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 If ``bgp bestpath aigp`` is enabled, and both paths that are compared have
152 AIGP attribute, BGP uses AIGP tie-breaking unless both of the paths have the
153 AIGP metric attribute. This means that the AIGP attribute is not evaluated
154 during the best path selection process between two paths when one path does
155 not have the AIGP attribute.
157 3. **Local route check**
159 Prefer local routes (statics, aggregates, redistributed) to received routes.
161 4. **AS path length check**
163 Prefer shortest hop-count AS_PATHs.
167 Prefer the lowest origin type route. That is, prefer IGP origin routes to
168 EGP, to Incomplete routes.
172 Where routes with a MED were received from the same AS, prefer the route
173 with the lowest MED. :ref:`bgp-med`.
175 7. **External check**
177 Prefer the route received from an external, eBGP peer over routes received
178 from other types of peers.
180 8. **IGP cost check**
182 Prefer the route with the lower IGP cost.
184 9. **Multi-path check**
186 If multi-pathing is enabled, then check whether the routes not yet
187 distinguished in preference may be considered equal. If
188 :clicmd:`bgp bestpath as-path multipath-relax` is set, all such routes are
189 considered equal, otherwise routes received via iBGP with identical AS_PATHs
190 or routes received from eBGP neighbours in the same AS are considered equal.
192 10. **Already-selected external check**
194 Where both routes were received from eBGP peers, then prefer the route
195 which is already selected. Note that this check is not applied if
196 :clicmd:`bgp bestpath compare-routerid` is configured. This check can
197 prevent some cases of oscillation.
199 11. **Router-ID check**
201 Prefer the route with the lowest `router-ID`. If the route has an
202 `ORIGINATOR_ID` attribute, through iBGP reflection, then that router ID is
203 used, otherwise the `router-ID` of the peer the route was received from is
206 12. **Cluster-List length check**
208 The route with the shortest cluster-list length is used. The cluster-list
209 reflects the iBGP reflection path the route has taken.
213 Prefer the route received from the peer with the higher transport layer
214 address, as a last-resort tie-breaker.
216 .. _bgp-capability-negotiation:
218 Capability Negotiation
219 ----------------------
221 When adding IPv6 routing information exchange feature to BGP. There were some
222 proposals. :abbr:`IETF (Internet Engineering Task Force)`
223 :abbr:`IDR (Inter Domain Routing)` adopted a proposal called Multiprotocol
224 Extension for BGP. The specification is described in :rfc:`2283`. The protocol
225 does not define new protocols. It defines new attributes to existing BGP. When
226 it is used exchanging IPv6 routing information it is called BGP-4+. When it is
227 used for exchanging multicast routing information it is called MBGP.
229 *bgpd* supports Multiprotocol Extension for BGP. So if a remote peer supports
230 the protocol, *bgpd* can exchange IPv6 and/or multicast routing information.
232 Traditional BGP did not have the feature to detect a remote peer's
233 capabilities, e.g. whether it can handle prefix types other than IPv4 unicast
234 routes. This was a big problem using Multiprotocol Extension for BGP in an
235 operational network. :rfc:`2842` adopted a feature called Capability
236 Negotiation. *bgpd* use this Capability Negotiation to detect the remote peer's
237 capabilities. If a peer is only configured as an IPv4 unicast neighbor, *bgpd*
238 does not send these Capability Negotiation packets (at least not unless other
239 optional BGP features require capability negotiation).
241 By default, FRR will bring up peering with minimal common capability for the
242 both sides. For example, if the local router has unicast and multicast
243 capabilities and the remote router only has unicast capability the local router
244 will establish the connection with unicast only capability. When there are no
245 common capabilities, FRR sends Unsupported Capability error and then resets the
248 .. _bgp-router-configuration:
250 BGP Router Configuration
251 ========================
256 First of all you must configure BGP router with the :clicmd:`router bgp ASN`
257 command. The AS number is an identifier for the autonomous system. The AS
258 identifier can either be a number or two numbers separated by a period. The
259 BGP protocol uses the AS identifier for detecting whether the BGP connection is
260 internal or external.
262 .. clicmd:: router bgp ASN
264 Enable a BGP protocol process with the specified ASN. After
265 this statement you can input any `BGP Commands`.
267 .. clicmd:: bgp router-id A.B.C.D
269 This command specifies the router-ID. If *bgpd* connects to *zebra* it gets
270 interface and address information. In that case default router ID value is
271 selected as the largest IP Address of the interfaces. When `router zebra` is
272 not enabled *bgpd* can't get interface information so `router-id` is set to
273 0.0.0.0. So please set router-id by hand.
276 .. _bgp-multiple-autonomous-systems:
278 Multiple Autonomous Systems
279 ---------------------------
281 FRR's BGP implementation is capable of running multiple autonomous systems at
282 once. Each configured AS corresponds to a :ref:`zebra-vrf`. In the past, to get
283 the same functionality the network administrator had to run a new *bgpd*
284 process; using VRFs allows multiple autonomous systems to be handled in a
287 When using multiple autonomous systems, all router config blocks after the
288 first one must specify a VRF to be the target of BGP's route selection. This
289 VRF must be unique within respect to all other VRFs being used for the same
290 purpose, i.e. two different autonomous systems cannot use the same VRF.
291 However, the same AS can be used with different VRFs.
295 The separated nature of VRFs makes it possible to peer a single *bgpd*
296 process to itself, on one machine. Note that this can be done fully within
297 BGP without a corresponding VRF in the kernel or Zebra, which enables some
298 practical use cases such as :ref:`route reflectors <bgp-route-reflector>`
301 Configuration of additional autonomous systems, or of a router that targets a
302 specific VRF, is accomplished with the following command:
304 .. clicmd:: router bgp ASN vrf VRFNAME
306 ``VRFNAME`` is matched against VRFs configured in the kernel. When ``vrf
307 VRFNAME`` is not specified, the BGP protocol process belongs to the default
310 An example configuration with multiple autonomous systems might look like this:
315 neighbor 10.0.0.1 remote-as 20
316 neighbor 10.0.0.2 remote-as 30
318 router bgp 2 vrf blue
319 neighbor 10.0.0.3 remote-as 40
320 neighbor 10.0.0.4 remote-as 50
323 neighbor 10.0.0.5 remote-as 60
324 neighbor 10.0.0.6 remote-as 70
327 .. seealso:: :ref:`bgp-vrf-route-leaking`
328 .. seealso:: :ref:`zebra-vrf`
336 In addition to supporting multiple autonomous systems, FRR's BGP implementation
337 also supports *views*.
339 BGP views are almost the same as normal BGP processes, except that routes
340 selected by BGP are not installed into the kernel routing table. Each BGP view
341 provides an independent set of routing information which is only distributed
342 via BGP. Multiple views can be supported, and BGP view information is always
343 independent from other routing protocols and Zebra/kernel routes. BGP views use
344 the core instance (i.e., default VRF) for communication with peers.
346 .. clicmd:: router bgp AS-NUMBER view NAME
348 Make a new BGP view. You can use an arbitrary word for the ``NAME``. Routes
349 selected by the view are not installed into the kernel routing table.
351 With this command, you can setup Route Server like below.
357 neighbor 10.0.0.1 remote-as 2
358 neighbor 10.0.0.2 remote-as 3
361 neighbor 10.0.0.3 remote-as 4
362 neighbor 10.0.0.4 remote-as 5
364 .. clicmd:: show [ip] bgp view NAME
366 Display the routing table of BGP view ``NAME``.
372 .. clicmd:: bgp bestpath as-path confed
374 This command specifies that the length of confederation path sets and
375 sequences should should be taken into account during the BGP best path
378 .. clicmd:: bgp bestpath as-path multipath-relax
380 This command specifies that BGP decision process should consider paths
381 of equal AS_PATH length candidates for multipath computation. Without
382 the knob, the entire AS_PATH must match for multipath computation.
384 .. clicmd:: bgp bestpath compare-routerid
386 Ensure that when comparing routes where both are equal on most metrics,
387 including local-pref, AS_PATH length, IGP cost, MED, that the tie is broken
390 If this option is enabled, then the already-selected check, where
391 already selected eBGP routes are preferred, is skipped.
393 If a route has an `ORIGINATOR_ID` attribute because it has been reflected,
394 that `ORIGINATOR_ID` will be used. Otherwise, the router-ID of the peer the
395 route was received from will be used.
397 The advantage of this is that the route-selection (at this point) will be
398 more deterministic. The disadvantage is that a few or even one lowest-ID
399 router may attract all traffic to otherwise-equal paths because of this
400 check. It may increase the possibility of MED or IGP oscillation, unless
401 other measures were taken to avoid these. The exact behaviour will be
402 sensitive to the iBGP and reflection topology.
404 .. clicmd:: bgp bestpath peer-type multipath-relax
406 This command specifies that BGP decision process should consider paths
407 from all peers for multipath computation. If this option is enabled,
408 paths learned from any of eBGP, iBGP, or confederation neighbors will
409 be multipath if they are otherwise considered equal cost.
411 .. clicmd:: bgp bestpath aigp
413 Use the bgp bestpath aigp command to evaluate the AIGP attribute during
414 the best path selection process between two paths that have the AIGP
417 When bgp bestpath aigp is disabled, BGP does not use AIGP tie-breaking
418 rules unless paths have the AIGP attribute.
422 .. clicmd:: maximum-paths (1-128)
424 Sets the maximum-paths value used for ecmp calculations for this
425 bgp instance in EBGP. The maximum value listed, 128, can be limited by
426 the ecmp cli for bgp or if the daemon was compiled with a lower
427 ecmp value. This value can also be set in ipv4/ipv6 unicast/labeled
428 unicast to only affect those particular afi/safi's.
430 .. clicmd:: maximum-paths ibgp (1-128) [equal-cluster-length]
432 Sets the maximum-paths value used for ecmp calculations for this
433 bgp instance in IBGP. The maximum value listed, 128, can be limited by
434 the ecmp cli for bgp or if the daemon was compiled with a lower
435 ecmp value. This value can also be set in ipv4/ipv6 unicast/labeled
436 unicast to only affect those particular afi/safi's.
440 Administrative Distance Metrics
441 -------------------------------
443 .. clicmd:: distance bgp (1-255) (1-255) (1-255)
445 This command changes distance value of BGP. The arguments are the distance
446 values for external routes, internal routes and local routes
449 .. clicmd:: distance (1-255) A.B.C.D/M
451 .. clicmd:: distance (1-255) A.B.C.D/M WORD
453 Sets the administrative distance for a particular route.
455 .. _bgp-requires-policy:
457 Require policy on EBGP
458 -------------------------------
460 .. clicmd:: bgp ebgp-requires-policy
462 This command requires incoming and outgoing filters to be applied
463 for eBGP sessions as part of RFC-8212 compliance. Without the incoming
464 filter, no routes will be accepted. Without the outgoing filter, no
465 routes will be announced.
467 This is enabled by default for the traditional configuration and
468 turned off by default for datacenter configuration.
470 When you enable/disable this option you MUST clear the session.
472 When the incoming or outgoing filter is missing you will see
473 "(Policy)" sign under ``show bgp summary``:
477 exit1# show bgp summary
479 IPv4 Unicast Summary (VRF default):
480 BGP router identifier 10.10.10.1, local AS number 65001 vrf-id 0
482 RIB entries 7, using 1344 bytes of memory
483 Peers 2, using 43 KiB of memory
485 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
486 192.168.0.2 4 65002 8 10 0 0 0 00:03:09 5 (Policy) N/A
487 fe80:1::2222 4 65002 9 11 0 0 0 00:03:09 (Policy) (Policy) N/A
489 Additionally a `show bgp neighbor` command would indicate in the `For address family:`
494 exit1# show bgp neighbor
496 For address family: IPv4 Unicast
497 Update group 1, subgroup 1
498 Packet Queue length 0
499 Inbound soft reconfiguration allowed
500 Community attribute sent to this neighbor(all)
501 Inbound updates discarded due to missing policy
502 Outbound updates discarded due to missing policy
505 Reject routes with AS_SET or AS_CONFED_SET types
506 ------------------------------------------------
508 .. clicmd:: bgp reject-as-sets
510 This command enables rejection of incoming and outgoing routes having AS_SET or AS_CONFED_SET type.
512 Suppress duplicate updates
513 --------------------------
515 .. clicmd:: bgp suppress-duplicates
517 For example, BGP routers can generate multiple identical announcements with
518 empty community attributes if stripped at egress. This is an undesired behavior.
519 Suppress duplicate updates if the route actually not changed.
522 Send Hard Reset CEASE Notification for Administrative Reset
523 -----------------------------------------------------------
525 .. clicmd:: bgp hard-administrative-reset
527 Send Hard Reset CEASE Notification for 'Administrative Reset' events.
529 When disabled, and Graceful Restart Notification capability is exchanged
530 between the peers, Graceful Restart procedures apply, and routes will be
535 Disable checking if nexthop is connected on EBGP sessions
536 ---------------------------------------------------------
538 .. clicmd:: bgp disable-ebgp-connected-route-check
540 This command is used to disable the connection verification process for EBGP peering sessions
541 that are reachable by a single hop but are configured on a loopback interface or otherwise
542 configured with a non-directly connected IP address.
544 .. _bgp-route-flap-dampening:
549 .. clicmd:: bgp dampening (1-45) (1-20000) (1-50000) (1-255)
551 This command enables BGP route-flap dampening and specifies dampening parameters.
554 Half-life time for the penalty
557 Value to start reusing a route
560 Value to start suppressing a route
563 Maximum duration to suppress a stable route
565 The route-flap damping algorithm is compatible with :rfc:`2439`. The use of
566 this command is not recommended nowadays.
568 At the moment, route-flap dampening is not working per VRF and is working only
569 for IPv4 unicast and multicast.
572 https://www.ripe.net/publications/docs/ripe-378
576 Multi-Exit Discriminator
577 ------------------------
579 The BGP :abbr:`MED (Multi-Exit Discriminator)` attribute has properties which
580 can cause subtle convergence problems in BGP. These properties and problems
581 have proven to be hard to understand, at least historically, and may still not
582 be widely understood. The following attempts to collect together and present
583 what is known about MED, to help operators and FRR users in designing and
584 configuring their networks.
586 The BGP :abbr:`MED` attribute is intended to allow one AS to indicate its
587 preferences for its ingress points to another AS. The MED attribute will not be
588 propagated on to another AS by the receiving AS - it is 'non-transitive' in the
591 E.g., if AS X and AS Y have 2 different BGP peering points, then AS X might set
592 a MED of 100 on routes advertised at one and a MED of 200 at the other. When AS
593 Y selects between otherwise equal routes to or via AS X, AS Y should prefer to
594 take the path via the lower MED peering of 100 with AS X. Setting the MED
595 allows an AS to influence the routing taken to it within another, neighbouring
598 In this use of MED it is not really meaningful to compare the MED value on
599 routes where the next AS on the paths differs. E.g., if AS Y also had a route
600 for some destination via AS Z in addition to the routes from AS X, and AS Z had
601 also set a MED, it wouldn't make sense for AS Y to compare AS Z's MED values to
602 those of AS X. The MED values have been set by different administrators, with
603 different frames of reference.
605 The default behaviour of BGP therefore is to not compare MED values across
606 routes received from different neighbouring ASes. In FRR this is done by
607 comparing the neighbouring, left-most AS in the received AS_PATHs of the routes
608 and only comparing MED if those are the same.
610 Unfortunately, this behaviour of MED, of sometimes being compared across routes
611 and sometimes not, depending on the properties of those other routes, means MED
612 can cause the order of preference over all the routes to be undefined. That is,
613 given routes A, B, and C, if A is preferred to B, and B is preferred to C, then
614 a well-defined order should mean the preference is transitive (in the sense of
615 orders [#med-transitivity-rant]_) and that A would be preferred to C.
617 However, when MED is involved this need not be the case. With MED it is
618 possible that C is actually preferred over A. So A is preferred to B, B is
619 preferred to C, but C is preferred to A. This can be true even where BGP
620 defines a deterministic 'most preferred' route out of the full set of A,B,C.
621 With MED, for any given set of routes there may be a deterministically
622 preferred route, but there need not be any way to arrange them into any order
623 of preference. With unmodified MED, the order of preference of routes literally
626 That MED can induce non-transitive preferences over routes can cause issues.
627 Firstly, it may be perceived to cause routing table churn locally at speakers;
628 secondly, and more seriously, it may cause routing instability in iBGP
629 topologies, where sets of speakers continually oscillate between different
632 The first issue arises from how speakers often implement routing decisions.
633 Though BGP defines a selection process that will deterministically select the
634 same route as best at any given speaker, even with MED, that process requires
635 evaluating all routes together. For performance and ease of implementation
636 reasons, many implementations evaluate route preferences in a pair-wise fashion
637 instead. Given there is no well-defined order when MED is involved, the best
638 route that will be chosen becomes subject to implementation details, such as
639 the order the routes are stored in. That may be (locally) non-deterministic,
640 e.g.: it may be the order the routes were received in.
642 This indeterminism may be considered undesirable, though it need not cause
643 problems. It may mean additional routing churn is perceived, as sometimes more
644 updates may be produced than at other times in reaction to some event .
646 This first issue can be fixed with a more deterministic route selection that
647 ensures routes are ordered by the neighbouring AS during selection.
648 :clicmd:`bgp deterministic-med`. This may reduce the number of updates as routes
649 are received, and may in some cases reduce routing churn. Though, it could
650 equally deterministically produce the largest possible set of updates in
651 response to the most common sequence of received updates.
653 A deterministic order of evaluation tends to imply an additional overhead of
654 sorting over any set of n routes to a destination. The implementation of
655 deterministic MED in FRR scales significantly worse than most sorting
656 algorithms at present, with the number of paths to a given destination. That
657 number is often low enough to not cause any issues, but where there are many
658 paths, the deterministic comparison may quickly become increasingly expensive
661 Deterministic local evaluation can *not* fix the second, more major, issue of
662 MED however. Which is that the non-transitive preference of routes MED can
663 cause may lead to routing instability or oscillation across multiple speakers
664 in iBGP topologies. This can occur with full-mesh iBGP, but is particularly
665 problematic in non-full-mesh iBGP topologies that further reduce the routing
666 information known to each speaker. This has primarily been documented with iBGP
667 :ref:`route-reflection <bgp-route-reflector>` topologies. However, any
668 route-hiding technologies potentially could also exacerbate oscillation with MED.
670 This second issue occurs where speakers each have only a subset of routes, and
671 there are cycles in the preferences between different combinations of routes -
672 as the undefined order of preference of MED allows - and the routes are
673 distributed in a way that causes the BGP speakers to 'chase' those cycles. This
674 can occur even if all speakers use a deterministic order of evaluation in route
677 E.g., speaker 4 in AS A might receive a route from speaker 2 in AS X, and from
678 speaker 3 in AS Y; while speaker 5 in AS A might receive that route from
679 speaker 1 in AS Y. AS Y might set a MED of 200 at speaker 1, and 100 at speaker
680 3. I.e, using ASN:ID:MED to label the speakers:
686 X:2------|--A:4-------A:5--|-Y:1:200
692 Assuming all other metrics are equal (AS_PATH, ORIGIN, 0 IGP costs), then based
693 on the RFC4271 decision process speaker 4 will choose X:2 over Y:3:100, based
694 on the lower ID of 2. Speaker 4 advertises X:2 to speaker 5. Speaker 5 will
695 continue to prefer Y:1:200 based on the ID, and advertise this to speaker 4.
696 Speaker 4 will now have the full set of routes, and the Y:1:200 it receives
697 from 5 will beat X:2, but when speaker 4 compares Y:1:200 to Y:3:100 the MED
698 check now becomes active as the ASes match, and now Y:3:100 is preferred.
699 Speaker 4 therefore now advertises Y:3:100 to 5, which will also agrees that
700 Y:3:100 is preferred to Y:1:200, and so withdraws the latter route from 4.
701 Speaker 4 now has only X:2 and Y:3:100, and X:2 beats Y:3:100, and so speaker 4
702 implicitly updates its route to speaker 5 to X:2. Speaker 5 sees that Y:1:200
703 beats X:2 based on the ID, and advertises Y:1:200 to speaker 4, and the cycle
706 The root cause is the lack of a clear order of preference caused by how MED
707 sometimes is and sometimes is not compared, leading to this cycle in the
708 preferences between the routes:
713 /---> X:2 ---beats---> Y:3:100 --\\
716 \\---beats--- Y:1:200 <---beats---/
720 This particular type of oscillation in full-mesh iBGP topologies can be
721 avoided by speakers preferring already selected, external routes rather than
722 choosing to update to new a route based on a post-MED metric (e.g. router-ID),
723 at the cost of a non-deterministic selection process. FRR implements this, as
724 do many other implementations, so long as it is not overridden by setting
725 :clicmd:`bgp bestpath compare-routerid`, and see also
726 :ref:`bgp-route-selection`.
728 However, more complex and insidious cycles of oscillation are possible with
729 iBGP route-reflection, which are not so easily avoided. These have been
730 documented in various places. See, e.g.:
732 - [bgp-route-osci-cond]_
733 - [stable-flexible-ibgp]_
734 - [ibgp-correctness]_
736 for concrete examples and further references.
738 There is as of this writing *no* known way to use MED for its original purpose;
739 *and* reduce routing information in iBGP topologies; *and* be sure to avoid the
740 instability problems of MED due the non-transitive routing preferences it can
741 induce; in general on arbitrary networks.
743 There may be iBGP topology specific ways to reduce the instability risks, even
744 while using MED, e.g.: by constraining the reflection topology and by tuning
745 IGP costs between route-reflector clusters, see :rfc:`3345` for details. In the
746 near future, the Add-Path extension to BGP may also solve MED oscillation while
747 still allowing MED to be used as intended, by distributing "best-paths per
748 neighbour AS". This would be at the cost of distributing at least as many
749 routes to all speakers as a full-mesh iBGP would, if not more, while also
750 imposing similar CPU overheads as the "Deterministic MED" feature at each
753 More generally, the instability problems that MED can introduce on more
754 complex, non-full-mesh, iBGP topologies may be avoided either by:
756 - Setting :clicmd:`bgp always-compare-med`, however this allows MED to be compared
757 across values set by different neighbour ASes, which may not produce
758 coherent desirable results, of itself.
759 - Effectively ignoring MED by setting MED to the same value (e.g.: 0) using
760 :clicmd:`set metric METRIC` on all received routes, in combination with
761 setting :clicmd:`bgp always-compare-med` on all speakers. This is the simplest
762 and most performant way to avoid MED oscillation issues, where an AS is happy
763 not to allow neighbours to inject this problematic metric.
765 As MED is evaluated after the AS_PATH length check, another possible use for
766 MED is for intra-AS steering of routes with equal AS_PATH length, as an
767 extension of the last case above. As MED is evaluated before IGP metric, this
768 can allow cold-potato routing to be implemented to send traffic to preferred
769 hand-offs with neighbours, rather than the closest hand-off according to the
772 Note that even if action is taken to address the MED non-transitivity issues,
773 other oscillations may still be possible. E.g., on IGP cost if iBGP and IGP
774 topologies are at cross-purposes with each other - see the Flavel and Roughan
775 paper above for an example. Hence the guideline that the iBGP topology should
776 follow the IGP topology.
778 .. clicmd:: bgp deterministic-med
780 Carry out route-selection in way that produces deterministic answers
781 locally, even in the face of MED and the lack of a well-defined order of
782 preference it can induce on routes. Without this option the preferred route
783 with MED may be determined largely by the order that routes were received
786 Setting this option will have a performance cost that may be noticeable when
787 there are many routes for each destination. Currently in FRR it is
788 implemented in a way that scales poorly as the number of routes per
789 destination increases.
791 The default is that this option is not set.
793 Note that there are other sources of indeterminism in the route selection
794 process, specifically, the preference for older and already selected routes
795 from eBGP peers, :ref:`bgp-route-selection`.
797 .. clicmd:: bgp always-compare-med
799 Always compare the MED on routes, even when they were received from
800 different neighbouring ASes. Setting this option makes the order of
801 preference of routes more defined, and should eliminate MED induced
804 If using this option, it may also be desirable to use
805 :clicmd:`set metric METRIC` to set MED to 0 on routes received from external
808 This option can be used, together with :clicmd:`set metric METRIC` to use
809 MED as an intra-AS metric to steer equal-length AS_PATH routes to, e.g.,
813 .. _bgp-graceful-restart:
818 BGP graceful restart functionality as defined in
819 `RFC-4724 <https://tools.ietf.org/html/rfc4724/>`_ defines the mechanisms that
820 allows BGP speaker to continue to forward data packets along known routes
821 while the routing protocol information is being restored.
824 Usually, when BGP on a router restarts, all the BGP peers detect that the
825 session went down and then came up. This "down/up" transition results in a
826 "routing flap" and causes BGP route re-computation, generation of BGP routing
827 updates, and unnecessary churn to the forwarding tables.
829 The following functionality is provided by graceful restart:
831 1. The feature allows the restarting router to indicate to the helping peer the
832 routes it can preserve in its forwarding plane during control plane restart
833 by sending graceful restart capability in the OPEN message sent during
834 session establishment.
835 2. The feature allows helping router to advertise to all other peers the routes
836 received from the restarting router which are preserved in the forwarding
837 plane of the restarting router during control plane restart.
844 (R1)-----------------------------------------------------------------(R2)
846 1. BGP Graceful Restart Capability exchanged between R1 & R2.
848 <--------------------------------------------------------------------->
850 2. Kill BGP Process at R1.
852 ---------------------------------------------------------------------->
854 3. R2 Detects the above BGP Restart & verifies BGP Restarting
857 4. Start BGP Process at R1.
859 5. Re-establish the BGP session between R1 & R2.
861 <--------------------------------------------------------------------->
863 6. R2 Send initial route updates, followed by End-Of-Rib.
865 <----------------------------------------------------------------------
867 7. R1 was waiting for End-Of-Rib from R2 & which has been received
870 8. R1 now runs BGP Best-Path algorithm. Send Initial BGP Update,
871 followed by End-Of Rib
873 <--------------------------------------------------------------------->
876 .. _bgp-GR-preserve-forwarding-state:
878 BGP-GR Preserve-Forwarding State
879 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
881 BGP OPEN message carrying optional capabilities for Graceful Restart has
882 8 bit “Flags for Address Family” for given AFI and SAFI. This field contains
883 bit flags relating to routes that were advertised with the given AFI and SAFI.
892 The most significant bit is defined as the Forwarding State (F) bit, which
893 can be used to indicate whether the forwarding state for routes that were
894 advertised with the given AFI and SAFI has indeed been preserved during the
895 previous BGP restart. When set (value 1), the bit indicates that the
896 forwarding state has been preserved.
897 The remaining bits are reserved and MUST be set to zero by the sender and
898 ignored by the receiver.
900 .. clicmd:: bgp graceful-restart preserve-fw-state
902 FRR gives us the option to enable/disable the "F" flag using this specific
903 vty command. However, it doesn't have the option to enable/disable
904 this flag only for specific AFI/SAFI i.e. when this command is used, it
905 applied to all the supported AFI/SAFI combinations for this peer.
907 .. _bgp-end-of-rib-message:
909 End-of-RIB (EOR) message
910 ^^^^^^^^^^^^^^^^^^^^^^^^
912 An UPDATE message with no reachable Network Layer Reachability Information
913 (NLRI) and empty withdrawn NLRI is specified as the End-of-RIB marker that can
914 be used by a BGP speaker to indicate to its peer the completion of the initial
915 routing update after the session is established.
917 For the IPv4 unicast address family, the End-of-RIB marker is an UPDATE message
918 with the minimum length. For any other address family, it is an UPDATE message
919 that contains only the MP_UNREACH_NLRI attribute with no withdrawn routes for
922 Although the End-of-RIB marker is specified for the purpose of BGP graceful
923 restart, it is noted that the generation of such a marker upon completion of
924 the initial update would be useful for routing convergence in general, and thus
925 the practice is recommended.
927 .. _bgp-route-selection-deferral-timer:
929 Route Selection Deferral Timer
930 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
932 Specifies the time the restarting router defers the route selection process
935 Restarting Router : The usage of route election deferral timer is specified
936 in https://tools.ietf.org/html/rfc4724#section-4.1
938 Once the session between the Restarting Speaker and the Receiving Speaker is
939 re-established, the Restarting Speaker will receive and process BGP messages
942 However, it MUST defer route selection for an address family until it either.
944 1. Receives the End-of-RIB marker from all its peers (excluding the ones with
945 the "Restart State" bit set in the received capability and excluding the ones
946 that do not advertise the graceful restart capability).
947 2. The Selection_Deferral_Timer timeout.
949 .. clicmd:: bgp graceful-restart select-defer-time (0-3600)
951 This is command, will set deferral time to value specified.
954 .. clicmd:: bgp graceful-restart rib-stale-time (1-3600)
956 This is command, will set the time for which stale routes are kept in RIB.
958 .. clicmd:: bgp graceful-restart restart-time (0-4095)
960 Set the time to wait to delete stale routes before a BGP open message
963 Using with Long-lived Graceful Restart capability, this is recommended
964 setting this timer to 0 and control stale routes with
965 ``bgp long-lived-graceful-restart stale-time``.
967 Default value is 120.
969 .. clicmd:: bgp graceful-restart stalepath-time (1-4095)
971 This is command, will set the max time (in seconds) to hold onto
972 restarting peer's stale paths.
974 It also controls Enhanced Route-Refresh timer.
976 If this command is configured and the router does not receive a Route-Refresh EoRR
977 message, the router removes the stale routes from the BGP table after the timer
978 expires. The stale path timer is started when the router receives a Route-Refresh
981 .. clicmd:: bgp graceful-restart notification
983 Indicate Graceful Restart support for BGP NOTIFICATION messages.
985 After changing this parameter, you have to reset the peers in order to advertise
986 N-bit in Graceful Restart capability.
988 Without Graceful-Restart Notification capability (N-bit not set), GR is not
989 activated when receiving CEASE/HOLDTIME expire notifications.
991 When sending ``CEASE/Administrative Reset`` (``clear bgp``), the session is closed
992 and routes are not retained. When N-bit is set and ``bgp hard-administrative-reset``
993 is turned off Graceful-Restart is activated and routes are retained.
997 .. _bgp-per-peer-graceful-restart:
999 BGP Per Peer Graceful Restart
1000 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1002 Ability to enable and disable graceful restart, helper and no GR at all mode
1003 functionality at peer level.
1005 So bgp graceful restart can be enabled at modes global BGP level or at per
1006 peer level. There are two FSM, one for BGP GR global mode and other for peer
1009 Default global mode is helper and default peer per mode is inherit from global.
1010 If per peer mode is configured, the GR mode of this particular peer will
1011 override the global mode.
1013 .. _bgp-GR-global-mode-cmd:
1015 BGP GR Global Mode Commands
1016 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
1018 .. clicmd:: bgp graceful-restart
1020 This command will enable BGP graceful restart functionality at the global
1023 .. clicmd:: bgp graceful-restart disable
1025 This command will disable both the functionality graceful restart and helper
1029 .. _bgp-GR-peer-mode-cmd:
1031 BGP GR Peer Mode Commands
1032 ^^^^^^^^^^^^^^^^^^^^^^^^^
1034 .. clicmd:: neighbor A.B.C.D graceful-restart
1036 This command will enable BGP graceful restart functionality at the peer
1039 .. clicmd:: neighbor A.B.C.D graceful-restart-helper
1041 This command will enable BGP graceful restart helper only functionality
1044 .. clicmd:: neighbor A.B.C.D graceful-restart-disable
1046 This command will disable the entire BGP graceful restart functionality
1050 Long-lived Graceful Restart
1051 ---------------------------
1053 Currently, only restarter mode is supported. This capability is advertised only
1054 if graceful restart capability is negotiated.
1056 .. clicmd:: bgp long-lived-graceful-restart stale-time (1-16777215)
1058 Specifies the maximum time to wait before purging long-lived stale routes for
1061 Default is 0, which means the feature is off by default. Only graceful
1062 restart takes into account.
1066 Administrative Shutdown
1067 -----------------------
1069 .. clicmd:: bgp shutdown [message MSG...]
1071 Administrative shutdown of all peers of a bgp instance. Drop all BGP peers,
1072 but preserve their configurations. The peers are notified in accordance with
1073 `RFC 8203 <https://tools.ietf.org/html/rfc8203/>`_ by sending a
1074 ``NOTIFICATION`` message with error code ``Cease`` and subcode
1075 ``Administrative Shutdown`` prior to terminating connections. This global
1076 shutdown is independent of the neighbor shutdown, meaning that individually
1077 shut down peers will not be affected by lifting it.
1079 An optional shutdown message `MSG` can be specified.
1087 .. clicmd:: network A.B.C.D/M
1089 This command adds the announcement network.
1094 address-family ipv4 unicast
1098 This configuration example says that network 10.0.0.0/8 will be
1099 announced to all neighbors. Some vendors' routers don't advertise
1100 routes if they aren't present in their IGP routing tables; `bgpd`
1101 doesn't care about IGP routes when announcing its routes.
1104 .. clicmd:: bgp network import-check
1106 This configuration modifies the behavior of the network statement.
1107 If you have this configured the underlying network must exist in
1108 the rib. If you have the [no] form configured then BGP will not
1109 check for the networks existence in the rib. For versions 7.3 and
1110 before frr defaults for datacenter were the network must exist,
1111 traditional did not check for existence. For versions 7.4 and beyond
1112 both traditional and datacenter the network must exist.
1114 .. _bgp-ipv6-support:
1119 .. clicmd:: neighbor A.B.C.D activate
1121 This configuration modifies whether to enable an address family for a
1122 specific neighbor. By default only the IPv4 unicast address family is
1128 address-family ipv6 unicast
1129 neighbor 2001:0DB8::1 activate
1130 network 2001:0DB8:5009::/64
1133 This configuration example says that network 2001:0DB8:5009::/64 will be
1134 announced and enables the neighbor 2001:0DB8::1 to receive this announcement.
1136 By default, only the IPv4 unicast address family is announced to all
1137 neighbors. Using the 'no bgp default ipv4-unicast' configuration overrides
1138 this default so that all address families need to be enabled explicitly.
1143 no bgp default ipv4-unicast
1144 neighbor 10.10.10.1 remote-as 2
1145 neighbor 2001:0DB8::1 remote-as 3
1146 address-family ipv4 unicast
1147 neighbor 10.10.10.1 activate
1148 network 192.168.1.0/24
1150 address-family ipv6 unicast
1151 neighbor 2001:0DB8::1 activate
1152 network 2001:0DB8:5009::/64
1155 This configuration demonstrates how the 'no bgp default ipv4-unicast' might
1156 be used in a setup with two upstreams where each of the upstreams should only
1157 receive either IPv4 or IPv6 announcements.
1159 Using the ``bgp default ipv6-unicast`` configuration, IPv6 unicast
1160 address family is enabled by default for all new neighbors.
1163 .. _bgp-route-aggregation:
1168 .. _bgp-route-aggregation-ipv4:
1170 Route Aggregation-IPv4 Address Family
1171 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1173 .. clicmd:: aggregate-address A.B.C.D/M
1175 This command specifies an aggregate address.
1177 In order to advertise an aggregated prefix, a more specific (longer) prefix
1178 MUST exist in the BGP table. For example, if you want to create an
1179 ``aggregate-address 10.0.0.0/24``, you should make sure you have something
1180 like ``10.0.0.5/32`` or ``10.0.0.0/26``, or any other smaller prefix in the
1181 BGP table. The routing information table (RIB) is not enough, you have to
1182 redistribute them into the BGP table.
1184 .. clicmd:: aggregate-address A.B.C.D/M route-map NAME
1186 Apply a route-map for an aggregated prefix.
1188 .. clicmd:: aggregate-address A.B.C.D/M origin <egp|igp|incomplete>
1190 Override ORIGIN for an aggregated prefix.
1192 .. clicmd:: aggregate-address A.B.C.D/M as-set
1194 This command specifies an aggregate address. Resulting routes include
1197 .. clicmd:: aggregate-address A.B.C.D/M summary-only
1199 This command specifies an aggregate address.
1201 Longer prefixes advertisements of more specific routes to all neighbors are suppressed.
1203 .. clicmd:: aggregate-address A.B.C.D/M matching-MED-only
1205 Configure the aggregated address to only be created when the routes MED
1206 match, otherwise no aggregated route will be created.
1208 .. clicmd:: aggregate-address A.B.C.D/M suppress-map NAME
1210 Similar to `summary-only`, but will only suppress more specific routes that
1211 are matched by the selected route-map.
1214 This configuration example sets up an ``aggregate-address`` under the ipv4
1220 address-family ipv4 unicast
1221 aggregate-address 10.0.0.0/8
1222 aggregate-address 20.0.0.0/8 as-set
1223 aggregate-address 40.0.0.0/8 summary-only
1224 aggregate-address 50.0.0.0/8 route-map aggr-rmap
1228 .. _bgp-route-aggregation-ipv6:
1230 Route Aggregation-IPv6 Address Family
1231 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1233 .. clicmd:: aggregate-address X:X::X:X/M
1235 This command specifies an aggregate address.
1237 .. clicmd:: aggregate-address X:X::X:X/M route-map NAME
1239 Apply a route-map for an aggregated prefix.
1241 .. clicmd:: aggregate-address X:X::X:X/M origin <egp|igp|incomplete>
1243 Override ORIGIN for an aggregated prefix.
1245 .. clicmd:: aggregate-address X:X::X:X/M as-set
1247 This command specifies an aggregate address. Resulting routes include
1250 .. clicmd:: aggregate-address X:X::X:X/M summary-only
1252 This command specifies an aggregate address.
1254 Longer prefixes advertisements of more specific routes to all neighbors are suppressed
1256 .. clicmd:: aggregate-address X:X::X:X/M matching-MED-only
1258 Configure the aggregated address to only be created when the routes MED
1259 match, otherwise no aggregated route will be created.
1261 .. clicmd:: aggregate-address X:X::X:X/M suppress-map NAME
1263 Similar to `summary-only`, but will only suppress more specific routes that
1264 are matched by the selected route-map.
1267 This configuration example sets up an ``aggregate-address`` under the ipv6
1273 address-family ipv6 unicast
1274 aggregate-address 10::0/64
1275 aggregate-address 20::0/64 as-set
1276 aggregate-address 40::0/64 summary-only
1277 aggregate-address 50::0/64 route-map aggr-rmap
1281 .. _bgp-redistribute-to-bgp:
1286 Redistribution configuration should be placed under the ``address-family``
1287 section for the specific AF to redistribute into. Protocol availability for
1288 redistribution is determined by BGP AF; for example, you cannot redistribute
1289 OSPFv3 into ``address-family ipv4 unicast`` as OSPFv3 supports IPv6.
1291 .. clicmd:: redistribute <babel|connected|eigrp|isis|kernel|openfabric|ospf|ospf6|rip|ripng|sharp|static|table> [metric (0-4294967295)] [route-map WORD]
1293 Redistribute routes from other protocols into BGP.
1295 .. clicmd:: redistribute vnc-direct
1297 Redistribute VNC direct (not via zebra) routes to BGP process.
1299 .. clicmd:: bgp update-delay MAX-DELAY
1301 .. clicmd:: bgp update-delay MAX-DELAY ESTABLISH-WAIT
1303 This feature is used to enable read-only mode on BGP process restart or when
1304 a BGP process is cleared using 'clear ip bgp \*'. Note that this command is
1305 configured at the global level and applies to all bgp instances/vrfs. It
1306 cannot be used at the same time as the "update-delay" command described below,
1307 which is entered in each bgp instance/vrf desired to delay update installation
1308 and advertisements. The global and per-vrf approaches to defining update-delay
1309 are mutually exclusive.
1311 When applicable, read-only mode would begin as soon as the first peer reaches
1312 Established status and a timer for max-delay seconds is started. During this
1313 mode BGP doesn't run any best-path or generate any updates to its peers. This
1314 mode continues until:
1316 1. All the configured peers, except the shutdown peers, have sent explicit EOR
1317 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
1318 Established is considered an implicit-EOR.
1319 If the establish-wait optional value is given, then BGP will wait for
1320 peers to reach established from the beginning of the update-delay till the
1321 establish-wait period is over, i.e. the minimum set of established peers for
1322 which EOR is expected would be peers established during the establish-wait
1323 window, not necessarily all the configured neighbors.
1324 2. max-delay period is over.
1326 On hitting any of the above two conditions, BGP resumes the decision process
1327 and generates updates to its peers.
1329 Default max-delay is 0, i.e. the feature is off by default.
1332 .. clicmd:: update-delay MAX-DELAY
1334 .. clicmd:: update-delay MAX-DELAY ESTABLISH-WAIT
1336 This feature is used to enable read-only mode on BGP process restart or when
1337 a BGP process is cleared using 'clear ip bgp \*'. Note that this command is
1338 configured under the specific bgp instance/vrf that the feature is enabled for.
1339 It cannot be used at the same time as the global "bgp update-delay" described
1340 above, which is entered at the global level and applies to all bgp instances.
1341 The global and per-vrf approaches to defining update-delay are mutually
1344 When applicable, read-only mode would begin as soon as the first peer reaches
1345 Established status and a timer for max-delay seconds is started. During this
1346 mode BGP doesn't run any best-path or generate any updates to its peers. This
1347 mode continues until:
1349 1. All the configured peers, except the shutdown peers, have sent explicit EOR
1350 (End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
1351 Established is considered an implicit-EOR.
1352 If the establish-wait optional value is given, then BGP will wait for
1353 peers to reach established from the beginning of the update-delay till the
1354 establish-wait period is over, i.e. the minimum set of established peers for
1355 which EOR is expected would be peers established during the establish-wait
1356 window, not necessarily all the configured neighbors.
1357 2. max-delay period is over.
1359 On hitting any of the above two conditions, BGP resumes the decision process
1360 and generates updates to its peers.
1362 Default max-delay is 0, i.e. the feature is off by default.
1364 .. clicmd:: table-map ROUTE-MAP-NAME
1366 This feature is used to apply a route-map on route updates from BGP to
1367 Zebra. All the applicable match operations are allowed, such as match on
1368 prefix, next-hop, communities, etc. Set operations for this attach-point are
1369 limited to metric and next-hop only. Any operation of this feature does not
1370 affect BGPs internal RIB.
1372 Supported for ipv4 and ipv6 address families. It works on multi-paths as
1373 well, however, metric setting is based on the best-path only.
1380 .. _bgp-defining-peers:
1385 .. clicmd:: neighbor PEER remote-as ASN
1387 Creates a new neighbor whose remote-as is ASN. PEER can be an IPv4 address
1388 or an IPv6 address or an interface to use for the connection.
1393 neighbor 10.0.0.1 remote-as 2
1395 In this case my router, in AS-1, is trying to peer with AS-2 at 10.0.0.1.
1397 This command must be the first command used when configuring a neighbor. If
1398 the remote-as is not specified, *bgpd* will complain like this: ::
1400 can't find neighbor 10.0.0.1
1402 .. clicmd:: neighbor PEER remote-as internal
1404 Create a peer as you would when you specify an ASN, except that if the
1405 peers ASN is different than mine as specified under the :clicmd:`router bgp ASN`
1406 command the connection will be denied.
1408 .. clicmd:: neighbor PEER remote-as external
1410 Create a peer as you would when you specify an ASN, except that if the
1411 peers ASN is the same as mine as specified under the :clicmd:`router bgp ASN`
1412 command the connection will be denied.
1414 .. clicmd:: bgp listen range <A.B.C.D/M|X:X::X:X/M> peer-group PGNAME
1416 Accept connections from any peers in the specified prefix. Configuration
1417 from the specified peer-group is used to configure these peers.
1421 When using BGP listen ranges, if the associated peer group has TCP MD5
1422 authentication configured, your kernel must support this on prefixes. On
1423 Linux, this support was added in kernel version 4.14. If your kernel does
1424 not support this feature you will get a warning in the log file, and the
1425 listen range will only accept connections from peers without MD5 configured.
1427 Additionally, we have observed that when using this option at scale (several
1428 hundred peers) the kernel may hit its option memory limit. In this situation
1429 you will see error messages like:
1431 ``bgpd: sockopt_tcp_signature: setsockopt(23): Cannot allocate memory``
1433 In this case you need to increase the value of the sysctl
1434 ``net.core.optmem_max`` to allow the kernel to allocate the necessary option
1437 .. clicmd:: bgp listen limit <1-65535>
1439 Define the maximum number of peers accepted for one BGP instance. This
1440 limit is set to 100 by default. Increasing this value will really be
1441 possible if more file descriptors are available in the BGP process. This
1442 value is defined by the underlying system (ulimit value), and can be
1443 overridden by `--limit-fds`. More information is available in chapter
1444 (:ref:`common-invocation-options`).
1446 .. clicmd:: coalesce-time (0-4294967295)
1448 The time in milliseconds that BGP will delay before deciding what peers
1449 can be put into an update-group together in order to generate a single
1450 update for them. The default time is 1000.
1452 .. _bgp-configuring-peers:
1457 .. clicmd:: neighbor PEER shutdown [message MSG...] [rtt (1-65535) [count (1-255)]]
1459 Shutdown the peer. We can delete the neighbor's configuration by
1460 ``no neighbor PEER remote-as ASN`` but all configuration of the neighbor
1461 will be deleted. When you want to preserve the configuration, but want to
1462 drop the BGP peer, use this syntax.
1464 Optionally you can specify a shutdown message `MSG`.
1466 Also, you can specify optionally ``rtt`` in milliseconds to automatically
1467 shutdown the peer if round-trip-time becomes higher than defined.
1469 Additional ``count`` parameter is the number of keepalive messages to count
1470 before shutdown the peer if round-trip-time becomes higher than defined.
1472 .. clicmd:: neighbor PEER disable-connected-check
1474 Allow peerings between directly connected eBGP peers using loopback
1477 .. clicmd:: neighbor PEER disable-link-bw-encoding-ieee
1479 By default bandwidth in extended communities is carried encoded as IEEE
1480 floating-point format, which is according to the draft.
1482 Older versions have the implementation where extended community bandwidth
1483 value is carried encoded as uint32. To enable backward compatibility we
1484 need to disable IEEE floating-point encoding option per-peer.
1486 .. clicmd:: neighbor PEER extended-optional-parameters
1488 Force Extended Optional Parameters Length format to be used for OPEN messages.
1490 By default, it's disabled. If the standard optional parameters length is
1491 higher than one-octet (255), then extended format is enabled automatically.
1493 For testing purposes, extended format can be enabled with this command.
1495 .. clicmd:: neighbor PEER ebgp-multihop
1497 Specifying ``ebgp-multihop`` allows sessions with eBGP neighbors to
1498 establish when they are multiple hops away. When the neighbor is not
1499 directly connected and this knob is not enabled, the session will not
1502 If the peer's IP address is not in the RIB and is reachable via the
1503 default route, then you have to enable ``ip nht resolve-via-default``.
1505 .. clicmd:: neighbor PEER description ...
1507 Set description of the peer.
1509 .. clicmd:: neighbor PEER interface IFNAME
1511 When you connect to a BGP peer over an IPv6 link-local address, you have to
1512 specify the IFNAME of the interface used for the connection. To specify
1513 IPv4 session addresses, see the ``neighbor PEER update-source`` command
1516 .. clicmd:: neighbor PEER interface remote-as <internal|external|ASN>
1518 Configure an unnumbered BGP peer. ``PEER`` should be an interface name. The
1519 session will be established via IPv6 link locals. Use ``internal`` for iBGP
1520 and ``external`` for eBGP sessions, or specify an ASN if you wish.
1522 .. clicmd:: neighbor PEER next-hop-self [force]
1524 This command specifies an announced route's nexthop as being equivalent to
1525 the address of the bgp router if it is learned via eBGP. This will also
1526 bypass third-party next-hops in favor of the local bgp address. If the
1527 optional keyword ``force`` is specified the modification is done also for
1528 routes learned via iBGP.
1530 .. clicmd:: neighbor PEER attribute-unchanged [{as-path|next-hop|med}]
1532 This command specifies attributes to be left unchanged for advertisements
1533 sent to a peer. Use this to leave the next-hop unchanged in ipv6
1534 configurations, as the route-map directive to leave the next-hop unchanged
1535 is only available for ipv4.
1537 .. clicmd:: neighbor PEER update-source <IFNAME|ADDRESS>
1539 Specify the IPv4 source address to use for the :abbr:`BGP` session to this
1540 neighbour, may be specified as either an IPv4 address directly or as an
1541 interface name (in which case the *zebra* daemon MUST be running in order
1542 for *bgpd* to be able to retrieve interface state).
1547 neighbor foo update-source 192.168.0.1
1548 neighbor bar update-source lo0
1551 .. clicmd:: neighbor PEER default-originate [route-map WORD]
1553 *bgpd*'s default is to not announce the default route (0.0.0.0/0) even if it
1554 is in routing table. When you want to announce default routes to the peer,
1557 If ``route-map`` keyword is specified, then the default route will be
1558 originated only if route-map conditions are met. For example, announce
1559 the default route only if ``10.10.10.10/32`` route exists and set an
1560 arbitrary community for a default route.
1565 address-family ipv4 unicast
1566 neighbor 192.168.255.1 default-originate route-map default
1568 ip prefix-list p1 seq 5 permit 10.10.10.10/32
1570 route-map default permit 10
1571 match ip address prefix-list p1
1572 set community 123:123
1575 .. clicmd:: neighbor PEER port PORT
1577 .. clicmd:: neighbor PEER password PASSWORD
1579 Set a MD5 password to be used with the tcp socket that is being used
1580 to connect to the remote peer. Please note if you are using this
1581 command with a large number of peers on linux you should consider
1582 modifying the `net.core.optmem_max` sysctl to a larger value to
1583 avoid out of memory errors from the linux kernel.
1585 .. clicmd:: neighbor PEER send-community
1587 .. clicmd:: neighbor PEER weight WEIGHT
1589 This command specifies a default `weight` value for the neighbor's routes.
1591 .. clicmd:: neighbor PEER maximum-prefix NUMBER [force]
1593 Sets a maximum number of prefixes we can receive from a given peer. If this
1594 number is exceeded, the BGP session will be destroyed.
1596 In practice, it is generally preferable to use a prefix-list to limit what
1597 prefixes are received from the peer instead of using this knob. Tearing down
1598 the BGP session when a limit is exceeded is far more destructive than merely
1599 rejecting undesired prefixes. The prefix-list method is also much more
1600 granular and offers much smarter matching criterion than number of received
1601 prefixes, making it more suited to implementing policy.
1603 If ``force`` is set, then ALL prefixes are counted for maximum instead of
1604 accepted only. This is useful for cases where an inbound filter is applied,
1605 but you want maximum-prefix to act on ALL (including filtered) prefixes. This
1606 option requires `soft-reconfiguration inbound` to be enabled for the peer.
1608 .. clicmd:: neighbor PEER maximum-prefix-out NUMBER
1610 Sets a maximum number of prefixes we can send to a given peer.
1612 Since sent prefix count is managed by update-groups, this option
1613 creates a separate update-group for outgoing updates.
1615 .. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend] [replace-as]
1617 Specify an alternate AS for this BGP process when interacting with the
1618 specified peer. With no modifiers, the specified local-as is prepended to
1619 the received AS_PATH when receiving routing updates from the peer, and
1620 prepended to the outgoing AS_PATH (after the process local AS) when
1621 transmitting local routes to the peer.
1623 If the no-prepend attribute is specified, then the supplied local-as is not
1624 prepended to the received AS_PATH.
1626 If the replace-as attribute is specified, then only the supplied local-as is
1627 prepended to the AS_PATH when transmitting local-route updates to this peer.
1629 Note that replace-as can only be specified if no-prepend is.
1631 This command is only allowed for eBGP peers.
1633 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> as-override
1635 Override AS number of the originating router with the local AS number.
1637 Usually this configuration is used in PEs (Provider Edge) to replace
1638 the incoming customer AS number so the connected CE (Customer Edge)
1639 can use the same AS number as the other customer sites. This allows
1640 customers of the provider network to use the same AS number across
1643 This command is only allowed for eBGP peers.
1645 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> allowas-in [<(1-10)|origin>]
1647 Accept incoming routes with AS path containing AS number with the same value
1648 as the current system AS.
1650 This is used when you want to use the same AS number in your sites, but you
1651 can't connect them directly. This is an alternative to
1652 `neighbor WORD as-override`.
1654 The parameter `(1-10)` configures the amount of accepted occurrences of the
1655 system AS number in AS path.
1657 The parameter `origin` configures BGP to only accept routes originated with
1658 the same AS number as the system.
1660 This command is only allowed for eBGP peers.
1662 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-all-paths
1664 Configure BGP to send all known paths to neighbor in order to preserve multi
1665 path capabilities inside a network.
1667 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-bestpath-per-AS
1669 Configure BGP to send best known paths to neighbor in order to preserve multi
1670 path capabilities inside a network.
1672 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> disable-addpath-rx
1674 Do not accept additional paths from this neighbor.
1676 .. clicmd:: neighbor PEER ttl-security hops NUMBER
1678 This command enforces Generalized TTL Security Mechanism (GTSM), as
1679 specified in RFC 5082. With this command, only neighbors that are the
1680 specified number of hops away will be allowed to become neighbors. This
1681 command is mutually exclusive with *ebgp-multihop*.
1683 .. clicmd:: neighbor PEER capability extended-nexthop
1685 Allow bgp to negotiate the extended-nexthop capability with it's peer.
1686 If you are peering over a v6 LL address then this capability is turned
1687 on automatically. If you are peering over a v6 Global Address then
1688 turning on this command will allow BGP to install v4 routes with
1689 v6 nexthops if you do not have v4 configured on interfaces.
1691 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> accept-own
1693 Enable handling of self-originated VPN routes containing ``accept-own`` community.
1695 This feature allows you to handle self-originated VPN routes, which a BGP speaker
1696 receives from a route-reflector. A 'self-originated' route is one that was
1697 originally advertised by the speaker itself. As per :rfc:`4271`, a BGP speaker rejects
1698 advertisements that originated the speaker itself. However, the BGP ACCEPT_OWN
1699 mechanism enables a router to accept the prefixes it has advertised, when reflected
1700 from a route-reflector that modifies certain attributes of the prefix.
1702 A special community called ``accept-own`` is attached to the prefix by the
1703 route-reflector, which is a signal to the receiving router to bypass the ORIGINATOR_ID
1704 and NEXTHOP/MP_REACH_NLRI check.
1708 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> path-attribute discard (1-255)...
1710 Drops specified path attributes from BGP UPDATE messages from the specified neighbor.
1712 If you do not want specific attributes, you can drop them using this command, and
1713 let the BGP proceed by ignoring those attributes.
1715 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> path-attribute treat-as-withdraw (1-255)...
1717 Received BGP UPDATES that contain specified path attributes are treat-as-withdraw. If
1718 there is an existing prefix in the BGP routing table, it will be removed.
1720 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> graceful-shutdown
1722 Mark all routes from this neighbor as less preferred by setting ``graceful-shutdown``
1723 community, and local-preference to 0.
1725 .. clicmd:: bgp fast-external-failover
1727 This command causes bgp to take down ebgp peers immediately
1728 when a link flaps. `bgp fast-external-failover` is the default
1729 and will not be displayed as part of a `show run`. The no form
1730 of the command turns off this ability.
1732 .. clicmd:: bgp default ipv4-unicast
1734 This command allows the user to specify that the IPv4 Unicast address
1735 family is turned on by default or not. This command defaults to on
1736 and is not displayed.
1737 The `no bgp default ipv4-unicast` form of the command is displayed.
1739 .. clicmd:: bgp default ipv4-multicast
1741 This command allows the user to specify that the IPv4 Multicast address
1742 family is turned on by default or not. This command defaults to off
1743 and is not displayed.
1744 The `bgp default ipv4-multicast` form of the command is displayed.
1746 .. clicmd:: bgp default ipv4-vpn
1748 This command allows the user to specify that the IPv4 MPLS VPN address
1749 family is turned on by default or not. This command defaults to off
1750 and is not displayed.
1751 The `bgp default ipv4-vpn` form of the command is displayed.
1753 .. clicmd:: bgp default ipv4-flowspec
1755 This command allows the user to specify that the IPv4 Flowspec address
1756 family is turned on by default or not. This command defaults to off
1757 and is not displayed.
1758 The `bgp default ipv4-flowspec` form of the command is displayed.
1760 .. clicmd:: bgp default ipv6-unicast
1762 This command allows the user to specify that the IPv6 Unicast address
1763 family is turned on by default or not. This command defaults to off
1764 and is not displayed.
1765 The `bgp default ipv6-unicast` form of the command is displayed.
1767 .. clicmd:: bgp default ipv6-multicast
1769 This command allows the user to specify that the IPv6 Multicast address
1770 family is turned on by default or not. This command defaults to off
1771 and is not displayed.
1772 The `bgp default ipv6-multicast` form of the command is displayed.
1774 .. clicmd:: bgp default ipv6-vpn
1776 This command allows the user to specify that the IPv6 MPLS VPN address
1777 family is turned on by default or not. This command defaults to off
1778 and is not displayed.
1779 The `bgp default ipv6-vpn` form of the command is displayed.
1781 .. clicmd:: bgp default ipv6-flowspec
1783 This command allows the user to specify that the IPv6 Flowspec address
1784 family is turned on by default or not. This command defaults to off
1785 and is not displayed.
1786 The `bgp default ipv6-flowspec` form of the command is displayed.
1788 .. clicmd:: bgp default l2vpn-evpn
1790 This command allows the user to specify that the L2VPN EVPN address
1791 family is turned on by default or not. This command defaults to off
1792 and is not displayed.
1793 The `bgp default l2vpn-evpn` form of the command is displayed.
1795 .. clicmd:: bgp default show-hostname
1797 This command shows the hostname of the peer in certain BGP commands
1798 outputs. It's easier to troubleshoot if you have a number of BGP peers.
1800 .. clicmd:: bgp default show-nexthop-hostname
1802 This command shows the hostname of the next-hop in certain BGP commands
1803 outputs. It's easier to troubleshoot if you have a number of BGP peers
1804 and a number of routes to check.
1806 .. clicmd:: neighbor PEER advertisement-interval (0-600)
1808 Setup the minimum route advertisement interval(mrai) for the
1809 peer in question. This number is between 0 and 600 seconds,
1810 with the default advertisement interval being 0.
1812 .. clicmd:: neighbor PEER timers (0-65535) (0-65535)
1814 Set keepalive and hold timers for a neighbor. The first value is keepalive
1815 and the second is hold time.
1817 .. clicmd:: neighbor PEER timers connect (1-65535)
1819 Set connect timer for a neighbor. The connect timer controls how long BGP
1820 waits between connection attempts to a neighbor.
1822 .. clicmd:: neighbor PEER timers delayopen (1-240)
1824 This command allows the user enable the
1825 `RFC 4271 <https://tools.ietf.org/html/rfc4271/>` DelayOpenTimer with the
1826 specified interval or disable it with the negating command for the peer. By
1827 default, the DelayOpenTimer is disabled. The timer interval may be set to a
1828 duration of 1 to 240 seconds.
1830 .. clicmd:: bgp minimum-holdtime (1-65535)
1832 This command allows user to prevent session establishment with BGP peers
1833 with lower holdtime less than configured minimum holdtime.
1834 When this command is not set, minimum holdtime does not work.
1836 .. clicmd:: bgp tcp-keepalive (1-65535) (1-65535) (1-30)
1838 This command allows user to configure TCP keepalive with new BGP peers.
1839 Each parameter respectively stands for TCP keepalive idle timer (seconds),
1840 interval (seconds), and maximum probes. By default, TCP keepalive is
1843 Displaying Information about Peers
1844 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1846 .. clicmd:: show bgp <afi> <safi> neighbors WORD bestpath-routes [detail] [json] [wide]
1848 For the given neighbor, WORD, that is specified list the routes selected
1849 by BGP as having the best path.
1851 If ``detail`` option is specified, the detailed version of all routes
1852 will be displayed. The same format as ``show [ip] bgp [afi] [safi] PREFIX``
1853 will be used, but for the whole table of received, advertised or filtered
1856 If ``json`` option is specified, output is displayed in JSON format.
1858 If ``wide`` option is specified, then the prefix table's width is increased
1859 to fully display the prefix and the nexthop.
1861 .. _bgp-peer-filtering:
1866 .. clicmd:: neighbor PEER distribute-list NAME [in|out]
1868 This command specifies a distribute-list for the peer. `direct` is
1871 .. clicmd:: neighbor PEER prefix-list NAME [in|out]
1873 .. clicmd:: neighbor PEER filter-list NAME [in|out]
1875 .. clicmd:: neighbor PEER route-map NAME [in|out]
1877 Apply a route-map on the neighbor. `direct` must be `in` or `out`.
1879 .. clicmd:: bgp route-reflector allow-outbound-policy
1881 By default, attribute modification via route-map policy out is not reflected
1882 on reflected routes. This option allows the modifications to be reflected as
1883 well. Once enabled, it affects all reflected routes.
1885 .. clicmd:: neighbor PEER sender-as-path-loop-detection
1887 Enable the detection of sender side AS path loops and filter the
1888 bad routes before they are sent.
1890 This setting is disabled by default.
1897 Peer groups are used to help improve scaling by generating the same
1898 update information to all members of a peer group. Note that this means
1899 that the routes generated by a member of a peer group will be sent back
1900 to that originating peer with the originator identifier attribute set to
1901 indicated the originating peer. All peers not associated with a
1902 specific peer group are treated as belonging to a default peer group,
1903 and will share updates.
1905 .. clicmd:: neighbor WORD peer-group
1907 This command defines a new peer group.
1909 .. clicmd:: neighbor PEER peer-group PGNAME
1911 This command bind specific peer to peer group WORD.
1913 .. clicmd:: neighbor PEER solo
1915 This command is used to indicate that routes advertised by the peer
1916 should not be reflected back to the peer. This command only is only
1917 meaningful when there is a single peer defined in the peer-group.
1919 .. clicmd:: show [ip] bgp peer-group [json]
1921 This command displays configured BGP peer-groups.
1925 exit1-debian-9# show bgp peer-group
1927 BGP peer-group test1, remote AS 65001
1928 Peer-group type is external
1929 Configured address-families: IPv4 Unicast; IPv6 Unicast;
1930 1 IPv4 listen range(s)
1932 2 IPv6 listen range(s)
1936 192.168.200.1 Active
1939 BGP peer-group test2
1940 Peer-group type is external
1941 Configured address-families: IPv4 Unicast;
1943 Optional ``json`` parameter is used to display JSON output.
1951 "addressFamiliesConfigured":[
1981 "addressFamiliesConfigured":[
1987 Capability Negotiation
1988 ^^^^^^^^^^^^^^^^^^^^^^
1990 .. clicmd:: neighbor PEER strict-capability-match
1993 Strictly compares remote capabilities and local capabilities. If
1994 capabilities are different, send Unsupported Capability error then reset
1997 You may want to disable sending Capability Negotiation OPEN message optional
1998 parameter to the peer when remote peer does not implement Capability
1999 Negotiation. Please use *dont-capability-negotiate* command to disable the
2002 .. clicmd:: neighbor PEER dont-capability-negotiate
2004 Suppress sending Capability Negotiation as OPEN message optional parameter
2005 to the peer. This command only affects the peer is configured other than
2006 IPv4 unicast configuration.
2008 When remote peer does not have capability negotiation feature, remote peer
2009 will not send any capabilities at all. In that case, bgp configures the peer
2010 with configured capabilities.
2012 You may prefer locally configured capabilities more than the negotiated
2013 capabilities even though remote peer sends capabilities. If the peer is
2014 configured by *override-capability*, *bgpd* ignores received capabilities
2015 then override negotiated capabilities with configured values.
2017 Additionally the operator should be reminded that this feature fundamentally
2018 disables the ability to use widely deployed BGP features. BGP unnumbered,
2019 hostname support, AS4, Addpath, Route Refresh, ORF, Dynamic Capabilities,
2020 and graceful restart.
2022 .. clicmd:: neighbor PEER override-capability
2024 Override the result of Capability Negotiation with local configuration.
2025 Ignore remote peer's capability value.
2027 .. clicmd:: neighbor PEER capability software-version
2029 Send the software version in the BGP OPEN message to the neighbor. This is
2030 very useful in environments with a large amount of peers with different
2031 versions of FRR or any other vendor.
2033 Disabled by default.
2035 .. _bgp-as-path-access-lists:
2037 AS Path Access Lists
2038 --------------------
2040 AS path access list is user defined AS path.
2042 .. clicmd:: bgp as-path access-list WORD [seq (0-4294967295)] permit|deny LINE
2044 This command defines a new AS path access list.
2046 .. clicmd:: show bgp as-path-access-list [json]
2048 Display all BGP AS Path access lists.
2050 If the ``json`` option is specified, output is displayed in JSON format.
2052 .. clicmd:: show bgp as-path-access-list WORD [json]
2054 Display the specified BGP AS Path access list.
2056 If the ``json`` option is specified, output is displayed in JSON format.
2058 .. _bgp-bogon-filter-example:
2060 Bogon ASN filter policy configuration example
2061 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2065 bgp as-path access-list 99 permit _0_
2066 bgp as-path access-list 99 permit _23456_
2067 bgp as-path access-list 99 permit _1310[0-6][0-9]_|_13107[0-1]_
2068 bgp as-path access-list 99 seq 20 permit ^65
2070 .. _bgp-using-as-path-in-route-map:
2072 Using AS Path in Route Map
2073 --------------------------
2075 .. clicmd:: match as-path WORD
2077 For a given as-path, WORD, match it on the BGP as-path given for the prefix
2078 and if it matches do normal route-map actions. The no form of the command
2079 removes this match from the route-map.
2081 .. clicmd:: set as-path prepend AS-PATH
2083 Prepend the given string of AS numbers to the AS_PATH of the BGP path's NLRI.
2084 The no form of this command removes this set operation from the route-map.
2086 .. clicmd:: set as-path prepend last-as NUM
2088 Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
2089 The no form of this command removes this set operation from the route-map.
2091 .. clicmd:: set as-path replace <any|ASN>
2093 Replace a specific AS number to local AS number. ``any`` replaces each
2094 AS number in the AS-PATH with the local AS number.
2096 .. _bgp-communities-attribute:
2098 Communities Attribute
2099 ---------------------
2101 The BGP communities attribute is widely used for implementing policy routing.
2102 Network operators can manipulate BGP communities attribute based on their
2103 network policy. BGP communities attribute is defined in :rfc:`1997` and
2104 :rfc:`1998`. It is an optional transitive attribute, therefore local policy can
2105 travel through different autonomous system.
2107 The communities attribute is a set of communities values. Each community value
2108 is 4 octet long. The following format is used to define the community value.
2111 This format represents 4 octet communities value. ``AS`` is high order 2
2112 octet in digit format. ``VAL`` is low order 2 octet in digit format. This
2113 format is useful to define AS oriented policy value. For example,
2114 ``7675:80`` can be used when AS 7675 wants to pass local policy value 80 to
2117 ``graceful-shutdown``
2118 ``graceful-shutdown`` represents well-known communities value
2119 ``GRACEFUL_SHUTDOWN`` ``0xFFFF0000`` ``65535:0``. :rfc:`8326` implements
2120 the purpose Graceful BGP Session Shutdown to reduce the amount of
2121 lost traffic when taking BGP sessions down for maintenance. The use
2122 of the community needs to be supported from your peers side to
2123 actually have any effect.
2126 ``accept-own`` represents well-known communities value ``ACCEPT_OWN``
2127 ``0xFFFF0001`` ``65535:1``. :rfc:`7611` implements a way to signal
2128 to a router to accept routes with a local nexthop address. This
2129 can be the case when doing policing and having traffic having a
2130 nexthop located in another VRF but still local interface to the
2131 router. It is recommended to read the RFC for full details.
2133 ``route-filter-translated-v4``
2134 ``route-filter-translated-v4`` represents well-known communities value
2135 ``ROUTE_FILTER_TRANSLATED_v4`` ``0xFFFF0002`` ``65535:2``.
2138 ``route-filter-v4`` represents well-known communities value
2139 ``ROUTE_FILTER_v4`` ``0xFFFF0003`` ``65535:3``.
2141 ``route-filter-translated-v6``
2142 ``route-filter-translated-v6`` represents well-known communities value
2143 ``ROUTE_FILTER_TRANSLATED_v6`` ``0xFFFF0004`` ``65535:4``.
2146 ``route-filter-v6`` represents well-known communities value
2147 ``ROUTE_FILTER_v6`` ``0xFFFF0005`` ``65535:5``.
2150 ``llgr-stale`` represents well-known communities value ``LLGR_STALE``
2151 ``0xFFFF0006`` ``65535:6``.
2152 Assigned and intended only for use with routers supporting the
2153 Long-lived Graceful Restart Capability as described in
2154 [Draft-IETF-uttaro-idr-bgp-persistence]_.
2155 Routers receiving routes with this community may (depending on
2156 implementation) choose allow to reject or modify routes on the
2157 presence or absence of this community.
2160 ``no-llgr`` represents well-known communities value ``NO_LLGR``
2161 ``0xFFFF0007`` ``65535:7``.
2162 Assigned and intended only for use with routers supporting the
2163 Long-lived Graceful Restart Capability as described in
2164 [Draft-IETF-uttaro-idr-bgp-persistence]_.
2165 Routers receiving routes with this community may (depending on
2166 implementation) choose allow to reject or modify routes on the
2167 presence or absence of this community.
2169 ``accept-own-nexthop``
2170 ``accept-own-nexthop`` represents well-known communities value
2171 ``accept-own-nexthop`` ``0xFFFF0008`` ``65535:8``.
2172 [Draft-IETF-agrewal-idr-accept-own-nexthop]_ describes
2173 how to tag and label VPN routes to be able to send traffic between VRFs
2174 via an internal layer 2 domain on the same PE device. Refer to
2175 [Draft-IETF-agrewal-idr-accept-own-nexthop]_ for full details.
2178 ``blackhole`` represents well-known communities value ``BLACKHOLE``
2179 ``0xFFFF029A`` ``65535:666``. :rfc:`7999` documents sending prefixes to
2180 EBGP peers and upstream for the purpose of blackholing traffic.
2181 Prefixes tagged with the this community should normally not be
2182 re-advertised from neighbors of the originating network. Upon receiving
2183 ``BLACKHOLE`` community from a BGP speaker, ``NO_ADVERTISE`` community
2184 is added automatically.
2187 ``no-export`` represents well-known communities value ``NO_EXPORT``
2188 ``0xFFFFFF01``. All routes carry this value must not be advertised to
2189 outside a BGP confederation boundary. If neighboring BGP peer is part of BGP
2190 confederation, the peer is considered as inside a BGP confederation
2191 boundary, so the route will be announced to the peer.
2194 ``no-advertise`` represents well-known communities value ``NO_ADVERTISE``
2195 ``0xFFFFFF02``. All routes carry this value must not be advertise to other
2199 ``local-AS`` represents well-known communities value ``NO_EXPORT_SUBCONFED``
2200 ``0xFFFFFF03``. All routes carry this value must not be advertised to
2201 external BGP peers. Even if the neighboring router is part of confederation,
2202 it is considered as external BGP peer, so the route will not be announced to
2206 ``no-peer`` represents well-known communities value ``NOPEER``
2207 ``0xFFFFFF04`` ``65535:65284``. :rfc:`3765` is used to communicate to
2208 another network how the originating network want the prefix propagated.
2210 When the communities attribute is received duplicate community values in the
2211 attribute are ignored and value is sorted in numerical order.
2213 .. [Draft-IETF-uttaro-idr-bgp-persistence] <https://tools.ietf.org/id/draft-uttaro-idr-bgp-persistence-04.txt>
2214 .. [Draft-IETF-agrewal-idr-accept-own-nexthop] <https://tools.ietf.org/id/draft-agrewal-idr-accept-own-nexthop-00.txt>
2216 .. _bgp-community-lists:
2220 Community lists are user defined lists of community attribute values. These
2221 lists can be used for matching or manipulating the communities attribute in
2224 There are two types of community list:
2227 This type accepts an explicit value for the attribute.
2230 This type accepts a regular expression. Because the regex must be
2231 interpreted on each use expanded community lists are slower than standard
2234 .. clicmd:: bgp community-list standard NAME permit|deny COMMUNITY
2236 This command defines a new standard community list. ``COMMUNITY`` is
2237 communities value. The ``COMMUNITY`` is compiled into community structure.
2238 We can define multiple community list under same name. In that case match
2239 will happen user defined order. Once the community list matches to
2240 communities attribute in BGP updates it return permit or deny by the
2241 community list definition. When there is no matched entry, deny will be
2242 returned. When ``COMMUNITY`` is empty it matches to any routes.
2244 .. clicmd:: bgp community-list expanded NAME permit|deny COMMUNITY
2246 This command defines a new expanded community list. ``COMMUNITY`` is a
2247 string expression of communities attribute. ``COMMUNITY`` can be a regular
2248 expression (:ref:`bgp-regular-expressions`) to match the communities
2249 attribute in BGP updates. The expanded community is only used to filter,
2253 It is recommended to use the more explicit versions of this command.
2255 .. clicmd:: bgp community-list NAME permit|deny COMMUNITY
2257 When the community list type is not specified, the community list type is
2258 automatically detected. If ``COMMUNITY`` can be compiled into communities
2259 attribute, the community list is defined as a standard community list.
2260 Otherwise it is defined as an expanded community list. This feature is left
2261 for backward compatibility. Use of this feature is not recommended.
2263 Note that all community lists share the same namespace, so it's not
2264 necessary to specify ``standard`` or ``expanded``; these modifiers are
2267 .. clicmd:: show bgp community-list [NAME detail]
2269 Displays community list information. When ``NAME`` is specified the
2270 specified community list's information is shown.
2274 # show bgp community-list
2275 Named Community standard list CLIST
2276 permit 7675:80 7675:100 no-export
2278 Named Community expanded list EXPAND
2281 # show bgp community-list CLIST detail
2282 Named Community standard list CLIST
2283 permit 7675:80 7675:100 no-export
2287 .. _bgp-numbered-community-lists:
2289 Numbered Community Lists
2290 ^^^^^^^^^^^^^^^^^^^^^^^^
2292 When number is used for BGP community list name, the number has
2293 special meanings. Community list number in the range from 1 and 99 is
2294 standard community list. Community list number in the range from 100
2295 to 500 is expanded community list. These community lists are called
2296 as numbered community lists. On the other hand normal community lists
2297 is called as named community lists.
2299 .. clicmd:: bgp community-list (1-99) permit|deny COMMUNITY
2301 This command defines a new community list. The argument to (1-99) defines
2302 the list identifier.
2304 .. clicmd:: bgp community-list (100-500) permit|deny COMMUNITY
2306 This command defines a new expanded community list. The argument to
2307 (100-500) defines the list identifier.
2309 .. _bgp-community-alias:
2314 BGP community aliases are useful to quickly identify what communities are set
2315 for a specific prefix in a human-readable format. Especially handy for a huge
2316 amount of communities. Accurately defined aliases can help you faster spot
2319 .. clicmd:: bgp community alias NAME ALIAS
2321 This command creates an alias name for a community that will be used
2322 later in various CLI outputs in a human-readable format.
2326 ~# vtysh -c 'show run' | grep 'bgp community alias'
2327 bgp community alias 65001:14 community-1
2328 bgp community alias 65001:123:1 lcommunity-1
2330 ~# vtysh -c 'show ip bgp 172.16.16.1/32'
2331 BGP routing table entry for 172.16.16.1/32, version 21
2332 Paths: (2 available, best #2, table default)
2333 Advertised to non peer-group peers:
2335 192.168.0.2 from 192.168.0.2 (172.16.16.1)
2336 Origin incomplete, metric 0, valid, external, best (Neighbor IP)
2337 Community: 65001:12 65001:13 community-1 65001:65534
2338 Large Community: lcommunity-1 65001:123:2
2339 Last update: Fri Apr 16 12:51:27 2021
2341 .. clicmd:: show bgp [afi] [safi] [all] alias WORD [wide|json]
2343 Display prefixes with matching BGP community alias.
2345 .. _bgp-using-communities-in-route-map:
2347 Using Communities in Route Maps
2348 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2350 In :ref:`route-map` we can match on or set the BGP communities attribute. Using
2351 this feature network operator can implement their network policy based on BGP
2352 communities attribute.
2354 The following commands can be used in route maps:
2356 .. clicmd:: match alias WORD
2358 This command performs match to BGP updates using community alias WORD. When
2359 the one of BGP communities value match to the one of community alias value in
2360 community alias, it is match.
2362 .. clicmd:: match community WORD exact-match [exact-match]
2364 This command perform match to BGP updates using community list WORD. When
2365 the one of BGP communities value match to the one of communities value in
2366 community list, it is match. When `exact-match` keyword is specified, match
2367 happen only when BGP updates have completely same communities value
2368 specified in the community list.
2370 .. clicmd:: set community <none|COMMUNITY> additive
2372 This command sets the community value in BGP updates. If the attribute is
2373 already configured, the newly provided value replaces the old one unless the
2374 ``additive`` keyword is specified, in which case the new value is appended
2375 to the existing value.
2377 If ``none`` is specified as the community value, the communities attribute
2380 It is not possible to set an expanded community list.
2382 .. clicmd:: set comm-list WORD delete
2384 This command remove communities value from BGP communities attribute. The
2385 ``word`` is community list name. When BGP route's communities value matches
2386 to the community list ``word``, the communities value is removed. When all
2387 of communities value is removed eventually, the BGP update's communities
2388 attribute is completely removed.
2390 .. _bgp-communities-example:
2392 Example Configuration
2393 ^^^^^^^^^^^^^^^^^^^^^
2395 The following configuration is exemplary of the most typical usage of BGP
2396 communities attribute. In the example, AS 7675 provides an upstream Internet
2397 connection to AS 100. When the following configuration exists in AS 7675, the
2398 network operator of AS 100 can set local preference in AS 7675 network by
2399 setting BGP communities attribute to the updates.
2404 neighbor 192.168.0.1 remote-as 100
2405 address-family ipv4 unicast
2406 neighbor 192.168.0.1 route-map RMAP in
2409 bgp community-list 70 permit 7675:70
2410 bgp community-list 80 permit 7675:80
2411 bgp community-list 90 permit 7675:90
2413 route-map RMAP permit 10
2415 set local-preference 70
2417 route-map RMAP permit 20
2419 set local-preference 80
2421 route-map RMAP permit 30
2423 set local-preference 90
2426 The following configuration announces ``10.0.0.0/8`` from AS 100 to AS 7675.
2427 The route has communities value ``7675:80`` so when above configuration exists
2428 in AS 7675, the announced routes' local preference value will be set to 80.
2434 neighbor 192.168.0.2 remote-as 7675
2435 address-family ipv4 unicast
2436 neighbor 192.168.0.2 route-map RMAP out
2439 ip prefix-list PLIST permit 10.0.0.0/8
2441 route-map RMAP permit 10
2442 match ip address prefix-list PLIST
2443 set community 7675:80
2446 The following configuration is an example of BGP route filtering using
2447 communities attribute. This configuration only permit BGP routes which has BGP
2448 communities value (``0:80`` and ``0:90``) or ``0:100``. The network operator can
2449 set special internal communities value at BGP border router, then limit the
2450 BGP route announcements into the internal network.
2455 neighbor 192.168.0.1 remote-as 100
2456 address-family ipv4 unicast
2457 neighbor 192.168.0.1 route-map RMAP in
2460 bgp community-list 1 permit 0:80 0:90
2461 bgp community-list 1 permit 0:100
2463 route-map RMAP permit in
2467 The following example filters BGP routes which have a community value of
2468 ``1:1``. When there is no match community-list returns ``deny``. To avoid
2469 filtering all routes, a ``permit`` line is set at the end of the
2475 neighbor 192.168.0.1 remote-as 100
2476 address-family ipv4 unicast
2477 neighbor 192.168.0.1 route-map RMAP in
2480 bgp community-list standard FILTER deny 1:1
2481 bgp community-list standard FILTER permit
2483 route-map RMAP permit 10
2484 match community FILTER
2487 The following configuration is an example of communities value deletion. With
2488 this configuration the community values ``100:1`` and ``100:2`` are removed
2489 from BGP updates. For communities value deletion, only ``permit``
2490 community-list is used. ``deny`` community-list is ignored.
2495 neighbor 192.168.0.1 remote-as 100
2496 address-family ipv4 unicast
2497 neighbor 192.168.0.1 route-map RMAP in
2500 bgp community-list standard DEL permit 100:1 100:2
2502 route-map RMAP permit 10
2503 set comm-list DEL delete
2506 .. _bgp-extended-communities-attribute:
2508 Extended Communities Attribute
2509 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2511 BGP extended communities attribute is introduced with MPLS VPN/BGP technology.
2512 MPLS VPN/BGP expands capability of network infrastructure to provide VPN
2513 functionality. At the same time it requires a new framework for policy routing.
2514 With BGP Extended Communities Attribute we can use Route Target or Site of
2515 Origin for implementing network policy for MPLS VPN/BGP.
2517 BGP Extended Communities Attribute is similar to BGP Communities Attribute. It
2518 is an optional transitive attribute. BGP Extended Communities Attribute can
2519 carry multiple Extended Community value. Each Extended Community value is
2522 BGP Extended Communities Attribute provides an extended range compared with BGP
2523 Communities Attribute. Adding to that there is a type field in each value to
2524 provides community space structure.
2526 There are two format to define Extended Community value. One is AS based format
2527 the other is IP address based format.
2530 This is a format to define AS based Extended Community value. ``AS`` part
2531 is 2 octets Global Administrator subfield in Extended Community value.
2532 ``VAL`` part is 4 octets Local Administrator subfield. ``7675:100``
2533 represents AS 7675 policy value 100.
2536 This is a format to define IP address based Extended Community value.
2537 ``IP-Address`` part is 4 octets Global Administrator subfield. ``VAL`` part
2538 is 2 octets Local Administrator subfield.
2540 .. _bgp-extended-community-lists:
2542 Extended Community Lists
2543 ^^^^^^^^^^^^^^^^^^^^^^^^
2545 .. clicmd:: bgp extcommunity-list standard NAME permit|deny EXTCOMMUNITY
2547 This command defines a new standard extcommunity-list. `extcommunity` is
2548 extended communities value. The `extcommunity` is compiled into extended
2549 community structure. We can define multiple extcommunity-list under same
2550 name. In that case match will happen user defined order. Once the
2551 extcommunity-list matches to extended communities attribute in BGP updates
2552 it return permit or deny based upon the extcommunity-list definition. When
2553 there is no matched entry, deny will be returned. When `extcommunity` is
2554 empty it matches to any routes.
2556 .. clicmd:: bgp extcommunity-list expanded NAME permit|deny LINE
2558 This command defines a new expanded extcommunity-list. `line` is a string
2559 expression of extended communities attribute. `line` can be a regular
2560 expression (:ref:`bgp-regular-expressions`) to match an extended communities
2561 attribute in BGP updates.
2563 Note that all extended community lists shares a single name space, so it's
2564 not necessary to specify their type when creating or destroying them.
2566 .. clicmd:: show bgp extcommunity-list [NAME detail]
2568 This command displays current extcommunity-list information. When `name` is
2569 specified the community list's information is shown.
2572 .. _bgp-extended-communities-in-route-map:
2574 BGP Extended Communities in Route Map
2575 """""""""""""""""""""""""""""""""""""
2577 .. clicmd:: match extcommunity WORD
2579 .. clicmd:: set extcommunity none
2581 This command resets the extended community value in BGP updates. If the attribute is
2582 already configured or received from the peer, the attribute is discarded and set to
2583 none. This is useful if you need to strip incoming extended communities.
2585 .. clicmd:: set extcommunity rt EXTCOMMUNITY
2587 This command set Route Target value.
2589 .. clicmd:: set extcommunity soo EXTCOMMUNITY
2591 This command set Site of Origin value.
2593 .. clicmd:: set extcommunity bandwidth <(1-25600) | cumulative | num-multipaths> [non-transitive]
2595 This command sets the BGP link-bandwidth extended community for the prefix
2596 (best path) for which it is applied. The link-bandwidth can be specified as
2597 an ``explicit value`` (specified in Mbps), or the router can be told to use
2598 the ``cumulative bandwidth`` of all multipaths for the prefix or to compute
2599 it based on the ``number of multipaths``. The link bandwidth extended
2600 community is encoded as ``transitive`` unless the set command explicitly
2601 configures it as ``non-transitive``.
2603 .. seealso:: :ref:`wecmp_linkbw`
2605 Note that the extended expanded community is only used for `match` rule, not for
2608 .. _bgp-large-communities-attribute:
2610 Large Communities Attribute
2611 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
2613 The BGP Large Communities attribute was introduced in Feb 2017 with
2616 The BGP Large Communities Attribute is similar to the BGP Communities Attribute
2617 except that it has 3 components instead of two and each of which are 4 octets
2618 in length. Large Communities bring additional functionality and convenience
2619 over traditional communities, specifically the fact that the ``GLOBAL`` part
2620 below is now 4 octets wide allowing seamless use in networks using 4-byte ASNs.
2622 ``GLOBAL:LOCAL1:LOCAL2``
2623 This is the format to define Large Community values. Referencing :rfc:`8195`
2624 the values are commonly referred to as follows:
2626 - The ``GLOBAL`` part is a 4 octet Global Administrator field, commonly used
2627 as the operators AS number.
2628 - The ``LOCAL1`` part is a 4 octet Local Data Part 1 subfield referred to as
2630 - The ``LOCAL2`` part is a 4 octet Local Data Part 2 field and referred to
2631 as the parameter subfield.
2633 As an example, ``65551:1:10`` represents AS 65551 function 1 and parameter
2634 10. The referenced RFC above gives some guidelines on recommended usage.
2636 .. _bgp-large-community-lists:
2638 Large Community Lists
2639 """""""""""""""""""""
2641 Two types of large community lists are supported, namely `standard` and
2644 .. clicmd:: bgp large-community-list standard NAME permit|deny LARGE-COMMUNITY
2646 This command defines a new standard large-community-list. `large-community`
2647 is the Large Community value. We can add multiple large communities under
2648 same name. In that case the match will happen in the user defined order.
2649 Once the large-community-list matches the Large Communities attribute in BGP
2650 updates it will return permit or deny based upon the large-community-list
2651 definition. When there is no matched entry, a deny will be returned. When
2652 `large-community` is empty it matches any routes.
2654 .. clicmd:: bgp large-community-list expanded NAME permit|deny LINE
2656 This command defines a new expanded large-community-list. Where `line` is a
2657 string matching expression, it will be compared to the entire Large
2658 Communities attribute as a string, with each large-community in order from
2659 lowest to highest. `line` can also be a regular expression which matches
2660 this Large Community attribute.
2662 Note that all community lists share the same namespace, so it's not
2663 necessary to specify ``standard`` or ``expanded``; these modifiers are
2666 .. clicmd:: show bgp large-community-list
2668 .. clicmd:: show bgp large-community-list NAME detail
2670 This command display current large-community-list information. When
2671 `name` is specified the community list information is shown.
2673 .. clicmd:: show ip bgp large-community-info
2675 This command displays the current large communities in use.
2677 .. _bgp-large-communities-in-route-map:
2679 Large Communities in Route Map
2680 """"""""""""""""""""""""""""""
2682 .. clicmd:: match large-community LINE [exact-match]
2684 Where `line` can be a simple string to match, or a regular expression. It
2685 is very important to note that this match occurs on the entire
2686 large-community string as a whole, where each large-community is ordered
2687 from lowest to highest. When `exact-match` keyword is specified, match
2688 happen only when BGP updates have completely same large communities value
2689 specified in the large community list.
2691 .. clicmd:: set large-community LARGE-COMMUNITY
2693 .. clicmd:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
2695 .. clicmd:: set large-community LARGE-COMMUNITY additive
2697 These commands are used for setting large-community values. The first
2698 command will overwrite any large-communities currently present.
2699 The second specifies two large-communities, which overwrites the current
2700 large-community list. The third will add a large-community value without
2701 overwriting other values. Multiple large-community values can be specified.
2703 Note that the large expanded community is only used for `match` rule, not for
2706 .. _bgp-roles-and-only-to-customers:
2708 BGP Roles and Only to Customers
2709 -------------------------------
2711 BGP roles are defined in :rfc:`9234` and provide an easy way to route leaks
2712 prevention, detection and mitigation.
2714 To enable its mechanics, you must set your local role to reflect your type of
2715 peering relationship with your neighbor. Possible values of ``LOCAL-ROLE`` are:
2723 The local Role value is negotiated with the new BGP Role capability with a
2724 built-in check of the corresponding value. In case of mismatch the new OPEN
2725 Roles Mismatch Notification <2, 11> would be sent.
2727 The correct Role pairs are:
2729 * Provider - Customer
2731 * RS-Server - RS-Client
2733 .. code-block:: shell
2735 ~# vtysh -c 'show bgp neighbor' | grep 'Role'
2736 Local Role: customer
2737 Neighbor Role: provider
2738 Role: advertised and received
2740 If strict-mode is set BGP session won't become established until BGP neighbor
2741 set local Role on its side. This configuration parameter is defined in
2742 :rfc:`9234` and used to enforce corresponding configuration at your
2743 counter-part side. Default value - disabled.
2745 Routes that sent from provider, rs-server, or peer local-role (or if received
2746 by customer, rs-clinet, or peer local-role) will be marked with a new
2747 Only to Customer (OTC) attribute.
2749 Routes with this attribute can only be sent to your neighbor if your
2750 local-role is provider or rs-server. Routes with this attribute can be
2751 received only if your local-role is customer or rs-client.
2753 In case of peer-peer relationship routes can be received only if
2754 OTC value is equal to your neighbor AS number.
2756 All these rules with OTC help to detect and mitigate route leaks and
2757 happened automatically if local-role is set.
2759 .. clicmd:: neighbor PEER local-role LOCAL-ROLE [strict-mode]
2761 This command set your local-role to ``LOCAL-ROLE``:
2762 <provider|rs-server|rs-client|customer|peer>.
2764 This role helps to detect and prevent route leaks.
2766 If ``strict-mode`` is set, your neighbor must send you Capability with the
2767 value of his role (by setting local-role on his side). Otherwise, a Role
2768 Mismatch Notification will be sent.
2775 *bgpd* supports :abbr:`L3VPN (Layer 3 Virtual Private Networks)` :abbr:`VRFs
2776 (Virtual Routing and Forwarding)` for IPv4 :rfc:`4364` and IPv6 :rfc:`4659`.
2777 L3VPN routes, and their associated VRF MPLS labels, can be distributed to VPN
2778 SAFI neighbors in the *default*, i.e., non VRF, BGP instance. VRF MPLS labels
2779 are reached using *core* MPLS labels which are distributed using LDP or BGP
2780 labeled unicast. *bgpd* also supports inter-VRF route leaking.
2783 L3VPN over GRE interfaces
2784 ^^^^^^^^^^^^^^^^^^^^^^^^^
2786 In MPLS-VPN or SRv6-VPN, an L3VPN next-hop entry requires that the path
2787 chosen respectively contains a labelled path or a valid SID IPv6 address.
2788 Otherwise the L3VPN entry will not be installed. It is possible to ignore
2789 that check when the path chosen by the next-hop uses a GRE interface, and
2790 there is a route-map configured at inbound side of ipv4-vpn or ipv6-vpn
2791 address family with following syntax:
2793 .. clicmd:: set l3vpn next-hop encapsulation gre
2795 The incoming BGP L3VPN entry is accepted, provided that the next hop of the
2796 L3VPN entry uses a path that takes the GRE tunnel as outgoing interface. The
2797 remote endpoint should be configured just behind the GRE tunnel; remote
2798 device configuration may vary depending whether it acts at edge endpoint or
2799 not: in any case, the expectation is that incoming MPLS traffic received at
2800 this endpoint should be considered as a valid path for L3VPN.
2802 .. _bgp-vrf-route-leaking:
2807 BGP routes may be leaked (i.e. copied) between a unicast VRF RIB and the VPN
2808 SAFI RIB of the default VRF for use in MPLS-based L3VPNs. Unicast routes may
2809 also be leaked between any VRFs (including the unicast RIB of the default BGP
2810 instanced). A shortcut syntax is also available for specifying leaking from one
2811 VRF to another VRF using the default instance's VPN RIB as the intermediary. A
2812 common application of the VRF-VRF feature is to connect a customer's private
2813 routing domain to a provider's VPN service. Leaking is configured from the
2814 point of view of an individual VRF: ``import`` refers to routes leaked from VPN
2815 to a unicast VRF, whereas ``export`` refers to routes leaked from a unicast VRF
2821 Routes exported from a unicast VRF to the VPN RIB must be augmented by two
2824 - an :abbr:`RD (Route Distinguisher)`
2825 - an :abbr:`RTLIST (Route-target List)`
2827 Configuration for these exported routes must, at a minimum, specify these two
2830 Routes imported from the VPN RIB to a unicast VRF are selected according to
2831 their RTLISTs. Routes whose RTLIST contains at least one route-target in
2832 common with the configured import RTLIST are leaked. Configuration for these
2833 imported routes must specify an RTLIST to be matched.
2835 The RD, which carries no semantic value, is intended to make the route unique
2836 in the VPN RIB among all routes of its prefix that originate from all the
2837 customers and sites that are attached to the provider's VPN service.
2838 Accordingly, each site of each customer is typically assigned an RD that is
2839 unique across the entire provider network.
2841 The RTLIST is a set of route-target extended community values whose purpose is
2842 to specify route-leaking policy. Typically, a customer is assigned a single
2843 route-target value for import and export to be used at all customer sites. This
2844 configuration specifies a simple topology wherein a customer has a single
2845 routing domain which is shared across all its sites. More complex routing
2846 topologies are possible through use of additional route-targets to augment the
2847 leaking of sets of routes in various ways.
2849 When using the shortcut syntax for vrf-to-vrf leaking, the RD and RT are
2852 General configuration
2853 ^^^^^^^^^^^^^^^^^^^^^
2855 Configuration of route leaking between a unicast VRF RIB and the VPN SAFI RIB
2856 of the default VRF is accomplished via commands in the context of a VRF
2859 .. clicmd:: rd vpn export AS:NN|IP:nn
2861 Specifies the route distinguisher to be added to a route exported from the
2862 current unicast VRF to VPN.
2864 .. clicmd:: rt vpn import|export|both RTLIST...
2866 Specifies the route-target list to be attached to a route (export) or the
2867 route-target list to match against (import) when exporting/importing between
2868 the current unicast VRF and VPN.
2870 The RTLIST is a space-separated list of route-targets, which are BGP
2871 extended community values as described in
2872 :ref:`bgp-extended-communities-attribute`.
2874 .. clicmd:: label vpn export (0..1048575)|auto
2876 Enables an MPLS label to be attached to a route exported from the current
2877 unicast VRF to VPN. If the value specified is ``auto``, the label value is
2878 automatically assigned from a pool maintained by the Zebra daemon. If Zebra
2879 is not running, or if this command is not configured, automatic label
2880 assignment will not complete, which will block corresponding route export.
2882 .. clicmd:: nexthop vpn export A.B.C.D|X:X::X:X
2884 Specifies an optional nexthop value to be assigned to a route exported from
2885 the current unicast VRF to VPN. If left unspecified, the nexthop will be set
2886 to 0.0.0.0 or 0:0::0:0 (self).
2888 .. clicmd:: route-map vpn import|export MAP
2890 Specifies an optional route-map to be applied to routes imported or exported
2891 between the current unicast VRF and VPN.
2893 .. clicmd:: import|export vpn
2895 Enables import or export of routes between the current unicast VRF and VPN.
2897 .. clicmd:: import vrf VRFNAME
2899 Shortcut syntax for specifying automatic leaking from vrf VRFNAME to
2900 the current VRF using the VPN RIB as intermediary. The RD and RT
2901 are auto derived and should not be specified explicitly for either the
2902 source or destination VRF's.
2904 This shortcut syntax mode is not compatible with the explicit
2905 `import vpn` and `export vpn` statements for the two VRF's involved.
2906 The CLI will disallow attempts to configure incompatible leaking
2909 .. clicmd:: bgp retain route-target all
2911 It is possible to retain or not VPN prefixes that are not imported by local
2912 VRF configuration. This can be done via the following command in the context
2913 of the global VPNv4/VPNv6 family. This command defaults to on and is not
2915 The `no bgp retain route-target all` form of the command is displayed.
2917 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> soo EXTCOMMUNITY
2919 Without this command, SoO extended community attribute is configured using
2920 an inbound route map that sets the SoO value during the update process.
2921 With the introduction of the new BGP per-neighbor Site-of-Origin (SoO) feature,
2922 two new commands configured in sub-modes under router configuration mode
2923 simplify the SoO value configuration.
2925 If we configure SoO per neighbor at PEs, the SoO community is automatically
2926 added for all routes from the CPEs. Routes are validated and prevented from
2927 being sent back to the same CPE (e.g.: multi-site). This is especially needed
2928 when using ``as-override`` or ``allowas-in`` to prevent routing loops.
2930 .. clicmd:: mpls bgp forwarding
2932 It is possible to permit BGP install VPN prefixes without transport labels,
2933 by issuing the following command under the interface configuration context.
2934 This configuration will install VPN prefixes originated from an e-bgp session,
2935 and with the next-hop directly connected.
2942 .. clicmd:: segment-routing srv6
2944 Use SRv6 backend with BGP L3VPN, and go to its configuration node.
2946 .. clicmd:: locator NAME
2948 Specify the SRv6 locator to be used for SRv6 L3VPN. The Locator name must
2949 be set in zebra, but user can set it in any order.
2951 General configuration
2952 ^^^^^^^^^^^^^^^^^^^^^
2954 Configuration of the SRv6 SID used to advertise a L3VPN for both IPv4 and IPv6
2955 is accomplished via the following command in the context of a VRF:
2957 .. clicmd:: sid vpn per-vrf export (1..1048575)|auto
2959 Enables a SRv6 SID to be attached to a route exported from the current
2960 unicast VRF to VPN. A single SID is used for both IPv4 and IPv6 address
2961 families. If you want to set a SID for only IPv4 address family or IPv6
2962 address family, you need to use the command ``sid vpn export (1..1048575)|auto``
2963 in the context of an address-family. If the value specified is ``auto``,
2964 the SID value is automatically assigned from a pool maintained by the Zebra
2965 daemon. If Zebra is not running, or if this command is not configured, automatic
2966 SID assignment will not complete, which will block corresponding route export.
2970 Ethernet Virtual Network - EVPN
2971 -------------------------------
2973 Note: When using EVPN features and if you have a large number of hosts, make
2974 sure to adjust the size of the arp neighbor cache to avoid neighbor table
2975 overflow and/or excessive garbage collection. On Linux, the size of the table
2976 and garbage collection frequency can be controlled via the following
2977 sysctl configurations:
2979 .. code-block:: shell
2981 net.ipv4.neigh.default.gc_thresh1
2982 net.ipv4.neigh.default.gc_thresh2
2983 net.ipv4.neigh.default.gc_thresh3
2985 net.ipv6.neigh.default.gc_thresh1
2986 net.ipv6.neigh.default.gc_thresh2
2987 net.ipv6.neigh.default.gc_thresh3
2989 For more information, see ``man 7 arp``.
2991 .. _bgp-enabling-evpn:
2996 EVPN should be enabled on the BGP instance corresponding to the VRF acting as
2997 the underlay for the VXLAN tunneling. In most circumstances this will be the
2998 default VRF. The command to enable EVPN for a BGP instance is
2999 ``advertise-all-vni`` which lives under ``address-family l2vpn evpn``:
3005 address-family l2vpn evpn
3008 A more comprehensive configuration example can be found in the :ref:`evpn` page.
3010 .. _bgp-evpn-l3-route-targets:
3012 EVPN L3 Route-Targets
3013 ^^^^^^^^^^^^^^^^^^^^^
3015 .. clicmd:: route-target <import|export|both> <RTLIST|auto>
3017 Modify the route-target set for EVPN advertised type-2/type-5 routes.
3018 RTLIST is a list of any of matching
3019 ``(A.B.C.D:MN|EF:OPQR|GHJK:MN|*:OPQR|*:MN)`` where ``*`` indicates wildcard
3020 matching for the AS number. It will be set to match any AS number. This is
3021 useful in datacenter deployments with Downstream VNI. ``auto`` is used to
3022 retain the autoconfigure that is default behavior for L3 RTs.
3024 .. _bgp-evpn-advertise-pip:
3029 In a EVPN symmetric routing MLAG deployment, all EVPN routes advertised
3030 with anycast-IP as next-hop IP and anycast MAC as the Router MAC (RMAC - in
3031 BGP EVPN Extended-Community).
3032 EVPN picks up the next-hop IP from the VxLAN interface's local tunnel IP and
3033 the RMAC is obtained from the MAC of the L3VNI's SVI interface.
3034 Note: Next-hop IP is used for EVPN routes whether symmetric routing is
3035 deployed or not but the RMAC is only relevant for symmetric routing scenario.
3037 Current behavior is not ideal for Prefix (type-5) and self (type-2)
3038 routes. This is because the traffic from remote VTEPs routed sub optimally
3039 if they land on the system where the route does not belong.
3041 The advertise-pip feature advertises Prefix (type-5) and self (type-2)
3042 routes with system's individual (primary) IP as the next-hop and individual
3043 (system) MAC as Router-MAC (RMAC), while leaving the behavior unchanged for
3046 To support this feature there needs to have ability to co-exist a
3047 (system-MAC, system-IP) pair with a (anycast-MAC, anycast-IP) pair with the
3048 ability to terminate VxLAN-encapsulated packets received for either pair on
3049 the same L3VNI (i.e associated VLAN). This capability is needed per tenant
3052 To derive the system-MAC and the anycast MAC, there must be a
3053 separate/additional MAC-VLAN interface corresponding to L3VNI’s SVI.
3054 The SVI interface’s MAC address can be interpreted as system-MAC
3055 and MAC-VLAN interface's MAC as anycast MAC.
3057 To derive system-IP and anycast-IP, the default BGP instance's router-id is used
3058 as system-IP and the VxLAN interface’s local tunnel IP as the anycast-IP.
3060 User has an option to configure the system-IP and/or system-MAC value if the
3061 auto derived value is not preferred.
3063 Note: By default, advertise-pip feature is enabled and user has an option to
3064 disable the feature via configuration CLI. Once the feature is disabled under
3065 bgp vrf instance or MAC-VLAN interface is not configured, all the routes follow
3066 the same behavior of using same next-hop and RMAC values.
3068 .. clicmd:: advertise-pip [ip <addr> [mac <addr>]]
3070 Enables or disables advertise-pip feature, specify system-IP and/or system-MAC
3073 EVPN advertise-svi-ip
3074 ^^^^^^^^^^^^^^^^^^^^^
3075 Typically, the SVI IP address is reused on VTEPs across multiple racks. However,
3076 if you have unique SVI IP addresses that you want to be reachable you can use the
3077 advertise-svi-ip option. This option advertises the SVI IP/MAC address as a type-2
3078 route and eliminates the need for any flooding over VXLAN to reach the IP from a
3081 .. clicmd:: advertise-svi-ip
3083 Note that you should not enable both the advertise-svi-ip and the advertise-default-gw
3086 .. _bgp-evpn-overlay-index-gateway-ip:
3088 EVPN Overlay Index Gateway IP
3089 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
3090 RFC https://datatracker.ietf.org/doc/html/rfc9136 explains the use of overlay
3091 indexes for recursive route resolution for EVPN type-5 route.
3093 We support gateway IP overlay index.
3094 A gateway IP, advertised with EVPN prefix route, is used to find an EVPN MAC/IP
3095 route with its IP field same as the gateway IP. This MAC/IP entry provides the
3096 nexthop VTEP and the tunnel information required for the VxLAN encapsulation.
3102 . +--------+ BGP +--------+ BGP +--------+ +--------+
3103 SN1 | | IPv4 | | EVPN | | | |
3104 ======+ Host1 +------+ PE1 +------+ PE2 +------+ Host2 +
3106 +--------+ +--------+ +--------+ +--------+
3108 Consider above topology where prefix SN1 is connected behind host1. Host1
3109 advertises SN1 to PE1 over BGP IPv4 session. PE1 advertises SN1 to PE2 using
3110 EVPN type-5 route with host1 IP as the gateway IP. PE1 also advertises
3111 Host1 MAC/IP as type-2 route which is used to resolve host1 gateway IP.
3113 PE2 receives this type-5 route and imports it into the vrf based on route
3114 targets. BGP prefix imported into the vrf uses gateway IP as its BGP nexthop.
3115 This route is installed into zebra if following conditions are satisfied:
3117 1. Gateway IP nexthop is L3 reachable.
3118 2. PE2 has received EVPN type-2 route with IP field set to gateway IP.
3120 Topology requirements:
3122 1. This feature is supported for asymmetric routing model only. While
3123 sending packets to SN1, ingress PE (PE2) performs routing and
3124 egress PE (PE1) performs only bridging.
3125 2. This feature supports only traditional(non vlan-aware) bridge model. Bridge
3126 interface associated with L2VNI is an L3 interface. i.e., this interface is
3127 configured with an address in the L2VNI subnet. Note that the gateway IP
3128 should also have an address in the same subnet.
3129 3. As this feature works in asymmetric routing model, all L2VNIs and corresponding
3130 VxLAN and bridge interfaces should be present at all the PEs.
3131 4. L3VNI configuration is required to generate and import EVPN type-5 routes.
3132 L3VNI VxLAN and bridge interfaces also should be present.
3134 A PE can use one of the following two mechanisms to advertise an EVPN type-5
3135 route with gateway IP.
3137 1. CLI to add gateway IP while generating EVPN type-5 route from a BGP IPv4/IPv6
3140 .. clicmd:: advertise <ipv4|ipv6> unicast [gateway-ip]
3142 When this CLI is configured for a BGP vrf under L2VPN EVPN address family, EVPN
3143 type-5 routes are generated for BGP prefixes in the vrf. Nexthop of the BGP
3144 prefix becomes the gateway IP of the corresponding type-5 route.
3146 If the above command is configured without the "gateway-ip" keyword, type-5
3147 routes are generated without overlay index.
3149 2. Add gateway IP to EVPN type-5 route using a route-map:
3151 .. clicmd:: set evpn gateway-ip <ipv4|ipv6> <addr>
3153 When route-map with above set clause is applied as outbound policy in BGP, it
3154 will set the gateway-ip in EVPN type-5 NLRI.
3156 Example configuration:
3161 neighbor 192.168.0.1 remote-as 101
3163 address-family ipv4 l2vpn evpn
3164 neighbor 192.168.0.1 route-map RMAP out
3167 route-map RMAP permit 10
3168 set evpn gateway-ip 10.0.0.1
3169 set evpn gateway-ip 10::1
3171 A PE that receives a type-5 route with gateway IP overlay index should have
3172 "enable-resolve-overlay-index" configuration enabled to recursively resolve the
3173 overlay index nexthop and install the prefix into zebra.
3175 .. clicmd:: enable-resolve-overlay-index
3177 Example configuration:
3182 bgp router-id 192.168.100.1
3183 no bgp ebgp-requires-policy
3184 neighbor 10.0.1.2 remote-as 65002
3186 address-family l2vpn evpn
3187 neighbor 10.0.1.2 activate
3189 enable-resolve-overlay-index
3198 All-Active Multihoming is used for redundancy and load sharing. Servers
3199 are attached to two or more PEs and the links are bonded (link-aggregation).
3200 This group of server links is referred to as an Ethernet Segment.
3204 An Ethernet Segment can be configured by specifying a system-MAC and a
3205 local discriminator or a complete ESINAME against the bond interface on the
3208 .. clicmd:: evpn mh es-id <(1-16777215)|ESINAME>
3210 .. clicmd:: evpn mh es-sys-mac X:X:X:X:X:X
3212 The sys-mac and local discriminator are used for generating a 10-byte,
3213 Type-3 Ethernet Segment ID. ESINAME is a 10-byte, Type-0 Ethernet Segment ID -
3214 "00:AA:BB:CC:DD:EE:FF:GG:HH:II".
3216 Type-1 (EAD-per-ES and EAD-per-EVI) routes are used to advertise the locally
3217 attached ESs and to learn off remote ESs in the network. Local Type-2/MAC-IP
3218 routes are also advertised with a destination ESI allowing for MAC-IP syncing
3219 between Ethernet Segment peers.
3220 Reference: RFC 7432, RFC 8365
3222 EVPN-MH is intended as a replacement for MLAG or Anycast VTEPs. In
3223 multihoming each PE has an unique VTEP address which requires the introduction
3224 of a new dataplane construct, MAC-ECMP. Here a MAC/FDB entry can point to a
3225 list of remote PEs/VTEPs.
3229 Type-4 (ESR) routes are used for Designated Forwarder (DF) election. DFs
3230 forward BUM traffic received via the overlay network. This implementation
3231 uses a preference based DF election specified by draft-ietf-bess-evpn-pref-df.
3232 The DF preference is configurable per-ES (via zebra) -
3234 .. clicmd:: evpn mh es-df-pref (1-16777215)
3236 BUM traffic is rxed via the overlay by all PEs attached to a server but
3237 only the DF can forward the de-capsulated traffic to the access port. To
3238 accommodate that non-DF filters are installed in the dataplane to drop
3241 Similarly traffic received from ES peers via the overlay cannot be forwarded
3242 to the server. This is split-horizon-filtering with local bias.
3246 Some vendors do not send EAD-per-EVI routes. To interop with them we
3247 need to relax the dependency on EAD-per-EVI routes and activate a remote
3248 ES-PE based on just the EAD-per-ES route.
3250 Note that by default we advertise and expect EAD-per-EVI routes.
3252 .. clicmd:: disable-ead-evi-rx
3254 .. clicmd:: disable-ead-evi-tx
3258 As the primary purpose of EVPN-MH is redundancy keeping the failover efficient
3259 is a recurring theme in the implementation. Following sub-features have
3260 been introduced for the express purpose of efficient ES failovers.
3262 - Layer-2 Nexthop Groups and MAC-ECMP via L2NHG.
3264 - Host routes (for symmetric IRB) via L3NHG.
3265 On dataplanes that support layer3 nexthop groups the feature can be turned
3266 on via the following BGP config -
3268 .. clicmd:: use-es-l3nhg
3270 - Local ES (MAC/Neigh) failover via ES-redirect.
3271 On dataplanes that do not have support for ES-redirect the feature can be
3272 turned off via the following zebra config -
3274 .. clicmd:: evpn mh redirect-off
3276 Uplink/Core tracking
3277 """"""""""""""""""""
3278 When all the underlay links go down the PE no longer has access to the VxLAN
3279 +overlay. To prevent blackholing of traffic the server/ES links are
3280 protodowned on the PE. A link can be setup for uplink tracking via the
3281 following zebra configuration -
3283 .. clicmd:: evpn mh uplink
3285 Proxy advertisements
3286 """"""""""""""""""""
3287 To handle hitless upgrades support for proxy advertisement has been added
3288 as specified by draft-rbickhart-evpn-ip-mac-proxy-adv. This allows a PE
3289 (say PE1) to proxy advertise a MAC-IP rxed from an ES peer (say PE2). When
3290 the ES peer (PE2) goes down PE1 continues to advertise hosts learnt from PE2
3291 for a holdtime during which it attempts to establish local reachability of
3292 the host. This holdtime is configurable via the following zebra commands -
3294 .. clicmd:: evpn mh neigh-holdtime (0-86400)
3296 .. clicmd:: evpn mh mac-holdtime (0-86400)
3300 When a switch is rebooted we wait for a brief period to allow the underlay
3301 and EVPN network to converge before enabling the ESs. For this duration the
3302 ES bonds are held protodown. The startup delay is configurable via the
3303 following zebra command -
3305 .. clicmd:: evpn mh startup-delay (0-3600)
3307 EAD-per-ES fragmentation
3308 """"""""""""""""""""""""
3309 The EAD-per-ES route carries the EVI route targets for all the broadcast
3310 domains associated with the ES. Depending on the EVI scale the EAD-per-ES
3311 route maybe fragmented.
3313 The number of EVIs per-EAD route can be configured via the following
3316 .. clicmd:: [no] ead-es-frag evi-limit (1-1000)
3318 Sample Configuration
3319 ^^^^^^^^^^^^^^^^^^^^^
3325 address-family l2vpn evpn
3326 ead-es-frag evi-limit 200
3331 EAD-per-ES route-target
3332 """""""""""""""""""""""
3333 The EAD-per-ES route by default carries all the EVI route targets. Depending
3334 on EVI scale that can result in route fragmentation. In some cases it maybe
3335 necessary to avoid this fragmentation and that can be done via the following
3337 1. Configure a single supplementary BD per-tenant VRF. This SBD needs to
3338 be provisioned on all EVPN PEs associated with the tenant-VRF.
3339 2. Config the SBD's RT as the EAD-per-ES route's export RT.
3341 Sample Configuration
3342 ^^^^^^^^^^^^^^^^^^^^^
3348 address-family l2vpn evpn
3349 ead-es-route-target export 5556:1001
3350 ead-es-route-target export 5556:1004
3351 ead-es-route-target export 5556:1008
3355 Support with VRF network namespace backend
3356 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
3357 It is possible to separate overlay networks contained in VXLAN interfaces from
3358 underlay networks by using VRFs. VRF-lite and VRF-netns backends can be used for
3359 that. In the latter case, it is necessary to set both bridge and vxlan interface
3360 in the same network namespace, as below example illustrates:
3362 .. code-block:: shell
3366 ip link add name vxlan101 type vxlan id 101 dstport 4789 dev eth0 local 10.1.1.1
3367 ip link set dev vxlan101 netns vrf1
3368 ip netns exec vrf1 ip link set dev lo up
3369 ip netns exec vrf1 brctl addbr bridge101
3370 ip netns exec vrf1 brctl addif bridge101 vxlan101
3372 This makes it possible to separate not only layer 3 networks like VRF-lite networks.
3373 Also, VRF netns based make possible to separate layer 2 networks on separate VRF
3376 .. _bgp-conditional-advertisement:
3378 BGP Conditional Advertisement
3379 -----------------------------
3380 The BGP conditional advertisement feature uses the ``non-exist-map`` or the
3381 ``exist-map`` and the ``advertise-map`` keywords of the neighbor advertise-map
3382 command in order to track routes by the route prefix.
3385 1. If a route prefix is not present in the output of non-exist-map command,
3386 then advertise the route specified by the advertise-map command.
3388 2. If a route prefix is present in the output of non-exist-map command,
3389 then do not advertise the route specified by the addvertise-map command.
3392 1. If a route prefix is present in the output of exist-map command,
3393 then advertise the route specified by the advertise-map command.
3395 2. If a route prefix is not present in the output of exist-map command,
3396 then do not advertise the route specified by the advertise-map command.
3398 This feature is useful when some prefixes are advertised to one of its peers
3399 only if the information from the other peer is not present (due to failure in
3400 peering session or partial reachability etc).
3402 The conditional BGP announcements are sent in addition to the normal
3403 announcements that a BGP router sends to its peer.
3405 The conditional advertisement process is triggered by the BGP scanner process,
3406 which runs every 60 by default. This means that the maximum time for the
3407 conditional advertisement to take effect is the value of the process timer.
3409 As an optimization, while the process always runs on each timer expiry, it
3410 determines whether or not the conditional advertisement policy or the routing
3411 table has changed; if neither have changed, no processing is necessary and the
3412 scanner exits early.
3414 .. clicmd:: neighbor A.B.C.D advertise-map NAME [exist-map|non-exist-map] NAME
3416 This command enables BGP scanner process to monitor routes specified by
3417 exist-map or non-exist-map command in BGP table and conditionally advertises
3418 the routes specified by advertise-map command.
3420 .. clicmd:: bgp conditional-advertisement timer (5-240)
3422 Set the period to rerun the conditional advertisement scanner process. The
3423 default is 60 seconds.
3425 Sample Configuration
3426 ^^^^^^^^^^^^^^^^^^^^^
3430 ip address 10.10.10.2/24
3433 ip address 10.10.20.2/24
3436 ip address 203.0.113.1/32
3439 bgp log-neighbor-changes
3440 no bgp ebgp-requires-policy
3441 neighbor 10.10.10.1 remote-as 1
3442 neighbor 10.10.20.3 remote-as 3
3444 address-family ipv4 unicast
3445 neighbor 10.10.10.1 soft-reconfiguration inbound
3446 neighbor 10.10.20.3 soft-reconfiguration inbound
3447 neighbor 10.10.20.3 advertise-map ADV-MAP non-exist-map EXIST-MAP
3450 ip prefix-list DEFAULT seq 5 permit 192.0.2.5/32
3451 ip prefix-list DEFAULT seq 10 permit 192.0.2.1/32
3452 ip prefix-list EXIST seq 5 permit 10.10.10.10/32
3453 ip prefix-list DEFAULT-ROUTE seq 5 permit 0.0.0.0/0
3454 ip prefix-list IP1 seq 5 permit 10.139.224.0/20
3456 bgp community-list standard DC-ROUTES seq 5 permit 64952:3008
3457 bgp community-list standard DC-ROUTES seq 10 permit 64671:501
3458 bgp community-list standard DC-ROUTES seq 15 permit 64950:3009
3459 bgp community-list standard DEFAULT-ROUTE seq 5 permit 65013:200
3461 route-map ADV-MAP permit 10
3462 match ip address prefix-list IP1
3464 route-map ADV-MAP permit 20
3465 match community DC-ROUTES
3467 route-map EXIST-MAP permit 10
3468 match community DEFAULT-ROUTE
3469 match ip address prefix-list DEFAULT-ROUTE
3475 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.
3479 Router2# show ip bgp
3480 BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
3481 Default local pref 100, local AS 2
3482 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3483 i internal, r RIB-failure, S Stale, R Removed
3484 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3485 Origin codes: i - IGP, e - EGP, ? - incomplete
3486 RPKI validation codes: V valid, I invalid, N Not found
3488 Network Next Hop Metric LocPrf Weight Path
3489 *> 0.0.0.0/0 10.10.10.1 0 0 1 i
3490 *> 10.139.224.0/20 10.10.10.1 0 0 1 ?
3491 *> 192.0.2.1/32 10.10.10.1 0 0 1 i
3492 *> 192.0.2.5/32 10.10.10.1 0 0 1 i
3494 Displayed 4 routes and 4 total paths
3495 Router2# show ip bgp neighbors 10.10.20.3
3497 !--- Output suppressed.
3499 For address family: IPv4 Unicast
3500 Update group 7, subgroup 7
3501 Packet Queue length 0
3502 Inbound soft reconfiguration allowed
3503 Community attribute sent to this neighbor(all)
3504 Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Withdraw
3507 !--- Output suppressed.
3509 Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
3510 BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
3511 Default local pref 100, local AS 2
3512 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3513 i internal, r RIB-failure, S Stale, R Removed
3514 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3515 Origin codes: i - IGP, e - EGP, ? - incomplete
3516 RPKI validation codes: V valid, I invalid, N Not found
3518 Network Next Hop Metric LocPrf Weight Path
3519 *> 0.0.0.0/0 0.0.0.0 0 1 i
3520 *> 192.0.2.5/32 0.0.0.0 0 1 i
3522 Total number of prefixes 2
3524 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.
3528 Router2# show ip bgp
3529 BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
3530 Default local pref 100, local AS 2
3531 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3532 i internal, r RIB-failure, S Stale, R Removed
3533 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3534 Origin codes: i - IGP, e - EGP, ? - incomplete
3535 RPKI validation codes: V valid, I invalid, N Not found
3537 Network Next Hop Metric LocPrf Weight Path
3538 *> 10.139.224.0/20 10.10.10.1 0 0 1 ?
3539 *> 192.0.2.1/32 10.10.10.1 0 0 1 i
3540 *> 192.0.2.5/32 10.10.10.1 0 0 1 i
3542 Displayed 3 routes and 3 total paths
3544 Router2# show ip bgp neighbors 10.10.20.3
3546 !--- Output suppressed.
3548 For address family: IPv4 Unicast
3549 Update group 7, subgroup 7
3550 Packet Queue length 0
3551 Inbound soft reconfiguration allowed
3552 Community attribute sent to this neighbor(all)
3553 Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Advertise
3556 !--- Output suppressed.
3558 Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
3559 BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
3560 Default local pref 100, local AS 2
3561 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
3562 i internal, r RIB-failure, S Stale, R Removed
3563 Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
3564 Origin codes: i - IGP, e - EGP, ? - incomplete
3565 RPKI validation codes: V valid, I invalid, N Not found
3567 Network Next Hop Metric LocPrf Weight Path
3568 *> 10.139.224.0/20 0.0.0.0 0 1 ?
3569 *> 192.0.2.1/32 0.0.0.0 0 1 i
3570 *> 192.0.2.5/32 0.0.0.0 0 1 i
3572 Total number of prefixes 3
3580 .. clicmd:: show debug
3582 Show all enabled debugs.
3584 .. clicmd:: show bgp listeners
3586 Display Listen sockets and the vrf that created them. Useful for debugging of when
3587 listen is not working and this is considered a developer debug statement.
3589 .. clicmd:: debug bgp allow-martian
3591 Enable or disable BGP accepting martian nexthops from a peer. Please note
3592 this is not an actual debug command and this command is also being deprecated
3593 and will be removed soon. The new command is :clicmd:`bgp allow-martian-nexthop`
3595 .. clicmd:: debug bgp bfd
3597 Enable or disable debugging for BFD events. This will show BFD integration
3598 library messages and BGP BFD integration messages that are mostly state
3599 transitions and validation problems.
3601 .. clicmd:: debug bgp conditional-advertisement
3603 Enable or disable debugging of BGP conditional advertisement.
3605 .. clicmd:: debug bgp neighbor-events
3607 Enable or disable debugging for neighbor events. This provides general
3608 information on BGP events such as peer connection / disconnection, session
3609 establishment / teardown, and capability negotiation.
3611 .. clicmd:: debug bgp updates
3613 Enable or disable debugging for BGP updates. This provides information on
3614 BGP UPDATE messages transmitted and received between local and remote
3617 .. clicmd:: debug bgp keepalives
3619 Enable or disable debugging for BGP keepalives. This provides information on
3620 BGP KEEPALIVE messages transmitted and received between local and remote
3623 .. clicmd:: debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
3625 Enable or disable debugging for bestpath selection on the specified prefix.
3627 .. clicmd:: debug bgp nht
3629 Enable or disable debugging of BGP nexthop tracking.
3631 .. clicmd:: debug bgp update-groups
3633 Enable or disable debugging of dynamic update groups. This provides general
3634 information on group creation, deletion, join and prune events.
3636 .. clicmd:: debug bgp zebra
3638 Enable or disable debugging of communications between *bgpd* and *zebra*.
3640 Dumping Messages and Routing Tables
3641 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
3643 .. clicmd:: dump bgp all PATH [INTERVAL]
3645 .. clicmd:: dump bgp all-et PATH [INTERVAL]
3648 Dump all BGP packet and events to `path` file.
3649 If `interval` is set, a new file will be created for echo `interval` of
3650 seconds. The path `path` can be set with date and time formatting
3651 (strftime). The type ‘all-et’ enables support for Extended Timestamp Header
3652 (:ref:`packet-binary-dump-format`).
3654 .. clicmd:: dump bgp updates PATH [INTERVAL]
3656 .. clicmd:: dump bgp updates-et PATH [INTERVAL]
3659 Dump only BGP updates messages to `path` file.
3660 If `interval` is set, a new file will be created for echo `interval` of
3661 seconds. The path `path` can be set with date and time formatting
3662 (strftime). The type ‘updates-et’ enables support for Extended Timestamp
3663 Header (:ref:`packet-binary-dump-format`).
3665 .. clicmd:: dump bgp routes-mrt PATH
3667 .. clicmd:: dump bgp routes-mrt PATH INTERVAL
3670 Dump whole BGP routing table to `path`. This is heavy process. The path
3671 `path` can be set with date and time formatting (strftime). If `interval` is
3672 set, a new file will be created for echo `interval` of seconds.
3674 Note: the interval variable can also be set using hours and minutes: 04h20m00.
3677 .. _bgp-other-commands:
3682 The following are available in the top level *enable* mode:
3684 .. clicmd:: clear bgp \*
3688 .. clicmd:: clear bgp ipv4|ipv6 \*
3690 Clear all peers with this address-family activated.
3692 .. clicmd:: clear bgp ipv4|ipv6 unicast \*
3694 Clear all peers with this address-family and sub-address-family activated.
3696 .. clicmd:: clear bgp ipv4|ipv6 PEER
3698 Clear peers with address of X.X.X.X and this address-family activated.
3700 .. clicmd:: clear bgp ipv4|ipv6 unicast PEER
3702 Clear peer with address of X.X.X.X and this address-family and sub-address-family activated.
3704 .. clicmd:: clear bgp ipv4|ipv6 PEER soft|in|out
3706 Clear peer using soft reconfiguration in this address-family.
3708 .. clicmd:: clear bgp ipv4|ipv6 unicast PEER soft|in|out
3710 Clear peer using soft reconfiguration in this address-family and sub-address-family.
3712 .. clicmd:: clear bgp [ipv4|ipv6] [unicast] PEER|\* message-stats
3714 Clear BGP message statistics for a specified peer or for all peers,
3715 optionally filtered by activated address-family and sub-address-family.
3717 The following are available in the ``router bgp`` mode:
3719 .. clicmd:: write-quanta (1-64)
3721 BGP message Tx I/O is vectored. This means that multiple packets are written
3722 to the peer socket at the same time each I/O cycle, in order to minimize
3723 system call overhead. This value controls how many are written at a time.
3724 Under certain load conditions, reducing this value could make peer traffic
3725 less 'bursty'. In practice, leave this settings on the default (64) unless
3726 you truly know what you are doing.
3728 .. clicmd:: read-quanta (1-10)
3730 Unlike Tx, BGP Rx traffic is not vectored. Packets are read off the wire one
3731 at a time in a loop. This setting controls how many iterations the loop runs
3732 for. As with write-quanta, it is best to leave this setting on the default.
3734 The following command is available in ``config`` mode as well as in the
3735 ``router bgp`` mode:
3737 .. clicmd:: bgp graceful-shutdown
3739 The purpose of this command is to initiate BGP Graceful Shutdown which
3740 is described in :rfc:`8326`. The use case for this is to minimize or
3741 eliminate the amount of traffic loss in a network when a planned
3742 maintenance activity such as software upgrade or hardware replacement
3743 is to be performed on a router. The feature works by re-announcing
3744 routes to eBGP peers with the GRACEFUL_SHUTDOWN community included.
3745 Peers are then expected to treat such paths with the lowest preference.
3746 This happens automatically on a receiver running FRR; with other
3747 routing protocol stacks, an inbound policy may have to be configured.
3748 In FRR, triggering graceful shutdown also results in announcing a
3749 LOCAL_PREF of 0 to iBGP peers.
3751 Graceful shutdown can be configured per BGP instance or globally for
3752 all of BGP. These two options are mutually exclusive. The no form of
3753 the command causes graceful shutdown to be stopped, and routes will
3754 be re-announced without the GRACEFUL_SHUTDOWN community and/or with
3755 the usual LOCAL_PREF value. Note that if this option is saved to
3756 the startup configuration, graceful shutdown will remain in effect
3757 across restarts of *bgpd* and will need to be explicitly disabled.
3759 .. clicmd:: bgp input-queue-limit (1-4294967295)
3761 Set the BGP Input Queue limit for all peers when messaging parsing. Increase
3762 this only if you have the memory to handle large queues of messages at once.
3764 .. clicmd:: bgp output-queue-limit (1-4294967295)
3766 Set the BGP Output Queue limit for all peers when messaging parsing. Increase
3767 this only if you have the memory to handle large queues of messages at once.
3769 .. _bgp-displaying-bgp-information:
3771 Displaying BGP Information
3772 ==========================
3774 The following four commands display the IPv6 and IPv4 routing tables, depending
3775 on whether or not the ``ip`` keyword is used.
3776 Actually, :clicmd:`show ip bgp` command was used on older `Quagga` routing
3777 daemon project, while :clicmd:`show bgp` command is the new format. The choice
3778 has been done to keep old format with IPv4 routing table, while new format
3779 displays IPv6 routing table.
3781 .. clicmd:: show ip bgp [all] [wide|json [detail]]
3783 .. clicmd:: show ip bgp A.B.C.D [json]
3785 .. clicmd:: show bgp [all] [wide|json [detail]]
3787 .. clicmd:: show bgp X:X::X:X [json]
3789 These commands display BGP routes. When no route is specified, the default
3790 is to display all BGP routes.
3794 BGP table version is 0, local router ID is 10.1.1.1
3795 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
3796 Origin codes: i - IGP, e - EGP, ? - incomplete
3798 Network Next Hop Metric LocPrf Weight Path
3799 \*> 1.1.1.1/32 0.0.0.0 0 32768 i
3801 Total number of prefixes 1
3803 If ``wide`` option is specified, then the prefix table's width is increased
3804 to fully display the prefix and the nexthop.
3806 This is especially handy dealing with IPv6 prefixes and
3807 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
3809 If ``all`` option is specified, ``ip`` keyword is ignored, show bgp all and
3810 show ip bgp all commands display routes for all AFIs and SAFIs.
3812 If ``json`` option is specified, output is displayed in JSON format.
3814 If ``detail`` option is specified after ``json``, more verbose JSON output
3817 Some other commands provide additional options for filtering the output.
3819 .. clicmd:: show [ip] bgp regexp LINE
3821 This command displays BGP routes using AS path regular expression
3822 (:ref:`bgp-regular-expressions`).
3824 .. clicmd:: show [ip] bgp [all] summary [wide] [json]
3826 Show a bgp peer summary for the specified address family.
3828 The old command structure :clicmd:`show ip bgp` may be removed in the future
3829 and should no longer be used. In order to reach the other BGP routing tables
3830 other than the IPv6 routing table given by :clicmd:`show bgp`, the new command
3831 structure is extended with :clicmd:`show bgp [afi] [safi]`.
3833 ``wide`` option gives more output like ``LocalAS`` and extended ``Desc`` to
3838 exit1# show ip bgp summary wide
3840 IPv4 Unicast Summary (VRF default):
3841 BGP router identifier 192.168.100.1, local AS number 65534 vrf-id 0
3843 RIB entries 5, using 920 bytes of memory
3844 Peers 1, using 27 KiB of memory
3846 Neighbor V AS LocalAS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
3847 192.168.0.2 4 65030 123 15 22 0 0 0 00:07:00 0 1 us-east1-rs1.frrouting.org
3849 Total number of neighbors 1
3852 .. clicmd:: show bgp [afi] [safi] [all] [wide|json]
3854 .. clicmd:: show bgp vrfs [<VRFNAME$vrf_name>] [json]
3856 The command displays all bgp vrf instances basic info like router-id,
3857 configured and established neighbors,
3858 evpn related basic info like l3vni, router-mac, vxlan-interface.
3859 User can get that information as JSON format when ``json`` keyword
3860 at the end of cli is presented.
3864 torc-11# show bgp vrfs
3865 Type Id routerId #PeersCfg #PeersEstb Name
3866 L3-VNI RouterMAC Interface
3867 DFLT 0 17.0.0.6 3 3 default
3868 0 00:00:00:00:00:00 unknown
3869 VRF 21 17.0.0.6 0 0 sym_1
3870 8888 34:11:12:22:22:01 vlan4034_l3
3871 VRF 32 17.0.0.6 0 0 sym_2
3872 8889 34:11:12:22:22:01 vlan4035_l3
3874 Total number of VRFs (including default): 3
3876 .. clicmd:: show bgp [<ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast|flowspec> | l2vpn evpn]
3878 These commands display BGP routes for the specific routing table indicated by
3879 the selected afi and the selected safi. If no afi and no safi value is given,
3880 the command falls back to the default IPv6 routing table.
3882 .. clicmd:: show bgp l2vpn evpn route [type <macip|2|multicast|3|es|4|prefix|5>]
3884 EVPN prefixes can also be filtered by EVPN route type.
3886 .. clicmd:: show bgp l2vpn evpn route [detail] [type <ead|1|macip|2|multicast|3|es|4|prefix|5>] self-originate [json]
3888 Display self-originated EVPN prefixes which can also be filtered by EVPN route type.
3890 .. clicmd:: show bgp vni <all|VNI> [vtep VTEP] [type <ead|1|macip|2|multicast|3>] [<detail|json>]
3892 Display per-VNI EVPN routing table in bgp. Filter route-type, vtep, or VNI.
3894 .. clicmd:: show bgp [afi] [safi] [all] summary [json]
3896 Show a bgp peer summary for the specified address family, and subsequent
3899 .. clicmd:: show bgp [afi] [safi] [all] summary failed [json]
3901 Show a bgp peer summary for peers that are not successfully exchanging routes
3902 for the specified address family, and subsequent address-family.
3904 .. clicmd:: show bgp [afi] [safi] [all] summary established [json]
3906 Show a bgp peer summary for peers that are successfully exchanging routes
3907 for the specified address family, and subsequent address-family.
3909 .. clicmd:: show bgp [afi] [safi] [all] summary neighbor [PEER] [json]
3911 Show a bgp summary for the specified peer, address family, and
3912 subsequent address-family. The neighbor filter can be used in combination
3913 with the failed, established filters.
3915 .. clicmd:: show bgp [afi] [safi] [all] summary remote-as <internal|external|ASN> [json]
3917 Show a bgp peer summary for the specified remote-as ASN or type (``internal``
3918 for iBGP and ``external`` for eBGP sessions), address family, and subsequent
3919 address-family. The remote-as filter can be used in combination with the
3920 failed, established filters.
3922 .. clicmd:: show bgp [afi] [safi] [all] summary terse [json]
3924 Shorten the output. Do not show the following information about the BGP
3925 instances: the number of RIB entries, the table version and the used memory.
3926 The ``terse`` option can be used in combination with the remote-as, neighbor,
3927 failed and established filters, and with the ``wide`` option as well.
3929 .. clicmd:: show bgp [afi] [safi] [neighbor [PEER] [routes|advertised-routes|received-routes] [<A.B.C.D/M|X:X::X:X/M> | detail] [json]
3931 This command shows information on a specific BGP peer of the relevant
3932 afi and safi selected.
3934 The ``routes`` keyword displays only routes in this address-family's BGP
3935 table that were received by this peer and accepted by inbound policy.
3937 The ``advertised-routes`` keyword displays only the routes in this
3938 address-family's BGP table that were permitted by outbound policy and
3939 advertised to to this peer.
3941 The ``received-routes`` keyword displays all routes belonging to this
3942 address-family (prior to inbound policy) that were received by this peer.
3944 If a specific prefix is specified, the detailed version of that prefix will
3947 If ``detail`` option is specified, the detailed version of all routes
3948 will be displayed. The same format as ``show [ip] bgp [afi] [safi] PREFIX``
3949 will be used, but for the whole table of received, advertised or filtered
3952 If ``json`` option is specified, output is displayed in JSON format.
3954 .. clicmd:: show bgp [<view|vrf> VIEWVRFNAME] [afi] [safi] neighbors PEER received prefix-filter [json]
3956 Display Address Prefix ORFs received from this peer.
3958 .. clicmd:: show bgp [afi] [safi] [all] dampening dampened-paths [wide|json]
3960 Display paths suppressed due to dampening of the selected afi and safi
3963 .. clicmd:: show bgp [afi] [safi] [all] dampening flap-statistics [wide|json]
3965 Display flap statistics of routes of the selected afi and safi selected.
3967 .. clicmd:: show bgp [afi] [safi] [all] dampening parameters [json]
3969 Display details of configured dampening parameters of the selected afi and
3972 If the ``json`` option is specified, output is displayed in JSON format.
3974 .. clicmd:: show bgp [afi] [safi] [all] version (1-4294967295) [wide|json]
3976 Display prefixes with matching version numbers. The version number and
3977 above having prefixes will be listed here.
3979 It helps to identify which prefixes were installed at some point.
3981 Here is an example of how to check what prefixes were installed starting
3982 with an arbitrary version:
3984 .. code-block:: shell
3986 # vtysh -c 'show bgp ipv4 unicast json' | jq '.tableVersion'
3988 # vtysh -c 'show ip bgp version 9 json' | jq -r '.routes | keys[]'
3990 # vtysh -c 'show ip bgp version 8 json' | jq -r '.routes | keys[]'
3994 .. clicmd:: show bgp [afi] [safi] statistics
3996 Display statistics of routes of the selected afi and safi.
3998 .. clicmd:: show bgp statistics-all
4000 Display statistics of routes of all the afi and safi.
4002 .. clicmd:: show [ip] bgp [afi] [safi] [all] cidr-only [wide|json]
4004 Display routes with non-natural netmasks.
4006 .. clicmd:: show [ip] bgp [afi] [safi] [all] prefix-list WORD [wide|json]
4008 Display routes that match the specified prefix-list.
4010 If ``wide`` option is specified, then the prefix table's width is increased
4011 to fully display the prefix and the nexthop.
4013 If the ``json`` option is specified, output is displayed in JSON format.
4015 .. clicmd:: show [ip] bgp [afi] [safi] [all] access-list WORD [wide|json]
4017 Display routes that match the specified access-list.
4019 .. clicmd:: show [ip] bgp [afi] [safi] [all] filter-list WORD [wide|json]
4021 Display routes that match the specified AS-Path filter-list.
4023 If ``wide`` option is specified, then the prefix table's width is increased
4024 to fully display the prefix and the nexthop.
4026 If the ``json`` option is specified, output is displayed in JSON format.
4028 .. clicmd:: show [ip] bgp [afi] [safi] [all] route-map WORD [wide|json]
4030 Display routes that match the specified route-map.
4032 If ``wide`` option is specified, then the prefix table's width is increased
4033 to fully display the prefix and the nexthop.
4035 If the ``json`` option is specified, output is displayed in JSON format.
4037 .. clicmd:: show [ip] bgp [afi] [safi] [all] <A.B.C.D/M|X:X::X:X/M> longer-prefixes [wide|json]
4039 Displays the specified route and all more specific routes.
4041 If ``wide`` option is specified, then the prefix table's width is increased
4042 to fully display the prefix and the nexthop.
4044 If the ``json`` option is specified, output is displayed in JSON format.
4046 .. clicmd:: show [ip] bgp [afi] [safi] [all] self-originate [wide|json]
4048 Display self-originated routes.
4050 If ``wide`` option is specified, then the prefix table's width is increased
4051 to fully display the prefix and the nexthop.
4053 If the ``json`` option is specified, output is displayed in JSON format.
4055 .. clicmd:: show [ip] bgp [afi] [safi] [all] neighbors A.B.C.D [advertised-routes|received-routes|filtered-routes] [<A.B.C.D/M|X:X::X:X/M> | detail] [json|wide]
4057 Display the routes advertised to a BGP neighbor or received routes
4058 from neighbor or filtered routes received from neighbor based on the
4061 If ``wide`` option is specified, then the prefix table's width is increased
4062 to fully display the prefix and the nexthop.
4064 This is especially handy dealing with IPv6 prefixes and
4065 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
4067 If ``all`` option is specified, ``ip`` keyword is ignored and,
4068 routes displayed for all AFIs and SAFIs.
4069 if afi is specified, with ``all`` option, routes will be displayed for
4070 each SAFI in the selcted AFI
4072 If a specific prefix is specified, the detailed version of that prefix will
4075 If ``detail`` option is specified, the detailed version of all routes
4076 will be displayed. The same format as ``show [ip] bgp [afi] [safi] PREFIX``
4077 will be used, but for the whole table of received, advertised or filtered
4080 If ``json`` option is specified, output is displayed in JSON format.
4082 .. clicmd:: show [ip] bgp [afi] [safi] [all] detail-routes
4084 Display the detailed version of all routes. The same format as using
4085 ``show [ip] bgp [afi] [safi] PREFIX``, but for the whole BGP table.
4087 If ``all`` option is specified, ``ip`` keyword is ignored and,
4088 routes displayed for all AFIs and SAFIs.
4090 If ``afi`` is specified, with ``all`` option, routes will be displayed for
4091 each SAFI in the selected AFI.
4093 .. _bgp-display-routes-by-community:
4095 Displaying Routes by Community Attribute
4096 ----------------------------------------
4098 The following commands allow displaying routes based on their community
4101 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community [wide|json]
4103 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY [wide|json]
4105 .. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY exact-match [wide|json]
4107 These commands display BGP routes which have the community attribute.
4108 attribute. When ``COMMUNITY`` is specified, BGP routes that match that
4109 community are displayed. When `exact-match` is specified, it display only
4110 routes that have an exact match.
4112 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD [json]
4114 .. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match [json]
4116 These commands display BGP routes for the address family specified that
4117 match the specified community list. When `exact-match` is specified, it
4118 displays only routes that have an exact match.
4120 If ``wide`` option is specified, then the prefix table's width is increased
4121 to fully display the prefix and the nexthop.
4123 This is especially handy dealing with IPv6 prefixes and
4124 if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
4126 If ``all`` option is specified, ``ip`` keyword is ignored and,
4127 routes displayed for all AFIs and SAFIs.
4128 if afi is specified, with ``all`` option, routes will be displayed for
4129 each SAFI in the selcted AFI
4131 If ``json`` option is specified, output is displayed in JSON format.
4133 .. clicmd:: show bgp labelpool <chunks|inuse|ledger|requests|summary> [json]
4135 These commands display information about the BGP labelpool used for
4136 the association of MPLS labels with routes for L3VPN and Labeled Unicast
4138 If ``chunks`` option is specified, output shows the current list of label
4139 chunks granted to BGP by Zebra, indicating the start and end label in
4142 If ``inuse`` option is specified, output shows the current inuse list of
4143 label to prefix mappings
4145 If ``ledger`` option is specified, output shows ledger list of all
4146 label requests made per prefix
4148 If ``requests`` option is specified, output shows current list of label
4149 requests which have not yet been fulfilled by the labelpool
4151 If ``summary`` option is specified, output is a summary of the counts for
4152 the chunks, inuse, ledger and requests list along with the count of
4153 outstanding chunk requests to Zebra and the number of zebra reconnects
4156 If ``json`` option is specified, output is displayed in JSON format.
4158 .. _bgp-display-routes-by-lcommunity:
4160 Displaying Routes by Large Community Attribute
4161 ----------------------------------------------
4163 The following commands allow displaying routes based on their
4164 large community attribute.
4166 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community
4168 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY
4170 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY exact-match
4172 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY json
4174 These commands display BGP routes which have the large community attribute.
4175 attribute. When ``LARGE-COMMUNITY`` is specified, BGP routes that match that
4176 large community are displayed. When `exact-match` is specified, it display
4177 only routes that have an exact match. When `json` is specified, it display
4178 routes in json format.
4180 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD
4182 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD exact-match
4184 .. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD json
4186 These commands display BGP routes for the address family specified that
4187 match the specified large community list. When `exact-match` is specified,
4188 it displays only routes that have an exact match. When `json` is specified,
4189 it display routes in json format.
4191 .. _bgp-display-routes-by-as-path:
4194 Displaying Routes by AS Path
4195 ----------------------------
4197 .. clicmd:: show bgp ipv4|ipv6 regexp LINE
4199 This commands displays BGP routes that matches a regular
4200 expression `line` (:ref:`bgp-regular-expressions`).
4202 .. clicmd:: show [ip] bgp ipv4 vpn
4204 .. clicmd:: show [ip] bgp ipv6 vpn
4206 Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
4208 .. clicmd:: show bgp ipv4 vpn summary
4210 .. clicmd:: show bgp ipv6 vpn summary
4212 Print a summary of neighbor connections for the specified AFI/SAFI combination.
4214 Displaying Routes by Route Distinguisher
4215 ----------------------------------------
4217 .. clicmd:: show bgp [<ipv4|ipv6> vpn | l2vpn evpn [route]] rd <all|RD>
4219 For L3VPN and EVPN address-families, routes can be displayed on a per-RD
4220 (Route Distinguisher) basis or for all RD's.
4222 .. clicmd:: show bgp l2vpn evpn rd <all|RD> [overlay | tags]
4224 Use the ``overlay`` or ``tags`` keywords to display the overlay/tag
4225 information about the EVPN prefixes in the selected Route Distinguisher.
4227 .. clicmd:: show bgp l2vpn evpn route rd <all|RD> mac <MAC> [ip <MAC>] [json]
4229 For EVPN Type 2 (macip) routes, a MAC address (and optionally an IP address)
4230 can be supplied to the command to only display matching prefixes in the
4233 Displaying Update Group Information
4234 -----------------------------------
4236 .. clicmd:: show bgp update-groups [advertise-queue|advertised-routes|packet-queue]
4238 Display Information about each individual update-group being used.
4239 If SUBGROUP-ID is specified only display about that particular group. If
4240 advertise-queue is specified the list of routes that need to be sent
4241 to the peers in the update-group is displayed, advertised-routes means
4242 the list of routes we have sent to the peers in the update-group and
4243 packet-queue specifies the list of packets in the queue to be sent.
4245 .. clicmd:: show bgp update-groups statistics
4247 Display Information about update-group events in FRR.
4249 Displaying Nexthop Information
4250 ------------------------------
4251 .. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] nexthop ipv4 [A.B.C.D] [detail] [json]
4253 .. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] nexthop ipv6 [X:X::X:X] [detail] [json]
4255 .. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] nexthop [<A.B.C.D|X:X::X:X>] [detail] [json]
4257 .. clicmd:: show [ip] bgp <view|vrf> all nexthop [json]
4259 Display information about nexthops to bgp neighbors. If a certain nexthop is
4260 specified, also provides information about paths associated with the nexthop.
4261 With detail option provides information about gates of each nexthop.
4263 .. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] import-check-table [detail] [json]
4265 Display information about nexthops from table that is used to check network's
4266 existence in the rib for network statements.
4268 Segment-Routing IPv6
4269 --------------------
4271 .. clicmd:: show bgp segment-routing srv6
4273 This command displays information about SRv6 L3VPN in bgpd. Specifically,
4274 what kind of Locator is being used, and its Locator chunk information.
4275 And the SID of the SRv6 Function that is actually managed on bgpd.
4276 In the following example, bgpd is using a Locator named loc1, and two SRv6
4277 Functions are managed to perform VPNv6 VRF redirect for vrf10 and vrf20.
4281 router# show bgp segment-routing srv6
4286 - sid: 2001:db8:1:1::100
4288 - sid: 2001:db8:1:1::200
4292 vpn_policy[AFI_IP].tovpn_sid: none
4293 vpn_policy[AFI_IP6].tovpn_sid: none
4295 vpn_policy[AFI_IP].tovpn_sid: none
4296 vpn_policy[AFI_IP6].tovpn_sid: 2001:db8:1:1::100
4298 vpn_policy[AFI_IP].tovpn_sid: none
4299 vpn_policy[AFI_IP6].tovpn_sid: 2001:db8:1:1::200
4304 By default, the ASN value output follows how the BGP ASN instance is
4305 expressed in the configuration. Three as-notation outputs are available:
4307 - plain output: both AS4B and AS2B use a single number.
4308 ` router bgp 65536`.
4310 - dot output: AS4B values are using two numbers separated by a period.
4311 `router bgp 1.1` means that the AS number is 65536.
4313 - dot+ output: AS2B and AS4B values are using two numbers separated by a
4314 period. `router bgp 0.5` means that the AS number is 5.
4316 The below option permits forcing the as-notation output:
4318 .. clicmd:: router bgp ASN as-notation dot|dot+|plain
4320 The chosen as-notation format will override the BGP ASN output.
4322 .. _bgp-route-reflector:
4327 BGP routers connected inside the same AS through BGP belong to an internal
4328 BGP session, or IBGP. In order to prevent routing table loops, IBGP does not
4329 advertise IBGP-learned routes to other routers in the same session. As such,
4330 IBGP requires a full mesh of all peers. For large networks, this quickly becomes
4331 unscalable. Introducing route reflectors removes the need for the full-mesh.
4333 When route reflectors are configured, these will reflect the routes announced
4334 by the peers configured as clients. A route reflector client is configured
4337 .. clicmd:: neighbor PEER route-reflector-client
4340 To avoid single points of failure, multiple route reflectors can be configured.
4342 A cluster is a collection of route reflectors and their clients, and is used
4343 by route reflectors to avoid looping.
4345 .. clicmd:: bgp cluster-id A.B.C.D
4347 .. clicmd:: bgp no-rib
4349 To set and unset the BGP daemon ``-n`` / ``--no_kernel`` options during runtime
4350 to disable BGP route installation to the RIB (Zebra), the ``[no] bgp no-rib``
4351 commands can be used;
4353 Please note that setting the option during runtime will withdraw all routes in
4354 the daemons RIB from Zebra and unsetting it will announce all routes in the
4355 daemons RIB to Zebra. If the option is passed as a command line argument when
4356 starting the daemon and the configuration gets saved, the option will persist
4357 unless removed from the configuration with the negating command prior to the
4358 configuration write operation. At this point in time non SAFI_UNICAST BGP
4359 data is not properly withdrawn from zebra when this command is issued.
4361 .. clicmd:: bgp allow-martian-nexthop
4363 When a peer receives a martian nexthop as part of the NLRI for a route
4364 permit the nexthop to be used as such, instead of rejecting and resetting
4367 .. clicmd:: bgp send-extra-data zebra
4369 This command turns on the ability of BGP to send extra data to zebra. Currently,
4370 it's the AS-Path, communities, and the path selection reason. The default
4371 behavior in BGP is not to send this data. If the routes were sent to zebra and
4372 the option is changed, bgpd doesn't reinstall the routes to comply with the new
4375 .. clicmd:: bgp session-dscp (0-63)
4377 This command allows bgp to control, at a global level, the TCP dscp values
4380 .. _bgp-suppress-fib:
4382 Suppressing routes not installed in FIB
4383 =======================================
4385 The FRR implementation of BGP advertises prefixes learnt from a peer to other
4386 peers even if the routes do not get installed in the FIB. There can be
4387 scenarios where the hardware tables in some of the routers (along the path from
4388 the source to destination) is full which will result in all routes not getting
4389 installed in the FIB. If these routes are advertised to the downstream routers
4390 then traffic will start flowing and will be dropped at the intermediate router.
4392 The solution is to provide a configurable option to check for the FIB install
4393 status of the prefixes and advertise to peers if the prefixes are successfully
4394 installed in the FIB. The advertisement of the prefixes are suppressed if it is
4395 not installed in FIB.
4397 The following conditions apply will apply when checking for route installation
4400 1. The advertisement or suppression of routes based on FIB install status
4401 applies only for newly learnt routes from peer (routes which are not in
4403 2. If the route received from peer already exists in BGP local RIB and route
4404 attributes have changed (best path changed), the old path is deleted and
4405 new path is installed in FIB. The FIB install status will not have any
4406 effect. Therefore only when the route is received first time the checks
4408 3. The feature will not apply for routes learnt through other means like
4409 redistribution to bgp from other protocols. This is applicable only to
4411 4. If a route is installed in FIB and then gets deleted from the dataplane,
4412 then routes will not be withdrawn from peers. This will be considered as
4414 5. The feature will slightly increase the time required to advertise the routes
4415 to peers since the route install status needs to be received from the FIB
4416 6. If routes are received by the peer before the configuration is applied, then
4417 the bgp sessions need to be reset for the configuration to take effect.
4418 7. If the route which is already installed in dataplane is removed for some
4419 reason, sending withdraw message to peers is not currently supported.
4421 .. clicmd:: bgp suppress-fib-pending
4423 This command is applicable at the global level and at an individual
4424 bgp level. If applied at the global level all bgp instances will
4425 wait for fib installation before announcing routes and there is no
4426 way to turn it off for a particular bgp vrf.
4433 You can set different routing policy for a peer. For example, you can set
4434 different filter for a peer.
4440 neighbor 10.0.0.1 remote-as 2
4441 address-family ipv4 unicast
4442 neighbor 10.0.0.1 distribute-list 1 in
4446 neighbor 10.0.0.1 remote-as 2
4447 address-family ipv4 unicast
4448 neighbor 10.0.0.1 distribute-list 2 in
4451 This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view 2.
4452 When the update is inserted into view 1, distribute-list 1 is applied. On the
4453 other hand, when the update is inserted into view 2, distribute-list 2 is
4457 .. _bgp-regular-expressions:
4459 BGP Regular Expressions
4460 =======================
4462 BGP regular expressions are based on :t:`POSIX 1003.2` regular expressions. The
4463 following description is just a quick subset of the POSIX regular expressions.
4467 Matches any single character.
4470 Matches 0 or more occurrences of pattern.
4473 Matches 1 or more occurrences of pattern.
4476 Match 0 or 1 occurrences of pattern.
4479 Matches the beginning of the line.
4482 Matches the end of the line.
4485 The ``_`` character has special meanings in BGP regular expressions. It
4486 matches to space and comma , and AS set delimiter ``{`` and ``}`` and AS
4487 confederation delimiter ``(`` and ``)``. And it also matches to the
4488 beginning of the line and the end of the line. So ``_`` can be used for AS
4489 value boundaries match. This character technically evaluates to
4493 .. _bgp-configuration-examples:
4495 Miscellaneous Configuration Examples
4496 ====================================
4498 Example of a session to an upstream, advertising only one prefix to it.
4503 bgp router-id 10.236.87.1
4504 neighbor upstream peer-group
4505 neighbor upstream remote-as 64515
4506 neighbor upstream capability dynamic
4507 neighbor 10.1.1.1 peer-group upstream
4508 neighbor 10.1.1.1 description ACME ISP
4510 address-family ipv4 unicast
4511 network 10.236.87.0/24
4512 neighbor upstream prefix-list pl-allowed-adv out
4515 ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
4516 ip prefix-list pl-allowed-adv seq 10 deny any
4518 A more complex example including upstream, peer and customer sessions
4519 advertising global prefixes and NO_EXPORT prefixes and providing actions for
4520 customer routes based on community values. Extensive use is made of route-maps
4521 and the 'call' feature to support selective advertising of prefixes. This
4522 example is intended as guidance only, it has NOT been tested and almost
4523 certainly contains silly mistakes, if not serious flaws.
4528 bgp router-id 10.236.87.1
4529 neighbor upstream capability dynamic
4530 neighbor cust capability dynamic
4531 neighbor peer capability dynamic
4532 neighbor 10.1.1.1 remote-as 64515
4533 neighbor 10.1.1.1 peer-group upstream
4534 neighbor 10.2.1.1 remote-as 64516
4535 neighbor 10.2.1.1 peer-group upstream
4536 neighbor 10.3.1.1 remote-as 64517
4537 neighbor 10.3.1.1 peer-group cust-default
4538 neighbor 10.3.1.1 description customer1
4539 neighbor 10.4.1.1 remote-as 64518
4540 neighbor 10.4.1.1 peer-group cust
4541 neighbor 10.4.1.1 description customer2
4542 neighbor 10.5.1.1 remote-as 64519
4543 neighbor 10.5.1.1 peer-group peer
4544 neighbor 10.5.1.1 description peer AS 1
4545 neighbor 10.6.1.1 remote-as 64520
4546 neighbor 10.6.1.1 peer-group peer
4547 neighbor 10.6.1.1 description peer AS 2
4549 address-family ipv4 unicast
4550 network 10.123.456.0/24
4551 network 10.123.456.128/25 route-map rm-no-export
4552 neighbor upstream route-map rm-upstream-out out
4553 neighbor cust route-map rm-cust-in in
4554 neighbor cust route-map rm-cust-out out
4555 neighbor cust send-community both
4556 neighbor peer route-map rm-peer-in in
4557 neighbor peer route-map rm-peer-out out
4558 neighbor peer send-community both
4559 neighbor 10.3.1.1 prefix-list pl-cust1-network in
4560 neighbor 10.4.1.1 prefix-list pl-cust2-network in
4561 neighbor 10.5.1.1 prefix-list pl-peer1-network in
4562 neighbor 10.6.1.1 prefix-list pl-peer2-network in
4565 ip prefix-list pl-default permit 0.0.0.0/0
4567 ip prefix-list pl-upstream-peers permit 10.1.1.1/32
4568 ip prefix-list pl-upstream-peers permit 10.2.1.1/32
4570 ip prefix-list pl-cust1-network permit 10.3.1.0/24
4571 ip prefix-list pl-cust1-network permit 10.3.2.0/24
4573 ip prefix-list pl-cust2-network permit 10.4.1.0/24
4575 ip prefix-list pl-peer1-network permit 10.5.1.0/24
4576 ip prefix-list pl-peer1-network permit 10.5.2.0/24
4577 ip prefix-list pl-peer1-network permit 192.168.0.0/24
4579 ip prefix-list pl-peer2-network permit 10.6.1.0/24
4580 ip prefix-list pl-peer2-network permit 10.6.2.0/24
4581 ip prefix-list pl-peer2-network permit 192.168.1.0/24
4582 ip prefix-list pl-peer2-network permit 192.168.2.0/24
4583 ip prefix-list pl-peer2-network permit 172.16.1/24
4585 bgp as-path access-list seq 5 asp-own-as permit ^$
4586 bgp as-path access-list seq 10 asp-own-as permit _64512_
4588 ! #################################################################
4589 ! Match communities we provide actions for, on routes receives from
4590 ! customers. Communities values of <our-ASN>:X, with X, have actions:
4592 ! 100 - blackhole the prefix
4593 ! 200 - set no_export
4594 ! 300 - advertise only to other customers
4595 ! 400 - advertise only to upstreams
4596 ! 500 - set no_export when advertising to upstreams
4597 ! 2X00 - set local_preference to X00
4599 ! blackhole the prefix of the route
4600 bgp community-list standard cm-blackhole permit 64512:100
4602 ! set no-export community before advertising
4603 bgp community-list standard cm-set-no-export permit 64512:200
4605 ! advertise only to other customers
4606 bgp community-list standard cm-cust-only permit 64512:300
4608 ! advertise only to upstreams
4609 bgp community-list standard cm-upstream-only permit 64512:400
4611 ! advertise to upstreams with no-export
4612 bgp community-list standard cm-upstream-noexport permit 64512:500
4614 ! set local-pref to least significant 3 digits of the community
4615 bgp community-list standard cm-prefmod-100 permit 64512:2100
4616 bgp community-list standard cm-prefmod-200 permit 64512:2200
4617 bgp community-list standard cm-prefmod-300 permit 64512:2300
4618 bgp community-list standard cm-prefmod-400 permit 64512:2400
4619 bgp community-list expanded cme-prefmod-range permit 64512:2...
4621 ! Informational communities
4623 ! 3000 - learned from upstream
4624 ! 3100 - learned from customer
4625 ! 3200 - learned from peer
4627 bgp community-list standard cm-learnt-upstream permit 64512:3000
4628 bgp community-list standard cm-learnt-cust permit 64512:3100
4629 bgp community-list standard cm-learnt-peer permit 64512:3200
4631 ! ###################################################################
4632 ! Utility route-maps
4634 ! These utility route-maps generally should not used to permit/deny
4635 ! routes, i.e. they do not have meaning as filters, and hence probably
4636 ! should be used with 'on-match next'. These all finish with an empty
4637 ! permit entry so as not interfere with processing in the caller.
4639 route-map rm-no-export permit 10
4640 set community additive no-export
4641 route-map rm-no-export permit 20
4643 route-map rm-blackhole permit 10
4644 description blackhole, up-pref and ensure it cannot escape this AS
4645 set ip next-hop 127.0.0.1
4646 set local-preference 10
4647 set community additive no-export
4648 route-map rm-blackhole permit 20
4650 ! Set local-pref as requested
4651 route-map rm-prefmod permit 10
4652 match community cm-prefmod-100
4653 set local-preference 100
4654 route-map rm-prefmod permit 20
4655 match community cm-prefmod-200
4656 set local-preference 200
4657 route-map rm-prefmod permit 30
4658 match community cm-prefmod-300
4659 set local-preference 300
4660 route-map rm-prefmod permit 40
4661 match community cm-prefmod-400
4662 set local-preference 400
4663 route-map rm-prefmod permit 50
4665 ! Community actions to take on receipt of route.
4666 route-map rm-community-in permit 10
4667 description check for blackholing, no point continuing if it matches.
4668 match community cm-blackhole
4670 route-map rm-community-in permit 20
4671 match community cm-set-no-export
4674 route-map rm-community-in permit 30
4675 match community cme-prefmod-range
4677 route-map rm-community-in permit 40
4679 ! #####################################################################
4680 ! Community actions to take when advertising a route.
4681 ! These are filtering route-maps,
4683 ! Deny customer routes to upstream with cust-only set.
4684 route-map rm-community-filt-to-upstream deny 10
4685 match community cm-learnt-cust
4686 match community cm-cust-only
4687 route-map rm-community-filt-to-upstream permit 20
4689 ! Deny customer routes to other customers with upstream-only set.
4690 route-map rm-community-filt-to-cust deny 10
4691 match community cm-learnt-cust
4692 match community cm-upstream-only
4693 route-map rm-community-filt-to-cust permit 20
4695 ! ###################################################################
4696 ! The top-level route-maps applied to sessions. Further entries could
4697 ! be added obviously..
4700 route-map rm-cust-in permit 10
4701 call rm-community-in
4703 route-map rm-cust-in permit 20
4704 set community additive 64512:3100
4705 route-map rm-cust-in permit 30
4707 route-map rm-cust-out permit 10
4708 call rm-community-filt-to-cust
4710 route-map rm-cust-out permit 20
4712 ! Upstream transit ASes
4713 route-map rm-upstream-out permit 10
4714 description filter customer prefixes which are marked cust-only
4715 call rm-community-filt-to-upstream
4717 route-map rm-upstream-out permit 20
4718 description only customer routes are provided to upstreams/peers
4719 match community cm-learnt-cust
4722 ! outbound policy is same as for upstream
4723 route-map rm-peer-out permit 10
4724 call rm-upstream-out
4726 route-map rm-peer-in permit 10
4727 set community additive 64512:3200
4730 Example of how to set up a 6-Bone connection.
4734 ! bgpd configuration
4735 ! ==================
4737 ! MP-BGP configuration
4740 bgp router-id 10.0.0.1
4741 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as `as-number`
4744 network 3ffe:506::/32
4745 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
4746 neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
4747 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as `as-number`
4748 neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
4751 ipv6 access-list all permit any
4753 ! Set output nexthop address.
4755 route-map set-nexthop permit 10
4756 match ipv6 address all
4757 set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
4758 set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
4767 TCP provides a mechanism for the user to specify the max segment size.
4768 setsockopt API is used to set the max segment size for TCP session. We
4769 can configure this as part of BGP neighbor configuration.
4771 This document explains how to avoid ICMP vulnerability issues by limiting
4772 TCP max segment size when you are using MTU discovery. Using MTU discovery
4773 on TCP paths is one method of avoiding BGP packet fragmentation.
4775 TCP negotiates a maximum segment size (MSS) value during session connection
4776 establishment between two peers. The MSS value negotiated is primarily based
4777 on the maximum transmission unit (MTU) of the interfaces to which the
4778 communicating peers are directly connected. However, due to variations in
4779 link MTU on the path taken by the TCP packets, some packets in the network
4780 that are well within the MSS value might be fragmented when the packet size
4781 exceeds the link's MTU.
4783 This feature is supported with TCP over IPv4 and TCP over IPv6.
4787 Below configuration can be done in router bgp mode and allows the user to
4788 configure the tcp-mss value per neighbor. The configuration gets applied
4789 only after hard reset is performed on that neighbor. If we configure tcp-mss
4790 on both the neighbors then both neighbors need to be reset.
4792 The configuration takes effect based on below rules, so there is a configured
4793 tcp-mss and a synced tcp-mss value per TCP session.
4795 By default if the configuration is not done then the TCP max segment size is
4796 set to the Maximum Transmission unit (MTU) – (IP/IP6 header size + TCP header
4797 size + ethernet header). For IPv4 its MTU – (20 bytes IP header + 20 bytes TCP
4798 header + 12 bytes ethernet header) and for IPv6 its MTU – (40 bytes IPv6 header
4799 + 20 bytes TCP header + 12 bytes ethernet header).
4801 If the config is done then it reduces 12-14 bytes for the ether header and
4802 uses it after synchronizing in TCP handshake.
4804 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> tcp-mss (1-65535)
4806 When tcp-mss is configured kernel reduces 12-14 bytes for ethernet header.
4807 E.g. if tcp-mss is configured as 150 the synced value will be 138.
4809 Note: configured and synced value is different since TCP module will reduce
4810 12 bytes for ethernet header.
4817 frr# show running-config
4818 Building configuration...
4820 Current configuration:
4823 bgp router-id 192.0.2.1
4824 neighbor 198.51.100.2 remote-as 100
4825 neighbor 198.51.100.2 tcp-mss 150 => new entry
4826 neighbor 2001:DB8::2 remote-as 100
4827 neighbor 2001:DB8::2 tcp-mss 400 => new entry
4834 frr# show bgp neighbors 198.51.100.2
4835 BGP neighbor is 198.51.100.2, remote AS 100, local AS 100, internal link
4837 BGP version 4, remote router ID 192.0.2.2, local router ID 192.0.2.1
4838 BGP state = Established, up for 02:15:28
4839 Last read 00:00:28, Last write 00:00:28
4840 Hold time is 180, keepalive interval is 60 seconds
4841 Configured tcp-mss is 150, synced tcp-mss is 138 => new display
4845 frr# show bgp neighbors 2001:DB8::2
4846 BGP neighbor is 2001:DB8::2, remote AS 100, local AS 100, internal link
4848 BGP version 4, remote router ID 192.0.2.2, local router ID 192.0.2.1
4849 BGP state = Established, up for 02:16:34
4850 Last read 00:00:34, Last write 00:00:34
4851 Hold time is 180, keepalive interval is 60 seconds
4852 Configured tcp-mss is 400, synced tcp-mss is 388 => new display
4854 Show command json output:
4855 -------------------------
4859 frr# show bgp neighbors 2001:DB8::2 json
4864 "nbrInternalLink":true,
4867 "remoteRouterId":"192.0.2.2",
4868 "localRouterId":"192.0.2.1",
4869 "bgpState":"Established",
4870 "bgpTimerUpMsec":8349000,
4871 "bgpTimerUpString":"02:19:09",
4872 "bgpTimerUpEstablishedEpoch":1613054251,
4873 "bgpTimerLastRead":9000,
4874 "bgpTimerLastWrite":9000,
4875 "bgpInUpdateElapsedTimeMsecs":8347000,
4876 "bgpTimerHoldTimeMsecs":180000,
4877 "bgpTimerKeepAliveIntervalMsecs":60000,
4878 "bgpTcpMssConfigured":400, => new entry
4879 "bgpTcpMssSynced":388, => new entry
4883 frr# show bgp neighbors 198.51.100.2 json
4888 "nbrInternalLink":true,
4891 "remoteRouterId":"192.0.2.2",
4892 "localRouterId":"192.0.2.1",
4893 "bgpState":"Established",
4894 "bgpTimerUpMsec":8370000,
4895 "bgpTimerUpString":"02:19:30",
4896 "bgpTimerUpEstablishedEpoch":1613054251,
4897 "bgpTimerLastRead":30000,
4898 "bgpTimerLastWrite":30000,
4899 "bgpInUpdateElapsedTimeMsecs":8368000,
4900 "bgpTimerHoldTimeMsecs":180000,
4901 "bgpTimerKeepAliveIntervalMsecs":60000,
4902 "bgpTcpMssConfigured":150, => new entry
4903 "bgpTcpMssSynced":138, => new entry
4905 .. include:: routeserver.rst
4907 .. include:: rpki.rst
4909 .. include:: wecmp_linkbw.rst
4911 .. include:: flowspec.rst
4913 .. [#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)
4914 .. [bgp-route-osci-cond] McPherson, D. and Gill, V. and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", IETF RFC3345
4915 .. [stable-flexible-ibgp] Flavel, A. and M. Roughan, "Stable and flexible iBGP", ACM SIGCOMM 2009
4916 .. [ibgp-correctness] Griffin, T. and G. Wilfong, "On the correctness of IBGP configuration", ACM SIGCOMM 2002
4918 .. _bgp-fast-convergence:
4920 BGP fast-convergence support
4921 ============================
4922 Whenever BGP peer address becomes unreachable we must bring down the BGP
4923 session immediately. Currently only single-hop EBGP sessions are brought
4924 down immediately.IBGP and multi-hop EBGP sessions wait for hold-timer
4925 expiry to bring down the sessions.
4927 This new configuration option helps user to teardown BGP sessions immediately
4928 whenever peer becomes unreachable.
4930 .. clicmd:: bgp fast-convergence
4932 This configuration is available at the bgp level. When enabled, configuration
4933 is applied to all the neighbors configured in that bgp instance.
4938 neighbor 10.0.0.2 remote-as 64496
4939 neighbor fd00::2 remote-as 64496
4940 bgp fast-convergence
4942 address-family ipv4 unicast
4946 address-family ipv6 unicast
4947 neighbor fd00::2 activate