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 specific IP addresses 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. Multiple addresses
39 In the following example, bgpd is started listening for connections on the
40 addresses 100.0.1.2 and fd00::2:2. The options -d (runs in daemon mode) and
41 -f (uses specific configuration file) are also used in this example as we
42 are likely to run multiple bgpd instances, each one with different
43 configurations, when using -l option.
45 Note that this option implies the --no_kernel option, and no learned routes will be installed into the linux kernel.
49 # /usr/lib/frr/bgpd -d -f /some-folder/bgpd.conf -l 100.0.1.2 -l fd00::2:2
51 .. option:: -n, --no_kernel
53 Do not install learned routes into the linux kernel. This option is useful
54 for a route-reflector environment or if you are running multiple bgp
55 processes in the same namespace. This option is different than the --no_zebra
56 option in that a ZAPI connection is made.
58 This option can also be toggled during runtime by using the
59 ``[no] bgp no-rib`` commands in VTY shell.
61 Note that this option will persist after saving the configuration during
62 runtime, unless unset by the ``no bgp no-rib`` command in VTY shell prior to
63 a configuration write operation.
65 .. option:: -S, --skip_runas
67 Skip the normal process of checking capabilities and changing user and group
70 .. option:: -e, --ecmp
72 Run BGP with a limited ecmp capability, that is different than what BGP
73 was compiled with. The value specified must be greater than 0 and less
74 than or equal to the MULTIPATH_NUM specified on compilation.
76 .. option:: -Z, --no_zebra
78 Do not communicate with zebra at all. This is different than the --no_kernel
79 option in that we do not even open a ZAPI connection to the zebra process.
81 .. option:: -s, --socket_size
83 When opening tcp connections to our peers, set the socket send buffer
84 size that the kernel will use for the peers socket. This option
85 is only really useful at a very large scale. Experimentation should
86 be done to see if this is helping or not at the scale you are running
92 .. option:: -I, --int_num
94 Set zclient id. This is required when using Zebra label manager in proxy mode.
96 .. _bgp-basic-concepts:
101 .. _bgp-autonomous-systems:
108 An AS is a connected group of one or more IP prefixes run by one or more
109 network operators which has a SINGLE and CLEARLY DEFINED routing policy.
111 Each AS has an identifying number associated with it called an :abbr:`ASN
112 (Autonomous System Number)`. This is a two octet value ranging in value from 1
113 to 65535. The AS numbers 64512 through 65535 are defined as private AS numbers.
114 Private AS numbers must not be advertised on the global Internet.
116 The :abbr:`ASN (Autonomous System Number)` is one of the essential elements of
117 BGP. BGP is a distance vector routing protocol, and the AS-Path framework
118 provides distance vector metric and loop detection to BGP.
120 .. seealso:: :rfc:`1930`
122 .. _bgp-address-families:
127 Multiprotocol extensions enable BGP to carry routing information for multiple
128 network layer protocols. BGP supports an Address Family Identifier (AFI) for
129 IPv4 and IPv6. Support is also provided for multiple sets of per-AFI
130 information via the BGP Subsequent Address Family Identifier (SAFI). FRR
131 supports SAFIs for unicast information, labeled information (:rfc:`3107` and
132 :rfc:`8277`), and Layer 3 VPN information (:rfc:`4364` and :rfc:`4659`).
134 .. _bgp-route-selection:
139 The route selection process used by FRR's BGP implementation uses the following
140 decision criterion, starting at the top of the list and going towards the
141 bottom until one of the factors can be used.
145 Prefer higher local weight routes to lower routes.
147 2. **Local preference check**
149 Prefer higher local preference routes to lower.
151 3. **Local route check**
153 Prefer local routes (statics, aggregates, redistributed) to received routes.
155 4. **AS path length check**
157 Prefer shortest hop-count AS_PATHs.
161 Prefer the lowest origin type route. That is, prefer IGP origin routes to
162 EGP, to Incomplete routes.
166 Where routes with a MED were received from the same AS, prefer the route
167 with the lowest MED. :ref:`bgp-med`.
169 7. **External check**
171 Prefer the route received from an external, eBGP peer over routes received
172 from other types of peers.
174 8. **IGP cost check**
176 Prefer the route with the lower IGP cost.
178 9. **Multi-path check**
180 If multi-pathing is enabled, then check whether the routes not yet
181 distinguished in preference may be considered equal. If
182 :clicmd:`bgp bestpath as-path multipath-relax` is set, all such routes are
183 considered equal, otherwise routes received via iBGP with identical AS_PATHs
184 or routes received from eBGP neighbours in the same AS are considered equal.
186 10. **Already-selected external check**
188 Where both routes were received from eBGP peers, then prefer the route
189 which is already selected. Note that this check is not applied if
190 :clicmd:`bgp bestpath compare-routerid` is configured. This check can
191 prevent some cases of oscillation.
193 11. **Router-ID check**
195 Prefer the route with the lowest `router-ID`. If the route has an
196 `ORIGINATOR_ID` attribute, through iBGP reflection, then that router ID is
197 used, otherwise the `router-ID` of the peer the route was received from is
200 12. **Cluster-List length check**
202 The route with the shortest cluster-list length is used. The cluster-list
203 reflects the iBGP reflection path the route has taken.
207 Prefer the route received from the peer with the higher transport layer
208 address, as a last-resort tie-breaker.
210 .. _bgp-capability-negotiation:
212 Capability Negotiation
213 ----------------------
215 When adding IPv6 routing information exchange feature to BGP. There were some
216 proposals. :abbr:`IETF (Internet Engineering Task Force)`
217 :abbr:`IDR (Inter Domain Routing)` adopted a proposal called Multiprotocol
218 Extension for BGP. The specification is described in :rfc:`2283`. The protocol
219 does not define new protocols. It defines new attributes to existing BGP. When
220 it is used exchanging IPv6 routing information it is called BGP-4+. When it is
221 used for exchanging multicast routing information it is called MBGP.
223 *bgpd* supports Multiprotocol Extension for BGP. So if a remote peer supports
224 the protocol, *bgpd* can exchange IPv6 and/or multicast routing information.
226 Traditional BGP did not have the feature to detect a remote peer's
227 capabilities, e.g. whether it can handle prefix types other than IPv4 unicast
228 routes. This was a big problem using Multiprotocol Extension for BGP in an
229 operational network. :rfc:`2842` adopted a feature called Capability
230 Negotiation. *bgpd* use this Capability Negotiation to detect the remote peer's
231 capabilities. If a peer is only configured as an IPv4 unicast neighbor, *bgpd*
232 does not send these Capability Negotiation packets (at least not unless other
233 optional BGP features require capability negotiation).
235 By default, FRR will bring up peering with minimal common capability for the
236 both sides. For example, if the local router has unicast and multicast
237 capabilities and the remote router only has unicast capability the local router
238 will establish the connection with unicast only capability. When there are no
239 common capabilities, FRR sends Unsupported Capability error and then resets the
242 .. _bgp-router-configuration:
244 BGP Router Configuration
245 ========================
250 First of all you must configure BGP router with the :clicmd:`router bgp ASN`
251 command. The AS number is an identifier for the autonomous system. The BGP
252 protocol uses the AS number for detecting whether the BGP connection is
253 internal or external.
255 .. clicmd:: router bgp ASN
257 Enable a BGP protocol process with the specified ASN. After
258 this statement you can input any `BGP Commands`.
260 .. clicmd:: bgp router-id A.B.C.D
262 This command specifies the router-ID. If *bgpd* connects to *zebra* it gets
263 interface and address information. In that case default router ID value is
264 selected as the largest IP Address of the interfaces. When `router zebra` is
265 not enabled *bgpd* can't get interface information so `router-id` is set to
266 0.0.0.0. So please set router-id by hand.
269 .. _bgp-multiple-autonomous-systems:
271 Multiple Autonomous Systems
272 ---------------------------
274 FRR's BGP implementation is capable of running multiple autonomous systems at
275 once. Each configured AS corresponds to a :ref:`zebra-vrf`. In the past, to get
276 the same functionality the network administrator had to run a new *bgpd*
277 process; using VRFs allows multiple autonomous systems to be handled in a
280 When using multiple autonomous systems, all router config blocks after the
281 first one must specify a VRF to be the target of BGP's route selection. This
282 VRF must be unique within respect to all other VRFs being used for the same
283 purpose, i.e. two different autonomous systems cannot use the same VRF.
284 However, the same AS can be used with different VRFs.
288 The separated nature of VRFs makes it possible to peer a single *bgpd*
289 process to itself, on one machine. Note that this can be done fully within
290 BGP without a corresponding VRF in the kernel or Zebra, which enables some
291 practical use cases such as :ref:`route reflectors <bgp-route-reflector>`
294 Configuration of additional autonomous systems, or of a router that targets a
295 specific VRF, is accomplished with the following command:
297 .. clicmd:: router bgp ASN vrf VRFNAME
299 ``VRFNAME`` is matched against VRFs configured in the kernel. When ``vrf
300 VRFNAME`` is not specified, the BGP protocol process belongs to the default
303 An example configuration with multiple autonomous systems might look like this:
308 neighbor 10.0.0.1 remote-as 20
309 neighbor 10.0.0.2 remote-as 30
311 router bgp 2 vrf blue
312 neighbor 10.0.0.3 remote-as 40
313 neighbor 10.0.0.4 remote-as 50
316 neighbor 10.0.0.5 remote-as 60
317 neighbor 10.0.0.6 remote-as 70
320 .. seealso:: :ref:`bgp-vrf-route-leaking`
321 .. seealso:: :ref:`zebra-vrf`
329 In addition to supporting multiple autonomous systems, FRR's BGP implementation
330 also supports *views*.
332 BGP views are almost the same as normal BGP processes, except that routes
333 selected by BGP are not installed into the kernel routing table. Each BGP view
334 provides an independent set of routing information which is only distributed
335 via BGP. Multiple views can be supported, and BGP view information is always
336 independent from other routing protocols and Zebra/kernel routes. BGP views use
337 the core instance (i.e., default VRF) for communication with peers.
339 .. clicmd:: router bgp AS-NUMBER view NAME
341 Make a new BGP view. You can use an arbitrary word for the ``NAME``. Routes
342 selected by the view are not installed into the kernel routing table.
344 With this command, you can setup Route Server like below.
350 neighbor 10.0.0.1 remote-as 2
351 neighbor 10.0.0.2 remote-as 3
354 neighbor 10.0.0.3 remote-as 4
355 neighbor 10.0.0.4 remote-as 5
357 .. clicmd:: show [ip] bgp view NAME
359 Display the routing table of BGP view ``NAME``.
365 .. clicmd:: bgp bestpath as-path confed
367 This command specifies that the length of confederation path sets and
368 sequences should should be taken into account during the BGP best path
371 .. clicmd:: bgp bestpath as-path multipath-relax
373 This command specifies that BGP decision process should consider paths
374 of equal AS_PATH length candidates for multipath computation. Without
375 the knob, the entire AS_PATH must match for multipath computation.
377 .. clicmd:: bgp bestpath compare-routerid
379 Ensure that when comparing routes where both are equal on most metrics,
380 including local-pref, AS_PATH length, IGP cost, MED, that the tie is broken
383 If this option is enabled, then the already-selected check, where
384 already selected eBGP routes are preferred, is skipped.
386 If a route has an `ORIGINATOR_ID` attribute because it has been reflected,
387 that `ORIGINATOR_ID` will be used. Otherwise, the router-ID of the peer the
388 route was received from will be used.
390 The advantage of this is that the route-selection (at this point) will be
391 more deterministic. The disadvantage is that a few or even one lowest-ID
392 router may attract all traffic to otherwise-equal paths because of this
393 check. It may increase the possibility of MED or IGP oscillation, unless
394 other measures were taken to avoid these. The exact behaviour will be
395 sensitive to the iBGP and reflection topology.
397 .. clicmd:: bgp bestpath peer-type multipath-relax
399 This command specifies that BGP decision process should consider paths
400 from all peers for multipath computation. If this option is enabled,
401 paths learned from any of eBGP, iBGP, or confederation neighbors will
402 be multipath if they are otherwise considered equal cost.
406 Administrative Distance Metrics
407 -------------------------------
409 .. clicmd:: distance bgp (1-255) (1-255) (1-255)
411 This command change distance value of BGP. The arguments are the distance
412 values for for external routes, internal routes and local routes
415 .. clicmd:: distance (1-255) A.B.C.D/M
417 .. clicmd:: distance (1-255) A.B.C.D/M WORD
419 Sets the administrative distance for a particular route.
421 .. _bgp-requires-policy:
423 Require policy on EBGP
424 -------------------------------
426 .. clicmd:: bgp ebgp-requires-policy
428 This command requires incoming and outgoing filters to be applied
429 for eBGP sessions as part of RFC-8212 compliance. Without the incoming
430 filter, no routes will be accepted. Without the outgoing filter, no
431 routes will be announced.
433 This is enabled by default for the traditional configuration and
434 turned off by default for datacenter configuration.
436 When you enable/disable this option you MUST clear the session.
438 When the incoming or outgoing filter is missing you will see
439 "(Policy)" sign under ``show bgp summary``:
443 exit1# show bgp summary
445 IPv4 Unicast Summary:
446 BGP router identifier 10.10.10.1, local AS number 65001 vrf-id 0
448 RIB entries 7, using 1344 bytes of memory
449 Peers 2, using 43 KiB of memory
451 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt
452 192.168.0.2 4 65002 8 10 0 0 0 00:03:09 5 (Policy)
453 fe80:1::2222 4 65002 9 11 0 0 0 00:03:09 (Policy) (Policy)
455 Additionally a `show bgp neighbor` command would indicate in the `For address family:`
460 exit1# show bgp neighbor
462 For address family: IPv4 Unicast
463 Update group 1, subgroup 1
464 Packet Queue length 0
465 Inbound soft reconfiguration allowed
466 Community attribute sent to this neighbor(all)
467 Inbound updates discarded due to missing policy
468 Outbound updates discarded due to missing policy
471 Reject routes with AS_SET or AS_CONFED_SET types
472 ------------------------------------------------
474 .. clicmd:: bgp reject-as-sets
476 This command enables rejection of incoming and outgoing routes having AS_SET or AS_CONFED_SET type.
478 Suppress duplicate updates
479 --------------------------
481 .. clicmd:: bgp suppress-duplicates
483 For example, BGP routers can generate multiple identical announcements with
484 empty community attributes if stripped at egress. This is an undesired behavior.
485 Suppress duplicate updates if the route actually not changed.
488 Disable checking if nexthop is connected on EBGP sessions
489 ---------------------------------------------------------
491 .. clicmd:: bgp disable-ebgp-connected-route-check
493 This command is used to disable the connection verification process for EBGP peering sessions
494 that are reachable by a single hop but are configured on a loopback interface or otherwise
495 configured with a non-directly connected IP address.
497 .. _bgp-route-flap-dampening:
502 .. clicmd:: bgp dampening [(1-45) [(1-20000) (1-20000) (1-255)]]
504 This command enables (with optionally specified dampening parameters) or
505 disables route-flap dampening for all routes of a BGP instance.
507 .. clicmd:: neighbor PEER dampening [(1-45) [(1-20000) (1-20000) (1-255)]]
509 This command enables (with optionally specified dampening parameters) or
510 disables route-flap dampening for all routes learned from a BGP peer.
512 .. clicmd:: neighbor GROUP dampening [(1-45) [(1-20000) (1-20000) (1-255)]]
514 This command enables (with optionally specified dampening parameters) or
515 disables route-flap dampening for all routes learned from peers of a peer
519 Half-life time for the penalty in minutes (default value: 15).
522 Value to start reusing a route (default value: 750).
525 Value to start suppressing a route (default value: 2000).
528 Maximum duration to suppress a stable route in minutes (default value:
531 The route-flap damping algorithm is compatible with :rfc:`2439`. The use of
532 these commands is not recommended nowadays.
534 At the moment, route-flap dampening is not working per VRF and is working only
535 for IPv4 unicast and multicast.
537 With different parameter sets configurable for BGP instances, peer groups and
538 peers, the active dampening profile for a route is chosen on the fly,
539 allowing for various changes in configuration (i.e. peer group memberships)
540 during runtime. The parameter sets are taking precedence in the following
547 The negating commands do not allow to exclude a peer/peer group from a peer
548 group/BGP instances configuration.
551 https://www.ripe.net/publications/docs/ripe-378
555 Multi-Exit Discriminator
556 ------------------------
558 The BGP :abbr:`MED (Multi-Exit Discriminator)` attribute has properties which
559 can cause subtle convergence problems in BGP. These properties and problems
560 have proven to be hard to understand, at least historically, and may still not
561 be widely understood. The following attempts to collect together and present
562 what is known about MED, to help operators and FRR users in designing and
563 configuring their networks.
565 The BGP :abbr:`MED` attribute is intended to allow one AS to indicate its
566 preferences for its ingress points to another AS. The MED attribute will not be
567 propagated on to another AS by the receiving AS - it is 'non-transitive' in the
570 E.g., if AS X and AS Y have 2 different BGP peering points, then AS X might set
571 a MED of 100 on routes advertised at one and a MED of 200 at the other. When AS
572 Y selects between otherwise equal routes to or via AS X, AS Y should prefer to
573 take the path via the lower MED peering of 100 with AS X. Setting the MED
574 allows an AS to influence the routing taken to it within another, neighbouring
577 In this use of MED it is not really meaningful to compare the MED value on
578 routes where the next AS on the paths differs. E.g., if AS Y also had a route
579 for some destination via AS Z in addition to the routes from AS X, and AS Z had
580 also set a MED, it wouldn't make sense for AS Y to compare AS Z's MED values to
581 those of AS X. The MED values have been set by different administrators, with
582 different frames of reference.
584 The default behaviour of BGP therefore is to not compare MED values across
585 routes received from different neighbouring ASes. In FRR this is done by
586 comparing the neighbouring, left-most AS in the received AS_PATHs of the routes
587 and only comparing MED if those are the same.
589 Unfortunately, this behaviour of MED, of sometimes being compared across routes
590 and sometimes not, depending on the properties of those other routes, means MED
591 can cause the order of preference over all the routes to be undefined. That is,
592 given routes A, B, and C, if A is preferred to B, and B is preferred to C, then
593 a well-defined order should mean the preference is transitive (in the sense of
594 orders [#med-transitivity-rant]_) and that A would be preferred to C.
596 However, when MED is involved this need not be the case. With MED it is
597 possible that C is actually preferred over A. So A is preferred to B, B is
598 preferred to C, but C is preferred to A. This can be true even where BGP
599 defines a deterministic 'most preferred' route out of the full set of A,B,C.
600 With MED, for any given set of routes there may be a deterministically
601 preferred route, but there need not be any way to arrange them into any order
602 of preference. With unmodified MED, the order of preference of routes literally
605 That MED can induce non-transitive preferences over routes can cause issues.
606 Firstly, it may be perceived to cause routing table churn locally at speakers;
607 secondly, and more seriously, it may cause routing instability in iBGP
608 topologies, where sets of speakers continually oscillate between different
611 The first issue arises from how speakers often implement routing decisions.
612 Though BGP defines a selection process that will deterministically select the
613 same route as best at any given speaker, even with MED, that process requires
614 evaluating all routes together. For performance and ease of implementation
615 reasons, many implementations evaluate route preferences in a pair-wise fashion
616 instead. Given there is no well-defined order when MED is involved, the best
617 route that will be chosen becomes subject to implementation details, such as
618 the order the routes are stored in. That may be (locally) non-deterministic,
619 e.g.: it may be the order the routes were received in.
621 This indeterminism may be considered undesirable, though it need not cause
622 problems. It may mean additional routing churn is perceived, as sometimes more
623 updates may be produced than at other times in reaction to some event .
625 This first issue can be fixed with a more deterministic route selection that
626 ensures routes are ordered by the neighbouring AS during selection.
627 :clicmd:`bgp deterministic-med`. This may reduce the number of updates as routes
628 are received, and may in some cases reduce routing churn. Though, it could
629 equally deterministically produce the largest possible set of updates in
630 response to the most common sequence of received updates.
632 A deterministic order of evaluation tends to imply an additional overhead of
633 sorting over any set of n routes to a destination. The implementation of
634 deterministic MED in FRR scales significantly worse than most sorting
635 algorithms at present, with the number of paths to a given destination. That
636 number is often low enough to not cause any issues, but where there are many
637 paths, the deterministic comparison may quickly become increasingly expensive
640 Deterministic local evaluation can *not* fix the second, more major, issue of
641 MED however. Which is that the non-transitive preference of routes MED can
642 cause may lead to routing instability or oscillation across multiple speakers
643 in iBGP topologies. This can occur with full-mesh iBGP, but is particularly
644 problematic in non-full-mesh iBGP topologies that further reduce the routing
645 information known to each speaker. This has primarily been documented with iBGP
646 :ref:`route-reflection <bgp-route-reflector>` topologies. However, any
647 route-hiding technologies potentially could also exacerbate oscillation with MED.
649 This second issue occurs where speakers each have only a subset of routes, and
650 there are cycles in the preferences between different combinations of routes -
651 as the undefined order of preference of MED allows - and the routes are
652 distributed in a way that causes the BGP speakers to 'chase' those cycles. This
653 can occur even if all speakers use a deterministic order of evaluation in route
656 E.g., speaker 4 in AS A might receive a route from speaker 2 in AS X, and from
657 speaker 3 in AS Y; while speaker 5 in AS A might receive that route from
658 speaker 1 in AS Y. AS Y might set a MED of 200 at speaker 1, and 100 at speaker
659 3. I.e, using ASN:ID:MED to label the speakers:
665 X:2------|--A:4-------A:5--|-Y:1:200
671 Assuming all other metrics are equal (AS_PATH, ORIGIN, 0 IGP costs), then based
672 on the RFC4271 decision process speaker 4 will choose X:2 over Y:3:100, based
673 on the lower ID of 2. Speaker 4 advertises X:2 to speaker 5. Speaker 5 will
674 continue to prefer Y:1:200 based on the ID, and advertise this to speaker 4.
675 Speaker 4 will now have the full set of routes, and the Y:1:200 it receives
676 from 5 will beat X:2, but when speaker 4 compares Y:1:200 to Y:3:100 the MED
677 check now becomes active as the ASes match, and now Y:3:100 is preferred.
678 Speaker 4 therefore now advertises Y:3:100 to 5, which will also agrees that
679 Y:3:100 is preferred to Y:1:200, and so withdraws the latter route from 4.
680 Speaker 4 now has only X:2 and Y:3:100, and X:2 beats Y:3:100, and so speaker 4
681 implicitly updates its route to speaker 5 to X:2. Speaker 5 sees that Y:1:200
682 beats X:2 based on the ID, and advertises Y:1:200 to speaker 4, and the cycle
685 The root cause is the lack of a clear order of preference caused by how MED
686 sometimes is and sometimes is not compared, leading to this cycle in the
687 preferences between the routes:
692 /---> X:2 ---beats---> Y:3:100 --\\
695 \\---beats--- Y:1:200 <---beats---/
699 This particular type of oscillation in full-mesh iBGP topologies can be
700 avoided by speakers preferring already selected, external routes rather than
701 choosing to update to new a route based on a post-MED metric (e.g. router-ID),
702 at the cost of a non-deterministic selection process. FRR implements this, as
703 do many other implementations, so long as it is not overridden by setting
704 :clicmd:`bgp bestpath compare-routerid`, and see also
705 :ref:`bgp-route-selection`.
707 However, more complex and insidious cycles of oscillation are possible with
708 iBGP route-reflection, which are not so easily avoided. These have been
709 documented in various places. See, e.g.:
711 - [bgp-route-osci-cond]_
712 - [stable-flexible-ibgp]_
713 - [ibgp-correctness]_
715 for concrete examples and further references.
717 There is as of this writing *no* known way to use MED for its original purpose;
718 *and* reduce routing information in iBGP topologies; *and* be sure to avoid the
719 instability problems of MED due the non-transitive routing preferences it can
720 induce; in general on arbitrary networks.
722 There may be iBGP topology specific ways to reduce the instability risks, even
723 while using MED, e.g.: by constraining the reflection topology and by tuning
724 IGP costs between route-reflector clusters, see :rfc:`3345` for details. In the
725 near future, the Add-Path extension to BGP may also solve MED oscillation while
726 still allowing MED to be used as intended, by distributing "best-paths per
727 neighbour AS". This would be at the cost of distributing at least as many
728 routes to all speakers as a full-mesh iBGP would, if not more, while also
729 imposing similar CPU overheads as the "Deterministic MED" feature at each
732 More generally, the instability problems that MED can introduce on more
733 complex, non-full-mesh, iBGP topologies may be avoided either by:
735 - Setting :clicmd:`bgp always-compare-med`, however this allows MED to be compared
736 across values set by different neighbour ASes, which may not produce
737 coherent desirable results, of itself.
738 - Effectively ignoring MED by setting MED to the same value (e.g.: 0) using
739 :clicmd:`set metric METRIC` on all received routes, in combination with
740 setting :clicmd:`bgp always-compare-med` on all speakers. This is the simplest
741 and most performant way to avoid MED oscillation issues, where an AS is happy
742 not to allow neighbours to inject this problematic metric.
744 As MED is evaluated after the AS_PATH length check, another possible use for
745 MED is for intra-AS steering of routes with equal AS_PATH length, as an
746 extension of the last case above. As MED is evaluated before IGP metric, this
747 can allow cold-potato routing to be implemented to send traffic to preferred
748 hand-offs with neighbours, rather than the closest hand-off according to the
751 Note that even if action is taken to address the MED non-transitivity issues,
752 other oscillations may still be possible. E.g., on IGP cost if iBGP and IGP
753 topologies are at cross-purposes with each other - see the Flavel and Roughan
754 paper above for an example. Hence the guideline that the iBGP topology should
755 follow the IGP topology.
757 .. clicmd:: bgp deterministic-med
759 Carry out route-selection in way that produces deterministic answers
760 locally, even in the face of MED and the lack of a well-defined order of
761 preference it can induce on routes. Without this option the preferred route
762 with MED may be determined largely by the order that routes were received
765 Setting this option will have a performance cost that may be noticeable when
766 there are many routes for each destination. Currently in FRR it is
767 implemented in a way that scales poorly as the number of routes per
768 destination increases.
770 The default is that this option is not set.
772 Note that there are other sources of indeterminism in the route selection
773 process, specifically, the preference for older and already selected routes
774 from eBGP peers, :ref:`bgp-route-selection`.
776 .. clicmd:: bgp always-compare-med
778 Always compare the MED on routes, even when they were received from
779 different neighbouring ASes. Setting this option makes the order of
780 preference of routes more defined, and should eliminate MED induced
783 If using this option, it may also be desirable to use
784 :clicmd:`set metric METRIC` to set MED to 0 on routes received from external
787 This option can be used, together with :clicmd:`set metric METRIC` to use
788 MED as an intra-AS metric to steer equal-length AS_PATH routes to, e.g.,
792 .. _bgp-graceful-restart:
797 BGP graceful restart functionality as defined in
798 `RFC-4724 <https://tools.ietf.org/html/rfc4724/>`_ defines the mechanisms that
799 allows BGP speaker to continue to forward data packets along known routes
800 while the routing protocol information is being restored.
803 Usually, when BGP on a router restarts, all the BGP peers detect that the
804 session went down and then came up. This "down/up" transition results in a
805 "routing flap" and causes BGP route re-computation, generation of BGP routing
806 updates, and unnecessary churn to the forwarding tables.
808 The following functionality is provided by graceful restart:
810 1. The feature allows the restarting router to indicate to the helping peer the
811 routes it can preserve in its forwarding plane during control plane restart
812 by sending graceful restart capability in the OPEN message sent during
813 session establishment.
814 2. The feature allows helping router to advertise to all other peers the routes
815 received from the restarting router which are preserved in the forwarding
816 plane of the restarting router during control plane restart.
823 (R1)-----------------------------------------------------------------(R2)
825 1. BGP Graceful Restart Capability exchanged between R1 & R2.
827 <--------------------------------------------------------------------->
829 2. Kill BGP Process at R1.
831 ---------------------------------------------------------------------->
833 3. R2 Detects the above BGP Restart & verifies BGP Restarting
836 4. Start BGP Process at R1.
838 5. Re-establish the BGP session between R1 & R2.
840 <--------------------------------------------------------------------->
842 6. R2 Send initial route updates, followed by End-Of-Rib.
844 <----------------------------------------------------------------------
846 7. R1 was waiting for End-Of-Rib from R2 & which has been received
849 8. R1 now runs BGP Best-Path algorithm. Send Initial BGP Update,
850 followed by End-Of Rib
852 <--------------------------------------------------------------------->
855 .. _bgp-GR-preserve-forwarding-state:
857 BGP-GR Preserve-Forwarding State
858 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
860 BGP OPEN message carrying optional capabilities for Graceful Restart has
861 8 bit “Flags for Address Family” for given AFI and SAFI. This field contains
862 bit flags relating to routes that were advertised with the given AFI and SAFI.
871 The most significant bit is defined as the Forwarding State (F) bit, which
872 can be used to indicate whether the forwarding state for routes that were
873 advertised with the given AFI and SAFI has indeed been preserved during the
874 previous BGP restart. When set (value 1), the bit indicates that the
875 forwarding state has been preserved.
876 The remaining bits are reserved and MUST be set to zero by the sender and
877 ignored by the receiver.
879 .. clicmd:: bgp graceful-restart preserve-fw-state
881 FRR gives us the option to enable/disable the "F" flag using this specific
882 vty command. However, it doesn't have the option to enable/disable
883 this flag only for specific AFI/SAFI i.e. when this command is used, it
884 applied to all the supported AFI/SAFI combinations for this peer.
886 .. _bgp-end-of-rib-message:
888 End-of-RIB (EOR) message
889 ^^^^^^^^^^^^^^^^^^^^^^^^
891 An UPDATE message with no reachable Network Layer Reachability Information
892 (NLRI) and empty withdrawn NLRI is specified as the End-of-RIB marker that can
893 be used by a BGP speaker to indicate to its peer the completion of the initial
894 routing update after the session is established.
896 For the IPv4 unicast address family, the End-of-RIB marker is an UPDATE message
897 with the minimum length. For any other address family, it is an UPDATE message
898 that contains only the MP_UNREACH_NLRI attribute with no withdrawn routes for
901 Although the End-of-RIB marker is specified for the purpose of BGP graceful
902 restart, it is noted that the generation of such a marker upon completion of
903 the initial update would be useful for routing convergence in general, and thus
904 the practice is recommended.
906 .. _bgp-route-selection-deferral-timer:
908 Route Selection Deferral Timer
909 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
911 Specifies the time the restarting router defers the route selection process
914 Restarting Router : The usage of route election deferral timer is specified
915 in https://tools.ietf.org/html/rfc4724#section-4.1
917 Once the session between the Restarting Speaker and the Receiving Speaker is
918 re-established, the Restarting Speaker will receive and process BGP messages
921 However, it MUST defer route selection for an address family until it either.
923 1. Receives the End-of-RIB marker from all its peers (excluding the ones with
924 the "Restart State" bit set in the received capability and excluding the ones
925 that do not advertise the graceful restart capability).
926 2. The Selection_Deferral_Timer timeout.
928 .. clicmd:: bgp graceful-restart select-defer-time (0-3600)
930 This is command, will set deferral time to value specified.
933 .. clicmd:: bgp graceful-restart rib-stale-time (1-3600)
935 This is command, will set the time for which stale routes are kept in RIB.
937 .. clicmd:: bgp graceful-restart stalepath-time (1-4095)
939 This is command, will set the max time (in seconds) to hold onto
940 restarting peer's stale paths.
942 It also controls Enhanced Route-Refresh timer.
944 If this command is configured and the router does not receive a Route-Refresh EoRR
945 message, the router removes the stale routes from the BGP table after the timer
946 expires. The stale path timer is started when the router receives a Route-Refresh
949 .. _bgp-per-peer-graceful-restart:
951 BGP Per Peer Graceful Restart
952 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
954 Ability to enable and disable graceful restart, helper and no GR at all mode
955 functionality at peer level.
957 So bgp graceful restart can be enabled at modes global BGP level or at per
958 peer level. There are two FSM, one for BGP GR global mode and other for peer
961 Default global mode is helper and default peer per mode is inherit from global.
962 If per peer mode is configured, the GR mode of this particular peer will
963 override the global mode.
965 .. _bgp-GR-global-mode-cmd:
967 BGP GR Global Mode Commands
968 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
970 .. clicmd:: bgp graceful-restart
972 This command will enable BGP graceful restart ifunctionality at the global
975 .. clicmd:: bgp graceful-restart disable
977 This command will disable both the functionality graceful restart and helper
981 .. _bgp-GR-peer-mode-cmd:
983 BGP GR Peer Mode Commands
984 ^^^^^^^^^^^^^^^^^^^^^^^^^
986 .. clicmd:: neighbor A.B.C.D graceful-restart
988 This command will enable BGP graceful restart ifunctionality at the peer
991 .. clicmd:: neighbor A.B.C.D graceful-restart-helper
993 This command will enable BGP graceful restart helper only functionality
996 .. clicmd:: neighbor A.B.C.D graceful-restart-disable
998 This command will disable the entire BGP graceful restart functionality
1004 Administrative Shutdown
1005 -----------------------
1007 .. clicmd:: bgp shutdown [message MSG...]
1009 Administrative shutdown of all peers of a bgp instance. Drop all BGP peers,
1010 but preserve their configurations. The peers are notified in accordance with
1011 `RFC 8203 <https://tools.ietf.org/html/rfc8203/>`_ by sending a
1012 ``NOTIFICATION`` message with error code ``Cease`` and subcode
1013 ``Administrative Shutdown`` prior to terminating connections. This global
1014 shutdown is independent of the neighbor shutdown, meaning that individually
1015 shut down peers will not be affected by lifting it.
1017 An optional shutdown message `MSG` can be specified.
1025 .. clicmd:: network A.B.C.D/M
1027 This command adds the announcement network.
1032 address-family ipv4 unicast
1036 This configuration example says that network 10.0.0.0/8 will be
1037 announced to all neighbors. Some vendors' routers don't advertise
1038 routes if they aren't present in their IGP routing tables; `bgpd`
1039 doesn't care about IGP routes when announcing its routes.
1042 .. clicmd:: bgp network import-check
1044 This configuration modifies the behavior of the network statement.
1045 If you have this configured the underlying network must exist in
1046 the rib. If you have the [no] form configured then BGP will not
1047 check for the networks existence in the rib. For versions 7.3 and
1048 before frr defaults for datacenter were the network must exist,
1049 traditional did not check for existence. For versions 7.4 and beyond
1050 both traditional and datacenter the network must exist.
1052 .. _bgp-ipv6-support:
1057 .. clicmd:: neighbor A.B.C.D activate
1059 This configuration modifies whether to enable an address family for a
1060 specific neighbor. By default only the IPv4 unicast address family is
1066 address-family ipv6 unicast
1067 neighbor 2001:0DB8::1 activate
1068 network 2001:0DB8:5009::/64
1071 This configuration example says that network 2001:0DB8:5009::/64 will be
1072 announced and enables the neighbor 2001:0DB8::1 to receive this announcement.
1074 By default, only the IPv4 unicast address family is announced to all
1075 neighbors. Using the 'no bgp default ipv4-unicast' configuration overrides
1076 this default so that all address families need to be enabled explicitly.
1081 no bgp default ipv4-unicast
1082 neighbor 10.10.10.1 remote-as 2
1083 neighbor 2001:0DB8::1 remote-as 3
1084 address-family ipv4 unicast
1085 neighbor 10.10.10.1 activate
1086 network 192.168.1.0/24
1088 address-family ipv6 unicast
1089 neighbor 2001:0DB8::1 activate
1090 network 2001:0DB8:5009::/64
1093 This configuration demonstrates how the 'no bgp default ipv4-unicast' might
1094 be used in a setup with two upstreams where each of the upstreams should only
1095 receive either IPv4 or IPv6 annocuments.
1097 Using the ``bgp default ipv6-unicast`` configuration, IPv6 unicast
1098 address family is enabled by default for all new neighbors.
1101 .. _bgp-route-aggregation:
1106 .. _bgp-route-aggregation-ipv4:
1108 Route Aggregation-IPv4 Address Family
1109 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1111 .. clicmd:: aggregate-address A.B.C.D/M
1113 This command specifies an aggregate address.
1115 .. clicmd:: aggregate-address A.B.C.D/M route-map NAME
1117 Apply a route-map for an aggregated prefix.
1119 .. clicmd:: aggregate-address A.B.C.D/M origin <egp|igp|incomplete>
1121 Override ORIGIN for an aggregated prefix.
1123 .. clicmd:: aggregate-address A.B.C.D/M as-set
1125 This command specifies an aggregate address. Resulting routes include
1128 .. clicmd:: aggregate-address A.B.C.D/M summary-only
1130 This command specifies an aggregate address. Aggregated routes will
1133 .. clicmd:: aggregate-address A.B.C.D/M matching-MED-only
1135 Configure the aggregated address to only be created when the routes MED
1136 match, otherwise no aggregated route will be created.
1138 .. clicmd:: aggregate-address A.B.C.D/M suppress-map NAME
1140 Similar to `summary-only`, but will only suppress more specific routes that
1141 are matched by the selected route-map.
1144 This configuration example sets up an ``aggregate-address`` under the ipv4
1150 address-family ipv4 unicast
1151 aggregate-address 10.0.0.0/8
1152 aggregate-address 20.0.0.0/8 as-set
1153 aggregate-address 40.0.0.0/8 summary-only
1154 aggregate-address 50.0.0.0/8 route-map aggr-rmap
1158 .. _bgp-route-aggregation-ipv6:
1160 Route Aggregation-IPv6 Address Family
1161 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1163 .. clicmd:: aggregate-address X:X::X:X/M
1165 This command specifies an aggregate address.
1167 .. clicmd:: aggregate-address X:X::X:X/M route-map NAME
1169 Apply a route-map for an aggregated prefix.
1171 .. clicmd:: aggregate-address X:X::X:X/M origin <egp|igp|incomplete>
1173 Override ORIGIN for an aggregated prefix.
1175 .. clicmd:: aggregate-address X:X::X:X/M as-set
1177 This command specifies an aggregate address. Resulting routes include
1180 .. clicmd:: aggregate-address X:X::X:X/M summary-only
1182 This command specifies an aggregate address. Aggregated routes will
1185 .. clicmd:: aggregate-address X:X::X:X/M matching-MED-only
1187 Configure the aggregated address to only be created when the routes MED
1188 match, otherwise no aggregated route will be created.
1190 .. clicmd:: aggregate-address X:X::X:X/M suppress-map NAME
1192 Similar to `summary-only`, but will only suppress more specific routes that
1193 are matched by the selected route-map.
1196 This configuration example sets up an ``aggregate-address`` under the ipv6
1202 address-family ipv6 unicast
1203 aggregate-address 10::0/64
1204 aggregate-address 20::0/64 as-set
1205 aggregate-address 40::0/64 summary-only
1206 aggregate-address 50::0/64 route-map aggr-rmap
1210 .. _bgp-redistribute-to-bgp:
1215 Redistribution configuration should be placed under the ``address-family``
1216 section for the specific AF to redistribute into. Protocol availability for
1217 redistribution is determined by BGP AF; for example, you cannot redistribute
1218 OSPFv3 into ``address-family ipv4 unicast`` as OSPFv3 supports IPv6.
1220 .. clicmd:: redistribute <babel|connected|eigrp|isis|kernel|openfabric|ospf|ospf6|rip|ripng|sharp|static|table> [metric (0-4294967295)] [route-map WORD]
1222 Redistribute routes from other protocols into BGP.
1224 .. clicmd:: redistribute vnc-direct
1226 Redistribute VNC direct (not via zebra) routes to BGP process.
1228 .. clicmd:: bgp update-delay MAX-DELAY
1230 .. clicmd:: bgp update-delay MAX-DELAY ESTABLISH-WAIT
1232 This feature is used to enable read-only mode on BGP process restart or when
1233 a BGP process is cleared using 'clear ip bgp \*'. Note that this command is
1234 configured at the global level and applies to all bgp instances/vrfs. It
1235 cannot be used at the same time as the "update-delay" command described below,
1236 which is entered in each bgp instance/vrf desired to delay update installation
1237 and advertisements. The global and per-vrf approaches to defining update-delay
1238 are mutually exclusive.
1240 When applicable, read-only mode would begin as soon as the first peer reaches
1241 Established status and a timer for max-delay seconds is started. During this
1242 mode BGP doesn't run any best-path or generate any updates to its peers. This
1243 mode continues until:
1245 1. All the configured peers, except the shutdown peers, have sent explicit EOR
1246 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
1247 Established is considered an implicit-EOR.
1248 If the establish-wait optional value is given, then BGP will wait for
1249 peers to reach established from the beginning of the update-delay till the
1250 establish-wait period is over, i.e. the minimum set of established peers for
1251 which EOR is expected would be peers established during the establish-wait
1252 window, not necessarily all the configured neighbors.
1253 2. max-delay period is over.
1255 On hitting any of the above two conditions, BGP resumes the decision process
1256 and generates updates to its peers.
1258 Default max-delay is 0, i.e. the feature is off by default.
1261 .. clicmd:: update-delay MAX-DELAY
1263 .. clicmd:: update-delay MAX-DELAY ESTABLISH-WAIT
1265 This feature is used to enable read-only mode on BGP process restart or when
1266 a BGP process is cleared using 'clear ip bgp \*'. Note that this command is
1267 configured under the specific bgp instance/vrf that the feaure is enabled for.
1268 It cannot be used at the same time as the global "bgp update-delay" described
1269 above, which is entered at the global level and applies to all bgp instances.
1270 The global and per-vrf approaches to defining update-delay are mutually
1273 When applicable, read-only mode would begin as soon as the first peer reaches
1274 Established status and a timer for max-delay seconds is started. During this
1275 mode BGP doesn't run any best-path or generate any updates to its peers. This
1276 mode continues until:
1278 1. All the configured peers, except the shutdown peers, have sent explicit EOR
1279 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
1280 Established is considered an implicit-EOR.
1281 If the establish-wait optional value is given, then BGP will wait for
1282 peers to reach established from the beginning of the update-delay till the
1283 establish-wait period is over, i.e. the minimum set of established peers for
1284 which EOR is expected would be peers established during the establish-wait
1285 window, not necessarily all the configured neighbors.
1286 2. max-delay period is over.
1288 On hitting any of the above two conditions, BGP resumes the decision process
1289 and generates updates to its peers.
1291 Default max-delay is 0, i.e. the feature is off by default.
1293 .. clicmd:: table-map ROUTE-MAP-NAME
1295 This feature is used to apply a route-map on route updates from BGP to
1296 Zebra. All the applicable match operations are allowed, such as match on
1297 prefix, next-hop, communities, etc. Set operations for this attach-point are
1298 limited to metric and next-hop only. Any operation of this feature does not
1299 affect BGPs internal RIB.
1301 Supported for ipv4 and ipv6 address families. It works on multi-paths as
1302 well, however, metric setting is based on the best-path only.
1309 .. _bgp-defining-peers:
1314 .. clicmd:: neighbor PEER remote-as ASN
1316 Creates a new neighbor whose remote-as is ASN. PEER can be an IPv4 address
1317 or an IPv6 address or an interface to use for the connection.
1322 neighbor 10.0.0.1 remote-as 2
1324 In this case my router, in AS-1, is trying to peer with AS-2 at 10.0.0.1.
1326 This command must be the first command used when configuring a neighbor. If
1327 the remote-as is not specified, *bgpd* will complain like this: ::
1329 can't find neighbor 10.0.0.1
1331 .. clicmd:: neighbor PEER remote-as internal
1333 Create a peer as you would when you specify an ASN, except that if the
1334 peers ASN is different than mine as specified under the :clicmd:`router bgp ASN`
1335 command the connection will be denied.
1337 .. clicmd:: neighbor PEER remote-as external
1339 Create a peer as you would when you specify an ASN, except that if the
1340 peers ASN is the same as mine as specified under the :clicmd:`router bgp ASN`
1341 command the connection will be denied.
1343 .. clicmd:: bgp listen range <A.B.C.D/M|X:X::X:X/M> peer-group PGNAME
1345 Accept connections from any peers in the specified prefix. Configuration
1346 from the specified peer-group is used to configure these peers.
1350 When using BGP listen ranges, if the associated peer group has TCP MD5
1351 authentication configured, your kernel must support this on prefixes. On
1352 Linux, this support was added in kernel version 4.14. If your kernel does
1353 not support this feature you will get a warning in the log file, and the
1354 listen range will only accept connections from peers without MD5 configured.
1356 Additionally, we have observed that when using this option at scale (several
1357 hundred peers) the kernel may hit its option memory limit. In this situation
1358 you will see error messages like:
1360 ``bgpd: sockopt_tcp_signature: setsockopt(23): Cannot allocate memory``
1362 In this case you need to increase the value of the sysctl
1363 ``net.core.optmem_max`` to allow the kernel to allocate the necessary option
1366 .. clicmd:: coalesce-time (0-4294967295)
1368 The time in milliseconds that BGP will delay before deciding what peers
1369 can be put into an update-group together in order to generate a single
1370 update for them. The default time is 1000.
1372 .. _bgp-configuring-peers:
1377 .. clicmd:: neighbor PEER shutdown [message MSG...] [rtt (1-65535) [count (1-255)]]
1379 Shutdown the peer. We can delete the neighbor's configuration by
1380 ``no neighbor PEER remote-as ASN`` but all configuration of the neighbor
1381 will be deleted. When you want to preserve the configuration, but want to
1382 drop the BGP peer, use this syntax.
1384 Optionally you can specify a shutdown message `MSG`.
1386 Also, you can specify optionally ``rtt`` in milliseconds to automatically
1387 shutdown the peer if round-trip-time becomes higher than defined.
1389 Additional ``count`` parameter is the number of keepalive messages to count
1390 before shutdown the peer if round-trip-time becomes higher than defined.
1392 .. clicmd:: neighbor PEER disable-connected-check
1394 Allow peerings between directly connected eBGP peers using loopback
1397 .. clicmd:: neighbor PEER ebgp-multihop
1399 Specifying ``ebgp-multihop`` allows sessions with eBGP neighbors to
1400 establish when they are multiple hops away. When the neighbor is not
1401 directly connected and this knob is not enabled, the session will not
1404 If the peer's IP address is not in the RIB and is reachable via the
1405 default route, then you have to enable ``ip nht resolve-via-default``.
1407 .. clicmd:: neighbor PEER description ...
1409 Set description of the peer.
1411 .. clicmd:: neighbor PEER version VERSION
1413 Set up the neighbor's BGP version. `version` can be `4`, `4+` or `4-`. BGP
1414 version `4` is the default value used for BGP peering. BGP version `4+`
1415 means that the neighbor supports Multiprotocol Extensions for BGP-4. BGP
1416 version `4-` is similar but the neighbor speaks the old Internet-Draft
1417 revision 00's Multiprotocol Extensions for BGP-4. Some routing software is
1418 still using this version.
1420 .. clicmd:: neighbor PEER interface IFNAME
1422 When you connect to a BGP peer over an IPv6 link-local address, you have to
1423 specify the IFNAME of the interface used for the connection. To specify
1424 IPv4 session addresses, see the ``neighbor PEER update-source`` command
1427 This command is deprecated and may be removed in a future release. Its use
1430 .. clicmd:: neighbor PEER interface remote-as <internal|external|ASN>
1432 Configure an unnumbered BGP peer. ``PEER`` should be an interface name. The
1433 session will be established via IPv6 link locals. Use ``internal`` for iBGP
1434 and ``external`` for eBGP sessions, or specify an ASN if you wish.
1436 .. clicmd:: neighbor PEER next-hop-self [all]
1438 This command specifies an announced route's nexthop as being equivalent to
1439 the address of the bgp router if it is learned via eBGP. If the optional
1440 keyword `all` is specified the modification is done also for routes learned
1443 .. clicmd:: neighbor PEER attribute-unchanged [{as-path|next-hop|med}]
1445 This command specifies attributes to be left unchanged for advertisements
1446 sent to a peer. Use this to leave the next-hop unchanged in ipv6
1447 configurations, as the route-map directive to leave the next-hop unchanged
1448 is only available for ipv4.
1450 .. clicmd:: neighbor PEER update-source <IFNAME|ADDRESS>
1452 Specify the IPv4 source address to use for the :abbr:`BGP` session to this
1453 neighbour, may be specified as either an IPv4 address directly or as an
1454 interface name (in which case the *zebra* daemon MUST be running in order
1455 for *bgpd* to be able to retrieve interface state).
1460 neighbor foo update-source 192.168.0.1
1461 neighbor bar update-source lo0
1464 .. clicmd:: neighbor PEER default-originate
1466 *bgpd*'s default is to not announce the default route (0.0.0.0/0) even if it
1467 is in routing table. When you want to announce default routes to the peer,
1470 .. clicmd:: neighbor PEER port PORT
1472 .. clicmd:: neighbor PEER password PASSWORD
1474 Set a MD5 password to be used with the tcp socket that is being used
1475 to connect to the remote peer. Please note if you are using this
1476 command with a large number of peers on linux you should consider
1477 modifying the `net.core.optmem_max` sysctl to a larger value to
1478 avoid out of memory errors from the linux kernel.
1480 .. clicmd:: neighbor PEER send-community
1482 .. clicmd:: neighbor PEER weight WEIGHT
1484 This command specifies a default `weight` value for the neighbor's routes.
1486 .. clicmd:: neighbor PEER maximum-prefix NUMBER [force]
1488 Sets a maximum number of prefixes we can receive from a given peer. If this
1489 number is exceeded, the BGP session will be destroyed.
1491 In practice, it is generally preferable to use a prefix-list to limit what
1492 prefixes are received from the peer instead of using this knob. Tearing down
1493 the BGP session when a limit is exceeded is far more destructive than merely
1494 rejecting undesired prefixes. The prefix-list method is also much more
1495 granular and offers much smarter matching criterion than number of received
1496 prefixes, making it more suited to implementing policy.
1498 If ``force`` is set, then ALL prefixes are counted for maximum instead of
1499 accepted only. This is useful for cases where an inbound filter is applied,
1500 but you want maximum-prefix to act on ALL (including filtered) prefixes. This
1501 option requires `soft-reconfiguration inbound` to be enabled for the peer.
1503 .. clicmd:: neighbor PEER maximum-prefix-out NUMBER
1505 Sets a maximum number of prefixes we can send to a given peer.
1507 Since sent prefix count is managed by update-groups, this option
1508 creates a separate update-group for outgoing updates.
1510 .. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend] [replace-as]
1512 Specify an alternate AS for this BGP process when interacting with the
1513 specified peer. With no modifiers, the specified local-as is prepended to
1514 the received AS_PATH when receiving routing updates from the peer, and
1515 prepended to the outgoing AS_PATH (after the process local AS) when
1516 transmitting local routes to the peer.
1518 If the no-prepend attribute is specified, then the supplied local-as is not
1519 prepended to the received AS_PATH.
1521 If the replace-as attribute is specified, then only the supplied local-as is
1522 prepended to the AS_PATH when transmitting local-route updates to this peer.
1524 Note that replace-as can only be specified if no-prepend is.
1526 This command is only allowed for eBGP peers.
1528 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> as-override
1530 Override AS number of the originating router with the local AS number.
1532 Usually this configuration is used in PEs (Provider Edge) to replace
1533 the incoming customer AS number so the connected CE (Customer Edge)
1534 can use the same AS number as the other customer sites. This allows
1535 customers of the provider network to use the same AS number across
1538 This command is only allowed for eBGP peers.
1540 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> allowas-in [<(1-10)|origin>]
1542 Accept incoming routes with AS path containing AS number with the same value
1543 as the current system AS.
1545 This is used when you want to use the same AS number in your sites, but you
1546 can't connect them directly. This is an alternative to
1547 `neighbor WORD as-override`.
1549 The parameter `(1-10)` configures the amount of accepted occurences of the
1550 system AS number in AS path.
1552 The parameter `origin` configures BGP to only accept routes originated with
1553 the same AS number as the system.
1555 This command is only allowed for eBGP peers.
1557 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-all-paths
1559 Configure BGP to send all known paths to neighbor in order to preserve multi
1560 path capabilities inside a network.
1562 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-bestpath-per-AS
1564 Configure BGP to send best known paths to neighbor in order to preserve multi
1565 path capabilities inside a network.
1567 .. clicmd:: neighbor PEER ttl-security hops NUMBER
1569 This command enforces Generalized TTL Security Mechanism (GTSM), as
1570 specified in RFC 5082. With this command, only neighbors that are the
1571 specified number of hops away will be allowed to become neighbors. This
1572 command is mutually exclusive with *ebgp-multihop*.
1574 .. clicmd:: neighbor PEER capability extended-nexthop
1576 Allow bgp to negotiate the extended-nexthop capability with it's peer.
1577 If you are peering over a v6 LL address then this capability is turned
1578 on automatically. If you are peering over a v6 Global Address then
1579 turning on this command will allow BGP to install v4 routes with
1580 v6 nexthops if you do not have v4 configured on interfaces.
1582 .. clicmd:: bgp fast-external-failover
1584 This command causes bgp to not take down ebgp peers immediately
1585 when a link flaps. `bgp fast-external-failover` is the default
1586 and will not be displayed as part of a `show run`. The no form
1587 of the command turns off this ability.
1589 .. clicmd:: bgp default ipv4-unicast
1591 This command allows the user to specify that v4 peering is turned
1592 on by default or not. This command defaults to on and is not displayed.
1593 The `no bgp default ipv4-unicast` form of the command is displayed.
1595 .. clicmd:: bgp default ipv6-unicast
1597 This command allows the user to specify that v6 peering is turned
1598 on by default or not. This command defaults to off and is not displayed.
1599 The `bgp default ipv6-unicast` form of the command is displayed.
1601 .. clicmd:: bgp default show-hostname
1603 This command shows the hostname of the peer in certain BGP commands
1604 outputs. It's easier to troubleshoot if you have a number of BGP peers.
1606 .. clicmd:: bgp default show-nexthop-hostname
1608 This command shows the hostname of the next-hop in certain BGP commands
1609 outputs. It's easier to troubleshoot if you have a number of BGP peers
1610 and a number of routes to check.
1612 .. clicmd:: neighbor PEER advertisement-interval (0-600)
1614 Setup the minimum route advertisement interval(mrai) for the
1615 peer in question. This number is between 0 and 600 seconds,
1616 with the default advertisement interval being 0.
1618 .. clicmd:: neighbor PEER timers delayopen (1-240)
1620 This command allows the user enable the
1621 `RFC 4271 <https://tools.ietf.org/html/rfc4271/>` DelayOpenTimer with the
1622 specified interval or disable it with the negating command for the peer. By
1623 default, the DelayOpenTimer is disabled. The timer interval may be set to a
1624 duration of 1 to 240 seconds.
1626 Displaying Information about Peers
1627 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1629 .. clicmd:: show bgp <afi> <safi> neighbors WORD bestpath-routes [json] [wide]
1631 For the given neighbor, WORD, that is specified list the routes selected
1632 by BGP as having the best path.
1634 .. _bgp-peer-filtering:
1639 .. clicmd:: neighbor PEER distribute-list NAME [in|out]
1641 This command specifies a distribute-list for the peer. `direct` is
1644 .. clicmd:: neighbor PEER prefix-list NAME [in|out]
1646 .. clicmd:: neighbor PEER filter-list NAME [in|out]
1648 .. clicmd:: neighbor PEER route-map NAME [in|out]
1650 Apply a route-map on the neighbor. `direct` must be `in` or `out`.
1652 .. clicmd:: bgp route-reflector allow-outbound-policy
1654 By default, attribute modification via route-map policy out is not reflected
1655 on reflected routes. This option allows the modifications to be reflected as
1656 well. Once enabled, it affects all reflected routes.
1658 .. clicmd:: neighbor PEER sender-as-path-loop-detection
1660 Enable the detection of sender side AS path loops and filter the
1661 bad routes before they are sent.
1663 This setting is disabled by default.
1670 Peer groups are used to help improve scaling by generating the same
1671 update information to all members of a peer group. Note that this means
1672 that the routes generated by a member of a peer group will be sent back
1673 to that originating peer with the originator identifier attribute set to
1674 indicated the originating peer. All peers not associated with a
1675 specific peer group are treated as belonging to a default peer group,
1676 and will share updates.
1678 .. clicmd:: neighbor WORD peer-group
1680 This command defines a new peer group.
1682 .. clicmd:: neighbor PEER peer-group PGNAME
1684 This command bind specific peer to peer group WORD.
1686 .. clicmd:: neighbor PEER solo
1688 This command is used to indicate that routes advertised by the peer
1689 should not be reflected back to the peer. This command only is only
1690 meaningful when there is a single peer defined in the peer-group.
1692 .. clicmd:: show [ip] bgp peer-group [json]
1694 This command displays configured BGP peer-groups.
1698 exit1-debian-9# show bgp peer-group
1700 BGP peer-group test1, remote AS 65001
1701 Peer-group type is external
1702 Configured address-families: IPv4 Unicast; IPv6 Unicast;
1703 1 IPv4 listen range(s)
1705 2 IPv6 listen range(s)
1709 192.168.200.1 Active
1712 BGP peer-group test2
1713 Peer-group type is external
1714 Configured address-families: IPv4 Unicast;
1716 Optional ``json`` parameter is used to display JSON output.
1724 "addressFamiliesConfigured":[
1754 "addressFamiliesConfigured":[
1760 Capability Negotiation
1761 ^^^^^^^^^^^^^^^^^^^^^^
1763 .. clicmd:: neighbor PEER strict-capability-match
1766 Strictly compares remote capabilities and local capabilities. If
1767 capabilities are different, send Unsupported Capability error then reset
1770 You may want to disable sending Capability Negotiation OPEN message optional
1771 parameter to the peer when remote peer does not implement Capability
1772 Negotiation. Please use *dont-capability-negotiate* command to disable the
1775 .. clicmd:: neighbor PEER dont-capability-negotiate
1777 Suppress sending Capability Negotiation as OPEN message optional parameter
1778 to the peer. This command only affects the peer is configured other than
1779 IPv4 unicast configuration.
1781 When remote peer does not have capability negotiation feature, remote peer
1782 will not send any capabilities at all. In that case, bgp configures the peer
1783 with configured capabilities.
1785 You may prefer locally configured capabilities more than the negotiated
1786 capabilities even though remote peer sends capabilities. If the peer is
1787 configured by *override-capability*, *bgpd* ignores received capabilities
1788 then override negotiated capabilities with configured values.
1790 Additionally the operator should be reminded that this feature fundamentally
1791 disables the ability to use widely deployed BGP features. BGP unnumbered,
1792 hostname support, AS4, Addpath, Route Refresh, ORF, Dynamic Capabilities,
1793 and graceful restart.
1795 .. clicmd:: neighbor PEER override-capability
1798 Override the result of Capability Negotiation with local configuration.
1799 Ignore remote peer's capability value.
1801 .. _bgp-as-path-access-lists:
1803 AS Path Access Lists
1804 --------------------
1806 AS path access list is user defined AS path.
1808 .. clicmd:: bgp as-path access-list WORD [seq (0-4294967295)] permit|deny LINE
1810 This command defines a new AS path access list.
1814 .. _bgp-bogon-filter-example:
1816 Bogon ASN filter policy configuration example
1817 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1821 bgp as-path access-list 99 permit _0_
1822 bgp as-path access-list 99 permit _23456_
1823 bgp as-path access-list 99 permit _1310[0-6][0-9]_|_13107[0-1]_
1824 bgp as-path access-list 99 seq 20 permit ^65
1826 .. _bgp-using-as-path-in-route-map:
1828 Using AS Path in Route Map
1829 --------------------------
1831 .. clicmd:: match as-path WORD
1833 For a given as-path, WORD, match it on the BGP as-path given for the prefix
1834 and if it matches do normal route-map actions. The no form of the command
1835 removes this match from the route-map.
1837 .. clicmd:: set as-path prepend AS-PATH
1839 Prepend the given string of AS numbers to the AS_PATH of the BGP path's NLRI.
1840 The no form of this command removes this set operation from the route-map.
1842 .. clicmd:: set as-path prepend last-as NUM
1844 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
1845 The no form of this command removes this set operation from the route-map.
1847 .. _bgp-communities-attribute:
1849 Communities Attribute
1850 ---------------------
1852 The BGP communities attribute is widely used for implementing policy routing.
1853 Network operators can manipulate BGP communities attribute based on their
1854 network policy. BGP communities attribute is defined in :rfc:`1997` and
1855 :rfc:`1998`. It is an optional transitive attribute, therefore local policy can
1856 travel through different autonomous system.
1858 The communities attribute is a set of communities values. Each community value
1859 is 4 octet long. The following format is used to define the community value.
1862 This format represents 4 octet communities value. ``AS`` is high order 2
1863 octet in digit format. ``VAL`` is low order 2 octet in digit format. This
1864 format is useful to define AS oriented policy value. For example,
1865 ``7675:80`` can be used when AS 7675 wants to pass local policy value 80 to
1869 ``internet`` represents well-known communities value 0.
1871 ``graceful-shutdown``
1872 ``graceful-shutdown`` represents well-known communities value
1873 ``GRACEFUL_SHUTDOWN`` ``0xFFFF0000`` ``65535:0``. :rfc:`8326` implements
1874 the purpose Graceful BGP Session Shutdown to reduce the amount of
1875 lost traffic when taking BGP sessions down for maintenance. The use
1876 of the community needs to be supported from your peers side to
1877 actually have any effect.
1880 ``accept-own`` represents well-known communities value ``ACCEPT_OWN``
1881 ``0xFFFF0001`` ``65535:1``. :rfc:`7611` implements a way to signal
1882 to a router to accept routes with a local nexthop address. This
1883 can be the case when doing policing and having traffic having a
1884 nexthop located in another VRF but still local interface to the
1885 router. It is recommended to read the RFC for full details.
1887 ``route-filter-translated-v4``
1888 ``route-filter-translated-v4`` represents well-known communities value
1889 ``ROUTE_FILTER_TRANSLATED_v4`` ``0xFFFF0002`` ``65535:2``.
1892 ``route-filter-v4`` represents well-known communities value
1893 ``ROUTE_FILTER_v4`` ``0xFFFF0003`` ``65535:3``.
1895 ``route-filter-translated-v6``
1896 ``route-filter-translated-v6`` represents well-known communities value
1897 ``ROUTE_FILTER_TRANSLATED_v6`` ``0xFFFF0004`` ``65535:4``.
1900 ``route-filter-v6`` represents well-known communities value
1901 ``ROUTE_FILTER_v6`` ``0xFFFF0005`` ``65535:5``.
1904 ``llgr-stale`` represents well-known communities value ``LLGR_STALE``
1905 ``0xFFFF0006`` ``65535:6``.
1906 Assigned and intended only for use with routers supporting the
1907 Long-lived Graceful Restart Capability as described in
1908 [Draft-IETF-uttaro-idr-bgp-persistence]_.
1909 Routers receiving routes with this community may (depending on
1910 implementation) choose allow to reject or modify routes on the
1911 presence or absence of this community.
1914 ``no-llgr`` represents well-known communities value ``NO_LLGR``
1915 ``0xFFFF0007`` ``65535:7``.
1916 Assigned and intended only for use with routers supporting the
1917 Long-lived Graceful Restart Capability as described in
1918 [Draft-IETF-uttaro-idr-bgp-persistence]_.
1919 Routers receiving routes with this community may (depending on
1920 implementation) choose allow to reject or modify routes on the
1921 presence or absence of this community.
1923 ``accept-own-nexthop``
1924 ``accept-own-nexthop`` represents well-known communities value
1925 ``accept-own-nexthop`` ``0xFFFF0008`` ``65535:8``.
1926 [Draft-IETF-agrewal-idr-accept-own-nexthop]_ describes
1927 how to tag and label VPN routes to be able to send traffic between VRFs
1928 via an internal layer 2 domain on the same PE device. Refer to
1929 [Draft-IETF-agrewal-idr-accept-own-nexthop]_ for full details.
1932 ``blackhole`` represents well-known communities value ``BLACKHOLE``
1933 ``0xFFFF029A`` ``65535:666``. :rfc:`7999` documents sending prefixes to
1934 EBGP peers and upstream for the purpose of blackholing traffic.
1935 Prefixes tagged with the this community should normally not be
1936 re-advertised from neighbors of the originating network. Upon receiving
1937 ``BLACKHOLE`` community from a BGP speaker, ``NO_ADVERTISE`` community
1938 is added automatically.
1941 ``no-export`` represents well-known communities value ``NO_EXPORT``
1942 ``0xFFFFFF01``. All routes carry this value must not be advertised to
1943 outside a BGP confederation boundary. If neighboring BGP peer is part of BGP
1944 confederation, the peer is considered as inside a BGP confederation
1945 boundary, so the route will be announced to the peer.
1948 ``no-advertise`` represents well-known communities value ``NO_ADVERTISE``
1949 ``0xFFFFFF02``. All routes carry this value must not be advertise to other
1953 ``local-AS`` represents well-known communities value ``NO_EXPORT_SUBCONFED``
1954 ``0xFFFFFF03``. All routes carry this value must not be advertised to
1955 external BGP peers. Even if the neighboring router is part of confederation,
1956 it is considered as external BGP peer, so the route will not be announced to
1960 ``no-peer`` represents well-known communities value ``NOPEER``
1961 ``0xFFFFFF04`` ``65535:65284``. :rfc:`3765` is used to communicate to
1962 another network how the originating network want the prefix propagated.
1964 When the communities attribute is received duplicate community values in the
1965 attribute are ignored and value is sorted in numerical order.
1967 .. [Draft-IETF-uttaro-idr-bgp-persistence] <https://tools.ietf.org/id/draft-uttaro-idr-bgp-persistence-04.txt>
1968 .. [Draft-IETF-agrewal-idr-accept-own-nexthop] <https://tools.ietf.org/id/draft-agrewal-idr-accept-own-nexthop-00.txt>
1970 .. _bgp-community-lists:
1974 Community lists are user defined lists of community attribute values. These
1975 lists can be used for matching or manipulating the communities attribute in
1978 There are two types of community list:
1981 This type accepts an explicit value for the attribute.
1984 This type accepts a regular expression. Because the regex must be
1985 interpreted on each use expanded community lists are slower than standard
1988 .. clicmd:: bgp community-list standard NAME permit|deny COMMUNITY
1990 This command defines a new standard community list. ``COMMUNITY`` is
1991 communities value. The ``COMMUNITY`` is compiled into community structure.
1992 We can define multiple community list under same name. In that case match
1993 will happen user defined order. Once the community list matches to
1994 communities attribute in BGP updates it return permit or deny by the
1995 community list definition. When there is no matched entry, deny will be
1996 returned. When ``COMMUNITY`` is empty it matches to any routes.
1998 .. clicmd:: bgp community-list expanded NAME permit|deny COMMUNITY
2000 This command defines a new expanded community list. ``COMMUNITY`` is a
2001 string expression of communities attribute. ``COMMUNITY`` can be a regular
2002 expression (:ref:`bgp-regular-expressions`) to match the communities
2003 attribute in BGP updates. The expanded community is only used to filter,
2007 It is recommended to use the more explicit versions of this command.
2009 .. clicmd:: bgp community-list NAME permit|deny COMMUNITY
2011 When the community list type is not specified, the community list type is
2012 automatically detected. If ``COMMUNITY`` can be compiled into communities
2013 attribute, the community list is defined as a standard community list.
2014 Otherwise it is defined as an expanded community list. This feature is left
2015 for backward compatibility. Use of this feature is not recommended.
2017 Note that all community lists share the same namespace, so it's not
2018 necessary to specify ``standard`` or ``expanded``; these modifiers are
2021 .. clicmd:: show bgp community-list [NAME detail]
2023 Displays community list information. When ``NAME`` is specified the
2024 specified community list's information is shown.
2028 # show bgp community-list
2029 Named Community standard list CLIST
2030 permit 7675:80 7675:100 no-export
2032 Named Community expanded list EXPAND
2035 # show bgp community-list CLIST detail
2036 Named Community standard list CLIST
2037 permit 7675:80 7675:100 no-export
2041 .. _bgp-numbered-community-lists:
2043 Numbered Community Lists
2044 ^^^^^^^^^^^^^^^^^^^^^^^^
2046 When number is used for BGP community list name, the number has
2047 special meanings. Community list number in the range from 1 and 99 is
2048 standard community list. Community list number in the range from 100
2049 to 199 is expanded community list. These community lists are called
2050 as numbered community lists. On the other hand normal community lists
2051 is called as named community lists.
2053 .. clicmd:: bgp community-list (1-99) permit|deny COMMUNITY
2055 This command defines a new community list. The argument to (1-99) defines
2056 the list identifier.
2058 .. clicmd:: bgp community-list (100-199) permit|deny COMMUNITY
2060 This command defines a new expanded community list. The argument to
2061 (100-199) defines the list identifier.
2063 .. _bgp-using-communities-in-route-map:
2065 Using Communities in Route Maps
2066 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2068 In :ref:`route-map` we can match on or set the BGP communities attribute. Using
2069 this feature network operator can implement their network policy based on BGP
2070 communities attribute.
2072 The following commands can be used in route maps:
2074 .. clicmd:: match community WORD exact-match [exact-match]
2076 This command perform match to BGP updates using community list WORD. When
2077 the one of BGP communities value match to the one of communities value in
2078 community list, it is match. When `exact-match` keyword is specified, match
2079 happen only when BGP updates have completely same communities value
2080 specified in the community list.
2082 .. clicmd:: set community <none|COMMUNITY> additive
2084 This command sets the community value in BGP updates. If the attribute is
2085 already configured, the newly provided value replaces the old one unless the
2086 ``additive`` keyword is specified, in which case the new value is appended
2087 to the existing value.
2089 If ``none`` is specified as the community value, the communities attribute
2092 It is not possible to set an expanded community list.
2094 .. clicmd:: set comm-list WORD delete
2096 This command remove communities value from BGP communities attribute. The
2097 ``word`` is community list name. When BGP route's communities value matches
2098 to the community list ``word``, the communities value is removed. When all
2099 of communities value is removed eventually, the BGP update's communities
2100 attribute is completely removed.
2102 .. _bgp-communities-example:
2104 Example Configuration
2105 ^^^^^^^^^^^^^^^^^^^^^
2107 The following configuration is exemplary of the most typical usage of BGP
2108 communities attribute. In the example, AS 7675 provides an upstream Internet
2109 connection to AS 100. When the following configuration exists in AS 7675, the
2110 network operator of AS 100 can set local preference in AS 7675 network by
2111 setting BGP communities attribute to the updates.
2116 neighbor 192.168.0.1 remote-as 100
2117 address-family ipv4 unicast
2118 neighbor 192.168.0.1 route-map RMAP in
2121 bgp community-list 70 permit 7675:70
2122 bgp community-list 70 deny
2123 bgp community-list 80 permit 7675:80
2124 bgp community-list 80 deny
2125 bgp community-list 90 permit 7675:90
2126 bgp community-list 90 deny
2128 route-map RMAP permit 10
2130 set local-preference 70
2132 route-map RMAP permit 20
2134 set local-preference 80
2136 route-map RMAP permit 30
2138 set local-preference 90
2141 The following configuration announces ``10.0.0.0/8`` from AS 100 to AS 7675.
2142 The route has communities value ``7675:80`` so when above configuration exists
2143 in AS 7675, the announced routes' local preference value will be set to 80.
2149 neighbor 192.168.0.2 remote-as 7675
2150 address-family ipv4 unicast
2151 neighbor 192.168.0.2 route-map RMAP out
2154 ip prefix-list PLIST permit 10.0.0.0/8
2156 route-map RMAP permit 10
2157 match ip address prefix-list PLIST
2158 set community 7675:80
2161 The following configuration is an example of BGP route filtering using
2162 communities attribute. This configuration only permit BGP routes which has BGP
2163 communities value ``0:80`` or ``0:90``. The network operator can set special
2164 internal communities value at BGP border router, then limit the BGP route
2165 announcements into the internal network.
2170 neighbor 192.168.0.1 remote-as 100
2171 address-family ipv4 unicast
2172 neighbor 192.168.0.1 route-map RMAP in
2175 bgp community-list 1 permit 0:80 0:90
2177 route-map RMAP permit in
2181 The following example filters BGP routes which have a community value of
2182 ``1:1``. When there is no match community-list returns ``deny``. To avoid
2183 filtering all routes, a ``permit`` line is set at the end of the
2189 neighbor 192.168.0.1 remote-as 100
2190 address-family ipv4 unicast
2191 neighbor 192.168.0.1 route-map RMAP in
2194 bgp community-list standard FILTER deny 1:1
2195 bgp community-list standard FILTER permit
2197 route-map RMAP permit 10
2198 match community FILTER
2201 The communities value keyword ``internet`` has special meanings in standard
2202 community lists. In the below example ``internet`` matches all BGP routes even
2203 if the route does not have communities attribute at all. So community list
2204 ``INTERNET`` is the same as ``FILTER`` in the previous example.
2208 bgp community-list standard INTERNET deny 1:1
2209 bgp community-list standard INTERNET permit internet
2212 The following configuration is an example of communities value deletion. With
2213 this configuration the community values ``100:1`` and ``100:2`` are removed
2214 from BGP updates. For communities value deletion, only ``permit``
2215 community-list is used. ``deny`` community-list is ignored.
2220 neighbor 192.168.0.1 remote-as 100
2221 address-family ipv4 unicast
2222 neighbor 192.168.0.1 route-map RMAP in
2225 bgp community-list standard DEL permit 100:1 100:2
2227 route-map RMAP permit 10
2228 set comm-list DEL delete
2231 .. _bgp-extended-communities-attribute:
2233 Extended Communities Attribute
2234 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2236 BGP extended communities attribute is introduced with MPLS VPN/BGP technology.
2237 MPLS VPN/BGP expands capability of network infrastructure to provide VPN
2238 functionality. At the same time it requires a new framework for policy routing.
2239 With BGP Extended Communities Attribute we can use Route Target or Site of
2240 Origin for implementing network policy for MPLS VPN/BGP.
2242 BGP Extended Communities Attribute is similar to BGP Communities Attribute. It
2243 is an optional transitive attribute. BGP Extended Communities Attribute can
2244 carry multiple Extended Community value. Each Extended Community value is
2247 BGP Extended Communities Attribute provides an extended range compared with BGP
2248 Communities Attribute. Adding to that there is a type field in each value to
2249 provides community space structure.
2251 There are two format to define Extended Community value. One is AS based format
2252 the other is IP address based format.
2255 This is a format to define AS based Extended Community value. ``AS`` part
2256 is 2 octets Global Administrator subfield in Extended Community value.
2257 ``VAL`` part is 4 octets Local Administrator subfield. ``7675:100``
2258 represents AS 7675 policy value 100.
2261 This is a format to define IP address based Extended Community value.
2262 ``IP-Address`` part is 4 octets Global Administrator subfield. ``VAL`` part
2263 is 2 octets Local Administrator subfield.
2265 .. _bgp-extended-community-lists:
2267 Extended Community Lists
2268 ^^^^^^^^^^^^^^^^^^^^^^^^
2270 .. clicmd:: bgp extcommunity-list standard NAME permit|deny EXTCOMMUNITY
2272 This command defines a new standard extcommunity-list. `extcommunity` is
2273 extended communities value. The `extcommunity` is compiled into extended
2274 community structure. We can define multiple extcommunity-list under same
2275 name. In that case match will happen user defined order. Once the
2276 extcommunity-list matches to extended communities attribute in BGP updates
2277 it return permit or deny based upon the extcommunity-list definition. When
2278 there is no matched entry, deny will be returned. When `extcommunity` is
2279 empty it matches to any routes.
2281 .. clicmd:: bgp extcommunity-list expanded NAME permit|deny LINE
2283 This command defines a new expanded extcommunity-list. `line` is a string
2284 expression of extended communities attribute. `line` can be a regular
2285 expression (:ref:`bgp-regular-expressions`) to match an extended communities
2286 attribute in BGP updates.
2288 Note that all extended community lists shares a single name space, so it's
2289 not necessary to specify their type when creating or destroying them.
2291 .. clicmd:: show bgp extcommunity-list [NAME detail]
2293 This command displays current extcommunity-list information. When `name` is
2294 specified the community list's information is shown.
2297 .. _bgp-extended-communities-in-route-map:
2299 BGP Extended Communities in Route Map
2300 """""""""""""""""""""""""""""""""""""
2302 .. clicmd:: match extcommunity WORD
2304 .. clicmd:: set extcommunity rt EXTCOMMUNITY
2306 This command set Route Target value.
2308 .. clicmd:: set extcommunity soo EXTCOMMUNITY
2310 This command set Site of Origin value.
2312 .. clicmd:: set extcommunity bandwidth <(1-25600) | cumulative | num-multipaths> [non-transitive]
2314 This command sets the BGP link-bandwidth extended community for the prefix
2315 (best path) for which it is applied. The link-bandwidth can be specified as
2316 an ``explicit value`` (specified in Mbps), or the router can be told to use
2317 the ``cumulative bandwidth`` of all multipaths for the prefix or to compute
2318 it based on the ``number of multipaths``. The link bandwidth extended
2319 community is encoded as ``transitive`` unless the set command explicitly
2320 configures it as ``non-transitive``.
2322 .. seealso:: :ref:`wecmp_linkbw`
2324 Note that the extended expanded community is only used for `match` rule, not for
2327 .. _bgp-large-communities-attribute:
2329 Large Communities Attribute
2330 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
2332 The BGP Large Communities attribute was introduced in Feb 2017 with
2335 The BGP Large Communities Attribute is similar to the BGP Communities Attribute
2336 except that it has 3 components instead of two and each of which are 4 octets
2337 in length. Large Communities bring additional functionality and convenience
2338 over traditional communities, specifically the fact that the ``GLOBAL`` part
2339 below is now 4 octets wide allowing seamless use in networks using 4-byte ASNs.
2341 ``GLOBAL:LOCAL1:LOCAL2``
2342 This is the format to define Large Community values. Referencing :rfc:`8195`
2343 the values are commonly referred to as follows:
2345 - The ``GLOBAL`` part is a 4 octet Global Administrator field, commonly used
2346 as the operators AS number.
2347 - The ``LOCAL1`` part is a 4 octet Local Data Part 1 subfield referred to as
2349 - The ``LOCAL2`` part is a 4 octet Local Data Part 2 field and referred to
2350 as the parameter subfield.
2352 As an example, ``65551:1:10`` represents AS 65551 function 1 and parameter
2353 10. The referenced RFC above gives some guidelines on recommended usage.
2355 .. _bgp-large-community-lists:
2357 Large Community Lists
2358 """""""""""""""""""""
2360 Two types of large community lists are supported, namely `standard` and
2363 .. clicmd:: bgp large-community-list standard NAME permit|deny LARGE-COMMUNITY
2365 This command defines a new standard large-community-list. `large-community`
2366 is the Large Community value. We can add multiple large communities under
2367 same name. In that case the match will happen in the user defined order.
2368 Once the large-community-list matches the Large Communities attribute in BGP
2369 updates it will return permit or deny based upon the large-community-list
2370 definition. When there is no matched entry, a deny will be returned. When
2371 `large-community` is empty it matches any routes.
2373 .. clicmd:: bgp large-community-list expanded NAME permit|deny LINE
2375 This command defines a new expanded large-community-list. Where `line` is a
2376 string matching expression, it will be compared to the entire Large
2377 Communities attribute as a string, with each large-community in order from
2378 lowest to highest. `line` can also be a regular expression which matches
2379 this Large Community attribute.
2381 Note that all community lists share the same namespace, so it's not
2382 necessary to specify ``standard`` or ``expanded``; these modifiers are
2385 .. clicmd:: show bgp large-community-list
2387 .. clicmd:: show bgp large-community-list NAME detail
2389 This command display current large-community-list information. When
2390 `name` is specified the community list information is shown.
2392 .. clicmd:: show ip bgp large-community-info
2394 This command displays the current large communities in use.
2396 .. _bgp-large-communities-in-route-map:
2398 Large Communities in Route Map
2399 """"""""""""""""""""""""""""""
2401 .. clicmd:: match large-community LINE [exact-match]
2403 Where `line` can be a simple string to match, or a regular expression. It
2404 is very important to note that this match occurs on the entire
2405 large-community string as a whole, where each large-community is ordered
2406 from lowest to highest. When `exact-match` keyword is specified, match
2407 happen only when BGP updates have completely same large communities value
2408 specified in the large community list.
2410 .. clicmd:: set large-community LARGE-COMMUNITY
2412 .. clicmd:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
2414 .. clicmd:: set large-community LARGE-COMMUNITY additive
2416 These commands are used for setting large-community values. The first
2417 command will overwrite any large-communities currently present.
2418 The second specifies two large-communities, which overwrites the current
2419 large-community list. The third will add a large-community value without
2420 overwriting other values. Multiple large-community values can be specified.
2422 Note that the large expanded community is only used for `match` rule, not for
2430 *bgpd* supports :abbr:`L3VPN (Layer 3 Virtual Private Networks)` :abbr:`VRFs
2431 (Virtual Routing and Forwarding)` for IPv4 :rfc:`4364` and IPv6 :rfc:`4659`.
2432 L3VPN routes, and their associated VRF MPLS labels, can be distributed to VPN
2433 SAFI neighbors in the *default*, i.e., non VRF, BGP instance. VRF MPLS labels
2434 are reached using *core* MPLS labels which are distributed using LDP or BGP
2435 labeled unicast. *bgpd* also supports inter-VRF route leaking.
2438 .. _bgp-vrf-route-leaking:
2443 BGP routes may be leaked (i.e. copied) between a unicast VRF RIB and the VPN
2444 SAFI RIB of the default VRF for use in MPLS-based L3VPNs. Unicast routes may
2445 also be leaked between any VRFs (including the unicast RIB of the default BGP
2446 instanced). A shortcut syntax is also available for specifying leaking from one
2447 VRF to another VRF using the default instance's VPN RIB as the intemediary. A
2448 common application of the VRF-VRF feature is to connect a customer's private
2449 routing domain to a provider's VPN service. Leaking is configured from the
2450 point of view of an individual VRF: ``import`` refers to routes leaked from VPN
2451 to a unicast VRF, whereas ``export`` refers to routes leaked from a unicast VRF
2457 Routes exported from a unicast VRF to the VPN RIB must be augmented by two
2460 - an :abbr:`RD (Route Distinguisher)`
2461 - an :abbr:`RTLIST (Route-target List)`
2463 Configuration for these exported routes must, at a minimum, specify these two
2466 Routes imported from the VPN RIB to a unicast VRF are selected according to
2467 their RTLISTs. Routes whose RTLIST contains at least one route-target in
2468 common with the configured import RTLIST are leaked. Configuration for these
2469 imported routes must specify an RTLIST to be matched.
2471 The RD, which carries no semantic value, is intended to make the route unique
2472 in the VPN RIB among all routes of its prefix that originate from all the
2473 customers and sites that are attached to the provider's VPN service.
2474 Accordingly, each site of each customer is typically assigned an RD that is
2475 unique across the entire provider network.
2477 The RTLIST is a set of route-target extended community values whose purpose is
2478 to specify route-leaking policy. Typically, a customer is assigned a single
2479 route-target value for import and export to be used at all customer sites. This
2480 configuration specifies a simple topology wherein a customer has a single
2481 routing domain which is shared across all its sites. More complex routing
2482 topologies are possible through use of additional route-targets to augment the
2483 leaking of sets of routes in various ways.
2485 When using the shortcut syntax for vrf-to-vrf leaking, the RD and RT are
2488 General configuration
2489 ^^^^^^^^^^^^^^^^^^^^^
2491 Configuration of route leaking between a unicast VRF RIB and the VPN SAFI RIB
2492 of the default VRF is accomplished via commands in the context of a VRF
2495 .. clicmd:: rd vpn export AS:NN|IP:nn
2497 Specifies the route distinguisher to be added to a route exported from the
2498 current unicast VRF to VPN.
2500 .. clicmd:: rt vpn import|export|both RTLIST...
2502 Specifies the route-target list to be attached to a route (export) or the
2503 route-target list to match against (import) when exporting/importing between
2504 the current unicast VRF and VPN.
2506 The RTLIST is a space-separated list of route-targets, which are BGP
2507 extended community values as described in
2508 :ref:`bgp-extended-communities-attribute`.
2510 .. clicmd:: label vpn export (0..1048575)|auto
2512 Enables an MPLS label to be attached to a route exported from the current
2513 unicast VRF to VPN. If the value specified is ``auto``, the label value is
2514 automatically assigned from a pool maintained by the Zebra daemon. If Zebra
2515 is not running, or if this command is not configured, automatic label
2516 assignment will not complete, which will block corresponding route export.
2518 .. clicmd:: nexthop vpn export A.B.C.D|X:X::X:X
2520 Specifies an optional nexthop value to be assigned to a route exported from
2521 the current unicast VRF to VPN. If left unspecified, the nexthop will be set
2522 to 0.0.0.0 or 0:0::0:0 (self).
2524 .. clicmd:: route-map vpn import|export MAP
2526 Specifies an optional route-map to be applied to routes imported or exported
2527 between the current unicast VRF and VPN.
2529 .. clicmd:: import|export vpn
2531 Enables import or export of routes between the current unicast VRF and VPN.
2533 .. clicmd:: import vrf VRFNAME
2535 Shortcut syntax for specifying automatic leaking from vrf VRFNAME to
2536 the current VRF using the VPN RIB as intermediary. The RD and RT
2537 are auto derived and should not be specified explicitly for either the
2538 source or destination VRF's.
2540 This shortcut syntax mode is not compatible with the explicit
2541 `import vpn` and `export vpn` statements for the two VRF's involved.
2542 The CLI will disallow attempts to configure incompatible leaking
2548 Ethernet Virtual Network - EVPN
2549 -------------------------------
2551 .. _bgp-evpn-advertise-pip:
2556 In a EVPN symmetric routing MLAG deployment, all EVPN routes advertised
2557 with anycast-IP as next-hop IP and anycast MAC as the Router MAC (RMAC - in
2558 BGP EVPN Extended-Community).
2559 EVPN picks up the next-hop IP from the VxLAN interface's local tunnel IP and
2560 the RMAC is obtained from the MAC of the L3VNI's SVI interface.
2561 Note: Next-hop IP is used for EVPN routes whether symmetric routing is
2562 deployed or not but the RMAC is only relevant for symmetric routing scenario.
2564 Current behavior is not ideal for Prefix (type-5) and self (type-2)
2565 routes. This is because the traffic from remote VTEPs routed sub optimally
2566 if they land on the system where the route does not belong.
2568 The advertise-pip feature advertises Prefix (type-5) and self (type-2)
2569 routes with system's individual (primary) IP as the next-hop and individual
2570 (system) MAC as Router-MAC (RMAC), while leaving the behavior unchanged for
2573 To support this feature there needs to have ability to co-exist a
2574 (system-MAC, system-IP) pair with a (anycast-MAC, anycast-IP) pair with the
2575 ability to terminate VxLAN-encapsulated packets received for either pair on
2576 the same L3VNI (i.e associated VLAN). This capability is need per tenant
2579 To derive the system-MAC and the anycast MAC, there needs to have a
2580 separate/additional MAC-VLAN interface corresponding to L3VNI’s SVI.
2581 The SVI interface’s MAC address can be interpreted as system-MAC
2582 and MAC-VLAN interface's MAC as anycast MAC.
2584 To derive system-IP and anycast-IP, the default BGP instance's router-id is used
2585 as system-IP and the VxLAN interface’s local tunnel IP as the anycast-IP.
2587 User has an option to configure the system-IP and/or system-MAC value if the
2588 auto derived value is not preferred.
2590 Note: By default, advertise-pip feature is enabled and user has an option to
2591 disable the feature via configuration CLI. Once the feature is disable under
2592 bgp vrf instance or MAC-VLAN interface is not configured, all the routes follow
2593 the same behavior of using same next-hop and RMAC values.
2595 .. clicmd:: advertise-pip [ip <addr> [mac <addr>]]
2597 Enables or disables advertise-pip feature, specifiy system-IP and/or system-MAC
2603 All-Active Multihoming is used for redundancy and load sharing. Servers
2604 are attached to two or more PEs and the links are bonded (link-aggregation).
2605 This group of server links is referred to as an Ethernet Segment.
2609 An Ethernet Segment can be configured by specifying a system-MAC and a
2610 local discriminatior against the bond interface on the PE (via zebra) -
2612 .. clicmd:: evpn mh es-id (1-16777215)
2614 .. clicmd:: evpn mh es-sys-mac X:X:X:X:X:X
2616 The sys-mac and local discriminator are used for generating a 10-byte,
2617 Type-3 Ethernet Segment ID.
2619 Type-1 (EAS-per-ES and EAD-per-EVI) routes are used to advertise the locally
2620 attached ESs and to learn off remote ESs in the network. Local Type-2/MAC-IP
2621 routes are also advertised with a destination ESI allowing for MAC-IP syncing
2622 between Ethernet Segment peers.
2623 Reference: RFC 7432, RFC 8365
2625 EVPN-MH is intended as a replacement for MLAG or Anycast VTEPs. In
2626 multihoming each PE has an unique VTEP address which requires the introduction
2627 of a new dataplane construct, MAC-ECMP. Here a MAC/FDB entry can point to a
2628 list of remote PEs/VTEPs.
2632 Type-4 (ESR) routes are used for Designated Forwarder (DF) election. DFs
2633 forward BUM traffic received via the overlay network. This implementation
2634 uses a preference based DF election specified by draft-ietf-bess-evpn-pref-df.
2635 The DF preference is configurable per-ES (via zebra) -
2637 .. clicmd:: evpn mh es-df-pref (1-16777215)
2639 BUM traffic is rxed via the overlay by all PEs attached to a server but
2640 only the DF can forward the de-capsulated traffic to the access port. To
2641 accomodate that non-DF filters are installed in the dataplane to drop
2644 Similarly traffic received from ES peers via the overlay cannot be forwarded
2645 to the server. This is split-horizon-filtering with local bias.
2649 Some vendors do not send EAD-per-EVI routes. To interop with them we
2650 need to relax the dependency on EAD-per-EVI routes and activate a remote
2651 ES-PE based on just the EAD-per-ES route.
2653 Note that by default we advertise and expect EAD-per-EVI routes.
2655 .. clicmd:: disable-ead-evi-rx
2657 .. clicmd:: disable-ead-evi-tx
2661 As the primary purpose of EVPN-MH is redundancy keeping the failover efficient
2662 is a recurring theme in the implementation. Following sub-features have
2663 been introduced for the express purpose of efficient ES failovers.
2665 - Layer-2 Nexthop Groups and MAC-ECMP via L2NHG.
2667 - Host routes (for symmetric IRB) via L3NHG.
2668 On dataplanes that support layer3 nexthop groups the feature can be turned
2669 on via the following BGP config -
2671 .. clicmd:: use-es-l3nhg
2673 - Local ES (MAC/Neigh) failover via ES-redirect.
2674 On dataplanes that do not have support for ES-redirect the feature can be
2675 turned off via the following zebra config -
2677 .. clicmd:: evpn mh redirect-off
2679 Uplink/Core tracking
2680 """"""""""""""""""""
2681 When all the underlay links go down the PE no longer has access to the VxLAN
2682 +overlay. To prevent blackholing of traffic the server/ES links are
2683 protodowned on the PE. A link can be setup for uplink tracking via the
2684 following zebra configuration -
2686 .. clicmd:: evpn mh uplink
2688 Proxy advertisements
2689 """"""""""""""""""""
2690 To handle hitless upgrades support for proxy advertisement has been added
2691 as specified by draft-rbickhart-evpn-ip-mac-proxy-adv. This allows a PE
2692 (say PE1) to proxy advertise a MAC-IP rxed from an ES peer (say PE2). When
2693 the ES peer (PE2) goes down PE1 continues to advertise hosts learnt from PE2
2694 for a holdtime during which it attempts to establish local reachability of
2695 the host. This holdtime is configurable via the following zebra commands -
2697 .. clicmd:: evpn mh neigh-holdtime (0-86400)
2699 .. clicmd:: evpn mh mac-holdtime (0-86400)
2703 When a switch is rebooted we wait for a brief period to allow the underlay
2704 and EVPN network to converge before enabling the ESs. For this duration the
2705 ES bonds are held protodown. The startup delay is configurable via the
2706 following zebra command -
2708 .. clicmd:: evpn mh startup-delay (0-3600)
2710 +Support with VRF network namespace backend
2711 +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2712 It is possible to separate overlay networks contained in VXLAN interfaces from
2713 underlay networks by using VRFs. VRF-lite and VRF-netns backends can be used for
2714 that. In the latter case, it is necessary to set both bridge and vxlan interface
2715 in the same network namespace, as below example illustrates:
2717 .. code-block:: shell
2721 ip link add name vxlan101 type vxlan id 101 dstport 4789 dev eth0 local 10.1.1.1
2722 ip link set dev vxlan101 netns vrf1
2723 ip netns exec vrf1 ip link set dev lo up
2724 ip netns exec vrf1 brctl addbr bridge101
2725 ip netns exec vrf1 brctl addif bridge101 vxlan101
2727 This makes it possible to separate not only layer 3 networks like VRF-lite networks.
2728 Also, VRF netns based make possible to separate layer 2 networks on separate VRF
2731 .. _bgp-conditional-advertisement:
2733 BGP Conditional Advertisement
2734 -----------------------------
2735 The BGP conditional advertisement feature uses the ``non-exist-map`` or the
2736 ``exist-map`` and the ``advertise-map`` keywords of the neighbor advertise-map
2737 command in order to track routes by the route prefix.
2740 1. If a route prefix is not present in the output of non-exist-map command,
2741 then advertise the route specified by the advertise-map command.
2743 2. If a route prefix is present in the output of non-exist-map command,
2744 then do not advertise the route specified by the addvertise-map command.
2747 1. If a route prefix is present in the output of exist-map command,
2748 then advertise the route specified by the advertise-map command.
2750 2. If a route prefix is not present in the output of exist-map command,
2751 then do not advertise the route specified by the advertise-map command.
2753 This feature is useful when some prefixes are advertised to one of its peers
2754 only if the information from the other peer is not present (due to failure in
2755 peering session or partial reachability etc).
2757 The conditional BGP announcements are sent in addition to the normal
2758 announcements that a BGP router sends to its peer.
2760 The conditional advertisement process is triggered by the BGP scanner process,
2761 which runs every 60 seconds. This means that the maximum time for the conditional
2762 advertisement to take effect is 60 seconds. The conditional advertisement can take
2763 effect depending on when the tracked route is removed from the BGP table and
2764 when the next instance of the BGP scanner occurs.
2766 .. clicmd:: neighbor A.B.C.D advertise-map NAME [exist-map|non-exist-map] NAME
2768 This command enables BGP scanner process to monitor routes specified by
2769 exist-map or non-exist-map command in BGP table and conditionally advertises
2770 the routes specified by advertise-map command.
2772 Sample Configuration
2773 ^^^^^^^^^^^^^^^^^^^^^
2777 ip address 10.10.10.2/24
2780 ip address 10.10.20.2/24
2783 ip address 203.0.113.1/32
2786 bgp log-neighbor-changes
2787 no bgp ebgp-requires-policy
2788 neighbor 10.10.10.1 remote-as 1
2789 neighbor 10.10.20.3 remote-as 3
2791 address-family ipv4 unicast
2792 neighbor 10.10.10.1 soft-reconfiguration inbound
2793 neighbor 10.10.20.3 soft-reconfiguration inbound
2794 neighbor 10.10.20.3 advertise-map ADV-MAP non-exist-map EXIST-MAP
2797 ip prefix-list DEFAULT seq 5 permit 192.0.2.5/32
2798 ip prefix-list DEFAULT seq 10 permit 192.0.2.1/32
2799 ip prefix-list EXIST seq 5 permit 10.10.10.10/32
2800 ip prefix-list DEFAULT-ROUTE seq 5 permit 0.0.0.0/0
2801 ip prefix-list IP1 seq 5 permit 10.139.224.0/20
2803 bgp community-list standard DC-ROUTES seq 5 permit 64952:3008
2804 bgp community-list standard DC-ROUTES seq 10 permit 64671:501
2805 bgp community-list standard DC-ROUTES seq 15 permit 64950:3009
2806 bgp community-list standard DEFAULT-ROUTE seq 5 permit 65013:200
2808 route-map ADV-MAP permit 10
2809 match ip address prefix-list IP1
2811 route-map ADV-MAP permit 20
2812 match community DC-ROUTES
2814 route-map EXIST-MAP permit 10
2815 match community DEFAULT-ROUTE
2816 match ip address prefix-list DEFAULT-ROUTE
2822 When default route is present in R2'2 BGP table, 10.139.224.0/20 and 192.0.2.1/32 are not advertised to R3.
2826 Router2# show ip bgp
2827 BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
2828 Default local pref 100, local AS 2
2829 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
2830 i internal, r RIB-failure, S Stale, R Removed
2831 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
2832 Origin codes: i - IGP, e - EGP, ? - incomplete
2834 Network Next Hop Metric LocPrf Weight Path
2835 *> 0.0.0.0/0 10.10.10.1 0 0 1 i
2836 *> 10.139.224.0/20 10.10.10.1 0 0 1 ?
2837 *> 192.0.2.1/32 10.10.10.1 0 0 1 i
2838 *> 192.0.2.5/32 10.10.10.1 0 0 1 i
2840 Displayed 4 routes and 4 total paths
2841 Router2# show ip bgp neighbors 10.10.20.3
2843 !--- Output suppressed.
2845 For address family: IPv4 Unicast
2846 Update group 7, subgroup 7
2847 Packet Queue length 0
2848 Inbound soft reconfiguration allowed
2849 Community attribute sent to this neighbor(all)
2850 Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Withdraw
2853 !--- Output suppressed.
2855 Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
2856 BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
2857 Default local pref 100, local AS 2
2858 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
2859 i internal, r RIB-failure, S Stale, R Removed
2860 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
2861 Origin codes: i - IGP, e - EGP, ? - incomplete
2863 Network Next Hop Metric LocPrf Weight Path
2864 *> 0.0.0.0/0 0.0.0.0 0 1 i
2865 *> 192.0.2.5/32 0.0.0.0 0 1 i
2867 Total number of prefixes 2
2869 When default route is not present in R2'2 BGP table, 10.139.224.0/20 and 192.0.2.1/32 are advertised to R3.
2873 Router2# show ip bgp
2874 BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
2875 Default local pref 100, local AS 2
2876 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
2877 i internal, r RIB-failure, S Stale, R Removed
2878 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
2879 Origin codes: i - IGP, e - EGP, ? - incomplete
2881 Network Next Hop Metric LocPrf Weight Path
2882 *> 10.139.224.0/20 10.10.10.1 0 0 1 ?
2883 *> 192.0.2.1/32 10.10.10.1 0 0 1 i
2884 *> 192.0.2.5/32 10.10.10.1 0 0 1 i
2886 Displayed 3 routes and 3 total paths
2888 Router2# show ip bgp neighbors 10.10.20.3
2890 !--- Output suppressed.
2892 For address family: IPv4 Unicast
2893 Update group 7, subgroup 7
2894 Packet Queue length 0
2895 Inbound soft reconfiguration allowed
2896 Community attribute sent to this neighbor(all)
2897 Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Advertise
2900 !--- Output suppressed.
2902 Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
2903 BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
2904 Default local pref 100, local AS 2
2905 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
2906 i internal, r RIB-failure, S Stale, R Removed
2907 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
2908 Origin codes: i - IGP, e - EGP, ? - incomplete
2910 Network Next Hop Metric LocPrf Weight Path
2911 *> 10.139.224.0/20 0.0.0.0 0 1 ?
2912 *> 192.0.2.1/32 0.0.0.0 0 1 i
2913 *> 192.0.2.5/32 0.0.0.0 0 1 i
2915 Total number of prefixes 3
2923 .. clicmd:: show debug
2925 Show all enabled debugs.
2927 .. clicmd:: show bgp listeners
2929 Display Listen sockets and the vrf that created them. Useful for debugging of when
2930 listen is not working and this is considered a developer debug statement.
2932 .. clicmd:: debug bgp bfd
2934 Enable or disable debugging for BFD events. This will show BFD integration
2935 library messages and BGP BFD integration messages that are mostly state
2936 transitions and validation problems.
2938 .. clicmd:: debug bgp neighbor-events
2940 Enable or disable debugging for neighbor events. This provides general
2941 information on BGP events such as peer connection / disconnection, session
2942 establishment / teardown, and capability negotiation.
2944 .. clicmd:: debug bgp updates
2946 Enable or disable debugging for BGP updates. This provides information on
2947 BGP UPDATE messages transmitted and received between local and remote
2950 .. clicmd:: debug bgp keepalives
2952 Enable or disable debugging for BGP keepalives. This provides information on
2953 BGP KEEPALIVE messages transmitted and received between local and remote
2956 .. clicmd:: debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
2958 Enable or disable debugging for bestpath selection on the specified prefix.
2960 .. clicmd:: debug bgp nht
2962 Enable or disable debugging of BGP nexthop tracking.
2964 .. clicmd:: debug bgp update-groups
2966 Enable or disable debugging of dynamic update groups. This provides general
2967 information on group creation, deletion, join and prune events.
2969 .. clicmd:: debug bgp zebra
2971 Enable or disable debugging of communications between *bgpd* and *zebra*.
2973 Dumping Messages and Routing Tables
2974 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2976 .. clicmd:: dump bgp all PATH [INTERVAL]
2978 .. clicmd:: dump bgp all-et PATH [INTERVAL]
2981 Dump all BGP packet and events to `path` file.
2982 If `interval` is set, a new file will be created for echo `interval` of
2983 seconds. The path `path` can be set with date and time formatting
2984 (strftime). The type ‘all-et’ enables support for Extended Timestamp Header
2985 (:ref:`packet-binary-dump-format`).
2987 .. clicmd:: dump bgp updates PATH [INTERVAL]
2989 .. clicmd:: dump bgp updates-et PATH [INTERVAL]
2992 Dump only BGP updates messages to `path` file.
2993 If `interval` is set, a new file will be created for echo `interval` of
2994 seconds. The path `path` can be set with date and time formatting
2995 (strftime). The type ‘updates-et’ enables support for Extended Timestamp
2996 Header (:ref:`packet-binary-dump-format`).
2998 .. clicmd:: dump bgp routes-mrt PATH
3000 .. clicmd:: dump bgp routes-mrt PATH INTERVAL
3003 Dump whole BGP routing table to `path`. This is heavy process. The path
3004 `path` can be set with date and time formatting (strftime). If `interval` is
3005 set, a new file will be created for echo `interval` of seconds.
3007 Note: the interval variable can also be set using hours and minutes: 04h20m00.
3010 .. _bgp-other-commands:
3015 The following are available in the top level *enable* mode:
3017 .. clicmd:: clear bgp \*
3021 .. clicmd:: clear bgp ipv4|ipv6 \*
3023 Clear all peers with this address-family activated.
3025 .. clicmd:: clear bgp ipv4|ipv6 unicast \*
3027 Clear all peers with this address-family and sub-address-family activated.
3029 .. clicmd:: clear bgp ipv4|ipv6 PEER
3031 Clear peers with address of X.X.X.X and this address-family activated.
3033 .. clicmd:: clear bgp ipv4|ipv6 unicast PEER
3035 Clear peer with address of X.X.X.X and this address-family and sub-address-family activated.
3037 .. clicmd:: clear bgp ipv4|ipv6 PEER soft|in|out
3039 Clear peer using soft reconfiguration in this address-family.
3041 .. clicmd:: clear bgp ipv4|ipv6 unicast PEER soft|in|out
3043 Clear peer using soft reconfiguration in this address-family and sub-address-family.
3045 The following are available in the ``router bgp`` mode:
3047 .. clicmd:: write-quanta (1-64)
3049 BGP message Tx I/O is vectored. This means that multiple packets are written
3050 to the peer socket at the same time each I/O cycle, in order to minimize
3051 system call overhead. This value controls how many are written at a time.
3052 Under certain load conditions, reducing this value could make peer traffic
3053 less 'bursty'. In practice, leave this settings on the default (64) unless
3054 you truly know what you are doing.
3056 .. clicmd:: read-quanta (1-10)
3058 Unlike Tx, BGP Rx traffic is not vectored. Packets are read off the wire one
3059 at a time in a loop. This setting controls how many iterations the loop runs
3060 for. As with write-quanta, it is best to leave this setting on the default.
3062 The following command is available in ``config`` mode as well as in the
3063 ``router bgp`` mode:
3065 .. clicmd:: bgp graceful-shutdown
3067 The purpose of this command is to initiate BGP Graceful Shutdown which
3068 is described in :rfc:`8326`. The use case for this is to minimize or
3069 eliminate the amount of traffic loss in a network when a planned
3070 maintenance activity such as software upgrade or hardware replacement
3071 is to be performed on a router. The feature works by re-announcing
3072 routes to eBGP peers with the GRACEFUL_SHUTDOWN community included.
3073 Peers are then expected to treat such paths with the lowest preference.
3074 This happens automatically on a receiver running FRR; with other
3075 routing protocol stacks, an inbound policy may have to be configured.
3076 In FRR, triggering graceful shutdown also results in announcing a
3077 LOCAL_PREF of 0 to iBGP peers.
3079 Graceful shutdown can be configured per BGP instance or globally for
3080 all of BGP. These two options are mutually exclusive. The no form of
3081 the command causes graceful shutdown to be stopped, and routes will
3082 be re-announced without the GRACEFUL_SHUTDOWN community and/or with
3083 the usual LOCAL_PREF value. Note that if this option is saved to
3084 the startup configuration, graceful shutdown will remain in effect
3085 across restarts of *bgpd* and will need to be explicitly disabled.
3087 .. _bgp-displaying-bgp-information:
3089 Displaying BGP Information
3090 ==========================
3092 The following four commands display the IPv6 and IPv4 routing tables, depending
3093 on whether or not the ``ip`` keyword is used.
3094 Actually, :clicmd:`show ip bgp` command was used on older `Quagga` routing
3095 daemon project, while :clicmd:`show bgp` command is the new format. The choice
3096 has been done to keep old format with IPv4 routing table, while new format
3097 displays IPv6 routing table.
3099 .. clicmd:: show ip bgp [all] [wide|json]
3101 .. clicmd:: show ip bgp A.B.C.D [json]
3103 .. clicmd:: show bgp [all] [wide|json]
3105 .. clicmd:: show bgp X:X::X:X [json]
3107 These commands display BGP routes. When no route is specified, the default
3108 is to display all BGP routes.
3112 BGP table version is 0, local router ID is 10.1.1.1
3113 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
3114 Origin codes: i - IGP, e - EGP, ? - incomplete
3116 Network Next Hop Metric LocPrf Weight Path
3117 \*> 1.1.1.1/32 0.0.0.0 0 32768 i
3119 Total number of prefixes 1
3121 If ``wide`` option is specified, then the prefix table's width is increased
3122 to fully display the prefix and the nexthop.
3124 This is especially handy dealing with IPv6 prefixes and
3125 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3127 If ``all`` option is specified, ``ip`` keyword is ignored, show bgp all and
3128 show ip bgp all commands display routes for all AFIs and SAFIs.
3130 If ``json`` option is specified, output is displayed in JSON format.
3132 Some other commands provide additional options for filtering the output.
3134 .. clicmd:: show [ip] bgp regexp LINE
3136 This command displays BGP routes using AS path regular expression
3137 (:ref:`bgp-regular-expressions`).
3139 .. clicmd:: show [ip] bgp [all] summary [wide] [json]
3141 Show a bgp peer summary for the specified address family.
3143 The old command structure :clicmd:`show ip bgp` may be removed in the future
3144 and should no longer be used. In order to reach the other BGP routing tables
3145 other than the IPv6 routing table given by :clicmd:`show bgp`, the new command
3146 structure is extended with :clicmd:`show bgp [afi] [safi]`.
3148 ``wide`` option gives more output like ``LocalAS`` and extended ``Desc`` to
3153 exit1# show ip bgp summary wide
3155 IPv4 Unicast Summary:
3156 BGP router identifier 192.168.100.1, local AS number 65534 vrf-id 0
3158 RIB entries 5, using 920 bytes of memory
3159 Peers 1, using 27 KiB of memory
3161 Neighbor V AS LocalAS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
3162 192.168.0.2 4 65030 123 15 22 0 0 0 00:07:00 0 1 us-east1-rs1.frrouting.org
3164 Total number of neighbors 1
3167 .. clicmd:: show bgp [afi] [safi] [all] [wide|json]
3169 .. clicmd:: show bgp <ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast>
3171 These commands display BGP routes for the specific routing table indicated by
3172 the selected afi and the selected safi. If no afi and no safi value is given,
3173 the command falls back to the default IPv6 routing table.
3174 For EVPN prefixes, you can display the full BGP table for this AFI/SAFI
3175 using the standard `show bgp [afi] [safi]` syntax.
3177 .. clicmd:: show bgp l2vpn evpn route [type <macip|2|multicast|3|es|4|prefix|5>]
3179 Additionally, you can also filter this output by route type.
3181 .. clicmd:: show bgp [afi] [safi] [all] summary [json]
3183 Show a bgp peer summary for the specified address family, and subsequent
3186 .. clicmd:: show bgp [afi] [safi] [all] summary failed [json]
3188 Show a bgp peer summary for peers that are not succesfully exchanging routes
3189 for the specified address family, and subsequent address-family.
3191 .. clicmd:: show bgp [afi] [safi] [all] summary established [json]
3193 Show a bgp peer summary for peers that are succesfully exchanging routes
3194 for the specified address family, and subsequent address-family.
3196 .. clicmd:: show bgp [afi] [safi] neighbor [PEER]
3198 This command shows information on a specific BGP peer of the relevant
3199 afi and safi selected.
3201 .. clicmd:: show bgp [afi] [safi] [all] dampening dampened-paths [wide|json]
3203 Display paths suppressed due to dampening of the selected afi and safi
3206 .. clicmd:: show bgp [afi] [safi] [all] dampening flap-statistics [wide|json]
3208 Display flap statistics of routes of the selected afi and safi selected.
3210 .. clicmd:: show bgp [afi] [safi] statistics
3212 Display statistics of routes of the selected afi and safi.
3214 .. clicmd:: show bgp statistics-all
3216 Display statistics of routes of all the afi and safi.
3218 .. clicmd:: show [ip] bgp [afi] [safi] [all] cidr-only [wide|json]
3220 Display routes with non-natural netmasks.
3222 .. clicmd:: show [ip] bgp [afi] [safi] [all] neighbors A.B.C.D [advertised-routes|received-routes|filtered-routes] [json|wide]
3224 Display the routes advertised to a BGP neighbor or received routes
3225 from neighbor or filtered routes received from neighbor based on the
3228 If ``wide`` option is specified, then the prefix table's width is increased
3229 to fully display the prefix and the nexthop.
3231 This is especially handy dealing with IPv6 prefixes and
3232 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3234 If ``all`` option is specified, ``ip`` keyword is ignored and,
3235 routes displayed for all AFIs and SAFIs.
3236 if afi is specified, with ``all`` option, routes will be displayed for
3237 each SAFI in the selcted AFI
3239 If ``json`` option is specified, output is displayed in JSON format.
3241 .. _bgp-display-routes-by-community:
3243 Displaying Routes by Community Attribute
3244 ----------------------------------------
3246 The following commands allow displaying routes based on their community
3249 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community [wide|json]
3251 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY [wide|json]
3253 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY exact-match [wide|json]
3255 These commands display BGP routes which have the community attribute.
3256 attribute. When ``COMMUNITY`` is specified, BGP routes that match that
3257 community are displayed. When `exact-match` is specified, it display only
3258 routes that have an exact match.
3260 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD
3262 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match
3264 These commands display BGP routes for the address family specified that
3265 match the specified community list. When `exact-match` is specified, it
3266 displays only routes that have an exact match.
3268 If ``wide`` option is specified, then the prefix table's width is increased
3269 to fully display the prefix and the nexthop.
3271 This is especially handy dealing with IPv6 prefixes and
3272 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3274 If ``all`` option is specified, ``ip`` keyword is ignored and,
3275 routes displayed for all AFIs and SAFIs.
3276 if afi is specified, with ``all`` option, routes will be displayed for
3277 each SAFI in the selcted AFI
3279 If ``json`` option is specified, output is displayed in JSON format.
3281 .. clicmd:: show bgp labelpool <chunks|inuse|ledger|requests|summary> [json]
3283 These commands display information about the BGP labelpool used for
3284 the association of MPLS labels with routes for L3VPN and Labeled Unicast
3286 If ``chunks`` option is specified, output shows the current list of label
3287 chunks granted to BGP by Zebra, indicating the start and end label in
3290 If ``inuse`` option is specified, output shows the current inuse list of
3291 label to prefix mappings
3293 If ``ledger`` option is specified, output shows ledger list of all
3294 label requests made per prefix
3296 If ``requests`` option is specified, output shows current list of label
3297 requests which have not yet been fulfilled by the labelpool
3299 If ``summary`` option is specified, output is a summary of the counts for
3300 the chunks, inuse, ledger and requests list along with the count of
3301 outstanding chunk requests to Zebra and the nummber of zebra reconnects
3304 If ``json`` option is specified, output is displayed in JSON format.
3306 .. _bgp-display-routes-by-lcommunity:
3308 Displaying Routes by Large Community Attribute
3309 ----------------------------------------------
3311 The following commands allow displaying routes based on their
3312 large community attribute.
3314 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community
3316 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY
3318 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY exact-match
3320 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY json
3322 These commands display BGP routes which have the large community attribute.
3323 attribute. When ``LARGE-COMMUNITY`` is specified, BGP routes that match that
3324 large community are displayed. When `exact-match` is specified, it display
3325 only routes that have an exact match. When `json` is specified, it display
3326 routes in json format.
3328 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD
3330 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD exact-match
3332 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD json
3334 These commands display BGP routes for the address family specified that
3335 match the specified large community list. When `exact-match` is specified,
3336 it displays only routes that have an exact match. When `json` is specified,
3337 it display routes in json format.
3339 .. _bgp-display-routes-by-as-path:
3342 Displaying Routes by AS Path
3343 ----------------------------
3345 .. clicmd:: show bgp ipv4|ipv6 regexp LINE
3347 This commands displays BGP routes that matches a regular
3348 expression `line` (:ref:`bgp-regular-expressions`).
3350 .. clicmd:: show [ip] bgp ipv4 vpn
3352 .. clicmd:: show [ip] bgp ipv6 vpn
3354 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
3356 .. clicmd:: show bgp ipv4 vpn summary
3358 .. clicmd:: show bgp ipv6 vpn summary
3360 Print a summary of neighbor connections for the specified AFI/SAFI combination.
3362 Displaying Update Group Information
3363 -----------------------------------
3365 .. clicmd:: show bgp update-groups [advertise-queue|advertised-routes|packet-queue]
3367 Display Information about each individual update-group being used.
3368 If SUBGROUP-ID is specified only display about that particular group. If
3369 advertise-queue is specified the list of routes that need to be sent
3370 to the peers in the update-group is displayed, advertised-routes means
3371 the list of routes we have sent to the peers in the update-group and
3372 packet-queue specifies the list of packets in the queue to be sent.
3374 .. clicmd:: show bgp update-groups statistics
3376 Display Information about update-group events in FRR.
3378 .. _bgp-route-reflector:
3383 BGP routers connected inside the same AS through BGP belong to an internal
3384 BGP session, or IBGP. In order to prevent routing table loops, IBGP does not
3385 advertise IBGP-learned routes to other routers in the same session. As such,
3386 IBGP requires a full mesh of all peers. For large networks, this quickly becomes
3387 unscalable. Introducing route reflectors removes the need for the full-mesh.
3389 When route reflectors are configured, these will reflect the routes announced
3390 by the peers configured as clients. A route reflector client is configured
3393 .. clicmd:: neighbor PEER route-reflector-client
3396 To avoid single points of failure, multiple route reflectors can be configured.
3398 A cluster is a collection of route reflectors and their clients, and is used
3399 by route reflectors to avoid looping.
3401 .. clicmd:: bgp cluster-id A.B.C.D
3403 .. clicmd:: bgp no-rib
3405 To set and unset the BGP daemon ``-n`` / ``--no_kernel`` options during runtime
3406 to disable BGP route installation to the RIB (Zebra), the ``[no] bgp no-rib``
3407 commands can be used;
3409 Please note that setting the option during runtime will withdraw all routes in
3410 the daemons RIB from Zebra and unsetting it will announce all routes in the
3411 daemons RIB to Zebra. If the option is passed as a command line argument when
3412 starting the daemon and the configuration gets saved, the option will persist
3413 unless removed from the configuration with the negating command prior to the
3414 configuration write operation.
3416 .. clicmd:: bgp send-extra-data zebra
3418 This Command turns off the ability of BGP to send extra data to zebra.
3419 In this case it's the AS-Path being used for the path. The default behavior
3420 in BGP is to send this data and to turn it off enter the no form of the command.
3421 If extra data was sent to zebra, and this command is turned on there is no
3422 effort to clean up this data in the rib.
3424 .. _bgp-suppress-fib:
3426 Suppressing routes not installed in FIB
3427 =======================================
3429 The FRR implementation of BGP advertises prefixes learnt from a peer to other
3430 peers even if the routes do not get installed in the FIB. There can be
3431 scenarios where the hardware tables in some of the routers (along the path from
3432 the source to destination) is full which will result in all routes not getting
3433 installed in the FIB. If these routes are advertised to the downstream routers
3434 then traffic will start flowing and will be dropped at the intermediate router.
3436 The solution is to provide a configurable option to check for the FIB install
3437 status of the prefixes and advertise to peers if the prefixes are successfully
3438 installed in the FIB. The advertisement of the prefixes are suppressed if it is
3439 not installed in FIB.
3441 The following conditions apply will apply when checking for route installation
3444 1. The advertisement or suppression of routes based on FIB install status
3445 applies only for newly learnt routes from peer (routes which are not in
3447 2. If the route received from peer already exists in BGP local RIB and route
3448 attributes have changed (best path changed), the old path is deleted and
3449 new path is installed in FIB. The FIB install status will not have any
3450 effect. Therefore only when the route is received first time the checks
3452 3. The feature will not apply for routes learnt through other means like
3453 redistribution to bgp from other protocols. This is applicable only to
3455 4. If a route is installed in FIB and then gets deleted from the dataplane,
3456 then routes will not be withdrawn from peers. This will be considered as
3458 5. The feature will slightly increase the time required to advertise the routes
3459 to peers since the route install status needs to be received from the FIB
3460 6. If routes are received by the peer before the configuration is applied, then
3461 the bgp sessions need to be reset for the configuration to take effect.
3462 7. If the route which is already installed in dataplane is removed for some
3463 reason, sending withdraw message to peers is not currently supported.
3465 .. clicmd:: bgp suppress-fib-pending
3467 This command is applicable at the global level and at an individual
3468 bgp level. If applied at the global level all bgp instances will
3469 wait for fib installation before announcing routes and there is no
3470 way to turn it off for a particular bgp vrf.
3477 You can set different routing policy for a peer. For example, you can set
3478 different filter for a peer.
3484 neighbor 10.0.0.1 remote-as 2
3485 address-family ipv4 unicast
3486 neighbor 10.0.0.1 distribute-list 1 in
3490 neighbor 10.0.0.1 remote-as 2
3491 address-family ipv4 unicast
3492 neighbor 10.0.0.1 distribute-list 2 in
3495 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view 2.
3496 When the update is inserted into view 1, distribute-list 1 is applied. On the
3497 other hand, when the update is inserted into view 2, distribute-list 2 is
3501 .. _bgp-regular-expressions:
3503 BGP Regular Expressions
3504 =======================
3506 BGP regular expressions are based on :t:`POSIX 1003.2` regular expressions. The
3507 following description is just a quick subset of the POSIX regular expressions.
3511 Matches any single character.
3514 Matches 0 or more occurrences of pattern.
3517 Matches 1 or more occurrences of pattern.
3520 Match 0 or 1 occurrences of pattern.
3523 Matches the beginning of the line.
3526 Matches the end of the line.
3529 The ``_`` character has special meanings in BGP regular expressions. It
3530 matches to space and comma , and AS set delimiter ``{`` and ``}`` and AS
3531 confederation delimiter ``(`` and ``)``. And it also matches to the
3532 beginning of the line and the end of the line. So ``_`` can be used for AS
3533 value boundaries match. This character technically evaluates to
3537 .. _bgp-configuration-examples:
3539 Miscellaneous Configuration Examples
3540 ====================================
3542 Example of a session to an upstream, advertising only one prefix to it.
3547 bgp router-id 10.236.87.1
3548 neighbor upstream peer-group
3549 neighbor upstream remote-as 64515
3550 neighbor upstream capability dynamic
3551 neighbor 10.1.1.1 peer-group upstream
3552 neighbor 10.1.1.1 description ACME ISP
3554 address-family ipv4 unicast
3555 network 10.236.87.0/24
3556 neighbor upstream prefix-list pl-allowed-adv out
3559 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
3560 ip prefix-list pl-allowed-adv seq 10 deny any
3562 A more complex example including upstream, peer and customer sessions
3563 advertising global prefixes and NO_EXPORT prefixes and providing actions for
3564 customer routes based on community values. Extensive use is made of route-maps
3565 and the 'call' feature to support selective advertising of prefixes. This
3566 example is intended as guidance only, it has NOT been tested and almost
3567 certainly contains silly mistakes, if not serious flaws.
3572 bgp router-id 10.236.87.1
3573 neighbor upstream capability dynamic
3574 neighbor cust capability dynamic
3575 neighbor peer capability dynamic
3576 neighbor 10.1.1.1 remote-as 64515
3577 neighbor 10.1.1.1 peer-group upstream
3578 neighbor 10.2.1.1 remote-as 64516
3579 neighbor 10.2.1.1 peer-group upstream
3580 neighbor 10.3.1.1 remote-as 64517
3581 neighbor 10.3.1.1 peer-group cust-default
3582 neighbor 10.3.1.1 description customer1
3583 neighbor 10.4.1.1 remote-as 64518
3584 neighbor 10.4.1.1 peer-group cust
3585 neighbor 10.4.1.1 description customer2
3586 neighbor 10.5.1.1 remote-as 64519
3587 neighbor 10.5.1.1 peer-group peer
3588 neighbor 10.5.1.1 description peer AS 1
3589 neighbor 10.6.1.1 remote-as 64520
3590 neighbor 10.6.1.1 peer-group peer
3591 neighbor 10.6.1.1 description peer AS 2
3593 address-family ipv4 unicast
3594 network 10.123.456.0/24
3595 network 10.123.456.128/25 route-map rm-no-export
3596 neighbor upstream route-map rm-upstream-out out
3597 neighbor cust route-map rm-cust-in in
3598 neighbor cust route-map rm-cust-out out
3599 neighbor cust send-community both
3600 neighbor peer route-map rm-peer-in in
3601 neighbor peer route-map rm-peer-out out
3602 neighbor peer send-community both
3603 neighbor 10.3.1.1 prefix-list pl-cust1-network in
3604 neighbor 10.4.1.1 prefix-list pl-cust2-network in
3605 neighbor 10.5.1.1 prefix-list pl-peer1-network in
3606 neighbor 10.6.1.1 prefix-list pl-peer2-network in
3609 ip prefix-list pl-default permit 0.0.0.0/0
3611 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
3612 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
3614 ip prefix-list pl-cust1-network permit 10.3.1.0/24
3615 ip prefix-list pl-cust1-network permit 10.3.2.0/24
3617 ip prefix-list pl-cust2-network permit 10.4.1.0/24
3619 ip prefix-list pl-peer1-network permit 10.5.1.0/24
3620 ip prefix-list pl-peer1-network permit 10.5.2.0/24
3621 ip prefix-list pl-peer1-network permit 192.168.0.0/24
3623 ip prefix-list pl-peer2-network permit 10.6.1.0/24
3624 ip prefix-list pl-peer2-network permit 10.6.2.0/24
3625 ip prefix-list pl-peer2-network permit 192.168.1.0/24
3626 ip prefix-list pl-peer2-network permit 192.168.2.0/24
3627 ip prefix-list pl-peer2-network permit 172.16.1/24
3629 bgp as-path access-list seq 5 asp-own-as permit ^$
3630 bgp as-path access-list seq 10 asp-own-as permit _64512_
3632 ! #################################################################
3633 ! Match communities we provide actions for, on routes receives from
3634 ! customers. Communities values of <our-ASN>:X, with X, have actions:
3636 ! 100 - blackhole the prefix
3637 ! 200 - set no_export
3638 ! 300 - advertise only to other customers
3639 ! 400 - advertise only to upstreams
3640 ! 500 - set no_export when advertising to upstreams
3641 ! 2X00 - set local_preference to X00
3643 ! blackhole the prefix of the route
3644 bgp community-list standard cm-blackhole permit 64512:100
3646 ! set no-export community before advertising
3647 bgp community-list standard cm-set-no-export permit 64512:200
3649 ! advertise only to other customers
3650 bgp community-list standard cm-cust-only permit 64512:300
3652 ! advertise only to upstreams
3653 bgp community-list standard cm-upstream-only permit 64512:400
3655 ! advertise to upstreams with no-export
3656 bgp community-list standard cm-upstream-noexport permit 64512:500
3658 ! set local-pref to least significant 3 digits of the community
3659 bgp community-list standard cm-prefmod-100 permit 64512:2100
3660 bgp community-list standard cm-prefmod-200 permit 64512:2200
3661 bgp community-list standard cm-prefmod-300 permit 64512:2300
3662 bgp community-list standard cm-prefmod-400 permit 64512:2400
3663 bgp community-list expanded cme-prefmod-range permit 64512:2...
3665 ! Informational communities
3667 ! 3000 - learned from upstream
3668 ! 3100 - learned from customer
3669 ! 3200 - learned from peer
3671 bgp community-list standard cm-learnt-upstream permit 64512:3000
3672 bgp community-list standard cm-learnt-cust permit 64512:3100
3673 bgp community-list standard cm-learnt-peer permit 64512:3200
3675 ! ###################################################################
3676 ! Utility route-maps
3678 ! These utility route-maps generally should not used to permit/deny
3679 ! routes, i.e. they do not have meaning as filters, and hence probably
3680 ! should be used with 'on-match next'. These all finish with an empty
3681 ! permit entry so as not interfere with processing in the caller.
3683 route-map rm-no-export permit 10
3684 set community additive no-export
3685 route-map rm-no-export permit 20
3687 route-map rm-blackhole permit 10
3688 description blackhole, up-pref and ensure it cannot escape this AS
3689 set ip next-hop 127.0.0.1
3690 set local-preference 10
3691 set community additive no-export
3692 route-map rm-blackhole permit 20
3694 ! Set local-pref as requested
3695 route-map rm-prefmod permit 10
3696 match community cm-prefmod-100
3697 set local-preference 100
3698 route-map rm-prefmod permit 20
3699 match community cm-prefmod-200
3700 set local-preference 200
3701 route-map rm-prefmod permit 30
3702 match community cm-prefmod-300
3703 set local-preference 300
3704 route-map rm-prefmod permit 40
3705 match community cm-prefmod-400
3706 set local-preference 400
3707 route-map rm-prefmod permit 50
3709 ! Community actions to take on receipt of route.
3710 route-map rm-community-in permit 10
3711 description check for blackholing, no point continuing if it matches.
3712 match community cm-blackhole
3714 route-map rm-community-in permit 20
3715 match community cm-set-no-export
3718 route-map rm-community-in permit 30
3719 match community cme-prefmod-range
3721 route-map rm-community-in permit 40
3723 ! #####################################################################
3724 ! Community actions to take when advertising a route.
3725 ! These are filtering route-maps,
3727 ! Deny customer routes to upstream with cust-only set.
3728 route-map rm-community-filt-to-upstream deny 10
3729 match community cm-learnt-cust
3730 match community cm-cust-only
3731 route-map rm-community-filt-to-upstream permit 20
3733 ! Deny customer routes to other customers with upstream-only set.
3734 route-map rm-community-filt-to-cust deny 10
3735 match community cm-learnt-cust
3736 match community cm-upstream-only
3737 route-map rm-community-filt-to-cust permit 20
3739 ! ###################################################################
3740 ! The top-level route-maps applied to sessions. Further entries could
3741 ! be added obviously..
3744 route-map rm-cust-in permit 10
3745 call rm-community-in
3747 route-map rm-cust-in permit 20
3748 set community additive 64512:3100
3749 route-map rm-cust-in permit 30
3751 route-map rm-cust-out permit 10
3752 call rm-community-filt-to-cust
3754 route-map rm-cust-out permit 20
3756 ! Upstream transit ASes
3757 route-map rm-upstream-out permit 10
3758 description filter customer prefixes which are marked cust-only
3759 call rm-community-filt-to-upstream
3761 route-map rm-upstream-out permit 20
3762 description only customer routes are provided to upstreams/peers
3763 match community cm-learnt-cust
3766 ! outbound policy is same as for upstream
3767 route-map rm-peer-out permit 10
3768 call rm-upstream-out
3770 route-map rm-peer-in permit 10
3771 set community additive 64512:3200
3774 Example of how to set up a 6-Bone connection.
3778 ! bgpd configuration
3779 ! ==================
3781 ! MP-BGP configuration
3784 bgp router-id 10.0.0.1
3785 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as `as-number`
3788 network 3ffe:506::/32
3789 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
3790 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
3791 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as `as-number`
3792 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
3795 ipv6 access-list all permit any
3797 ! Set output nexthop address.
3799 route-map set-nexthop permit 10
3800 match ipv6 address all
3801 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
3802 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
3808 .. include:: routeserver.rst
3810 .. include:: rpki.rst
3812 .. include:: wecmp_linkbw.rst
3814 .. include:: flowspec.rst
3816 .. [#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)
3817 .. [bgp-route-osci-cond] McPherson, D. and Gill, V. and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", IETF RFC3345
3818 .. [stable-flexible-ibgp] Flavel, A. and M. Roughan, "Stable and flexible iBGP", ACM SIGCOMM 2009
3819 .. [ibgp-correctness] Griffin, T. and G. Wilfong, "On the correctness of IBGP configuration", ACM SIGCOMM 2002