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 (VRF default):
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:: bgp listen limit <1-65535>
1368 Define the maximum number of peers accepted for one BGP instance. This
1369 limit is set to 100 by default. Increasing this value will really be
1370 possible if more file descriptors are available in the BGP process. This
1371 value is defined by the underlying system (ulimit value), and can be
1372 overriden by `--limit-fds`. More information is available in chapter
1373 (:ref:`common-invocation-options`).
1375 .. clicmd:: coalesce-time (0-4294967295)
1377 The time in milliseconds that BGP will delay before deciding what peers
1378 can be put into an update-group together in order to generate a single
1379 update for them. The default time is 1000.
1381 .. _bgp-configuring-peers:
1386 .. clicmd:: neighbor PEER shutdown [message MSG...] [rtt (1-65535) [count (1-255)]]
1388 Shutdown the peer. We can delete the neighbor's configuration by
1389 ``no neighbor PEER remote-as ASN`` but all configuration of the neighbor
1390 will be deleted. When you want to preserve the configuration, but want to
1391 drop the BGP peer, use this syntax.
1393 Optionally you can specify a shutdown message `MSG`.
1395 Also, you can specify optionally ``rtt`` in milliseconds to automatically
1396 shutdown the peer if round-trip-time becomes higher than defined.
1398 Additional ``count`` parameter is the number of keepalive messages to count
1399 before shutdown the peer if round-trip-time becomes higher than defined.
1401 .. clicmd:: neighbor PEER disable-connected-check
1403 Allow peerings between directly connected eBGP peers using loopback
1406 .. clicmd:: neighbor PEER ebgp-multihop
1408 Specifying ``ebgp-multihop`` allows sessions with eBGP neighbors to
1409 establish when they are multiple hops away. When the neighbor is not
1410 directly connected and this knob is not enabled, the session will not
1413 If the peer's IP address is not in the RIB and is reachable via the
1414 default route, then you have to enable ``ip nht resolve-via-default``.
1416 .. clicmd:: neighbor PEER description ...
1418 Set description of the peer.
1420 .. clicmd:: neighbor PEER version VERSION
1422 Set up the neighbor's BGP version. `version` can be `4`, `4+` or `4-`. BGP
1423 version `4` is the default value used for BGP peering. BGP version `4+`
1424 means that the neighbor supports Multiprotocol Extensions for BGP-4. BGP
1425 version `4-` is similar but the neighbor speaks the old Internet-Draft
1426 revision 00's Multiprotocol Extensions for BGP-4. Some routing software is
1427 still using this version.
1429 .. clicmd:: neighbor PEER interface IFNAME
1431 When you connect to a BGP peer over an IPv6 link-local address, you have to
1432 specify the IFNAME of the interface used for the connection. To specify
1433 IPv4 session addresses, see the ``neighbor PEER update-source`` command
1436 This command is deprecated and may be removed in a future release. Its use
1439 .. clicmd:: neighbor PEER interface remote-as <internal|external|ASN>
1441 Configure an unnumbered BGP peer. ``PEER`` should be an interface name. The
1442 session will be established via IPv6 link locals. Use ``internal`` for iBGP
1443 and ``external`` for eBGP sessions, or specify an ASN if you wish.
1445 .. clicmd:: neighbor PEER next-hop-self [all]
1447 This command specifies an announced route's nexthop as being equivalent to
1448 the address of the bgp router if it is learned via eBGP. If the optional
1449 keyword `all` is specified the modification is done also for routes learned
1452 .. clicmd:: neighbor PEER attribute-unchanged [{as-path|next-hop|med}]
1454 This command specifies attributes to be left unchanged for advertisements
1455 sent to a peer. Use this to leave the next-hop unchanged in ipv6
1456 configurations, as the route-map directive to leave the next-hop unchanged
1457 is only available for ipv4.
1459 .. clicmd:: neighbor PEER update-source <IFNAME|ADDRESS>
1461 Specify the IPv4 source address to use for the :abbr:`BGP` session to this
1462 neighbour, may be specified as either an IPv4 address directly or as an
1463 interface name (in which case the *zebra* daemon MUST be running in order
1464 for *bgpd* to be able to retrieve interface state).
1469 neighbor foo update-source 192.168.0.1
1470 neighbor bar update-source lo0
1473 .. clicmd:: neighbor PEER default-originate
1475 *bgpd*'s default is to not announce the default route (0.0.0.0/0) even if it
1476 is in routing table. When you want to announce default routes to the peer,
1479 .. clicmd:: neighbor PEER port PORT
1481 .. clicmd:: neighbor PEER password PASSWORD
1483 Set a MD5 password to be used with the tcp socket that is being used
1484 to connect to the remote peer. Please note if you are using this
1485 command with a large number of peers on linux you should consider
1486 modifying the `net.core.optmem_max` sysctl to a larger value to
1487 avoid out of memory errors from the linux kernel.
1489 .. clicmd:: neighbor PEER send-community
1491 .. clicmd:: neighbor PEER weight WEIGHT
1493 This command specifies a default `weight` value for the neighbor's routes.
1495 .. clicmd:: neighbor PEER maximum-prefix NUMBER [force]
1497 Sets a maximum number of prefixes we can receive from a given peer. If this
1498 number is exceeded, the BGP session will be destroyed.
1500 In practice, it is generally preferable to use a prefix-list to limit what
1501 prefixes are received from the peer instead of using this knob. Tearing down
1502 the BGP session when a limit is exceeded is far more destructive than merely
1503 rejecting undesired prefixes. The prefix-list method is also much more
1504 granular and offers much smarter matching criterion than number of received
1505 prefixes, making it more suited to implementing policy.
1507 If ``force`` is set, then ALL prefixes are counted for maximum instead of
1508 accepted only. This is useful for cases where an inbound filter is applied,
1509 but you want maximum-prefix to act on ALL (including filtered) prefixes. This
1510 option requires `soft-reconfiguration inbound` to be enabled for the peer.
1512 .. clicmd:: neighbor PEER maximum-prefix-out NUMBER
1514 Sets a maximum number of prefixes we can send to a given peer.
1516 Since sent prefix count is managed by update-groups, this option
1517 creates a separate update-group for outgoing updates.
1519 .. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend] [replace-as]
1521 Specify an alternate AS for this BGP process when interacting with the
1522 specified peer. With no modifiers, the specified local-as is prepended to
1523 the received AS_PATH when receiving routing updates from the peer, and
1524 prepended to the outgoing AS_PATH (after the process local AS) when
1525 transmitting local routes to the peer.
1527 If the no-prepend attribute is specified, then the supplied local-as is not
1528 prepended to the received AS_PATH.
1530 If the replace-as attribute is specified, then only the supplied local-as is
1531 prepended to the AS_PATH when transmitting local-route updates to this peer.
1533 Note that replace-as can only be specified if no-prepend is.
1535 This command is only allowed for eBGP peers.
1537 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> as-override
1539 Override AS number of the originating router with the local AS number.
1541 Usually this configuration is used in PEs (Provider Edge) to replace
1542 the incoming customer AS number so the connected CE (Customer Edge)
1543 can use the same AS number as the other customer sites. This allows
1544 customers of the provider network to use the same AS number across
1547 This command is only allowed for eBGP peers.
1549 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> allowas-in [<(1-10)|origin>]
1551 Accept incoming routes with AS path containing AS number with the same value
1552 as the current system AS.
1554 This is used when you want to use the same AS number in your sites, but you
1555 can't connect them directly. This is an alternative to
1556 `neighbor WORD as-override`.
1558 The parameter `(1-10)` configures the amount of accepted occurences of the
1559 system AS number in AS path.
1561 The parameter `origin` configures BGP to only accept routes originated with
1562 the same AS number as the system.
1564 This command is only allowed for eBGP peers.
1566 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-all-paths
1568 Configure BGP to send all known paths to neighbor in order to preserve multi
1569 path capabilities inside a network.
1571 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-bestpath-per-AS
1573 Configure BGP to send best known paths to neighbor in order to preserve multi
1574 path capabilities inside a network.
1576 .. clicmd:: neighbor PEER ttl-security hops NUMBER
1578 This command enforces Generalized TTL Security Mechanism (GTSM), as
1579 specified in RFC 5082. With this command, only neighbors that are the
1580 specified number of hops away will be allowed to become neighbors. This
1581 command is mutually exclusive with *ebgp-multihop*.
1583 .. clicmd:: neighbor PEER capability extended-nexthop
1585 Allow bgp to negotiate the extended-nexthop capability with it's peer.
1586 If you are peering over a v6 LL address then this capability is turned
1587 on automatically. If you are peering over a v6 Global Address then
1588 turning on this command will allow BGP to install v4 routes with
1589 v6 nexthops if you do not have v4 configured on interfaces.
1591 .. clicmd:: bgp fast-external-failover
1593 This command causes bgp to not take down ebgp peers immediately
1594 when a link flaps. `bgp fast-external-failover` is the default
1595 and will not be displayed as part of a `show run`. The no form
1596 of the command turns off this ability.
1598 .. clicmd:: bgp default ipv4-unicast
1600 This command allows the user to specify that the IPv4 Unicast address
1601 family is turned on by default or not. This command defaults to on
1602 and is not displayed.
1603 The `no bgp default ipv4-unicast` form of the command is displayed.
1605 .. clicmd:: bgp default ipv4-multicast
1607 This command allows the user to specify that the IPv4 Multicast address
1608 family is turned on by default or not. This command defaults to off
1609 and is not displayed.
1610 The `bgp default ipv4-multicast` form of the command is displayed.
1612 .. clicmd:: bgp default ipv4-vpn
1614 This command allows the user to specify that the IPv4 MPLS VPN address
1615 family is turned on by default or not. This command defaults to off
1616 and is not displayed.
1617 The `bgp default ipv4-vpn` form of the command is displayed.
1619 .. clicmd:: bgp default ipv4-flowspec
1621 This command allows the user to specify that the IPv4 Flowspec address
1622 family is turned on by default or not. This command defaults to off
1623 and is not displayed.
1624 The `bgp default ipv4-flowspec` form of the command is displayed.
1626 .. clicmd:: bgp default ipv6-unicast
1628 This command allows the user to specify that the IPv6 Unicast address
1629 family is turned on by default or not. This command defaults to off
1630 and is not displayed.
1631 The `bgp default ipv6-unicast` form of the command is displayed.
1633 .. clicmd:: bgp default ipv6-multicast
1635 This command allows the user to specify that the IPv6 Multicast address
1636 family is turned on by default or not. This command defaults to off
1637 and is not displayed.
1638 The `bgp default ipv6-multicast` form of the command is displayed.
1640 .. clicmd:: bgp default ipv6-vpn
1642 This command allows the user to specify that the IPv6 MPLS VPN address
1643 family is turned on by default or not. This command defaults to off
1644 and is not displayed.
1645 The `bgp default ipv6-vpn` form of the command is displayed.
1647 .. clicmd:: bgp default ipv6-flowspec
1649 This command allows the user to specify that the IPv6 Flowspec address
1650 family is turned on by default or not. This command defaults to off
1651 and is not displayed.
1652 The `bgp default ipv6-flowspec` form of the command is displayed.
1654 .. clicmd:: bgp default l2vpn-evpn
1656 This command allows the user to specify that the L2VPN EVPN address
1657 family is turned on by default or not. This command defaults to off
1658 and is not displayed.
1659 The `bgp default l2vpn-evpn` form of the command is displayed.
1661 .. clicmd:: bgp default show-hostname
1663 This command shows the hostname of the peer in certain BGP commands
1664 outputs. It's easier to troubleshoot if you have a number of BGP peers.
1666 .. clicmd:: bgp default show-nexthop-hostname
1668 This command shows the hostname of the next-hop in certain BGP commands
1669 outputs. It's easier to troubleshoot if you have a number of BGP peers
1670 and a number of routes to check.
1672 .. clicmd:: neighbor PEER advertisement-interval (0-600)
1674 Setup the minimum route advertisement interval(mrai) for the
1675 peer in question. This number is between 0 and 600 seconds,
1676 with the default advertisement interval being 0.
1678 .. clicmd:: neighbor PEER timers (0-65535) (0-65535)
1680 Set keepalive and hold timers for a neighbor. The first value is keepalive
1681 and the second is hold time.
1683 .. clicmd:: neighbor PEER connect (1-65535)
1685 Set connect timer for a neighbor. The connect timer controls how long BGP
1686 waits between connection attempts to a neighbor.
1688 .. clicmd:: neighbor PEER timers delayopen (1-240)
1690 This command allows the user enable the
1691 `RFC 4271 <https://tools.ietf.org/html/rfc4271/>` DelayOpenTimer with the
1692 specified interval or disable it with the negating command for the peer. By
1693 default, the DelayOpenTimer is disabled. The timer interval may be set to a
1694 duration of 1 to 240 seconds.
1696 Displaying Information about Peers
1697 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1699 .. clicmd:: show bgp <afi> <safi> neighbors WORD bestpath-routes [json] [wide]
1701 For the given neighbor, WORD, that is specified list the routes selected
1702 by BGP as having the best path.
1704 .. _bgp-peer-filtering:
1709 .. clicmd:: neighbor PEER distribute-list NAME [in|out]
1711 This command specifies a distribute-list for the peer. `direct` is
1714 .. clicmd:: neighbor PEER prefix-list NAME [in|out]
1716 .. clicmd:: neighbor PEER filter-list NAME [in|out]
1718 .. clicmd:: neighbor PEER route-map NAME [in|out]
1720 Apply a route-map on the neighbor. `direct` must be `in` or `out`.
1722 .. clicmd:: bgp route-reflector allow-outbound-policy
1724 By default, attribute modification via route-map policy out is not reflected
1725 on reflected routes. This option allows the modifications to be reflected as
1726 well. Once enabled, it affects all reflected routes.
1728 .. clicmd:: neighbor PEER sender-as-path-loop-detection
1730 Enable the detection of sender side AS path loops and filter the
1731 bad routes before they are sent.
1733 This setting is disabled by default.
1740 Peer groups are used to help improve scaling by generating the same
1741 update information to all members of a peer group. Note that this means
1742 that the routes generated by a member of a peer group will be sent back
1743 to that originating peer with the originator identifier attribute set to
1744 indicated the originating peer. All peers not associated with a
1745 specific peer group are treated as belonging to a default peer group,
1746 and will share updates.
1748 .. clicmd:: neighbor WORD peer-group
1750 This command defines a new peer group.
1752 .. clicmd:: neighbor PEER peer-group PGNAME
1754 This command bind specific peer to peer group WORD.
1756 .. clicmd:: neighbor PEER solo
1758 This command is used to indicate that routes advertised by the peer
1759 should not be reflected back to the peer. This command only is only
1760 meaningful when there is a single peer defined in the peer-group.
1762 .. clicmd:: show [ip] bgp peer-group [json]
1764 This command displays configured BGP peer-groups.
1768 exit1-debian-9# show bgp peer-group
1770 BGP peer-group test1, remote AS 65001
1771 Peer-group type is external
1772 Configured address-families: IPv4 Unicast; IPv6 Unicast;
1773 1 IPv4 listen range(s)
1775 2 IPv6 listen range(s)
1779 192.168.200.1 Active
1782 BGP peer-group test2
1783 Peer-group type is external
1784 Configured address-families: IPv4 Unicast;
1786 Optional ``json`` parameter is used to display JSON output.
1794 "addressFamiliesConfigured":[
1824 "addressFamiliesConfigured":[
1830 Capability Negotiation
1831 ^^^^^^^^^^^^^^^^^^^^^^
1833 .. clicmd:: neighbor PEER strict-capability-match
1836 Strictly compares remote capabilities and local capabilities. If
1837 capabilities are different, send Unsupported Capability error then reset
1840 You may want to disable sending Capability Negotiation OPEN message optional
1841 parameter to the peer when remote peer does not implement Capability
1842 Negotiation. Please use *dont-capability-negotiate* command to disable the
1845 .. clicmd:: neighbor PEER dont-capability-negotiate
1847 Suppress sending Capability Negotiation as OPEN message optional parameter
1848 to the peer. This command only affects the peer is configured other than
1849 IPv4 unicast configuration.
1851 When remote peer does not have capability negotiation feature, remote peer
1852 will not send any capabilities at all. In that case, bgp configures the peer
1853 with configured capabilities.
1855 You may prefer locally configured capabilities more than the negotiated
1856 capabilities even though remote peer sends capabilities. If the peer is
1857 configured by *override-capability*, *bgpd* ignores received capabilities
1858 then override negotiated capabilities with configured values.
1860 Additionally the operator should be reminded that this feature fundamentally
1861 disables the ability to use widely deployed BGP features. BGP unnumbered,
1862 hostname support, AS4, Addpath, Route Refresh, ORF, Dynamic Capabilities,
1863 and graceful restart.
1865 .. clicmd:: neighbor PEER override-capability
1868 Override the result of Capability Negotiation with local configuration.
1869 Ignore remote peer's capability value.
1871 .. _bgp-as-path-access-lists:
1873 AS Path Access Lists
1874 --------------------
1876 AS path access list is user defined AS path.
1878 .. clicmd:: bgp as-path access-list WORD [seq (0-4294967295)] permit|deny LINE
1880 This command defines a new AS path access list.
1884 .. _bgp-bogon-filter-example:
1886 Bogon ASN filter policy configuration example
1887 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1891 bgp as-path access-list 99 permit _0_
1892 bgp as-path access-list 99 permit _23456_
1893 bgp as-path access-list 99 permit _1310[0-6][0-9]_|_13107[0-1]_
1894 bgp as-path access-list 99 seq 20 permit ^65
1896 .. _bgp-using-as-path-in-route-map:
1898 Using AS Path in Route Map
1899 --------------------------
1901 .. clicmd:: match as-path WORD
1903 For a given as-path, WORD, match it on the BGP as-path given for the prefix
1904 and if it matches do normal route-map actions. The no form of the command
1905 removes this match from the route-map.
1907 .. clicmd:: set as-path prepend AS-PATH
1909 Prepend the given string of AS numbers to the AS_PATH of the BGP path's NLRI.
1910 The no form of this command removes this set operation from the route-map.
1912 .. clicmd:: set as-path prepend last-as NUM
1914 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
1915 The no form of this command removes this set operation from the route-map.
1917 .. _bgp-communities-attribute:
1919 Communities Attribute
1920 ---------------------
1922 The BGP communities attribute is widely used for implementing policy routing.
1923 Network operators can manipulate BGP communities attribute based on their
1924 network policy. BGP communities attribute is defined in :rfc:`1997` and
1925 :rfc:`1998`. It is an optional transitive attribute, therefore local policy can
1926 travel through different autonomous system.
1928 The communities attribute is a set of communities values. Each community value
1929 is 4 octet long. The following format is used to define the community value.
1932 This format represents 4 octet communities value. ``AS`` is high order 2
1933 octet in digit format. ``VAL`` is low order 2 octet in digit format. This
1934 format is useful to define AS oriented policy value. For example,
1935 ``7675:80`` can be used when AS 7675 wants to pass local policy value 80 to
1939 ``internet`` represents well-known communities value 0.
1941 ``graceful-shutdown``
1942 ``graceful-shutdown`` represents well-known communities value
1943 ``GRACEFUL_SHUTDOWN`` ``0xFFFF0000`` ``65535:0``. :rfc:`8326` implements
1944 the purpose Graceful BGP Session Shutdown to reduce the amount of
1945 lost traffic when taking BGP sessions down for maintenance. The use
1946 of the community needs to be supported from your peers side to
1947 actually have any effect.
1950 ``accept-own`` represents well-known communities value ``ACCEPT_OWN``
1951 ``0xFFFF0001`` ``65535:1``. :rfc:`7611` implements a way to signal
1952 to a router to accept routes with a local nexthop address. This
1953 can be the case when doing policing and having traffic having a
1954 nexthop located in another VRF but still local interface to the
1955 router. It is recommended to read the RFC for full details.
1957 ``route-filter-translated-v4``
1958 ``route-filter-translated-v4`` represents well-known communities value
1959 ``ROUTE_FILTER_TRANSLATED_v4`` ``0xFFFF0002`` ``65535:2``.
1962 ``route-filter-v4`` represents well-known communities value
1963 ``ROUTE_FILTER_v4`` ``0xFFFF0003`` ``65535:3``.
1965 ``route-filter-translated-v6``
1966 ``route-filter-translated-v6`` represents well-known communities value
1967 ``ROUTE_FILTER_TRANSLATED_v6`` ``0xFFFF0004`` ``65535:4``.
1970 ``route-filter-v6`` represents well-known communities value
1971 ``ROUTE_FILTER_v6`` ``0xFFFF0005`` ``65535:5``.
1974 ``llgr-stale`` represents well-known communities value ``LLGR_STALE``
1975 ``0xFFFF0006`` ``65535:6``.
1976 Assigned and intended only for use with routers supporting the
1977 Long-lived Graceful Restart Capability as described in
1978 [Draft-IETF-uttaro-idr-bgp-persistence]_.
1979 Routers receiving routes with this community may (depending on
1980 implementation) choose allow to reject or modify routes on the
1981 presence or absence of this community.
1984 ``no-llgr`` represents well-known communities value ``NO_LLGR``
1985 ``0xFFFF0007`` ``65535:7``.
1986 Assigned and intended only for use with routers supporting the
1987 Long-lived Graceful Restart Capability as described in
1988 [Draft-IETF-uttaro-idr-bgp-persistence]_.
1989 Routers receiving routes with this community may (depending on
1990 implementation) choose allow to reject or modify routes on the
1991 presence or absence of this community.
1993 ``accept-own-nexthop``
1994 ``accept-own-nexthop`` represents well-known communities value
1995 ``accept-own-nexthop`` ``0xFFFF0008`` ``65535:8``.
1996 [Draft-IETF-agrewal-idr-accept-own-nexthop]_ describes
1997 how to tag and label VPN routes to be able to send traffic between VRFs
1998 via an internal layer 2 domain on the same PE device. Refer to
1999 [Draft-IETF-agrewal-idr-accept-own-nexthop]_ for full details.
2002 ``blackhole`` represents well-known communities value ``BLACKHOLE``
2003 ``0xFFFF029A`` ``65535:666``. :rfc:`7999` documents sending prefixes to
2004 EBGP peers and upstream for the purpose of blackholing traffic.
2005 Prefixes tagged with the this community should normally not be
2006 re-advertised from neighbors of the originating network. Upon receiving
2007 ``BLACKHOLE`` community from a BGP speaker, ``NO_ADVERTISE`` community
2008 is added automatically.
2011 ``no-export`` represents well-known communities value ``NO_EXPORT``
2012 ``0xFFFFFF01``. All routes carry this value must not be advertised to
2013 outside a BGP confederation boundary. If neighboring BGP peer is part of BGP
2014 confederation, the peer is considered as inside a BGP confederation
2015 boundary, so the route will be announced to the peer.
2018 ``no-advertise`` represents well-known communities value ``NO_ADVERTISE``
2019 ``0xFFFFFF02``. All routes carry this value must not be advertise to other
2023 ``local-AS`` represents well-known communities value ``NO_EXPORT_SUBCONFED``
2024 ``0xFFFFFF03``. All routes carry this value must not be advertised to
2025 external BGP peers. Even if the neighboring router is part of confederation,
2026 it is considered as external BGP peer, so the route will not be announced to
2030 ``no-peer`` represents well-known communities value ``NOPEER``
2031 ``0xFFFFFF04`` ``65535:65284``. :rfc:`3765` is used to communicate to
2032 another network how the originating network want the prefix propagated.
2034 When the communities attribute is received duplicate community values in the
2035 attribute are ignored and value is sorted in numerical order.
2037 .. [Draft-IETF-uttaro-idr-bgp-persistence] <https://tools.ietf.org/id/draft-uttaro-idr-bgp-persistence-04.txt>
2038 .. [Draft-IETF-agrewal-idr-accept-own-nexthop] <https://tools.ietf.org/id/draft-agrewal-idr-accept-own-nexthop-00.txt>
2040 .. _bgp-community-lists:
2044 Community lists are user defined lists of community attribute values. These
2045 lists can be used for matching or manipulating the communities attribute in
2048 There are two types of community list:
2051 This type accepts an explicit value for the attribute.
2054 This type accepts a regular expression. Because the regex must be
2055 interpreted on each use expanded community lists are slower than standard
2058 .. clicmd:: bgp community-list standard NAME permit|deny COMMUNITY
2060 This command defines a new standard community list. ``COMMUNITY`` is
2061 communities value. The ``COMMUNITY`` is compiled into community structure.
2062 We can define multiple community list under same name. In that case match
2063 will happen user defined order. Once the community list matches to
2064 communities attribute in BGP updates it return permit or deny by the
2065 community list definition. When there is no matched entry, deny will be
2066 returned. When ``COMMUNITY`` is empty it matches to any routes.
2068 .. clicmd:: bgp community-list expanded NAME permit|deny COMMUNITY
2070 This command defines a new expanded community list. ``COMMUNITY`` is a
2071 string expression of communities attribute. ``COMMUNITY`` can be a regular
2072 expression (:ref:`bgp-regular-expressions`) to match the communities
2073 attribute in BGP updates. The expanded community is only used to filter,
2077 It is recommended to use the more explicit versions of this command.
2079 .. clicmd:: bgp community-list NAME permit|deny COMMUNITY
2081 When the community list type is not specified, the community list type is
2082 automatically detected. If ``COMMUNITY`` can be compiled into communities
2083 attribute, the community list is defined as a standard community list.
2084 Otherwise it is defined as an expanded community list. This feature is left
2085 for backward compatibility. Use of this feature is not recommended.
2087 Note that all community lists share the same namespace, so it's not
2088 necessary to specify ``standard`` or ``expanded``; these modifiers are
2091 .. clicmd:: show bgp community-list [NAME detail]
2093 Displays community list information. When ``NAME`` is specified the
2094 specified community list's information is shown.
2098 # show bgp community-list
2099 Named Community standard list CLIST
2100 permit 7675:80 7675:100 no-export
2102 Named Community expanded list EXPAND
2105 # show bgp community-list CLIST detail
2106 Named Community standard list CLIST
2107 permit 7675:80 7675:100 no-export
2111 .. _bgp-numbered-community-lists:
2113 Numbered Community Lists
2114 ^^^^^^^^^^^^^^^^^^^^^^^^
2116 When number is used for BGP community list name, the number has
2117 special meanings. Community list number in the range from 1 and 99 is
2118 standard community list. Community list number in the range from 100
2119 to 199 is expanded community list. These community lists are called
2120 as numbered community lists. On the other hand normal community lists
2121 is called as named community lists.
2123 .. clicmd:: bgp community-list (1-99) permit|deny COMMUNITY
2125 This command defines a new community list. The argument to (1-99) defines
2126 the list identifier.
2128 .. clicmd:: bgp community-list (100-199) permit|deny COMMUNITY
2130 This command defines a new expanded community list. The argument to
2131 (100-199) defines the list identifier.
2133 .. _bgp-community-alias:
2138 BGP community aliases are useful to quickly identify what communities are set
2139 for a specific prefix in a human-readable format. Especially handy for a huge
2140 amount of communities. Accurately defined aliases can help you faster spot
2143 .. clicmd:: bgp community alias NAME ALIAS
2145 This command creates an alias name for a community that will be used
2146 later in various CLI outputs in a human-readable format.
2150 ~# vtysh -c 'show run' | grep 'bgp community alias'
2151 bgp community alias 65001:14 community-1
2152 bgp community alias 65001:123:1 lcommunity-1
2154 ~# vtysh -c 'show ip bgp 172.16.16.1/32'
2155 BGP routing table entry for 172.16.16.1/32, version 21
2156 Paths: (2 available, best #2, table default)
2157 Advertised to non peer-group peers:
2159 192.168.0.2 from 192.168.0.2 (172.16.16.1)
2160 Origin incomplete, metric 0, valid, external, best (Neighbor IP)
2161 Community: 65001:12 65001:13 community-1 65001:65534
2162 Large Community: lcommunity-1 65001:123:2
2163 Last update: Fri Apr 16 12:51:27 2021
2165 .. clicmd:: show bgp [afi] [safi] [all] alias WORD [wide|json]
2167 Display prefixes with matching BGP community alias.
2169 .. _bgp-using-communities-in-route-map:
2171 Using Communities in Route Maps
2172 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2174 In :ref:`route-map` we can match on or set the BGP communities attribute. Using
2175 this feature network operator can implement their network policy based on BGP
2176 communities attribute.
2178 The following commands can be used in route maps:
2180 .. clicmd:: match community WORD exact-match [exact-match]
2182 This command perform match to BGP updates using community list WORD. When
2183 the one of BGP communities value match to the one of communities value in
2184 community list, it is match. When `exact-match` keyword is specified, match
2185 happen only when BGP updates have completely same communities value
2186 specified in the community list.
2188 .. clicmd:: set community <none|COMMUNITY> additive
2190 This command sets the community value in BGP updates. If the attribute is
2191 already configured, the newly provided value replaces the old one unless the
2192 ``additive`` keyword is specified, in which case the new value is appended
2193 to the existing value.
2195 If ``none`` is specified as the community value, the communities attribute
2198 It is not possible to set an expanded community list.
2200 .. clicmd:: set comm-list WORD delete
2202 This command remove communities value from BGP communities attribute. The
2203 ``word`` is community list name. When BGP route's communities value matches
2204 to the community list ``word``, the communities value is removed. When all
2205 of communities value is removed eventually, the BGP update's communities
2206 attribute is completely removed.
2208 .. _bgp-communities-example:
2210 Example Configuration
2211 ^^^^^^^^^^^^^^^^^^^^^
2213 The following configuration is exemplary of the most typical usage of BGP
2214 communities attribute. In the example, AS 7675 provides an upstream Internet
2215 connection to AS 100. When the following configuration exists in AS 7675, the
2216 network operator of AS 100 can set local preference in AS 7675 network by
2217 setting BGP communities attribute to the updates.
2222 neighbor 192.168.0.1 remote-as 100
2223 address-family ipv4 unicast
2224 neighbor 192.168.0.1 route-map RMAP in
2227 bgp community-list 70 permit 7675:70
2228 bgp community-list 70 deny
2229 bgp community-list 80 permit 7675:80
2230 bgp community-list 80 deny
2231 bgp community-list 90 permit 7675:90
2232 bgp community-list 90 deny
2234 route-map RMAP permit 10
2236 set local-preference 70
2238 route-map RMAP permit 20
2240 set local-preference 80
2242 route-map RMAP permit 30
2244 set local-preference 90
2247 The following configuration announces ``10.0.0.0/8`` from AS 100 to AS 7675.
2248 The route has communities value ``7675:80`` so when above configuration exists
2249 in AS 7675, the announced routes' local preference value will be set to 80.
2255 neighbor 192.168.0.2 remote-as 7675
2256 address-family ipv4 unicast
2257 neighbor 192.168.0.2 route-map RMAP out
2260 ip prefix-list PLIST permit 10.0.0.0/8
2262 route-map RMAP permit 10
2263 match ip address prefix-list PLIST
2264 set community 7675:80
2267 The following configuration is an example of BGP route filtering using
2268 communities attribute. This configuration only permit BGP routes which has BGP
2269 communities value ``0:80`` or ``0:90``. The network operator can set special
2270 internal communities value at BGP border router, then limit the BGP route
2271 announcements into the internal network.
2276 neighbor 192.168.0.1 remote-as 100
2277 address-family ipv4 unicast
2278 neighbor 192.168.0.1 route-map RMAP in
2281 bgp community-list 1 permit 0:80 0:90
2283 route-map RMAP permit in
2287 The following example filters BGP routes which have a community value of
2288 ``1:1``. When there is no match community-list returns ``deny``. To avoid
2289 filtering all routes, a ``permit`` line is set at the end of the
2295 neighbor 192.168.0.1 remote-as 100
2296 address-family ipv4 unicast
2297 neighbor 192.168.0.1 route-map RMAP in
2300 bgp community-list standard FILTER deny 1:1
2301 bgp community-list standard FILTER permit
2303 route-map RMAP permit 10
2304 match community FILTER
2307 The communities value keyword ``internet`` has special meanings in standard
2308 community lists. In the below example ``internet`` matches all BGP routes even
2309 if the route does not have communities attribute at all. So community list
2310 ``INTERNET`` is the same as ``FILTER`` in the previous example.
2314 bgp community-list standard INTERNET deny 1:1
2315 bgp community-list standard INTERNET permit internet
2318 The following configuration is an example of communities value deletion. With
2319 this configuration the community values ``100:1`` and ``100:2`` are removed
2320 from BGP updates. For communities value deletion, only ``permit``
2321 community-list is used. ``deny`` community-list is ignored.
2326 neighbor 192.168.0.1 remote-as 100
2327 address-family ipv4 unicast
2328 neighbor 192.168.0.1 route-map RMAP in
2331 bgp community-list standard DEL permit 100:1 100:2
2333 route-map RMAP permit 10
2334 set comm-list DEL delete
2337 .. _bgp-extended-communities-attribute:
2339 Extended Communities Attribute
2340 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2342 BGP extended communities attribute is introduced with MPLS VPN/BGP technology.
2343 MPLS VPN/BGP expands capability of network infrastructure to provide VPN
2344 functionality. At the same time it requires a new framework for policy routing.
2345 With BGP Extended Communities Attribute we can use Route Target or Site of
2346 Origin for implementing network policy for MPLS VPN/BGP.
2348 BGP Extended Communities Attribute is similar to BGP Communities Attribute. It
2349 is an optional transitive attribute. BGP Extended Communities Attribute can
2350 carry multiple Extended Community value. Each Extended Community value is
2353 BGP Extended Communities Attribute provides an extended range compared with BGP
2354 Communities Attribute. Adding to that there is a type field in each value to
2355 provides community space structure.
2357 There are two format to define Extended Community value. One is AS based format
2358 the other is IP address based format.
2361 This is a format to define AS based Extended Community value. ``AS`` part
2362 is 2 octets Global Administrator subfield in Extended Community value.
2363 ``VAL`` part is 4 octets Local Administrator subfield. ``7675:100``
2364 represents AS 7675 policy value 100.
2367 This is a format to define IP address based Extended Community value.
2368 ``IP-Address`` part is 4 octets Global Administrator subfield. ``VAL`` part
2369 is 2 octets Local Administrator subfield.
2371 .. _bgp-extended-community-lists:
2373 Extended Community Lists
2374 ^^^^^^^^^^^^^^^^^^^^^^^^
2376 .. clicmd:: bgp extcommunity-list standard NAME permit|deny EXTCOMMUNITY
2378 This command defines a new standard extcommunity-list. `extcommunity` is
2379 extended communities value. The `extcommunity` is compiled into extended
2380 community structure. We can define multiple extcommunity-list under same
2381 name. In that case match will happen user defined order. Once the
2382 extcommunity-list matches to extended communities attribute in BGP updates
2383 it return permit or deny based upon the extcommunity-list definition. When
2384 there is no matched entry, deny will be returned. When `extcommunity` is
2385 empty it matches to any routes.
2387 .. clicmd:: bgp extcommunity-list expanded NAME permit|deny LINE
2389 This command defines a new expanded extcommunity-list. `line` is a string
2390 expression of extended communities attribute. `line` can be a regular
2391 expression (:ref:`bgp-regular-expressions`) to match an extended communities
2392 attribute in BGP updates.
2394 Note that all extended community lists shares a single name space, so it's
2395 not necessary to specify their type when creating or destroying them.
2397 .. clicmd:: show bgp extcommunity-list [NAME detail]
2399 This command displays current extcommunity-list information. When `name` is
2400 specified the community list's information is shown.
2403 .. _bgp-extended-communities-in-route-map:
2405 BGP Extended Communities in Route Map
2406 """""""""""""""""""""""""""""""""""""
2408 .. clicmd:: match extcommunity WORD
2410 .. clicmd:: set extcommunity rt EXTCOMMUNITY
2412 This command set Route Target value.
2414 .. clicmd:: set extcommunity soo EXTCOMMUNITY
2416 This command set Site of Origin value.
2418 .. clicmd:: set extcommunity bandwidth <(1-25600) | cumulative | num-multipaths> [non-transitive]
2420 This command sets the BGP link-bandwidth extended community for the prefix
2421 (best path) for which it is applied. The link-bandwidth can be specified as
2422 an ``explicit value`` (specified in Mbps), or the router can be told to use
2423 the ``cumulative bandwidth`` of all multipaths for the prefix or to compute
2424 it based on the ``number of multipaths``. The link bandwidth extended
2425 community is encoded as ``transitive`` unless the set command explicitly
2426 configures it as ``non-transitive``.
2428 .. seealso:: :ref:`wecmp_linkbw`
2430 Note that the extended expanded community is only used for `match` rule, not for
2433 .. _bgp-large-communities-attribute:
2435 Large Communities Attribute
2436 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
2438 The BGP Large Communities attribute was introduced in Feb 2017 with
2441 The BGP Large Communities Attribute is similar to the BGP Communities Attribute
2442 except that it has 3 components instead of two and each of which are 4 octets
2443 in length. Large Communities bring additional functionality and convenience
2444 over traditional communities, specifically the fact that the ``GLOBAL`` part
2445 below is now 4 octets wide allowing seamless use in networks using 4-byte ASNs.
2447 ``GLOBAL:LOCAL1:LOCAL2``
2448 This is the format to define Large Community values. Referencing :rfc:`8195`
2449 the values are commonly referred to as follows:
2451 - The ``GLOBAL`` part is a 4 octet Global Administrator field, commonly used
2452 as the operators AS number.
2453 - The ``LOCAL1`` part is a 4 octet Local Data Part 1 subfield referred to as
2455 - The ``LOCAL2`` part is a 4 octet Local Data Part 2 field and referred to
2456 as the parameter subfield.
2458 As an example, ``65551:1:10`` represents AS 65551 function 1 and parameter
2459 10. The referenced RFC above gives some guidelines on recommended usage.
2461 .. _bgp-large-community-lists:
2463 Large Community Lists
2464 """""""""""""""""""""
2466 Two types of large community lists are supported, namely `standard` and
2469 .. clicmd:: bgp large-community-list standard NAME permit|deny LARGE-COMMUNITY
2471 This command defines a new standard large-community-list. `large-community`
2472 is the Large Community value. We can add multiple large communities under
2473 same name. In that case the match will happen in the user defined order.
2474 Once the large-community-list matches the Large Communities attribute in BGP
2475 updates it will return permit or deny based upon the large-community-list
2476 definition. When there is no matched entry, a deny will be returned. When
2477 `large-community` is empty it matches any routes.
2479 .. clicmd:: bgp large-community-list expanded NAME permit|deny LINE
2481 This command defines a new expanded large-community-list. Where `line` is a
2482 string matching expression, it will be compared to the entire Large
2483 Communities attribute as a string, with each large-community in order from
2484 lowest to highest. `line` can also be a regular expression which matches
2485 this Large Community attribute.
2487 Note that all community lists share the same namespace, so it's not
2488 necessary to specify ``standard`` or ``expanded``; these modifiers are
2491 .. clicmd:: show bgp large-community-list
2493 .. clicmd:: show bgp large-community-list NAME detail
2495 This command display current large-community-list information. When
2496 `name` is specified the community list information is shown.
2498 .. clicmd:: show ip bgp large-community-info
2500 This command displays the current large communities in use.
2502 .. _bgp-large-communities-in-route-map:
2504 Large Communities in Route Map
2505 """"""""""""""""""""""""""""""
2507 .. clicmd:: match large-community LINE [exact-match]
2509 Where `line` can be a simple string to match, or a regular expression. It
2510 is very important to note that this match occurs on the entire
2511 large-community string as a whole, where each large-community is ordered
2512 from lowest to highest. When `exact-match` keyword is specified, match
2513 happen only when BGP updates have completely same large communities value
2514 specified in the large community list.
2516 .. clicmd:: set large-community LARGE-COMMUNITY
2518 .. clicmd:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
2520 .. clicmd:: set large-community LARGE-COMMUNITY additive
2522 These commands are used for setting large-community values. The first
2523 command will overwrite any large-communities currently present.
2524 The second specifies two large-communities, which overwrites the current
2525 large-community list. The third will add a large-community value without
2526 overwriting other values. Multiple large-community values can be specified.
2528 Note that the large expanded community is only used for `match` rule, not for
2536 *bgpd* supports :abbr:`L3VPN (Layer 3 Virtual Private Networks)` :abbr:`VRFs
2537 (Virtual Routing and Forwarding)` for IPv4 :rfc:`4364` and IPv6 :rfc:`4659`.
2538 L3VPN routes, and their associated VRF MPLS labels, can be distributed to VPN
2539 SAFI neighbors in the *default*, i.e., non VRF, BGP instance. VRF MPLS labels
2540 are reached using *core* MPLS labels which are distributed using LDP or BGP
2541 labeled unicast. *bgpd* also supports inter-VRF route leaking.
2544 .. _bgp-vrf-route-leaking:
2549 BGP routes may be leaked (i.e. copied) between a unicast VRF RIB and the VPN
2550 SAFI RIB of the default VRF for use in MPLS-based L3VPNs. Unicast routes may
2551 also be leaked between any VRFs (including the unicast RIB of the default BGP
2552 instanced). A shortcut syntax is also available for specifying leaking from one
2553 VRF to another VRF using the default instance's VPN RIB as the intemediary. A
2554 common application of the VRF-VRF feature is to connect a customer's private
2555 routing domain to a provider's VPN service. Leaking is configured from the
2556 point of view of an individual VRF: ``import`` refers to routes leaked from VPN
2557 to a unicast VRF, whereas ``export`` refers to routes leaked from a unicast VRF
2563 Routes exported from a unicast VRF to the VPN RIB must be augmented by two
2566 - an :abbr:`RD (Route Distinguisher)`
2567 - an :abbr:`RTLIST (Route-target List)`
2569 Configuration for these exported routes must, at a minimum, specify these two
2572 Routes imported from the VPN RIB to a unicast VRF are selected according to
2573 their RTLISTs. Routes whose RTLIST contains at least one route-target in
2574 common with the configured import RTLIST are leaked. Configuration for these
2575 imported routes must specify an RTLIST to be matched.
2577 The RD, which carries no semantic value, is intended to make the route unique
2578 in the VPN RIB among all routes of its prefix that originate from all the
2579 customers and sites that are attached to the provider's VPN service.
2580 Accordingly, each site of each customer is typically assigned an RD that is
2581 unique across the entire provider network.
2583 The RTLIST is a set of route-target extended community values whose purpose is
2584 to specify route-leaking policy. Typically, a customer is assigned a single
2585 route-target value for import and export to be used at all customer sites. This
2586 configuration specifies a simple topology wherein a customer has a single
2587 routing domain which is shared across all its sites. More complex routing
2588 topologies are possible through use of additional route-targets to augment the
2589 leaking of sets of routes in various ways.
2591 When using the shortcut syntax for vrf-to-vrf leaking, the RD and RT are
2594 General configuration
2595 ^^^^^^^^^^^^^^^^^^^^^
2597 Configuration of route leaking between a unicast VRF RIB and the VPN SAFI RIB
2598 of the default VRF is accomplished via commands in the context of a VRF
2601 .. clicmd:: rd vpn export AS:NN|IP:nn
2603 Specifies the route distinguisher to be added to a route exported from the
2604 current unicast VRF to VPN.
2606 .. clicmd:: rt vpn import|export|both RTLIST...
2608 Specifies the route-target list to be attached to a route (export) or the
2609 route-target list to match against (import) when exporting/importing between
2610 the current unicast VRF and VPN.
2612 The RTLIST is a space-separated list of route-targets, which are BGP
2613 extended community values as described in
2614 :ref:`bgp-extended-communities-attribute`.
2616 .. clicmd:: label vpn export (0..1048575)|auto
2618 Enables an MPLS label to be attached to a route exported from the current
2619 unicast VRF to VPN. If the value specified is ``auto``, the label value is
2620 automatically assigned from a pool maintained by the Zebra daemon. If Zebra
2621 is not running, or if this command is not configured, automatic label
2622 assignment will not complete, which will block corresponding route export.
2624 .. clicmd:: nexthop vpn export A.B.C.D|X:X::X:X
2626 Specifies an optional nexthop value to be assigned to a route exported from
2627 the current unicast VRF to VPN. If left unspecified, the nexthop will be set
2628 to 0.0.0.0 or 0:0::0:0 (self).
2630 .. clicmd:: route-map vpn import|export MAP
2632 Specifies an optional route-map to be applied to routes imported or exported
2633 between the current unicast VRF and VPN.
2635 .. clicmd:: import|export vpn
2637 Enables import or export of routes between the current unicast VRF and VPN.
2639 .. clicmd:: import vrf VRFNAME
2641 Shortcut syntax for specifying automatic leaking from vrf VRFNAME to
2642 the current VRF using the VPN RIB as intermediary. The RD and RT
2643 are auto derived and should not be specified explicitly for either the
2644 source or destination VRF's.
2646 This shortcut syntax mode is not compatible with the explicit
2647 `import vpn` and `export vpn` statements for the two VRF's involved.
2648 The CLI will disallow attempts to configure incompatible leaking
2656 .. clicmd:: segment-routing srv6
2658 Use SRv6 backend with BGP L3VPN, and go to its configuration node.
2660 .. clicmd:: locator NAME
2662 Specify the SRv6 locator to be used for SRv6 L3VPN. The Locator name must
2663 be set in zebra, but user can set it in any order.
2667 Ethernet Virtual Network - EVPN
2668 -------------------------------
2670 Note: When using EVPN features and if you have a large number of hosts, make
2671 sure to adjust the size of the arp neighbor cache to avoid neighbor table
2672 overflow and/or excessive garbage collection. On Linux, the size of the table
2673 and garbage collection frequency can be controlled via the following
2674 sysctl configurations:
2676 .. code-block:: shell
2678 net.ipv4.neigh.default.gc_thresh1
2679 net.ipv4.neigh.default.gc_thresh2
2680 net.ipv4.neigh.default.gc_thresh3
2682 net.ipv6.neigh.default.gc_thresh1
2683 net.ipv6.neigh.default.gc_thresh2
2684 net.ipv6.neigh.default.gc_thresh3
2686 For more information, see ``man 7 arp``.
2688 .. _bgp-evpn-advertise-pip:
2693 In a EVPN symmetric routing MLAG deployment, all EVPN routes advertised
2694 with anycast-IP as next-hop IP and anycast MAC as the Router MAC (RMAC - in
2695 BGP EVPN Extended-Community).
2696 EVPN picks up the next-hop IP from the VxLAN interface's local tunnel IP and
2697 the RMAC is obtained from the MAC of the L3VNI's SVI interface.
2698 Note: Next-hop IP is used for EVPN routes whether symmetric routing is
2699 deployed or not but the RMAC is only relevant for symmetric routing scenario.
2701 Current behavior is not ideal for Prefix (type-5) and self (type-2)
2702 routes. This is because the traffic from remote VTEPs routed sub optimally
2703 if they land on the system where the route does not belong.
2705 The advertise-pip feature advertises Prefix (type-5) and self (type-2)
2706 routes with system's individual (primary) IP as the next-hop and individual
2707 (system) MAC as Router-MAC (RMAC), while leaving the behavior unchanged for
2710 To support this feature there needs to have ability to co-exist a
2711 (system-MAC, system-IP) pair with a (anycast-MAC, anycast-IP) pair with the
2712 ability to terminate VxLAN-encapsulated packets received for either pair on
2713 the same L3VNI (i.e associated VLAN). This capability is needed per tenant
2716 To derive the system-MAC and the anycast MAC, there must be a
2717 separate/additional MAC-VLAN interface corresponding to L3VNI’s SVI.
2718 The SVI interface’s MAC address can be interpreted as system-MAC
2719 and MAC-VLAN interface's MAC as anycast MAC.
2721 To derive system-IP and anycast-IP, the default BGP instance's router-id is used
2722 as system-IP and the VxLAN interface’s local tunnel IP as the anycast-IP.
2724 User has an option to configure the system-IP and/or system-MAC value if the
2725 auto derived value is not preferred.
2727 Note: By default, advertise-pip feature is enabled and user has an option to
2728 disable the feature via configuration CLI. Once the feature is disabled under
2729 bgp vrf instance or MAC-VLAN interface is not configured, all the routes follow
2730 the same behavior of using same next-hop and RMAC values.
2732 .. clicmd:: advertise-pip [ip <addr> [mac <addr>]]
2734 Enables or disables advertise-pip feature, specifiy system-IP and/or system-MAC
2737 EVPN advertise-svi-ip
2738 ^^^^^^^^^^^^^^^^^^^^^
2739 Typically, the SVI IP address is reused on VTEPs across multiple racks. However,
2740 if you have unique SVI IP addresses that you want to be reachable you can use the
2741 advertise-svi-ip option. This option advertises the SVI IP/MAC address as a type-2
2742 route and eliminates the need for any flooding over VXLAN to reach the IP from a
2745 .. clicmd:: advertise-svi-ip
2747 Note that you should not enable both the advertise-svi-ip and the advertise-default-gw
2750 .. _bgp-evpn-overlay-index-gateway-ip:
2752 EVPN Overlay Index Gateway IP
2753 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2754 Draft https://tools.ietf.org/html/draft-ietf-bess-evpn-prefix-advertisement-11
2755 explains the use of overlay indexes for recursive route resolution for EVPN
2758 We support gateway IP overlay index.
2759 A gateway IP, advertised with EVPN prefix route, is used to find an EVPN MAC/IP
2760 route with its IP field same as the gateway IP. This MAC/IP entry provides the
2761 nexthop VTEP and the tunnel information required for the VxLAN encapsulation.
2767 . +--------+ BGP +--------+ BGP +--------+ +--------+
2768 SN1 | | IPv4 | | EVPN | | | |
2769 ======+ Host1 +------+ PE1 +------+ PE2 +------+ Host2 +
2771 +--------+ +--------+ +--------+ +--------+
2773 Consider above topology where prefix SN1 is connected behind host1. Host1
2774 advertises SN1 to PE1 over BGP IPv4 session. PE1 advertises SN1 to PE2 using
2775 EVPN type-5 route with host1 IP as the gateway IP. PE1 also advertises
2776 Host1 MAC/IP as type-2 route which is used to resolve host1 gateway IP.
2778 PE2 receives this type-5 route and imports it into the vrf based on route
2779 targets. BGP prefix imported into the vrf uses gateway IP as its BGP nexthop.
2780 This route is installed into zebra if following conditions are satisfied:
2782 1. Gateway IP nexthop is L3 reachable.
2783 2. PE2 has received EVPN type-2 route with IP field set to gateway IP.
2785 Topology requirements:
2787 1. This feature is supported for asymmetric routing model only. While
2788 sending packets to SN1, ingress PE (PE2) performs routing and
2789 egress PE (PE1) performs only bridging.
2790 2. This feature supports only tratitional(non vlan-aware) bridge model. Bridge
2791 interface associated with L2VNI is an L3 interface. i.e., this interface is
2792 configured with an address in the L2VNI subnet. Note that the gateway IP
2793 should also have an address in the same subnet.
2794 3. As this feature works in asymmetric routing model, all L2VNIs and corresponding
2795 VxLAN and bridge interfaces should be present at all the PEs.
2796 4. L3VNI configuration is required to generate and import EVPN type-5 routes.
2797 L3VNI VxLAN and bridge interfaces also should be present.
2799 A PE can use one of the following two mechanisms to advertise an EVPN type-5
2800 route with gateway IP.
2802 1. CLI to add gateway IP while generating EVPN type-5 route from a BGP IPv4/IPv6
2805 .. index:: advertise <ipv4|ipv6> unicast [gateway-ip]
2806 .. clicmd:: [no] advertise <ipv4|ipv6> unicast [gateway-ip]
2808 When this CLI is configured for a BGP vrf under L2VPN EVPN address family, EVPN
2809 type-5 routes are generated for BGP prefixes in the vrf. Nexthop of the BGP
2810 prefix becomes the gateway IP of the corresponding type-5 route.
2812 If the above command is configured without the "gateway-ip" keyword, type-5
2813 routes are generated without overlay index.
2815 2. Add gateway IP to EVPN type-5 route using a route-map:
2817 .. index:: set evpn gateway-ip <ipv4|ipv6> <addr>
2818 .. clicmd:: [no] set evpn gateway-ip <ipv4|ipv6> <addr>
2820 When route-map with above set clause is applied as outbound policy in BGP, it
2821 will set the gateway-ip in EVPN type-5 NLRI.
2823 Example configuration:
2828 neighbor 192.168.0.1 remote-as 101
2830 address-family ipv4 l2vpn evpn
2831 neighbor 192.168.0.1 route-map RMAP out
2834 route-map RMAP permit 10
2835 set evpn gateway-ip 10.0.0.1
2836 set evpn gateway-ip 10::1
2838 A PE that receives a type-5 route with gateway IP overlay index should have
2839 "enable-resolve-overlay-index" configuration enabled to recursively resolve the
2840 overlay index nexthop and install the prefix into zebra.
2842 .. index:: enable-resolve-overlay-index
2843 .. clicmd:: [no] enable-resolve-overlay-index
2845 Example configuration:
2850 bgp router-id 192.168.100.1
2851 no bgp ebgp-requires-policy
2852 neighbor 10.0.1.2 remote-as 65002
2854 address-family l2vpn evpn
2855 neighbor 10.0.1.2 activate
2857 enable-resolve-overlay-index
2864 All-Active Multihoming is used for redundancy and load sharing. Servers
2865 are attached to two or more PEs and the links are bonded (link-aggregation).
2866 This group of server links is referred to as an Ethernet Segment.
2870 An Ethernet Segment can be configured by specifying a system-MAC and a
2871 local discriminatior against the bond interface on the PE (via zebra) -
2873 .. clicmd:: evpn mh es-id (1-16777215)
2875 .. clicmd:: evpn mh es-sys-mac X:X:X:X:X:X
2877 The sys-mac and local discriminator are used for generating a 10-byte,
2878 Type-3 Ethernet Segment ID.
2880 Type-1 (EAS-per-ES and EAD-per-EVI) routes are used to advertise the locally
2881 attached ESs and to learn off remote ESs in the network. Local Type-2/MAC-IP
2882 routes are also advertised with a destination ESI allowing for MAC-IP syncing
2883 between Ethernet Segment peers.
2884 Reference: RFC 7432, RFC 8365
2886 EVPN-MH is intended as a replacement for MLAG or Anycast VTEPs. In
2887 multihoming each PE has an unique VTEP address which requires the introduction
2888 of a new dataplane construct, MAC-ECMP. Here a MAC/FDB entry can point to a
2889 list of remote PEs/VTEPs.
2893 Type-4 (ESR) routes are used for Designated Forwarder (DF) election. DFs
2894 forward BUM traffic received via the overlay network. This implementation
2895 uses a preference based DF election specified by draft-ietf-bess-evpn-pref-df.
2896 The DF preference is configurable per-ES (via zebra) -
2898 .. clicmd:: evpn mh es-df-pref (1-16777215)
2900 BUM traffic is rxed via the overlay by all PEs attached to a server but
2901 only the DF can forward the de-capsulated traffic to the access port. To
2902 accomodate that non-DF filters are installed in the dataplane to drop
2905 Similarly traffic received from ES peers via the overlay cannot be forwarded
2906 to the server. This is split-horizon-filtering with local bias.
2910 Some vendors do not send EAD-per-EVI routes. To interop with them we
2911 need to relax the dependency on EAD-per-EVI routes and activate a remote
2912 ES-PE based on just the EAD-per-ES route.
2914 Note that by default we advertise and expect EAD-per-EVI routes.
2916 .. clicmd:: disable-ead-evi-rx
2918 .. clicmd:: disable-ead-evi-tx
2922 As the primary purpose of EVPN-MH is redundancy keeping the failover efficient
2923 is a recurring theme in the implementation. Following sub-features have
2924 been introduced for the express purpose of efficient ES failovers.
2926 - Layer-2 Nexthop Groups and MAC-ECMP via L2NHG.
2928 - Host routes (for symmetric IRB) via L3NHG.
2929 On dataplanes that support layer3 nexthop groups the feature can be turned
2930 on via the following BGP config -
2932 .. clicmd:: use-es-l3nhg
2934 - Local ES (MAC/Neigh) failover via ES-redirect.
2935 On dataplanes that do not have support for ES-redirect the feature can be
2936 turned off via the following zebra config -
2938 .. clicmd:: evpn mh redirect-off
2940 Uplink/Core tracking
2941 """"""""""""""""""""
2942 When all the underlay links go down the PE no longer has access to the VxLAN
2943 +overlay. To prevent blackholing of traffic the server/ES links are
2944 protodowned on the PE. A link can be setup for uplink tracking via the
2945 following zebra configuration -
2947 .. clicmd:: evpn mh uplink
2949 Proxy advertisements
2950 """"""""""""""""""""
2951 To handle hitless upgrades support for proxy advertisement has been added
2952 as specified by draft-rbickhart-evpn-ip-mac-proxy-adv. This allows a PE
2953 (say PE1) to proxy advertise a MAC-IP rxed from an ES peer (say PE2). When
2954 the ES peer (PE2) goes down PE1 continues to advertise hosts learnt from PE2
2955 for a holdtime during which it attempts to establish local reachability of
2956 the host. This holdtime is configurable via the following zebra commands -
2958 .. clicmd:: evpn mh neigh-holdtime (0-86400)
2960 .. clicmd:: evpn mh mac-holdtime (0-86400)
2964 When a switch is rebooted we wait for a brief period to allow the underlay
2965 and EVPN network to converge before enabling the ESs. For this duration the
2966 ES bonds are held protodown. The startup delay is configurable via the
2967 following zebra command -
2969 .. clicmd:: evpn mh startup-delay (0-3600)
2971 +Support with VRF network namespace backend
2972 +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2973 It is possible to separate overlay networks contained in VXLAN interfaces from
2974 underlay networks by using VRFs. VRF-lite and VRF-netns backends can be used for
2975 that. In the latter case, it is necessary to set both bridge and vxlan interface
2976 in the same network namespace, as below example illustrates:
2978 .. code-block:: shell
2982 ip link add name vxlan101 type vxlan id 101 dstport 4789 dev eth0 local 10.1.1.1
2983 ip link set dev vxlan101 netns vrf1
2984 ip netns exec vrf1 ip link set dev lo up
2985 ip netns exec vrf1 brctl addbr bridge101
2986 ip netns exec vrf1 brctl addif bridge101 vxlan101
2988 This makes it possible to separate not only layer 3 networks like VRF-lite networks.
2989 Also, VRF netns based make possible to separate layer 2 networks on separate VRF
2992 .. _bgp-conditional-advertisement:
2994 BGP Conditional Advertisement
2995 -----------------------------
2996 The BGP conditional advertisement feature uses the ``non-exist-map`` or the
2997 ``exist-map`` and the ``advertise-map`` keywords of the neighbor advertise-map
2998 command in order to track routes by the route prefix.
3001 1. If a route prefix is not present in the output of non-exist-map command,
3002 then advertise the route specified by the advertise-map command.
3004 2. If a route prefix is present in the output of non-exist-map command,
3005 then do not advertise the route specified by the addvertise-map command.
3008 1. If a route prefix is present in the output of exist-map command,
3009 then advertise the route specified by the advertise-map command.
3011 2. If a route prefix is not present in the output of exist-map command,
3012 then do not advertise the route specified by the advertise-map command.
3014 This feature is useful when some prefixes are advertised to one of its peers
3015 only if the information from the other peer is not present (due to failure in
3016 peering session or partial reachability etc).
3018 The conditional BGP announcements are sent in addition to the normal
3019 announcements that a BGP router sends to its peer.
3021 The conditional advertisement process is triggered by the BGP scanner process,
3022 which runs every 60 seconds. This means that the maximum time for the conditional
3023 advertisement to take effect is 60 seconds. The conditional advertisement can take
3024 effect depending on when the tracked route is removed from the BGP table and
3025 when the next instance of the BGP scanner occurs.
3027 .. clicmd:: neighbor A.B.C.D advertise-map NAME [exist-map|non-exist-map] NAME
3029 This command enables BGP scanner process to monitor routes specified by
3030 exist-map or non-exist-map command in BGP table and conditionally advertises
3031 the routes specified by advertise-map command.
3033 Sample Configuration
3034 ^^^^^^^^^^^^^^^^^^^^^
3038 ip address 10.10.10.2/24
3041 ip address 10.10.20.2/24
3044 ip address 203.0.113.1/32
3047 bgp log-neighbor-changes
3048 no bgp ebgp-requires-policy
3049 neighbor 10.10.10.1 remote-as 1
3050 neighbor 10.10.20.3 remote-as 3
3052 address-family ipv4 unicast
3053 neighbor 10.10.10.1 soft-reconfiguration inbound
3054 neighbor 10.10.20.3 soft-reconfiguration inbound
3055 neighbor 10.10.20.3 advertise-map ADV-MAP non-exist-map EXIST-MAP
3058 ip prefix-list DEFAULT seq 5 permit 192.0.2.5/32
3059 ip prefix-list DEFAULT seq 10 permit 192.0.2.1/32
3060 ip prefix-list EXIST seq 5 permit 10.10.10.10/32
3061 ip prefix-list DEFAULT-ROUTE seq 5 permit 0.0.0.0/0
3062 ip prefix-list IP1 seq 5 permit 10.139.224.0/20
3064 bgp community-list standard DC-ROUTES seq 5 permit 64952:3008
3065 bgp community-list standard DC-ROUTES seq 10 permit 64671:501
3066 bgp community-list standard DC-ROUTES seq 15 permit 64950:3009
3067 bgp community-list standard DEFAULT-ROUTE seq 5 permit 65013:200
3069 route-map ADV-MAP permit 10
3070 match ip address prefix-list IP1
3072 route-map ADV-MAP permit 20
3073 match community DC-ROUTES
3075 route-map EXIST-MAP permit 10
3076 match community DEFAULT-ROUTE
3077 match ip address prefix-list DEFAULT-ROUTE
3083 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.
3087 Router2# show ip bgp
3088 BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
3089 Default local pref 100, local AS 2
3090 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3091 i internal, r RIB-failure, S Stale, R Removed
3092 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3093 Origin codes: i - IGP, e - EGP, ? - incomplete
3094 RPKI validation codes: V valid, I invalid, N Not found
3096 Network Next Hop Metric LocPrf Weight Path
3097 *> 0.0.0.0/0 10.10.10.1 0 0 1 i
3098 *> 10.139.224.0/20 10.10.10.1 0 0 1 ?
3099 *> 192.0.2.1/32 10.10.10.1 0 0 1 i
3100 *> 192.0.2.5/32 10.10.10.1 0 0 1 i
3102 Displayed 4 routes and 4 total paths
3103 Router2# show ip bgp neighbors 10.10.20.3
3105 !--- Output suppressed.
3107 For address family: IPv4 Unicast
3108 Update group 7, subgroup 7
3109 Packet Queue length 0
3110 Inbound soft reconfiguration allowed
3111 Community attribute sent to this neighbor(all)
3112 Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Withdraw
3115 !--- Output suppressed.
3117 Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
3118 BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
3119 Default local pref 100, local AS 2
3120 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3121 i internal, r RIB-failure, S Stale, R Removed
3122 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3123 Origin codes: i - IGP, e - EGP, ? - incomplete
3124 RPKI validation codes: V valid, I invalid, N Not found
3126 Network Next Hop Metric LocPrf Weight Path
3127 *> 0.0.0.0/0 0.0.0.0 0 1 i
3128 *> 192.0.2.5/32 0.0.0.0 0 1 i
3130 Total number of prefixes 2
3132 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.
3136 Router2# show ip bgp
3137 BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
3138 Default local pref 100, local AS 2
3139 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3140 i internal, r RIB-failure, S Stale, R Removed
3141 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3142 Origin codes: i - IGP, e - EGP, ? - incomplete
3143 RPKI validation codes: V valid, I invalid, N Not found
3145 Network Next Hop Metric LocPrf Weight Path
3146 *> 10.139.224.0/20 10.10.10.1 0 0 1 ?
3147 *> 192.0.2.1/32 10.10.10.1 0 0 1 i
3148 *> 192.0.2.5/32 10.10.10.1 0 0 1 i
3150 Displayed 3 routes and 3 total paths
3152 Router2# show ip bgp neighbors 10.10.20.3
3154 !--- Output suppressed.
3156 For address family: IPv4 Unicast
3157 Update group 7, subgroup 7
3158 Packet Queue length 0
3159 Inbound soft reconfiguration allowed
3160 Community attribute sent to this neighbor(all)
3161 Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Advertise
3164 !--- Output suppressed.
3166 Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
3167 BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
3168 Default local pref 100, local AS 2
3169 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3170 i internal, r RIB-failure, S Stale, R Removed
3171 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3172 Origin codes: i - IGP, e - EGP, ? - incomplete
3173 RPKI validation codes: V valid, I invalid, N Not found
3175 Network Next Hop Metric LocPrf Weight Path
3176 *> 10.139.224.0/20 0.0.0.0 0 1 ?
3177 *> 192.0.2.1/32 0.0.0.0 0 1 i
3178 *> 192.0.2.5/32 0.0.0.0 0 1 i
3180 Total number of prefixes 3
3188 .. clicmd:: show debug
3190 Show all enabled debugs.
3192 .. clicmd:: show bgp listeners
3194 Display Listen sockets and the vrf that created them. Useful for debugging of when
3195 listen is not working and this is considered a developer debug statement.
3197 .. clicmd:: debug bgp bfd
3199 Enable or disable debugging for BFD events. This will show BFD integration
3200 library messages and BGP BFD integration messages that are mostly state
3201 transitions and validation problems.
3203 .. clicmd:: debug bgp neighbor-events
3205 Enable or disable debugging for neighbor events. This provides general
3206 information on BGP events such as peer connection / disconnection, session
3207 establishment / teardown, and capability negotiation.
3209 .. clicmd:: debug bgp updates
3211 Enable or disable debugging for BGP updates. This provides information on
3212 BGP UPDATE messages transmitted and received between local and remote
3215 .. clicmd:: debug bgp keepalives
3217 Enable or disable debugging for BGP keepalives. This provides information on
3218 BGP KEEPALIVE messages transmitted and received between local and remote
3221 .. clicmd:: debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
3223 Enable or disable debugging for bestpath selection on the specified prefix.
3225 .. clicmd:: debug bgp nht
3227 Enable or disable debugging of BGP nexthop tracking.
3229 .. clicmd:: debug bgp update-groups
3231 Enable or disable debugging of dynamic update groups. This provides general
3232 information on group creation, deletion, join and prune events.
3234 .. clicmd:: debug bgp zebra
3236 Enable or disable debugging of communications between *bgpd* and *zebra*.
3238 Dumping Messages and Routing Tables
3239 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
3241 .. clicmd:: dump bgp all PATH [INTERVAL]
3243 .. clicmd:: dump bgp all-et PATH [INTERVAL]
3246 Dump all BGP packet and events to `path` file.
3247 If `interval` is set, a new file will be created for echo `interval` of
3248 seconds. The path `path` can be set with date and time formatting
3249 (strftime). The type ‘all-et’ enables support for Extended Timestamp Header
3250 (:ref:`packet-binary-dump-format`).
3252 .. clicmd:: dump bgp updates PATH [INTERVAL]
3254 .. clicmd:: dump bgp updates-et PATH [INTERVAL]
3257 Dump only BGP updates messages to `path` file.
3258 If `interval` is set, a new file will be created for echo `interval` of
3259 seconds. The path `path` can be set with date and time formatting
3260 (strftime). The type ‘updates-et’ enables support for Extended Timestamp
3261 Header (:ref:`packet-binary-dump-format`).
3263 .. clicmd:: dump bgp routes-mrt PATH
3265 .. clicmd:: dump bgp routes-mrt PATH INTERVAL
3268 Dump whole BGP routing table to `path`. This is heavy process. The path
3269 `path` can be set with date and time formatting (strftime). If `interval` is
3270 set, a new file will be created for echo `interval` of seconds.
3272 Note: the interval variable can also be set using hours and minutes: 04h20m00.
3275 .. _bgp-other-commands:
3280 The following are available in the top level *enable* mode:
3282 .. clicmd:: clear bgp \*
3286 .. clicmd:: clear bgp ipv4|ipv6 \*
3288 Clear all peers with this address-family activated.
3290 .. clicmd:: clear bgp ipv4|ipv6 unicast \*
3292 Clear all peers with this address-family and sub-address-family activated.
3294 .. clicmd:: clear bgp ipv4|ipv6 PEER
3296 Clear peers with address of X.X.X.X and this address-family activated.
3298 .. clicmd:: clear bgp ipv4|ipv6 unicast PEER
3300 Clear peer with address of X.X.X.X and this address-family and sub-address-family activated.
3302 .. clicmd:: clear bgp ipv4|ipv6 PEER soft|in|out
3304 Clear peer using soft reconfiguration in this address-family.
3306 .. clicmd:: clear bgp ipv4|ipv6 unicast PEER soft|in|out
3308 Clear peer using soft reconfiguration in this address-family and sub-address-family.
3310 The following are available in the ``router bgp`` mode:
3312 .. clicmd:: write-quanta (1-64)
3314 BGP message Tx I/O is vectored. This means that multiple packets are written
3315 to the peer socket at the same time each I/O cycle, in order to minimize
3316 system call overhead. This value controls how many are written at a time.
3317 Under certain load conditions, reducing this value could make peer traffic
3318 less 'bursty'. In practice, leave this settings on the default (64) unless
3319 you truly know what you are doing.
3321 .. clicmd:: read-quanta (1-10)
3323 Unlike Tx, BGP Rx traffic is not vectored. Packets are read off the wire one
3324 at a time in a loop. This setting controls how many iterations the loop runs
3325 for. As with write-quanta, it is best to leave this setting on the default.
3327 The following command is available in ``config`` mode as well as in the
3328 ``router bgp`` mode:
3330 .. clicmd:: bgp graceful-shutdown
3332 The purpose of this command is to initiate BGP Graceful Shutdown which
3333 is described in :rfc:`8326`. The use case for this is to minimize or
3334 eliminate the amount of traffic loss in a network when a planned
3335 maintenance activity such as software upgrade or hardware replacement
3336 is to be performed on a router. The feature works by re-announcing
3337 routes to eBGP peers with the GRACEFUL_SHUTDOWN community included.
3338 Peers are then expected to treat such paths with the lowest preference.
3339 This happens automatically on a receiver running FRR; with other
3340 routing protocol stacks, an inbound policy may have to be configured.
3341 In FRR, triggering graceful shutdown also results in announcing a
3342 LOCAL_PREF of 0 to iBGP peers.
3344 Graceful shutdown can be configured per BGP instance or globally for
3345 all of BGP. These two options are mutually exclusive. The no form of
3346 the command causes graceful shutdown to be stopped, and routes will
3347 be re-announced without the GRACEFUL_SHUTDOWN community and/or with
3348 the usual LOCAL_PREF value. Note that if this option is saved to
3349 the startup configuration, graceful shutdown will remain in effect
3350 across restarts of *bgpd* and will need to be explicitly disabled.
3352 .. _bgp-displaying-bgp-information:
3354 Displaying BGP Information
3355 ==========================
3357 The following four commands display the IPv6 and IPv4 routing tables, depending
3358 on whether or not the ``ip`` keyword is used.
3359 Actually, :clicmd:`show ip bgp` command was used on older `Quagga` routing
3360 daemon project, while :clicmd:`show bgp` command is the new format. The choice
3361 has been done to keep old format with IPv4 routing table, while new format
3362 displays IPv6 routing table.
3364 .. clicmd:: show ip bgp [all] [wide|json [detail]]
3366 .. clicmd:: show ip bgp A.B.C.D [json]
3368 .. clicmd:: show bgp [all] [wide|json [detail]]
3370 .. clicmd:: show bgp X:X::X:X [json]
3372 These commands display BGP routes. When no route is specified, the default
3373 is to display all BGP routes.
3377 BGP table version is 0, local router ID is 10.1.1.1
3378 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
3379 Origin codes: i - IGP, e - EGP, ? - incomplete
3381 Network Next Hop Metric LocPrf Weight Path
3382 \*> 1.1.1.1/32 0.0.0.0 0 32768 i
3384 Total number of prefixes 1
3386 If ``wide`` option is specified, then the prefix table's width is increased
3387 to fully display the prefix and the nexthop.
3389 This is especially handy dealing with IPv6 prefixes and
3390 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3392 If ``all`` option is specified, ``ip`` keyword is ignored, show bgp all and
3393 show ip bgp all commands display routes for all AFIs and SAFIs.
3395 If ``json`` option is specified, output is displayed in JSON format.
3397 If ``detail`` option is specified after ``json``, more verbose JSON output
3400 Some other commands provide additional options for filtering the output.
3402 .. clicmd:: show [ip] bgp regexp LINE
3404 This command displays BGP routes using AS path regular expression
3405 (:ref:`bgp-regular-expressions`).
3407 .. clicmd:: show [ip] bgp [all] summary [wide] [json]
3409 Show a bgp peer summary for the specified address family.
3411 The old command structure :clicmd:`show ip bgp` may be removed in the future
3412 and should no longer be used. In order to reach the other BGP routing tables
3413 other than the IPv6 routing table given by :clicmd:`show bgp`, the new command
3414 structure is extended with :clicmd:`show bgp [afi] [safi]`.
3416 ``wide`` option gives more output like ``LocalAS`` and extended ``Desc`` to
3421 exit1# show ip bgp summary wide
3423 IPv4 Unicast Summary (VRF default):
3424 BGP router identifier 192.168.100.1, local AS number 65534 vrf-id 0
3426 RIB entries 5, using 920 bytes of memory
3427 Peers 1, using 27 KiB of memory
3429 Neighbor V AS LocalAS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
3430 192.168.0.2 4 65030 123 15 22 0 0 0 00:07:00 0 1 us-east1-rs1.frrouting.org
3432 Total number of neighbors 1
3435 .. clicmd:: show bgp [afi] [safi] [all] [wide|json]
3437 .. clicmd:: show bgp [<ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast|flowspec> | l2vpn evpn]
3439 These commands display BGP routes for the specific routing table indicated by
3440 the selected afi and the selected safi. If no afi and no safi value is given,
3441 the command falls back to the default IPv6 routing table.
3443 .. clicmd:: show bgp l2vpn evpn route [type <macip|2|multicast|3|es|4|prefix|5>]
3445 EVPN prefixes can also be filtered by EVPN route type.
3447 .. clicmd:: show bgp [afi] [safi] [all] summary [json]
3449 Show a bgp peer summary for the specified address family, and subsequent
3452 .. clicmd:: show bgp [afi] [safi] [all] summary failed [json]
3454 Show a bgp peer summary for peers that are not succesfully exchanging routes
3455 for the specified address family, and subsequent address-family.
3457 .. clicmd:: show bgp [afi] [safi] [all] summary established [json]
3459 Show a bgp peer summary for peers that are succesfully exchanging routes
3460 for the specified address family, and subsequent address-family.
3462 .. clicmd:: show bgp [afi] [safi] [all] summary neighbor [PEER] [json]
3464 Show a bgp summary for the specified peer, address family, and
3465 subsequent address-family. The neighbor filter can be used in combination
3466 with the failed, established filters.
3468 .. clicmd:: show bgp [afi] [safi] [all] summary remote-as <internal|external|ASN> [json]
3470 Show a bgp peer summary for the specified remote-as ASN or type (``internal``
3471 for iBGP and ``external`` for eBGP sessions), address family, and subsequent
3472 address-family. The remote-as filter can be used in combination with the
3473 failed, established filters.
3475 .. clicmd:: show bgp [afi] [safi] [all] summary terse [json]
3477 Shorten the output. Do not show the following information about the BGP
3478 instances: the number of RIB entries, the table version and the used memory.
3479 The ``terse`` option can be used in combination with the remote-as, neighbor,
3480 failed and established filters, and with the ``wide`` option as well.
3482 .. clicmd:: show bgp [afi] [safi] [neighbor [PEER] [routes|advertised-routes|received-routes] [json]
3484 This command shows information on a specific BGP peer of the relevant
3485 afi and safi selected.
3487 The ``routes`` keyword displays only routes in this address-family's BGP
3488 table that were received by this peer and accepted by inbound policy.
3490 The ``advertised-routes`` keyword displays only the routes in this
3491 address-family's BGP table that were permitted by outbound policy and
3492 advertised to to this peer.
3494 The ``received-routes`` keyword displays all routes belonging to this
3495 address-family (prior to inbound policy) that were received by this peer.
3497 .. clicmd:: show bgp [afi] [safi] [all] dampening dampened-paths [wide|json]
3499 Display paths suppressed due to dampening of the selected afi and safi
3502 .. clicmd:: show bgp [afi] [safi] [all] dampening flap-statistics [wide|json]
3504 Display flap statistics of routes of the selected afi and safi selected.
3506 .. clicmd:: show bgp [afi] [safi] [all] version (1-4294967295) [wide|json]
3508 Display prefixes with matching version numbers. The version number and
3509 above having prefixes will be listed here.
3511 It helps to identify which prefixes were installed at some point.
3513 Here is an example of how to check what prefixes were installed starting
3514 with an arbitrary version::
3518 ~# vtysh -c 'show bgp ipv4 unicast json' | jq '.tableVersion'
3520 ~# vtysh -c 'show ip bgp version 9 json' | jq -r '.routes | keys[]'
3522 ~# vtysh -c 'show ip bgp version 8 json' | jq -r '.routes | keys[]'
3526 .. clicmd:: show bgp [afi] [safi] statistics
3528 Display statistics of routes of the selected afi and safi.
3530 .. clicmd:: show bgp statistics-all
3532 Display statistics of routes of all the afi and safi.
3534 .. clicmd:: show [ip] bgp [afi] [safi] [all] cidr-only [wide|json]
3536 Display routes with non-natural netmasks.
3538 .. clicmd:: show [ip] bgp [afi] [safi] [all] neighbors A.B.C.D [advertised-routes|received-routes|filtered-routes] [json|wide]
3540 Display the routes advertised to a BGP neighbor or received routes
3541 from neighbor or filtered routes received from neighbor based on the
3544 If ``wide`` option is specified, then the prefix table's width is increased
3545 to fully display the prefix and the nexthop.
3547 This is especially handy dealing with IPv6 prefixes and
3548 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3550 If ``all`` option is specified, ``ip`` keyword is ignored and,
3551 routes displayed for all AFIs and SAFIs.
3552 if afi is specified, with ``all`` option, routes will be displayed for
3553 each SAFI in the selcted AFI
3555 If ``json`` option is specified, output is displayed in JSON format.
3557 .. _bgp-display-routes-by-community:
3559 Displaying Routes by Community Attribute
3560 ----------------------------------------
3562 The following commands allow displaying routes based on their community
3565 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community [wide|json]
3567 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY [wide|json]
3569 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY exact-match [wide|json]
3571 These commands display BGP routes which have the community attribute.
3572 attribute. When ``COMMUNITY`` is specified, BGP routes that match that
3573 community are displayed. When `exact-match` is specified, it display only
3574 routes that have an exact match.
3576 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD
3578 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match
3580 These commands display BGP routes for the address family specified that
3581 match the specified community list. When `exact-match` is specified, it
3582 displays only routes that have an exact match.
3584 If ``wide`` option is specified, then the prefix table's width is increased
3585 to fully display the prefix and the nexthop.
3587 This is especially handy dealing with IPv6 prefixes and
3588 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3590 If ``all`` option is specified, ``ip`` keyword is ignored and,
3591 routes displayed for all AFIs and SAFIs.
3592 if afi is specified, with ``all`` option, routes will be displayed for
3593 each SAFI in the selcted AFI
3595 If ``json`` option is specified, output is displayed in JSON format.
3597 .. clicmd:: show bgp labelpool <chunks|inuse|ledger|requests|summary> [json]
3599 These commands display information about the BGP labelpool used for
3600 the association of MPLS labels with routes for L3VPN and Labeled Unicast
3602 If ``chunks`` option is specified, output shows the current list of label
3603 chunks granted to BGP by Zebra, indicating the start and end label in
3606 If ``inuse`` option is specified, output shows the current inuse list of
3607 label to prefix mappings
3609 If ``ledger`` option is specified, output shows ledger list of all
3610 label requests made per prefix
3612 If ``requests`` option is specified, output shows current list of label
3613 requests which have not yet been fulfilled by the labelpool
3615 If ``summary`` option is specified, output is a summary of the counts for
3616 the chunks, inuse, ledger and requests list along with the count of
3617 outstanding chunk requests to Zebra and the nummber of zebra reconnects
3620 If ``json`` option is specified, output is displayed in JSON format.
3622 .. _bgp-display-routes-by-lcommunity:
3624 Displaying Routes by Large Community Attribute
3625 ----------------------------------------------
3627 The following commands allow displaying routes based on their
3628 large community attribute.
3630 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community
3632 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY
3634 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY exact-match
3636 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY json
3638 These commands display BGP routes which have the large community attribute.
3639 attribute. When ``LARGE-COMMUNITY`` is specified, BGP routes that match that
3640 large community are displayed. When `exact-match` is specified, it display
3641 only routes that have an exact match. When `json` is specified, it display
3642 routes in json format.
3644 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD
3646 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD exact-match
3648 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD json
3650 These commands display BGP routes for the address family specified that
3651 match the specified large community list. When `exact-match` is specified,
3652 it displays only routes that have an exact match. When `json` is specified,
3653 it display routes in json format.
3655 .. _bgp-display-routes-by-as-path:
3658 Displaying Routes by AS Path
3659 ----------------------------
3661 .. clicmd:: show bgp ipv4|ipv6 regexp LINE
3663 This commands displays BGP routes that matches a regular
3664 expression `line` (:ref:`bgp-regular-expressions`).
3666 .. clicmd:: show [ip] bgp ipv4 vpn
3668 .. clicmd:: show [ip] bgp ipv6 vpn
3670 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
3672 .. clicmd:: show bgp ipv4 vpn summary
3674 .. clicmd:: show bgp ipv6 vpn summary
3676 Print a summary of neighbor connections for the specified AFI/SAFI combination.
3678 Displaying Routes by Route Distinguisher
3679 ----------------------------------------
3681 .. clicmd:: show bgp [<ipv4|ipv6> vpn | l2vpn evpn [route]] rd <all|RD>
3683 For L3VPN and EVPN address-families, routes can be displayed on a per-RD
3684 (Route Distinguisher) basis or for all RD's.
3686 .. clicmd:: show bgp l2vpn evpn rd <all|RD> [overlay | tags]
3688 Use the ``overlay`` or ``tags`` keywords to display the overlay/tag
3689 information about the EVPN prefixes in the selected Route Distinguisher.
3691 .. clicmd:: show bgp l2vpn evpn route rd <all|RD> mac <MAC> [ip <MAC>] [json]
3693 For EVPN Type 2 (macip) routes, a MAC address (and optionally an IP address)
3694 can be supplied to the command to only display matching prefixes in the
3697 Displaying Update Group Information
3698 -----------------------------------
3700 .. clicmd:: show bgp update-groups [advertise-queue|advertised-routes|packet-queue]
3702 Display Information about each individual update-group being used.
3703 If SUBGROUP-ID is specified only display about that particular group. If
3704 advertise-queue is specified the list of routes that need to be sent
3705 to the peers in the update-group is displayed, advertised-routes means
3706 the list of routes we have sent to the peers in the update-group and
3707 packet-queue specifies the list of packets in the queue to be sent.
3709 .. clicmd:: show bgp update-groups statistics
3711 Display Information about update-group events in FRR.
3713 Segment-Routing IPv6
3714 --------------------
3716 .. clicmd:: show bgp segment-routing srv6
3718 This command displays information about SRv6 L3VPN in bgpd. Specifically,
3719 what kind of Locator is being used, and its Locator chunk information.
3720 And the SID of the SRv6 Function that is actually managed on bgpd.
3721 In the following example, bgpd is using a Locator named loc1, and two SRv6
3722 Functions are managed to perform VPNv6 VRF redirect for vrf10 and vrf20.
3726 router# show bgp segment-routing srv6
3731 - sid: 2001:db8:1:1::100
3733 - sid: 2001:db8:1:1::200
3737 vpn_policy[AFI_IP].tovpn_sid: none
3738 vpn_policy[AFI_IP6].tovpn_sid: none
3740 vpn_policy[AFI_IP].tovpn_sid: none
3741 vpn_policy[AFI_IP6].tovpn_sid: 2001:db8:1:1::100
3743 vpn_policy[AFI_IP].tovpn_sid: none
3744 vpn_policy[AFI_IP6].tovpn_sid: 2001:db8:1:1::200
3747 .. _bgp-route-reflector:
3752 BGP routers connected inside the same AS through BGP belong to an internal
3753 BGP session, or IBGP. In order to prevent routing table loops, IBGP does not
3754 advertise IBGP-learned routes to other routers in the same session. As such,
3755 IBGP requires a full mesh of all peers. For large networks, this quickly becomes
3756 unscalable. Introducing route reflectors removes the need for the full-mesh.
3758 When route reflectors are configured, these will reflect the routes announced
3759 by the peers configured as clients. A route reflector client is configured
3762 .. clicmd:: neighbor PEER route-reflector-client
3765 To avoid single points of failure, multiple route reflectors can be configured.
3767 A cluster is a collection of route reflectors and their clients, and is used
3768 by route reflectors to avoid looping.
3770 .. clicmd:: bgp cluster-id A.B.C.D
3772 .. clicmd:: bgp no-rib
3774 To set and unset the BGP daemon ``-n`` / ``--no_kernel`` options during runtime
3775 to disable BGP route installation to the RIB (Zebra), the ``[no] bgp no-rib``
3776 commands can be used;
3778 Please note that setting the option during runtime will withdraw all routes in
3779 the daemons RIB from Zebra and unsetting it will announce all routes in the
3780 daemons RIB to Zebra. If the option is passed as a command line argument when
3781 starting the daemon and the configuration gets saved, the option will persist
3782 unless removed from the configuration with the negating command prior to the
3783 configuration write operation.
3785 .. clicmd:: bgp send-extra-data zebra
3787 This Command turns off the ability of BGP to send extra data to zebra.
3788 In this case it's the AS-Path being used for the path. The default behavior
3789 in BGP is to send this data and to turn it off enter the no form of the command.
3790 If extra data was sent to zebra, and this command is turned on there is no
3791 effort to clean up this data in the rib.
3793 .. _bgp-suppress-fib:
3795 Suppressing routes not installed in FIB
3796 =======================================
3798 The FRR implementation of BGP advertises prefixes learnt from a peer to other
3799 peers even if the routes do not get installed in the FIB. There can be
3800 scenarios where the hardware tables in some of the routers (along the path from
3801 the source to destination) is full which will result in all routes not getting
3802 installed in the FIB. If these routes are advertised to the downstream routers
3803 then traffic will start flowing and will be dropped at the intermediate router.
3805 The solution is to provide a configurable option to check for the FIB install
3806 status of the prefixes and advertise to peers if the prefixes are successfully
3807 installed in the FIB. The advertisement of the prefixes are suppressed if it is
3808 not installed in FIB.
3810 The following conditions apply will apply when checking for route installation
3813 1. The advertisement or suppression of routes based on FIB install status
3814 applies only for newly learnt routes from peer (routes which are not in
3816 2. If the route received from peer already exists in BGP local RIB and route
3817 attributes have changed (best path changed), the old path is deleted and
3818 new path is installed in FIB. The FIB install status will not have any
3819 effect. Therefore only when the route is received first time the checks
3821 3. The feature will not apply for routes learnt through other means like
3822 redistribution to bgp from other protocols. This is applicable only to
3824 4. If a route is installed in FIB and then gets deleted from the dataplane,
3825 then routes will not be withdrawn from peers. This will be considered as
3827 5. The feature will slightly increase the time required to advertise the routes
3828 to peers since the route install status needs to be received from the FIB
3829 6. If routes are received by the peer before the configuration is applied, then
3830 the bgp sessions need to be reset for the configuration to take effect.
3831 7. If the route which is already installed in dataplane is removed for some
3832 reason, sending withdraw message to peers is not currently supported.
3834 .. clicmd:: bgp suppress-fib-pending
3836 This command is applicable at the global level and at an individual
3837 bgp level. If applied at the global level all bgp instances will
3838 wait for fib installation before announcing routes and there is no
3839 way to turn it off for a particular bgp vrf.
3846 You can set different routing policy for a peer. For example, you can set
3847 different filter for a peer.
3853 neighbor 10.0.0.1 remote-as 2
3854 address-family ipv4 unicast
3855 neighbor 10.0.0.1 distribute-list 1 in
3859 neighbor 10.0.0.1 remote-as 2
3860 address-family ipv4 unicast
3861 neighbor 10.0.0.1 distribute-list 2 in
3864 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view 2.
3865 When the update is inserted into view 1, distribute-list 1 is applied. On the
3866 other hand, when the update is inserted into view 2, distribute-list 2 is
3870 .. _bgp-regular-expressions:
3872 BGP Regular Expressions
3873 =======================
3875 BGP regular expressions are based on :t:`POSIX 1003.2` regular expressions. The
3876 following description is just a quick subset of the POSIX regular expressions.
3880 Matches any single character.
3883 Matches 0 or more occurrences of pattern.
3886 Matches 1 or more occurrences of pattern.
3889 Match 0 or 1 occurrences of pattern.
3892 Matches the beginning of the line.
3895 Matches the end of the line.
3898 The ``_`` character has special meanings in BGP regular expressions. It
3899 matches to space and comma , and AS set delimiter ``{`` and ``}`` and AS
3900 confederation delimiter ``(`` and ``)``. And it also matches to the
3901 beginning of the line and the end of the line. So ``_`` can be used for AS
3902 value boundaries match. This character technically evaluates to
3906 .. _bgp-configuration-examples:
3908 Miscellaneous Configuration Examples
3909 ====================================
3911 Example of a session to an upstream, advertising only one prefix to it.
3916 bgp router-id 10.236.87.1
3917 neighbor upstream peer-group
3918 neighbor upstream remote-as 64515
3919 neighbor upstream capability dynamic
3920 neighbor 10.1.1.1 peer-group upstream
3921 neighbor 10.1.1.1 description ACME ISP
3923 address-family ipv4 unicast
3924 network 10.236.87.0/24
3925 neighbor upstream prefix-list pl-allowed-adv out
3928 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
3929 ip prefix-list pl-allowed-adv seq 10 deny any
3931 A more complex example including upstream, peer and customer sessions
3932 advertising global prefixes and NO_EXPORT prefixes and providing actions for
3933 customer routes based on community values. Extensive use is made of route-maps
3934 and the 'call' feature to support selective advertising of prefixes. This
3935 example is intended as guidance only, it has NOT been tested and almost
3936 certainly contains silly mistakes, if not serious flaws.
3941 bgp router-id 10.236.87.1
3942 neighbor upstream capability dynamic
3943 neighbor cust capability dynamic
3944 neighbor peer capability dynamic
3945 neighbor 10.1.1.1 remote-as 64515
3946 neighbor 10.1.1.1 peer-group upstream
3947 neighbor 10.2.1.1 remote-as 64516
3948 neighbor 10.2.1.1 peer-group upstream
3949 neighbor 10.3.1.1 remote-as 64517
3950 neighbor 10.3.1.1 peer-group cust-default
3951 neighbor 10.3.1.1 description customer1
3952 neighbor 10.4.1.1 remote-as 64518
3953 neighbor 10.4.1.1 peer-group cust
3954 neighbor 10.4.1.1 description customer2
3955 neighbor 10.5.1.1 remote-as 64519
3956 neighbor 10.5.1.1 peer-group peer
3957 neighbor 10.5.1.1 description peer AS 1
3958 neighbor 10.6.1.1 remote-as 64520
3959 neighbor 10.6.1.1 peer-group peer
3960 neighbor 10.6.1.1 description peer AS 2
3962 address-family ipv4 unicast
3963 network 10.123.456.0/24
3964 network 10.123.456.128/25 route-map rm-no-export
3965 neighbor upstream route-map rm-upstream-out out
3966 neighbor cust route-map rm-cust-in in
3967 neighbor cust route-map rm-cust-out out
3968 neighbor cust send-community both
3969 neighbor peer route-map rm-peer-in in
3970 neighbor peer route-map rm-peer-out out
3971 neighbor peer send-community both
3972 neighbor 10.3.1.1 prefix-list pl-cust1-network in
3973 neighbor 10.4.1.1 prefix-list pl-cust2-network in
3974 neighbor 10.5.1.1 prefix-list pl-peer1-network in
3975 neighbor 10.6.1.1 prefix-list pl-peer2-network in
3978 ip prefix-list pl-default permit 0.0.0.0/0
3980 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
3981 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
3983 ip prefix-list pl-cust1-network permit 10.3.1.0/24
3984 ip prefix-list pl-cust1-network permit 10.3.2.0/24
3986 ip prefix-list pl-cust2-network permit 10.4.1.0/24
3988 ip prefix-list pl-peer1-network permit 10.5.1.0/24
3989 ip prefix-list pl-peer1-network permit 10.5.2.0/24
3990 ip prefix-list pl-peer1-network permit 192.168.0.0/24
3992 ip prefix-list pl-peer2-network permit 10.6.1.0/24
3993 ip prefix-list pl-peer2-network permit 10.6.2.0/24
3994 ip prefix-list pl-peer2-network permit 192.168.1.0/24
3995 ip prefix-list pl-peer2-network permit 192.168.2.0/24
3996 ip prefix-list pl-peer2-network permit 172.16.1/24
3998 bgp as-path access-list seq 5 asp-own-as permit ^$
3999 bgp as-path access-list seq 10 asp-own-as permit _64512_
4001 ! #################################################################
4002 ! Match communities we provide actions for, on routes receives from
4003 ! customers. Communities values of <our-ASN>:X, with X, have actions:
4005 ! 100 - blackhole the prefix
4006 ! 200 - set no_export
4007 ! 300 - advertise only to other customers
4008 ! 400 - advertise only to upstreams
4009 ! 500 - set no_export when advertising to upstreams
4010 ! 2X00 - set local_preference to X00
4012 ! blackhole the prefix of the route
4013 bgp community-list standard cm-blackhole permit 64512:100
4015 ! set no-export community before advertising
4016 bgp community-list standard cm-set-no-export permit 64512:200
4018 ! advertise only to other customers
4019 bgp community-list standard cm-cust-only permit 64512:300
4021 ! advertise only to upstreams
4022 bgp community-list standard cm-upstream-only permit 64512:400
4024 ! advertise to upstreams with no-export
4025 bgp community-list standard cm-upstream-noexport permit 64512:500
4027 ! set local-pref to least significant 3 digits of the community
4028 bgp community-list standard cm-prefmod-100 permit 64512:2100
4029 bgp community-list standard cm-prefmod-200 permit 64512:2200
4030 bgp community-list standard cm-prefmod-300 permit 64512:2300
4031 bgp community-list standard cm-prefmod-400 permit 64512:2400
4032 bgp community-list expanded cme-prefmod-range permit 64512:2...
4034 ! Informational communities
4036 ! 3000 - learned from upstream
4037 ! 3100 - learned from customer
4038 ! 3200 - learned from peer
4040 bgp community-list standard cm-learnt-upstream permit 64512:3000
4041 bgp community-list standard cm-learnt-cust permit 64512:3100
4042 bgp community-list standard cm-learnt-peer permit 64512:3200
4044 ! ###################################################################
4045 ! Utility route-maps
4047 ! These utility route-maps generally should not used to permit/deny
4048 ! routes, i.e. they do not have meaning as filters, and hence probably
4049 ! should be used with 'on-match next'. These all finish with an empty
4050 ! permit entry so as not interfere with processing in the caller.
4052 route-map rm-no-export permit 10
4053 set community additive no-export
4054 route-map rm-no-export permit 20
4056 route-map rm-blackhole permit 10
4057 description blackhole, up-pref and ensure it cannot escape this AS
4058 set ip next-hop 127.0.0.1
4059 set local-preference 10
4060 set community additive no-export
4061 route-map rm-blackhole permit 20
4063 ! Set local-pref as requested
4064 route-map rm-prefmod permit 10
4065 match community cm-prefmod-100
4066 set local-preference 100
4067 route-map rm-prefmod permit 20
4068 match community cm-prefmod-200
4069 set local-preference 200
4070 route-map rm-prefmod permit 30
4071 match community cm-prefmod-300
4072 set local-preference 300
4073 route-map rm-prefmod permit 40
4074 match community cm-prefmod-400
4075 set local-preference 400
4076 route-map rm-prefmod permit 50
4078 ! Community actions to take on receipt of route.
4079 route-map rm-community-in permit 10
4080 description check for blackholing, no point continuing if it matches.
4081 match community cm-blackhole
4083 route-map rm-community-in permit 20
4084 match community cm-set-no-export
4087 route-map rm-community-in permit 30
4088 match community cme-prefmod-range
4090 route-map rm-community-in permit 40
4092 ! #####################################################################
4093 ! Community actions to take when advertising a route.
4094 ! These are filtering route-maps,
4096 ! Deny customer routes to upstream with cust-only set.
4097 route-map rm-community-filt-to-upstream deny 10
4098 match community cm-learnt-cust
4099 match community cm-cust-only
4100 route-map rm-community-filt-to-upstream permit 20
4102 ! Deny customer routes to other customers with upstream-only set.
4103 route-map rm-community-filt-to-cust deny 10
4104 match community cm-learnt-cust
4105 match community cm-upstream-only
4106 route-map rm-community-filt-to-cust permit 20
4108 ! ###################################################################
4109 ! The top-level route-maps applied to sessions. Further entries could
4110 ! be added obviously..
4113 route-map rm-cust-in permit 10
4114 call rm-community-in
4116 route-map rm-cust-in permit 20
4117 set community additive 64512:3100
4118 route-map rm-cust-in permit 30
4120 route-map rm-cust-out permit 10
4121 call rm-community-filt-to-cust
4123 route-map rm-cust-out permit 20
4125 ! Upstream transit ASes
4126 route-map rm-upstream-out permit 10
4127 description filter customer prefixes which are marked cust-only
4128 call rm-community-filt-to-upstream
4130 route-map rm-upstream-out permit 20
4131 description only customer routes are provided to upstreams/peers
4132 match community cm-learnt-cust
4135 ! outbound policy is same as for upstream
4136 route-map rm-peer-out permit 10
4137 call rm-upstream-out
4139 route-map rm-peer-in permit 10
4140 set community additive 64512:3200
4143 Example of how to set up a 6-Bone connection.
4147 ! bgpd configuration
4148 ! ==================
4150 ! MP-BGP configuration
4153 bgp router-id 10.0.0.1
4154 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as `as-number`
4157 network 3ffe:506::/32
4158 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
4159 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
4160 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as `as-number`
4161 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
4164 ipv6 access-list all permit any
4166 ! Set output nexthop address.
4168 route-map set-nexthop permit 10
4169 match ipv6 address all
4170 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
4171 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
4180 TCP provides a mechanism for the user to specify the max segment size.
4181 setsockopt API is used to set the max segment size for TCP session. We
4182 can configure this as part of BGP neighbor configuration.
4184 This document explains how to avoid ICMP vulnerability issues by limiting
4185 TCP max segment size when you are using MTU discovery. Using MTU discovery
4186 on TCP paths is one method of avoiding BGP packet fragmentation.
4188 TCP negotiates a maximum segment size (MSS) value during session connection
4189 establishment between two peers. The MSS value negotiated is primarily based
4190 on the maximum transmission unit (MTU) of the interfaces to which the
4191 communicating peers are directly connected. However, due to variations in
4192 link MTU on the path taken by the TCP packets, some packets in the network
4193 that are well within the MSS value might be fragmented when the packet size
4194 exceeds the link's MTU.
4196 This feature is supported with TCP over IPv4 and TCP over IPv6.
4200 Below configuration can be done in router bgp mode and allows the user to
4201 configure the tcp-mss value per neighbor. The configuration gets applied
4202 only after hard reset is performed on that neighbor. If we configure tcp-mss
4203 on both the neighbors then both neighbors need to be reset.
4205 The configuration takes effect based on below rules, so there is a configured
4206 tcp-mss and a synced tcp-mss value per TCP session.
4208 By default if the configuration is not done then the TCP max segment size is
4209 set to the Maximum Transmission unit (MTU) – (IP/IP6 header size + TCP header
4210 size + ethernet header). For IPv4 its MTU – (20 bytes IP header + 20 bytes TCP
4211 header + 12 bytes ethernet header) and for IPv6 its MTU – (40 bytes IPv6 header
4212 + 20 bytes TCP header + 12 bytes ethernet header).
4214 If the config is done then it reduces 12-14 bytes for the ether header and
4215 uses it after synchronizing in TCP handshake.
4217 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> tcp-mss (1-65535)
4219 When tcp-mss is configured kernel reduces 12-14 bytes for ethernet header.
4220 E.g. if tcp-mss is configured as 150 the synced value will be 138.
4222 Note: configured and synced value is different since TCP module will reduce
4223 12 bytes for ethernet header.
4230 frr# show running-config
4231 Building configuration...
4233 Current configuration:
4236 bgp router-id 192.0.2.1
4237 neighbor 198.51.100.2 remote-as 100
4238 neighbor 198.51.100.2 tcp-mss 150 => new entry
4239 neighbor 2001:DB8::2 remote-as 100
4240 neighbor 2001:DB8::2 tcp-mss 400 => new entry
4247 frr# show bgp neighbors 198.51.100.2
4248 BGP neighbor is 198.51.100.2, remote AS 100, local AS 100, internal link
4250 BGP version 4, remote router ID 192.0.2.2, local router ID 192.0.2.1
4251 BGP state = Established, up for 02:15:28
4252 Last read 00:00:28, Last write 00:00:28
4253 Hold time is 180, keepalive interval is 60 seconds
4254 Configured tcp-mss is 150, synced tcp-mss is 138 => new display
4258 frr# show bgp neighbors 2001:DB8::2
4259 BGP neighbor is 2001:DB8::2, remote AS 100, local AS 100, internal link
4261 BGP version 4, remote router ID 192.0.2.2, local router ID 192.0.2.1
4262 BGP state = Established, up for 02:16:34
4263 Last read 00:00:34, Last write 00:00:34
4264 Hold time is 180, keepalive interval is 60 seconds
4265 Configured tcp-mss is 400, synced tcp-mss is 388 => new display
4267 Show command json output:
4268 -------------------------
4272 frr# show bgp neighbors 2001:DB8::2 json
4277 "nbrInternalLink":true,
4280 "remoteRouterId":"192.0.2.2",
4281 "localRouterId":"192.0.2.1",
4282 "bgpState":"Established",
4283 "bgpTimerUpMsec":8349000,
4284 "bgpTimerUpString":"02:19:09",
4285 "bgpTimerUpEstablishedEpoch":1613054251,
4286 "bgpTimerLastRead":9000,
4287 "bgpTimerLastWrite":9000,
4288 "bgpInUpdateElapsedTimeMsecs":8347000,
4289 "bgpTimerHoldTimeMsecs":180000,
4290 "bgpTimerKeepAliveIntervalMsecs":60000,
4291 "bgpTcpMssConfigured":400, => new entry
4292 "bgpTcpMssSynced":388, => new entry
4296 frr# show bgp neighbors 198.51.100.2 json
4301 "nbrInternalLink":true,
4304 "remoteRouterId":"192.0.2.2",
4305 "localRouterId":"192.0.2.1",
4306 "bgpState":"Established",
4307 "bgpTimerUpMsec":8370000,
4308 "bgpTimerUpString":"02:19:30",
4309 "bgpTimerUpEstablishedEpoch":1613054251,
4310 "bgpTimerLastRead":30000,
4311 "bgpTimerLastWrite":30000,
4312 "bgpInUpdateElapsedTimeMsecs":8368000,
4313 "bgpTimerHoldTimeMsecs":180000,
4314 "bgpTimerKeepAliveIntervalMsecs":60000,
4315 "bgpTcpMssConfigured":150, => new entry
4316 "bgpTcpMssSynced":138, => new entry
4318 .. include:: routeserver.rst
4320 .. include:: rpki.rst
4322 .. include:: wecmp_linkbw.rst
4324 .. include:: flowspec.rst
4326 .. [#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)
4327 .. [bgp-route-osci-cond] McPherson, D. and Gill, V. and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", IETF RFC3345
4328 .. [stable-flexible-ibgp] Flavel, A. and M. Roughan, "Stable and flexible iBGP", ACM SIGCOMM 2009
4329 .. [ibgp-correctness] Griffin, T. and G. Wilfong, "On the correctness of IBGP configuration", ACM SIGCOMM 2002