-list standard cm-prefmod-300 permit 64512:2300
2427 ip community-list standard cm-prefmod-400 permit 64512:2400
2428 ip community-list expanded cme-prefmod-range permit 64512:2...
2430 ! Informational communities
2432 ! 3000 - learned from upstream
2433 ! 3100 - learned from customer
2434 ! 3200 - learned from peer
2436 ip community-list standard cm-learnt-upstream permit 64512:3000
2437 ip community-list standard cm-learnt-cust permit 64512:3100
2438 ip community-list standard cm-learnt-peer permit 64512:3200
2440 ! ###################################################################
2441 ! Utility route-maps
2443 ! These utility route-maps generally should not used to permit/deny
2444 ! routes, i.e. they do not have meaning as filters, and hence probably
2445 ! should be used with 'on-match next'. These all finish with an empty
2446 ! permit entry so as not interfere with processing in the caller.
2448 route-map rm-no-export permit 10
2449 set community additive no-export
2450 route-map rm-no-export permit 20
2452 route-map rm-blackhole permit 10
2453 description blackhole, up-pref and ensure it cant escape this AS
2454 set ip next-hop 127.0.0.1
2455 set local-preference 10
2456 set community additive no-export
2457 route-map rm-blackhole permit 20
2459 ! Set local-pref as requested
2460 route-map rm-prefmod permit 10
2461 match community cm-prefmod-100
2462 set local-preference 100
2463 route-map rm-prefmod permit 20
2464 match community cm-prefmod-200
2465 set local-preference 200
2466 route-map rm-prefmod permit 30
2467 match community cm-prefmod-300
2468 set local-preference 300
2469 route-map rm-prefmod permit 40
2470 match community cm-prefmod-400
2471 set local-preference 400
2472 route-map rm-prefmod permit 50
2474 ! Community actions to take on receipt of route.
2475 route-map rm-community-in permit 10
2476 description check for blackholing, no point continuing if it matches.
2477 match community cm-blackhole
2479 route-map rm-community-in permit 20
2480 match community cm-set-no-export
2483 route-map rm-community-in permit 30
2484 match community cme-prefmod-range
2486 route-map rm-community-in permit 40
2488 ! #####################################################################
2489 ! Community actions to take when advertising a route.
2490 ! These are filtering route-maps,
2492 ! Deny customer routes to upstream with cust-only set.
2493 route-map rm-community-filt-to-upstream deny 10
2494 match community cm-learnt-cust
2495 match community cm-cust-only
2496 route-map rm-community-filt-to-upstream permit 20
2498 ! Deny customer routes to other customers with upstream-only set.
2499 route-map rm-community-filt-to-cust deny 10
2500 match community cm-learnt-cust
2501 match community cm-upstream-only
2502 route-map rm-community-filt-to-cust permit 20
2504 ! ###################################################################
2505 ! The top-level route-maps applied to sessions. Further entries could
2506 ! be added obviously..
2509 route-map rm-cust-in permit 10
2510 call rm-community-in
2512 route-map rm-cust-in permit 20
2513 set community additive 64512:3100
2514 route-map rm-cust-in permit 30
2516 route-map rm-cust-out permit 10
2517 call rm-community-filt-to-cust
2519 route-map rm-cust-out permit 20
2521 ! Upstream transit ASes
2522 route-map rm-upstream-out permit 10
2523 description filter customer prefixes which are marked cust-only
2524 call rm-community-filt-to-upstream
2526 route-map rm-upstream-out permit 20
2527 description only customer routes are provided to upstreams/peers
2528 match community cm-learnt-cust
2531 ! outbound policy is same as for upstream
2532 route-map rm-peer-out permit 10
2533 call rm-upstream-out
2535 route-map rm-peer-in permit 10
2536 set community additive 64512:3200
2539 Example of how to set up a 6-Bone connection.
2543 ! bgpd configuration
2544 ! ==================
2546 ! MP-BGP configuration
2549 bgp router-id 10.0.0.1
2550 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as `as-number`
2553 network 3ffe:506::/32
2554 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
2555 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
2556 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as `as-number`
2557 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
2560 ipv6 access-list all permit any
2562 ! Set output nexthop address.
2564 route-map set-nexthop permit 10
2565 match ipv6 address all
2566 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
2567 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
2573 .. include:: routeserver.rst
2575 .. include:: rpki.rst
2577 .. include:: flowspec.rst
2579 .. [#med-transitivity-rant] For some set of objects to have an order, there *must* be some binary ordering relation that is defined for *every* combination of those objects, and that relation *must* be transitive. I.e.:, if the relation operator is <, and if a < b and b < c then that relation must carry over and it *must* be that a < c for the objects to have an order. The ordering relation may allow for equality, i.e. a < b and b < a may both be true and imply that a and b are equal in the order and not distinguished by it, in which case the set has a partial order. Otherwise, if there is an order, all the objects have a distinct place in the order and the set has a total order)
2580 .. [bgp-route-osci-cond] McPherson, D. and Gill, V. and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", IETF RFC3345
2581 .. [stable-flexible-ibgp] Flavel, A. and M. Roughan, "Stable and flexible iBGP", ACM SIGCOMM 2009
2582 .. [ibgp-correctness] Griffin, T. and G. Wilfong, "On the correctness of IBGP configuration", ACM SIGCOMM 2002