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.. _bgp:
***
BGP
***
:abbr:`BGP` stands for Border Gateway Protocol. The latest BGP version is 4.
BGP-4 is one of the Exterior Gateway Protocols and the de facto standard
interdomain routing protocol. BGP-4 is described in :rfc:`1771` and updated by
:rfc:`4271`. :rfc:`2858` adds multiprotocol support to BGP-4.
.. _starting-bgp:
Starting BGP
============
.. include:: config-include.rst
*bgpd* specific invocation options are described below. Common options may also
be specified (:ref:`common-invocation-options`).
.. program:: bgpd
.. option:: -p, --bgp_port <port>
Set the bgp protocol's port number. When port number is 0, that means do not
listen bgp port.
.. option:: -l, --listenon
Specify specific IP addresses for bgpd to listen on, rather than its default
of ``0.0.0.0`` / ``::``. This can be useful to constrain bgpd to an internal
address, or to run multiple bgpd processes on one host. Multiple addresses
can be specified.
In the following example, bgpd is started listening for connections on the
addresses 100.0.1.2 and fd00::2:2. The options -d (runs in daemon mode) and
-f (uses specific configuration file) are also used in this example as we
are likely to run multiple bgpd instances, each one with different
configurations, when using -l option.
Note that this option implies the --no_kernel option, and no learned routes will be installed into the linux kernel.
.. code-block:: shell
# /usr/lib/frr/bgpd -d -f /some-folder/bgpd.conf -l 100.0.1.2 -l fd00::2:2
.. option:: -n, --no_kernel
Do not install learned routes into the linux kernel. This option is useful
for a route-reflector environment or if you are running multiple bgp
processes in the same namespace. This option is different than the --no_zebra
option in that a ZAPI connection is made.
This option can also be toggled during runtime by using the
``[no] bgp no-rib`` commands in VTY shell.
Note that this option will persist after saving the configuration during
runtime, unless unset by the ``no bgp no-rib`` command in VTY shell prior to
a configuration write operation.
.. option:: -S, --skip_runas
Skip the normal process of checking capabilities and changing user and group
information.
.. option:: -e, --ecmp
Run BGP with a limited ecmp capability, that is different than what BGP
was compiled with. The value specified must be greater than 0 and less
than or equal to the MULTIPATH_NUM specified on compilation.
.. option:: -Z, --no_zebra
Do not communicate with zebra at all. This is different than the --no_kernel
option in that we do not even open a ZAPI connection to the zebra process.
.. option:: -s, --socket_size
When opening tcp connections to our peers, set the socket send buffer
size that the kernel will use for the peers socket. This option
is only really useful at a very large scale. Experimentation should
be done to see if this is helping or not at the scale you are running
at.
.. option:: -x, --v6-with-v4-nexthops
Allow BGP to peer in the V6 afi, when the interface only has v4 addresses.
This allows bgp to install the v6 routes with a v6 nexthop that has the
v4 address encoded in the nexthop. Zebra's equivalent option currently
overrides the bgp setting. This setting is only really usable when
the operator has turned off communication to zebra and is running bgpd
as a complete standalone process.
.. option:: -K, --graceful_restart
Bgpd will use this option to denote either a planned FRR graceful
restart or a bgpd-only graceful restart, and this will drive the BGP
GR restarting router procedures.
LABEL MANAGER
-------------
.. option:: -I, --int_num
Set zclient id. This is required when using Zebra label manager in proxy mode.
.. _bgp-basic-concepts:
Basic Concepts
==============
.. _bgp-autonomous-systems:
Autonomous Systems
------------------
From :rfc:`1930`:
An AS is a connected group of one or more IP prefixes run by one or more
network operators which has a SINGLE and CLEARLY DEFINED routing policy.
Each AS has an identifying number associated with it called an :abbr:`ASN
(Autonomous System Number)`. This is a two octet value ranging in value from 1
to 65535. The AS numbers 64512 through 65535 are defined as private AS numbers.
Private AS numbers must not be advertised on the global Internet.
The :abbr:`ASN (Autonomous System Number)` is one of the essential elements of
BGP. BGP is a distance vector routing protocol, and the AS-Path framework
provides distance vector metric and loop detection to BGP.
.. seealso:: :rfc:`1930`
.. _bgp-address-families:
Address Families
----------------
Multiprotocol extensions enable BGP to carry routing information for multiple
network layer protocols. BGP supports an Address Family Identifier (AFI) for
IPv4 and IPv6. Support is also provided for multiple sets of per-AFI
information via the BGP Subsequent Address Family Identifier (SAFI). FRR
supports SAFIs for unicast information, labeled information (:rfc:`3107` and
:rfc:`8277`), and Layer 3 VPN information (:rfc:`4364` and :rfc:`4659`).
.. _bgp-route-selection:
Route Selection
---------------
The route selection process used by FRR's BGP implementation uses the following
decision criterion, starting at the top of the list and going towards the
bottom until one of the factors can be used.
1. **Weight check**
Prefer higher local weight routes to lower routes.
2. **Local preference check**
Prefer higher local preference routes to lower.
3. **Local route check**
Prefer local routes (statics, aggregates, redistributed) to received routes.
If ``bgp bestpath aigp`` is enabled, and both paths that are compared have
AIGP attribute, BGP uses AIGP tie-breaking unless both of the paths have the
AIGP metric attribute. This means that the AIGP attribute is not evaluated
during the best path selection process between two paths when one path does
not have the AIGP attribute.
4. **AS path length check**
Prefer shortest hop-count AS_PATHs.
5. **Origin check**
Prefer the lowest origin type route. That is, prefer IGP origin routes to
EGP, to Incomplete routes.
6. **MED check**
Where routes with a MED were received from the same AS, prefer the route
with the lowest MED. :ref:`bgp-med`.
7. **External check**
Prefer the route received from an external, eBGP peer over routes received
from other types of peers.
8. **IGP cost check**
Prefer the route with the lower IGP cost.
9. **Multi-path check**
If multi-pathing is enabled, then check whether the routes not yet
distinguished in preference may be considered equal. If
:clicmd:`bgp bestpath as-path multipath-relax` is set, all such routes are
considered equal, otherwise routes received via iBGP with identical AS_PATHs
or routes received from eBGP neighbours in the same AS are considered equal.
10. **Already-selected external check**
Where both routes were received from eBGP peers, then prefer the route
which is already selected. Note that this check is not applied if
:clicmd:`bgp bestpath compare-routerid` is configured. This check can
prevent some cases of oscillation.
11. **Router-ID check**
Prefer the route with the lowest `router-ID`. If the route has an
`ORIGINATOR_ID` attribute, through iBGP reflection, then that router ID is
used, otherwise the `router-ID` of the peer the route was received from is
used.
12. **Cluster-List length check**
The route with the shortest cluster-list length is used. The cluster-list
reflects the iBGP reflection path the route has taken.
13. **Peer address**
Prefer the route received from the peer with the higher transport layer
address, as a last-resort tie-breaker.
.. _bgp-capability-negotiation:
Capability Negotiation
----------------------
When adding IPv6 routing information exchange feature to BGP. There were some
proposals. :abbr:`IETF (Internet Engineering Task Force)`
:abbr:`IDR (Inter Domain Routing)` adopted a proposal called Multiprotocol
Extension for BGP. The specification is described in :rfc:`2283`. The protocol
does not define new protocols. It defines new attributes to existing BGP. When
it is used exchanging IPv6 routing information it is called BGP-4+. When it is
used for exchanging multicast routing information it is called MBGP.
*bgpd* supports Multiprotocol Extension for BGP. So if a remote peer supports
the protocol, *bgpd* can exchange IPv6 and/or multicast routing information.
Traditional BGP did not have the feature to detect a remote peer's
capabilities, e.g. whether it can handle prefix types other than IPv4 unicast
routes. This was a big problem using Multiprotocol Extension for BGP in an
operational network. :rfc:`2842` adopted a feature called Capability
Negotiation. *bgpd* use this Capability Negotiation to detect the remote peer's
capabilities. If a peer is only configured as an IPv4 unicast neighbor, *bgpd*
does not send these Capability Negotiation packets (at least not unless other
optional BGP features require capability negotiation).
By default, FRR will bring up peering with minimal common capability for the
both sides. For example, if the local router has unicast and multicast
capabilities and the remote router only has unicast capability the local router
will establish the connection with unicast only capability. When there are no
common capabilities, FRR sends Unsupported Capability error and then resets the
connection.
.. _bgp-router-configuration:
BGP Router Configuration
========================
ASN and Router ID
-----------------
First of all you must configure BGP router with the :clicmd:`router bgp ASN`
command. The AS number is an identifier for the autonomous system. The AS
identifier can either be a number or two numbers separated by a period. The
BGP protocol uses the AS identifier for detecting whether the BGP connection is
internal or external.
.. clicmd:: router bgp ASN
Enable a BGP protocol process with the specified ASN. After
this statement you can input any `BGP Commands`.
.. clicmd:: bgp router-id A.B.C.D
This command specifies the router-ID. If *bgpd* connects to *zebra* it gets
interface and address information. In that case default router ID value is
selected as the largest IP Address of the interfaces. When `router zebra` is
not enabled *bgpd* can't get interface information so `router-id` is set to
0.0.0.0. So please set router-id by hand.
.. _bgp-multiple-autonomous-systems:
Multiple Autonomous Systems
---------------------------
FRR's BGP implementation is capable of running multiple autonomous systems at
once. Each configured AS corresponds to a :ref:`zebra-vrf`. In the past, to get
the same functionality the network administrator had to run a new *bgpd*
process; using VRFs allows multiple autonomous systems to be handled in a
single process.
When using multiple autonomous systems, all router config blocks after the
first one must specify a VRF to be the target of BGP's route selection. This
VRF must be unique within respect to all other VRFs being used for the same
purpose, i.e. two different autonomous systems cannot use the same VRF.
However, the same AS can be used with different VRFs.
.. note::
The separated nature of VRFs makes it possible to peer a single *bgpd*
process to itself, on one machine. Note that this can be done fully within
BGP without a corresponding VRF in the kernel or Zebra, which enables some
practical use cases such as :ref:`route reflectors <bgp-route-reflector>`
and route servers.
Configuration of additional autonomous systems, or of a router that targets a
specific VRF, is accomplished with the following command:
.. clicmd:: router bgp ASN vrf VRFNAME
``VRFNAME`` is matched against VRFs configured in the kernel. When ``vrf
VRFNAME`` is not specified, the BGP protocol process belongs to the default
VRF.
An example configuration with multiple autonomous systems might look like this:
.. code-block:: frr
router bgp 1
neighbor 10.0.0.1 remote-as 20
neighbor 10.0.0.2 remote-as 30
!
router bgp 2 vrf blue
neighbor 10.0.0.3 remote-as 40
neighbor 10.0.0.4 remote-as 50
!
router bgp 3 vrf red
neighbor 10.0.0.5 remote-as 60
neighbor 10.0.0.6 remote-as 70
...
.. seealso:: :ref:`bgp-vrf-route-leaking`
.. seealso:: :ref:`zebra-vrf`
.. _bgp-views:
Views
-----
In addition to supporting multiple autonomous systems, FRR's BGP implementation
also supports *views*.
BGP views are almost the same as normal BGP processes, except that routes
selected by BGP are not installed into the kernel routing table. Each BGP view
provides an independent set of routing information which is only distributed
via BGP. Multiple views can be supported, and BGP view information is always
independent from other routing protocols and Zebra/kernel routes. BGP views use
the core instance (i.e., default VRF) for communication with peers.
.. clicmd:: router bgp AS-NUMBER view NAME
Make a new BGP view. You can use an arbitrary word for the ``NAME``. Routes
selected by the view are not installed into the kernel routing table.
With this command, you can setup Route Server like below.
.. code-block:: frr
!
router bgp 1 view 1
neighbor 10.0.0.1 remote-as 2
neighbor 10.0.0.2 remote-as 3
!
router bgp 2 view 2
neighbor 10.0.0.3 remote-as 4
neighbor 10.0.0.4 remote-as 5
.. clicmd:: show [ip] bgp view NAME
Display the routing table of BGP view ``NAME``.
Route Selection
---------------
.. clicmd:: bgp bestpath as-path confed
This command specifies that the length of confederation path sets and
sequences should should be taken into account during the BGP best path
decision process.
.. clicmd:: bgp bestpath as-path multipath-relax
This command specifies that BGP decision process should consider paths
of equal AS_PATH length candidates for multipath computation. Without
the knob, the entire AS_PATH must match for multipath computation.
.. clicmd:: bgp bestpath compare-routerid
Ensure that when comparing routes where both are equal on most metrics,
including local-pref, AS_PATH length, IGP cost, MED, that the tie is broken
based on router-ID.
If this option is enabled, then the already-selected check, where
already selected eBGP routes are preferred, is skipped.
If a route has an `ORIGINATOR_ID` attribute because it has been reflected,
that `ORIGINATOR_ID` will be used. Otherwise, the router-ID of the peer the
route was received from will be used.
The advantage of this is that the route-selection (at this point) will be
more deterministic. The disadvantage is that a few or even one lowest-ID
router may attract all traffic to otherwise-equal paths because of this
check. It may increase the possibility of MED or IGP oscillation, unless
other measures were taken to avoid these. The exact behaviour will be
sensitive to the iBGP and reflection topology.
.. clicmd:: bgp bestpath peer-type multipath-relax
This command specifies that BGP decision process should consider paths
from all peers for multipath computation. If this option is enabled,
paths learned from any of eBGP, iBGP, or confederation neighbors will
be multipath if they are otherwise considered equal cost.
.. clicmd:: bgp bestpath aigp
Use the bgp bestpath aigp command to evaluate the AIGP attribute during
the best path selection process between two paths that have the AIGP
attribute.
When bgp bestpath aigp is disabled, BGP does not use AIGP tie-breaking
rules unless paths have the AIGP attribute.
Disabled by default.
.. clicmd:: bgp bestpath med missing-as-worst
If the paths MED value is missing and this command is configured
then treat it as the worse possible value that it can be.
.. clicmd:: maximum-paths (1-128)
Sets the maximum-paths value used for ecmp calculations for this
bgp instance in EBGP. The maximum value listed, 128, can be limited by
the ecmp cli for bgp or if the daemon was compiled with a lower
ecmp value. This value can also be set in ipv4/ipv6 unicast/labeled
unicast to only affect those particular afi/safi's.
.. clicmd:: maximum-paths ibgp (1-128) [equal-cluster-length]
Sets the maximum-paths value used for ecmp calculations for this
bgp instance in IBGP. The maximum value listed, 128, can be limited by
the ecmp cli for bgp or if the daemon was compiled with a lower
ecmp value. This value can also be set in ipv4/ipv6 unicast/labeled
unicast to only affect those particular afi/safi's.
.. _bgp-distance:
Administrative Distance Metrics
-------------------------------
.. clicmd:: distance bgp (1-255) (1-255) (1-255)
This command changes distance value of BGP. The arguments are the distance
values for external routes, internal routes and local routes
respectively.
.. clicmd:: distance (1-255) A.B.C.D/M
.. clicmd:: distance (1-255) A.B.C.D/M WORD
Sets the administrative distance for a particular route.
If the system has a static route configured from the kernel, it has a
distance of 0. In some cases, it might be useful to override the route
from the FRR. E.g.: Kernel has a statically configured default route,
and you received another default route from the BGP and want to install
it to be preferred over the static route. In such a case, you MUST set
a higher distance from the kernel.
.. seealso:: :ref:`administrative-distance`
.. _bgp-requires-policy:
Require policy on EBGP
----------------------
.. clicmd:: bgp ebgp-requires-policy
This command requires incoming and outgoing filters to be applied
for eBGP sessions as part of RFC-8212 compliance. Without the incoming
filter, no routes will be accepted. Without the outgoing filter, no
routes will be announced.
This is enabled by default for the traditional configuration and
turned off by default for datacenter configuration.
When you enable/disable this option you MUST clear the session.
When the incoming or outgoing filter is missing you will see
"(Policy)" sign under ``show bgp summary``:
.. code-block:: frr
exit1# show bgp summary
IPv4 Unicast Summary:
BGP router identifier 10.10.10.1, local AS number 65001 VRF default vrf-id 0
BGP table version 4
RIB entries 7, using 1344 bytes of memory
Peers 2, using 43 KiB of memory
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
192.168.0.2 4 65002 8 10 0 0 0 00:03:09 5 (Policy) N/A
fe80:1::2222 4 65002 9 11 0 0 0 00:03:09 (Policy) (Policy) N/A
Additionally a `show bgp neighbor` command would indicate in the `For address family:`
block that:
.. code-block:: frr
exit1# show bgp neighbor
...
For address family: IPv4 Unicast
Update group 1, subgroup 1
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Inbound updates discarded due to missing policy
Outbound updates discarded due to missing policy
0 accepted prefixes
Reject routes with AS_SET or AS_CONFED_SET types
------------------------------------------------
.. clicmd:: bgp reject-as-sets
This command enables rejection of incoming and outgoing routes having AS_SET or AS_CONFED_SET type.
Enforce first AS
----------------
.. clicmd:: bgp enforce-first-as
To configure a router to deny an update received from an external BGP (eBGP)
peer that does not list its autonomous system number at the beginning of
the `AS_PATH` in the incoming update, use the ``bgp enforce-first-as`` command
in router configuration mode.
In order to exclude an arbitrary neighbor from this enforcement, use the
command ``no neighbor NAME enforce-first-as``. And vice-versa if a global
enforcement is disabled, you can override this behavior per neighbor too.
Default: enabled.
.. note::
If you have a peering to RS (Route-Server), most likely you MUST disable the
first AS enforcement.
Suppress duplicate updates
--------------------------
.. clicmd:: bgp suppress-duplicates
For example, BGP routers can generate multiple identical announcements with
empty community attributes if stripped at egress. This is an undesired behavior.
Suppress duplicate updates if the route actually not changed.
Default: enabled.
Send Hard Reset CEASE Notification for Administrative Reset
-----------------------------------------------------------
.. clicmd:: bgp hard-administrative-reset
Send Hard Reset CEASE Notification for 'Administrative Reset' events.
When disabled, and Graceful Restart Notification capability is exchanged
between the peers, Graceful Restart procedures apply, and routes will be
retained.
Enabled by default.
Disable checking if nexthop is connected on EBGP sessions
---------------------------------------------------------
.. clicmd:: bgp disable-ebgp-connected-route-check
This command is used to disable the connection verification process for EBGP peering sessions
that are reachable by a single hop but are configured on a loopback interface or otherwise
configured with a non-directly connected IP address.
.. _bgp-route-flap-dampening:
Route Flap Dampening
--------------------
.. clicmd:: bgp dampening (1-45) (1-20000) (1-50000) (1-255)
This command enables (with optionally specified dampening parameters) or
disables route-flap dampening for all routes of a BGP instance.
.. clicmd:: neighbor PEER dampening [(1-45) [(1-20000) (1-20000) (1-255)]]
This command enables (with optionally specified dampening parameters) or
disables route-flap dampening for all routes learned from a BGP peer.
.. clicmd:: neighbor GROUP dampening [(1-45) [(1-20000) (1-20000) (1-255)]]
This command enables (with optionally specified dampening parameters) or
disables route-flap dampening for all routes learned from peers of a peer
group.
half-life
Half-life time for the penalty in minutes (default value: 15).
reuse-threshold
Value to start reusing a route (default value: 750).
suppress-threshold
Value to start suppressing a route (default value: 2000).
max-suppress
Maximum duration to suppress a stable route in minutes (default value:
60).
The route-flap damping algorithm is compatible with :rfc:`2439`. The use of
these commands is not recommended nowadays.
At the moment, route-flap dampening is not working per VRF and is working only
for IPv4 unicast and multicast.
With different parameter sets configurable for BGP instances, peer groups and
peers, the active dampening profile for a route is chosen on the fly,
allowing for various changes in configuration (i.e. peer group memberships)
during runtime. The parameter sets are taking precedence in the following
order:
1. Peer
2. Peer group
3. BGP instance
The negating commands do not allow to exclude a peer/peer group from a peer
group/BGP instances configuration.
.. seealso::
https://www.ripe.net/publications/docs/ripe-378
.. _bgp-med:
Multi-Exit Discriminator
------------------------
The BGP :abbr:`MED (Multi-Exit Discriminator)` attribute has properties which
can cause subtle convergence problems in BGP. These properties and problems
have proven to be hard to understand, at least historically, and may still not
be widely understood. The following attempts to collect together and present
what is known about MED, to help operators and FRR users in designing and
configuring their networks.
The BGP :abbr:`MED` attribute is intended to allow one AS to indicate its
preferences for its ingress points to another AS. The MED attribute will not be
propagated on to another AS by the receiving AS - it is 'non-transitive' in the
BGP sense.
E.g., if AS X and AS Y have 2 different BGP peering points, then AS X might set
a MED of 100 on routes advertised at one and a MED of 200 at the other. When AS
Y selects between otherwise equal routes to or via AS X, AS Y should prefer to
take the path via the lower MED peering of 100 with AS X. Setting the MED
allows an AS to influence the routing taken to it within another, neighbouring
AS.
In this use of MED it is not really meaningful to compare the MED value on
routes where the next AS on the paths differs. E.g., if AS Y also had a route
for some destination via AS Z in addition to the routes from AS X, and AS Z had
also set a MED, it wouldn't make sense for AS Y to compare AS Z's MED values to
those of AS X. The MED values have been set by different administrators, with
different frames of reference.
The default behaviour of BGP therefore is to not compare MED values across
routes received from different neighbouring ASes. In FRR this is done by
comparing the neighbouring, left-most AS in the received AS_PATHs of the routes
and only comparing MED if those are the same.
Unfortunately, this behaviour of MED, of sometimes being compared across routes
and sometimes not, depending on the properties of those other routes, means MED
can cause the order of preference over all the routes to be undefined. That is,
given routes A, B, and C, if A is preferred to B, and B is preferred to C, then
a well-defined order should mean the preference is transitive (in the sense of
orders [#med-transitivity-rant]_) and that A would be preferred to C.
However, when MED is involved this need not be the case. With MED it is
possible that C is actually preferred over A. So A is preferred to B, B is
preferred to C, but C is preferred to A. This can be true even where BGP
defines a deterministic 'most preferred' route out of the full set of A,B,C.
With MED, for any given set of routes there may be a deterministically
preferred route, but there need not be any way to arrange them into any order
of preference. With unmodified MED, the order of preference of routes literally
becomes undefined.
That MED can induce non-transitive preferences over routes can cause issues.
Firstly, it may be perceived to cause routing table churn locally at speakers;
secondly, and more seriously, it may cause routing instability in iBGP
topologies, where sets of speakers continually oscillate between different
paths.
The first issue arises from how speakers often implement routing decisions.
Though BGP defines a selection process that will deterministically select the
same route as best at any given speaker, even with MED, that process requires
evaluating all routes together. For performance and ease of implementation
reasons, many implementations evaluate route preferences in a pair-wise fashion
instead. Given there is no well-defined order when MED is involved, the best
route that will be chosen becomes subject to implementation details, such as
the order the routes are stored in. That may be (locally) non-deterministic,
e.g.: it may be the order the routes were received in.
This indeterminism may be considered undesirable, though it need not cause
problems. It may mean additional routing churn is perceived, as sometimes more
updates may be produced than at other times in reaction to some event .
This first issue can be fixed with a more deterministic route selection that
ensures routes are ordered by the neighbouring AS during selection.
:clicmd:`bgp deterministic-med`. This may reduce the number of updates as routes
are received, and may in some cases reduce routing churn. Though, it could
equally deterministically produce the largest possible set of updates in
response to the most common sequence of received updates.
A deterministic order of evaluation tends to imply an additional overhead of
sorting over any set of n routes to a destination. The implementation of
deterministic MED in FRR scales significantly worse than most sorting
algorithms at present, with the number of paths to a given destination. That
number is often low enough to not cause any issues, but where there are many
paths, the deterministic comparison may quickly become increasingly expensive
in terms of CPU.
Deterministic local evaluation can *not* fix the second, more major, issue of
MED however. Which is that the non-transitive preference of routes MED can
cause may lead to routing instability or oscillation across multiple speakers
in iBGP topologies. This can occur with full-mesh iBGP, but is particularly
problematic in non-full-mesh iBGP topologies that further reduce the routing
information known to each speaker. This has primarily been documented with iBGP
:ref:`route-reflection <bgp-route-reflector>` topologies. However, any
route-hiding technologies potentially could also exacerbate oscillation with MED.
This second issue occurs where speakers each have only a subset of routes, and
there are cycles in the preferences between different combinations of routes -
as the undefined order of preference of MED allows - and the routes are
distributed in a way that causes the BGP speakers to 'chase' those cycles. This
can occur even if all speakers use a deterministic order of evaluation in route
selection.
E.g., speaker 4 in AS A might receive a route from speaker 2 in AS X, and from
speaker 3 in AS Y; while speaker 5 in AS A might receive that route from
speaker 1 in AS Y. AS Y might set a MED of 200 at speaker 1, and 100 at speaker
3. I.e, using ASN:ID:MED to label the speakers:
::
.
/---------------\\
X:2------|--A:4-------A:5--|-Y:1:200
Y:3:100--|-/ |
\\---------------/
Assuming all other metrics are equal (AS_PATH, ORIGIN, 0 IGP costs), then based
on the RFC4271 decision process speaker 4 will choose X:2 over Y:3:100, based
on the lower ID of 2. Speaker 4 advertises X:2 to speaker 5. Speaker 5 will
continue to prefer Y:1:200 based on the ID, and advertise this to speaker 4.
Speaker 4 will now have the full set of routes, and the Y:1:200 it receives
from 5 will beat X:2, but when speaker 4 compares Y:1:200 to Y:3:100 the MED
check now becomes active as the ASes match, and now Y:3:100 is preferred.
Speaker 4 therefore now advertises Y:3:100 to 5, which will also agrees that
Y:3:100 is preferred to Y:1:200, and so withdraws the latter route from 4.
Speaker 4 now has only X:2 and Y:3:100, and X:2 beats Y:3:100, and so speaker 4
implicitly updates its route to speaker 5 to X:2. Speaker 5 sees that Y:1:200
beats X:2 based on the ID, and advertises Y:1:200 to speaker 4, and the cycle
continues.
The root cause is the lack of a clear order of preference caused by how MED
sometimes is and sometimes is not compared, leading to this cycle in the
preferences between the routes:
::
.
/---> X:2 ---beats---> Y:3:100 --\\
| |
| |
\\---beats--- Y:1:200 <---beats---/
This particular type of oscillation in full-mesh iBGP topologies can be
avoided by speakers preferring already selected, external routes rather than
choosing to update to new a route based on a post-MED metric (e.g. router-ID),
at the cost of a non-deterministic selection process. FRR implements this, as
do many other implementations, so long as it is not overridden by setting
:clicmd:`bgp bestpath compare-routerid`, and see also
:ref:`bgp-route-selection`.
However, more complex and insidious cycles of oscillation are possible with
iBGP route-reflection, which are not so easily avoided. These have been
documented in various places. See, e.g.:
- [bgp-route-osci-cond]_
- [stable-flexible-ibgp]_
- [ibgp-correctness]_
for concrete examples and further references.
There is as of this writing *no* known way to use MED for its original purpose;
*and* reduce routing information in iBGP topologies; *and* be sure to avoid the
instability problems of MED due the non-transitive routing preferences it can
induce; in general on arbitrary networks.
There may be iBGP topology specific ways to reduce the instability risks, even
while using MED, e.g.: by constraining the reflection topology and by tuning
IGP costs between route-reflector clusters, see :rfc:`3345` for details. In the
near future, the Add-Path extension to BGP may also solve MED oscillation while
still allowing MED to be used as intended, by distributing "best-paths per
neighbour AS". This would be at the cost of distributing at least as many
routes to all speakers as a full-mesh iBGP would, if not more, while also
imposing similar CPU overheads as the "Deterministic MED" feature at each
Add-Path reflector.
More generally, the instability problems that MED can introduce on more
complex, non-full-mesh, iBGP topologies may be avoided either by:
- Setting :clicmd:`bgp always-compare-med`, however this allows MED to be compared
across values set by different neighbour ASes, which may not produce
coherent desirable results, of itself.
- Effectively ignoring MED by setting MED to the same value (e.g.: 0) using
:clicmd:`set metric METRIC` on all received routes, in combination with
setting :clicmd:`bgp always-compare-med` on all speakers. This is the simplest
and most performant way to avoid MED oscillation issues, where an AS is happy
not to allow neighbours to inject this problematic metric.
As MED is evaluated after the AS_PATH length check, another possible use for
MED is for intra-AS steering of routes with equal AS_PATH length, as an
extension of the last case above. As MED is evaluated before IGP metric, this
can allow cold-potato routing to be implemented to send traffic to preferred
hand-offs with neighbours, rather than the closest hand-off according to the
IGP metric.
Note that even if action is taken to address the MED non-transitivity issues,
other oscillations may still be possible. E.g., on IGP cost if iBGP and IGP
topologies are at cross-purposes with each other - see the Flavel and Roughan
paper above for an example. Hence the guideline that the iBGP topology should
follow the IGP topology.
.. clicmd:: bgp deterministic-med
Carry out route-selection in way that produces deterministic answers
locally, even in the face of MED and the lack of a well-defined order of
preference it can induce on routes. Without this option the preferred route
with MED may be determined largely by the order that routes were received
in.
Setting this option will have a performance cost that may be noticeable when
there are many routes for each destination. Currently in FRR it is
implemented in a way that scales poorly as the number of routes per
destination increases.
The default is that this option is not set.
Note that there are other sources of indeterminism in the route selection
process, specifically, the preference for older and already selected routes
from eBGP peers, :ref:`bgp-route-selection`.
.. clicmd:: bgp always-compare-med
Always compare the MED on routes, even when they were received from
different neighbouring ASes. Setting this option makes the order of
preference of routes more defined, and should eliminate MED induced
oscillations.
If using this option, it may also be desirable to use
:clicmd:`set metric METRIC` to set MED to 0 on routes received from external
neighbours.
This option can be used, together with :clicmd:`set metric METRIC` to use
MED as an intra-AS metric to steer equal-length AS_PATH routes to, e.g.,
desired exit points.
.. _bgp-graceful-restart:
Graceful Restart
----------------
BGP graceful restart functionality as defined in
`RFC-4724 <https://tools.ietf.org/html/rfc4724/>`_ defines the mechanisms that
allows BGP speaker to continue to forward data packets along known routes
while the routing protocol information is being restored.
Usually, when BGP on a router restarts, all the BGP peers detect that the
session went down and then came up. This "down/up" transition results in a
"routing flap" and causes BGP route re-computation, generation of BGP routing
updates, and unnecessary churn to the forwarding tables.
The following functionality is provided by graceful restart:
1. The feature allows the restarting router to indicate to the helping peer the
routes it can preserve in its forwarding plane during control plane restart
by sending graceful restart capability in the OPEN message sent during
session establishment. Graceful restart notification flag and/or restart
time can also be changed during the dynamic BGP capabilities. If using
dynamic capabilities, no session reset is required, thus it's very useful
to increase restart time before doing a software upgrade or so.
2. The feature allows helping router to advertise to all other peers the routes
received from the restarting router which are preserved in the forwarding
plane of the restarting router during control plane restart.
::
(R1)-----------------------------------------------------------------(R2)
1. BGP Graceful Restart Capability exchanged between R1 & R2.
<--------------------------------------------------------------------->
2. Kill BGP Process at R1.
---------------------------------------------------------------------->
3. R2 Detects the above BGP Restart & verifies BGP Restarting
Capability of R1.
4. Start BGP Process at R1.
5. Re-establish the BGP session between R1 & R2.
<--------------------------------------------------------------------->
6. R2 Send initial route updates, followed by End-Of-Rib.
<----------------------------------------------------------------------
7. R1 was waiting for End-Of-Rib from R2 & which has been received
now.
8. R1 now runs BGP Best-Path algorithm. Send Initial BGP Update,
followed by End-Of Rib
<--------------------------------------------------------------------->
.. _bgp-GR-preserve-forwarding-state:
BGP-GR Preserve-Forwarding State
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
BGP OPEN message carrying optional capabilities for Graceful Restart has
8 bit “Flags for Address Family” for given AFI and SAFI. This field contains
bit flags relating to routes that were advertised with the given AFI and SAFI.
.. code-block:: frr
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F| Reserved |
+-+-+-+-+-+-+-+-+
The most significant bit is defined as the Forwarding State (F) bit, which
can be used to indicate whether the forwarding state for routes that were
advertised with the given AFI and SAFI has indeed been preserved during the
previous BGP restart. When set (value 1), the bit indicates that the
forwarding state has been preserved.
The remaining bits are reserved and MUST be set to zero by the sender and
ignored by the receiver.
.. clicmd:: bgp graceful-restart preserve-fw-state
FRR gives us the option to enable/disable the "F" flag using this specific
vty command. However, it doesn't have the option to enable/disable
this flag only for specific AFI/SAFI i.e. when this command is used, it
applied to all the supported AFI/SAFI combinations for this peer.
.. _bgp-end-of-rib-message:
End-of-RIB (EOR) message
^^^^^^^^^^^^^^^^^^^^^^^^
An UPDATE message with no reachable Network Layer Reachability Information
(NLRI) and empty withdrawn NLRI is specified as the End-of-RIB marker that can
be used by a BGP speaker to indicate to its peer the completion of the initial
routing update after the session is established.
For the IPv4 unicast address family, the End-of-RIB marker is an UPDATE message
with the minimum length. For any other address family, it is an UPDATE message
that contains only the MP_UNREACH_NLRI attribute with no withdrawn routes for
that <AFI, SAFI>.
Although the End-of-RIB marker is specified for the purpose of BGP graceful
restart, it is noted that the generation of such a marker upon completion of
the initial update would be useful for routing convergence in general, and thus
the practice is recommended.
.. _bgp-route-selection-deferral-timer:
Route Selection Deferral Timer
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Specifies the time the restarting router defers the route selection process
after restart.
Restarting Router : The usage of route election deferral timer is specified
in https://tools.ietf.org/html/rfc4724#section-4.1
Once the session between the Restarting Speaker and the Receiving Speaker is
re-established, the Restarting Speaker will receive and process BGP messages
from its peers.
However, it MUST defer route selection for an address family until it either.
1. Receives the End-of-RIB marker from all its peers (excluding the ones with
the "Restart State" bit set in the received capability and excluding the ones
that do not advertise the graceful restart capability).
2. The Selection_Deferral_Timer timeout.
.. clicmd:: bgp graceful-restart select-defer-time (0-3600)
This is command, will set deferral time to value specified.
.. clicmd:: bgp graceful-restart rib-stale-time (1-3600)
This is command, will set the time for which stale routes are kept in RIB.
.. clicmd:: bgp graceful-restart restart-time (0-4095)
Set the time to wait to delete stale routes before a BGP open message
is received.
Using with Long-lived Graceful Restart capability, this is recommended
setting this timer to 0 and control stale routes with
``bgp long-lived-graceful-restart stale-time``.
Default value is 120.
.. clicmd:: bgp graceful-restart stalepath-time (1-4095)
This is command, will set the max time (in seconds) to hold onto
restarting peer's stale paths.
It also controls Enhanced Route-Refresh timer.
If this command is configured and the router does not receive a Route-Refresh EoRR
message, the router removes the stale routes from the BGP table after the timer
expires. The stale path timer is started when the router receives a Route-Refresh
BoRR message.
.. clicmd:: bgp graceful-restart notification
Indicate Graceful Restart support for BGP NOTIFICATION messages.
After changing this parameter, you have to reset the peers in order to advertise
N-bit in Graceful Restart capability.
Without Graceful-Restart Notification capability (N-bit not set), GR is not
activated when receiving CEASE/HOLDTIME expire notifications.
When sending ``CEASE/Administrative Reset`` (``clear bgp``), the session is closed
and routes are not retained. When N-bit is set and ``bgp hard-administrative-reset``
is turned off Graceful-Restart is activated and routes are retained.
Enabled by default.
.. _bgp-per-peer-graceful-restart:
BGP Per Peer Graceful Restart
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Ability to enable and disable graceful restart, helper and no GR at all mode
functionality at peer level.
So bgp graceful restart can be enabled at modes global BGP level or at per
peer level. There are two FSM, one for BGP GR global mode and other for peer
per GR.
Default global mode is helper and default peer per mode is inherit from global.
If per peer mode is configured, the GR mode of this particular peer will
override the global mode.
.. _bgp-GR-config-mode-cmd:
BGP GR Config Mode Commands
^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: bgp graceful-restart
This command will enable BGP graceful restart functionality for all BGP instances.
.. clicmd:: bgp graceful-restart-disable
This command will disable both the functionality graceful restart and helper
mode for all BGP instances
.. clicmd:: bgp graceful-restart select-defer-time (0-3600)
This is command, will set deferral time to value specified.
.. clicmd:: bgp graceful-restart rib-stale-time (1-3600)
This is command, will set the time for which stale routes are kept in RIB.
.. clicmd:: bgp graceful-restart restart-time (0-4095)
Set the time to wait to delete stale routes before a BGP open message
is received.
Using with Long-lived Graceful Restart capability, this is recommended
setting this timer to 0 and control stale routes with
``bgp long-lived-graceful-restart stale-time``.
Default value is 120.
.. clicmd:: bgp graceful-restart stalepath-time (1-4095)
This is command, will set the max time (in seconds) to hold onto
restarting peer's stale paths.
It also controls Enhanced Route-Refresh timer.
If this command is configured and the router does not receive a Route-Refresh EoRR
message, the router removes the stale routes from the BGP table after the timer
expires. The stale path timer is started when the router receives a Route-Refresh
BoRR message
.. _bgp-GR-global-mode-cmd:
BGP GR Global Mode Commands
^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: bgp graceful-restart
This command will enable BGP graceful restart functionality at the global
level.
.. clicmd:: bgp graceful-restart-disable
This command will disable both the functionality graceful restart and helper
mode.
.. _bgp-GR-peer-mode-cmd:
BGP GR Peer Mode Commands
^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: neighbor A.B.C.D graceful-restart
This command will enable BGP graceful restart functionality at the peer
level.
.. clicmd:: neighbor A.B.C.D graceful-restart-helper
This command will enable BGP graceful restart helper only functionality
at the peer level.
.. clicmd:: neighbor A.B.C.D graceful-restart-disable
This command will disable the entire BGP graceful restart functionality
at the peer level.
Long-lived Graceful Restart
---------------------------
Currently, only restarter mode is supported. This capability is advertised only
if graceful restart capability is negotiated.
.. clicmd:: bgp long-lived-graceful-restart stale-time (1-16777215)
Specifies the maximum time to wait before purging long-lived stale routes for
helper routers.
Default is 0, which means the feature is off by default. Only graceful
restart takes into account.
.. _bgp-shutdown:
Administrative Shutdown
-----------------------
.. clicmd:: bgp shutdown [message MSG...]
Administrative shutdown of all peers of a bgp instance. Drop all BGP peers,
but preserve their configurations. The peers are notified in accordance with
`RFC 8203 <https://tools.ietf.org/html/rfc8203/>`_ by sending a
``NOTIFICATION`` message with error code ``Cease`` and subcode
``Administrative Shutdown`` prior to terminating connections. This global
shutdown is independent of the neighbor shutdown, meaning that individually
shut down peers will not be affected by lifting it.
An optional shutdown message `MSG` can be specified.
.. _bgp-network:
Networks
--------
.. clicmd:: network A.B.C.D/M
This command adds the announcement network.
.. code-block:: frr
router bgp 1
address-family ipv4 unicast
network 10.0.0.0/8
exit-address-family
This configuration example says that network 10.0.0.0/8 will be
announced to all neighbors. Some vendors' routers don't advertise
routes if they aren't present in their IGP routing tables; `bgpd`
doesn't care about IGP routes when announcing its routes.
.. clicmd:: bgp network import-check
This configuration modifies the behavior of the network statement.
If you have this configured the underlying network must exist in
the rib. If you have the [no] form configured then BGP will not
check for the networks existence in the rib. For versions 7.3 and
before frr defaults for datacenter were the network must exist,
traditional did not check for existence. For versions 7.4 and beyond
both traditional and datacenter the network must exist.
.. _bgp-ipv6-support:
IPv6 Support
------------
.. clicmd:: neighbor A.B.C.D activate
This configuration modifies whether to enable an address family for a
specific neighbor. By default only the IPv4 unicast address family is
enabled.
.. code-block:: frr
router bgp 1
address-family ipv6 unicast
neighbor 2001:0DB8::1 activate
network 2001:0DB8:5009::/64
exit-address-family
This configuration example says that network 2001:0DB8:5009::/64 will be
announced and enables the neighbor 2001:0DB8::1 to receive this announcement.
By default, only the IPv4 unicast address family is announced to all
neighbors. Using the 'no bgp default ipv4-unicast' configuration overrides
this default so that all address families need to be enabled explicitly.
.. code-block:: frr
router bgp 1
no bgp default ipv4-unicast
neighbor 10.10.10.1 remote-as 2
neighbor 2001:0DB8::1 remote-as 3
address-family ipv4 unicast
neighbor 10.10.10.1 activate
network 192.168.1.0/24
exit-address-family
address-family ipv6 unicast
neighbor 2001:0DB8::1 activate
network 2001:0DB8:5009::/64
exit-address-family
This configuration demonstrates how the 'no bgp default ipv4-unicast' might
be used in a setup with two upstreams where each of the upstreams should only
receive either IPv4 or IPv6 announcements.
Using the ``bgp default ipv6-unicast`` configuration, IPv6 unicast
address family is enabled by default for all new neighbors.
.. clicmd:: bgp ipv6-auto-ra
By default, bgpd can ask Zebra to enable sending IPv6 router advertisement
messages on interfaces. For example, this happens for unnumbered peers
support or when extended-nexthop capability is used. The ``no`` form of this
command disables such behaviour.
.. _bgp-route-aggregation:
Route Aggregation
-----------------
.. _bgp-route-aggregation-ipv4:
Route Aggregation-IPv4 Address Family
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: aggregate-address A.B.C.D/M
This command specifies an aggregate address.
In order to advertise an aggregated prefix, a more specific (longer) prefix
MUST exist in the BGP table. For example, if you want to create an
``aggregate-address 10.0.0.0/24``, you should make sure you have something
like ``10.0.0.5/32`` or ``10.0.0.0/26``, or any other smaller prefix in the
BGP table. The routing information table (RIB) is not enough, you have to
redistribute them into the BGP table.
.. clicmd:: aggregate-address A.B.C.D/M route-map NAME
Apply a route-map for an aggregated prefix.
.. clicmd:: aggregate-address A.B.C.D/M origin <egp|igp|incomplete>
Override ORIGIN for an aggregated prefix.
.. clicmd:: aggregate-address A.B.C.D/M as-set
This command specifies an aggregate address. Resulting routes include
AS set.
.. clicmd:: aggregate-address A.B.C.D/M summary-only
This command specifies an aggregate address.
Longer prefixes advertisements of more specific routes to all neighbors are suppressed.
.. clicmd:: aggregate-address A.B.C.D/M matching-MED-only
Configure the aggregated address to only be created when the routes MED
match, otherwise no aggregated route will be created.
.. clicmd:: aggregate-address A.B.C.D/M suppress-map NAME
Similar to `summary-only`, but will only suppress more specific routes that
are matched by the selected route-map.
This configuration example sets up an ``aggregate-address`` under the ipv4
address-family.
.. code-block:: frr
router bgp 1
address-family ipv4 unicast
aggregate-address 10.0.0.0/8
aggregate-address 20.0.0.0/8 as-set
aggregate-address 40.0.0.0/8 summary-only
aggregate-address 50.0.0.0/8 route-map aggr-rmap
exit-address-family
.. _bgp-route-aggregation-ipv6:
Route Aggregation-IPv6 Address Family
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: aggregate-address X:X::X:X/M
This command specifies an aggregate address.
.. clicmd:: aggregate-address X:X::X:X/M route-map NAME
Apply a route-map for an aggregated prefix.
.. clicmd:: aggregate-address X:X::X:X/M origin <egp|igp|incomplete>
Override ORIGIN for an aggregated prefix.
.. clicmd:: aggregate-address X:X::X:X/M as-set
This command specifies an aggregate address. Resulting routes include
AS set.
.. clicmd:: aggregate-address X:X::X:X/M summary-only
This command specifies an aggregate address.
Longer prefixes advertisements of more specific routes to all neighbors are suppressed
.. clicmd:: aggregate-address X:X::X:X/M matching-MED-only
Configure the aggregated address to only be created when the routes MED
match, otherwise no aggregated route will be created.
.. clicmd:: aggregate-address X:X::X:X/M suppress-map NAME
Similar to `summary-only`, but will only suppress more specific routes that
are matched by the selected route-map.
This configuration example sets up an ``aggregate-address`` under the ipv6
address-family.
.. code-block:: frr
router bgp 1
address-family ipv6 unicast
aggregate-address 10::0/64
aggregate-address 20::0/64 as-set
aggregate-address 40::0/64 summary-only
aggregate-address 50::0/64 route-map aggr-rmap
exit-address-family
.. _bgp-redistribute-to-bgp:
Redistribution
--------------
Redistribution configuration should be placed under the ``address-family``
section for the specific AF to redistribute into. Protocol availability for
redistribution is determined by BGP AF; for example, you cannot redistribute
OSPFv3 into ``address-family ipv4 unicast`` as OSPFv3 supports IPv6.
.. clicmd:: redistribute <babel|connected|eigrp|isis|kernel|openfabric|ospf|ospf6|rip|ripng|sharp|static> [metric (0-4294967295)] [route-map WORD]
Redistribute routes from other protocols into BGP.
Note - When redistributing a static route, or any better Admin Distance route,
into BGP for which the same path is learned dynamically from another BGP
speaker, if the redistribute path is more preferred from a BGP Best Path
standpoint than the dynamically learned path, then BGP will not export
the best path to Zebra(RIB) for installation into the routing table,
unless BGP receives the path before the static route is created.
.. clicmd:: redistribute <table|table-direct> (1-65535)] [metric (0-4294967295)] [route-map WORD]
Redistribute routes from a routing table ID into BGP. There are two
techniques for redistribution:
- Standard Table Redistribution ``table (1-65535)``:
- Routes from the specified routing table ID are imported into the
default routing table using the ``ip import-table ID`` command.
- These routes are identified by the protocol type "T[ID]" when
displayed with ``show (ip|ipv6) route``.
- The ``redistribute table ID`` command then integrates these routes
into BGP.
- Direct Table Redistribution ``table-direct (1-65535)``:
- This method directly imports routes from the designated routing table
ID into BGP, omitting the step of adding to the default routing table.
- This method is especially relevant when the specified table ID is
checked against routing by appending the appropriate `ip rules`.
Redistribute routes from a routing table number into BGP.
.. clicmd:: redistribute vnc-direct
Redistribute VNC direct (not via zebra) routes to BGP process.
.. clicmd:: bgp update-delay MAX-DELAY
.. clicmd:: bgp update-delay MAX-DELAY ESTABLISH-WAIT
This feature is used to enable read-only mode on BGP process restart or when
a BGP process is cleared using 'clear ip bgp \*'. Note that this command is
configured at the global level and applies to all bgp instances/vrfs. It
cannot be used at the same time as the "update-delay" command described below,
which is entered in each bgp instance/vrf desired to delay update installation
and advertisements. The global and per-vrf approaches to defining update-delay
are mutually exclusive.
When applicable, read-only mode would begin as soon as the first peer reaches
Established status and a timer for max-delay seconds is started. During this
mode BGP doesn't run any best-path or generate any updates to its peers. This
mode continues until:
1. All the configured peers, except the shutdown peers, have sent explicit EOR
(End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
Established is considered an implicit-EOR.
If the establish-wait optional value is given, then BGP will wait for
peers to reach established from the beginning of the update-delay till the
establish-wait period is over, i.e. the minimum set of established peers for
which EOR is expected would be peers established during the establish-wait
window, not necessarily all the configured neighbors.
2. max-delay period is over.
On hitting any of the above two conditions, BGP resumes the decision process
and generates updates to its peers.
Default max-delay is 0, i.e. the feature is off by default.
.. clicmd:: update-delay MAX-DELAY
.. clicmd:: update-delay MAX-DELAY ESTABLISH-WAIT
This feature is used to enable read-only mode on BGP process restart or when
a BGP process is cleared using 'clear ip bgp \*'. Note that this command is
configured under the specific bgp instance/vrf that the feature is enabled for.
It cannot be used at the same time as the global "bgp update-delay" described
above, which is entered at the global level and applies to all bgp instances.
The global and per-vrf approaches to defining update-delay are mutually
exclusive.
When applicable, read-only mode would begin as soon as the first peer reaches
Established status and a timer for max-delay seconds is started. During this
mode BGP doesn't run any best-path or generate any updates to its peers. This
mode continues until:
1. All the configured peers, except the shutdown peers, have sent explicit EOR
(End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
Established is considered an implicit-EOR.
If the establish-wait optional value is given, then BGP will wait for
peers to reach established from the beginning of the update-delay till the
establish-wait period is over, i.e. the minimum set of established peers for
which EOR is expected would be peers established during the establish-wait
window, not necessarily all the configured neighbors.
2. max-delay period is over.
On hitting any of the above two conditions, BGP resumes the decision process
and generates updates to its peers.
Default max-delay is 0, i.e. the feature is off by default.
.. clicmd:: table-map ROUTE-MAP-NAME
This feature is used to apply a route-map on route updates from BGP to
Zebra. All the applicable match operations are allowed, such as match on
prefix, next-hop, communities, etc. Set operations for this attach-point are
limited to metric and next-hop only. Any operation of this feature does not
affect BGPs internal RIB.
Supported for ipv4 and ipv6 address families. It works on multi-paths as
well, however, metric setting is based on the best-path only.
.. _bgp-peers:
Peers
-----
.. _bgp-defining-peers:
Defining Peers
^^^^^^^^^^^^^^
.. clicmd:: neighbor PEER remote-as ASN
Creates a new neighbor whose remote-as is ASN. PEER can be an IPv4 address
or an IPv6 address or an interface to use for the connection.
.. code-block:: frr
router bgp 1
neighbor 10.0.0.1 remote-as 2
In this case my router, in AS-1, is trying to peer with AS-2 at 10.0.0.1.
This command must be the first command used when configuring a neighbor. If
the remote-as is not specified, *bgpd* will complain like this: ::
can't find neighbor 10.0.0.1
.. clicmd:: neighbor PEER remote-as internal
Create a peer as you would when you specify an ASN, except that if the
peers ASN is different than mine as specified under the :clicmd:`router bgp ASN`
command the connection will be denied.
.. clicmd:: neighbor PEER remote-as external
Create a peer as you would when you specify an ASN, except that if the
peers ASN is the same as mine as specified under the :clicmd:`router bgp ASN`
command the connection will be denied.
.. clicmd:: neighbor PEER remote-as auto
The neighbor's ASN is detected automatically from the OPEN message.
.. clicmd:: neighbor PEER oad
Mark a peer belonging to the One Administrative Domain.
Some networks span more than one autonomous system and require more
flexibility in the propagation of path attributes.It is worth noting that
these multi-AS networks have a common or single administrative entity.
These networks are said to belong to One Administrative Domain (OAD).
It is desirable to carry IBGP-only attributes across EBGP peerings when
the peers belong to an OAD.
Enabling this peering sub-type will allow the propagation of non-transitive
attributes across EBGP peerings (e.g. local-preference). Make sure to
turn this peering type on for all peers in the OAD.
Disabled by default.
.. clicmd:: bgp listen range <A.B.C.D/M|X:X::X:X/M> peer-group PGNAME
Accept connections from any peers in the specified prefix. Configuration
from the specified peer-group is used to configure these peers.
.. note::
When using BGP listen ranges, if the associated peer group has TCP MD5
authentication configured, your kernel must support this on prefixes. On
Linux, this support was added in kernel version 4.14. If your kernel does
not support this feature you will get a warning in the log file, and the
listen range will only accept connections from peers without MD5 configured.
Additionally, we have observed that when using this option at scale (several
hundred peers) the kernel may hit its option memory limit. In this situation
you will see error messages like:
``bgpd: sockopt_tcp_signature: setsockopt(23): Cannot allocate memory``
In this case you need to increase the value of the sysctl
``net.core.optmem_max`` to allow the kernel to allocate the necessary option
memory.
.. clicmd:: bgp listen limit <1-65535>
Define the maximum number of peers accepted for one BGP instance. This
limit is set to 100 by default. Increasing this value will really be
possible if more file descriptors are available in the BGP process. This
value is defined by the underlying system (ulimit value), and can be
overridden by `--limit-fds`. More information is available in chapter
(:ref:`common-invocation-options`).
.. clicmd:: coalesce-time (0-4294967295)
The time in milliseconds that BGP will delay before deciding what peers
can be put into an update-group together in order to generate a single
update for them. The default time is 1000.
.. _bgp-configuring-peers:
Configuring Peers
^^^^^^^^^^^^^^^^^
.. clicmd:: neighbor PEER shutdown [message MSG...] [rtt (1-65535) [count (1-255)]]
Shutdown the peer. We can delete the neighbor's configuration by
``no neighbor PEER remote-as ASN`` but all configuration of the neighbor
will be deleted. When you want to preserve the configuration, but want to
drop the BGP peer, use this syntax.
Optionally you can specify a shutdown message `MSG`.
Also, you can specify optionally ``rtt`` in milliseconds to automatically
shutdown the peer if round-trip-time becomes higher than defined.
Additional ``count`` parameter is the number of keepalive messages to count
before shutdown the peer if round-trip-time becomes higher than defined.
.. clicmd:: neighbor PEER disable-connected-check
Allow peerings between directly connected eBGP peers using loopback
addresses.
.. clicmd:: neighbor PEER disable-link-bw-encoding-ieee
By default bandwidth in extended communities is carried encoded as IEEE
floating-point format, which is according to the draft.
Older versions have the implementation where extended community bandwidth
value is carried encoded as uint32. To enable backward compatibility we
need to disable IEEE floating-point encoding option per-peer.
.. clicmd:: neighbor PEER extended-link-bandwidth
By default bandwidth in extended communities is carried encoded as IEEE
floating-point format, and is limited to maximum of 25 Gbps.
Enabling this parameter, you can use the bandwidth of to 4294967295 Mbps.
This is disabled by default.
.. clicmd:: neighbor PEER enforce-first-as
Discard updates received from the specified (eBGP) peer if the AS_PATH
attribute does not contain the PEER's ASN as the first AS_PATH segment.
You can enable or disable this enforcement globally too using
``bgp enforce-first-as`` command.
Default: enabled.
.. clicmd:: neighbor PEER extended-optional-parameters
Force Extended Optional Parameters Length format to be used for OPEN messages.
By default, it's disabled. If the standard optional parameters length is
higher than one-octet (255), then extended format is enabled automatically.
For testing purposes, extended format can be enabled with this command.
.. clicmd:: neighbor PEER ebgp-multihop
Specifying ``ebgp-multihop`` allows sessions with eBGP neighbors to
establish when they are multiple hops away. When the neighbor is not
directly connected and this knob is not enabled, the session will not
establish.
If the peer's IP address is not in the RIB and is reachable via the
default route, then you have to enable ``ip nht resolve-via-default``.
.. clicmd:: neighbor PEER description ...
Set description of the peer.
.. clicmd:: neighbor PEER interface IFNAME
When you connect to a BGP peer over an IPv6 link-local address, you have to
specify the IFNAME of the interface used for the connection. To specify
IPv4 session addresses, see the ``neighbor PEER update-source`` command
below.
.. clicmd:: neighbor PEER interface remote-as <internal|external|auto|ASN>
Configure an unnumbered BGP peer. ``PEER`` should be an interface name. The
session will be established via IPv6 link locals. Use ``internal`` for iBGP
and ``external`` for eBGP sessions, or specify an ASN if you wish. Finally
this connection type is meant for point to point connections. If you are
on an ethernet segment and attempt to use this with more than one bgp
neighbor, only one neighbor will come up, due to how this feature works.
.. clicmd:: neighbor PEER next-hop-self [force]
This command specifies an announced route's nexthop as being equivalent to
the address of the bgp router if it is learned via eBGP. This will also
bypass third-party next-hops in favor of the local bgp address. If the
optional keyword ``force`` is specified the modification is done also for
routes learned via iBGP.
.. clicmd:: neighbor PEER attribute-unchanged [{as-path|next-hop|med}]
This command specifies attributes to be left unchanged for advertisements
sent to a peer. Use this to leave the next-hop unchanged in ipv6
configurations, as the route-map directive to leave the next-hop unchanged
is only available for ipv4.
.. clicmd:: neighbor PEER update-source <IFNAME|ADDRESS>
Specify the IPv4 or IPv6 source address to use for the :abbr:`BGP` session to this
neighbour, may be specified as either an IP address directly or as an
interface name (in which case the *zebra* daemon MUST be running in order
for *bgpd* to be able to retrieve interface state). When there are multiple
addresses on the choosen IFNAME then BGP will use the address that matches
the most number of bits in comparison to the destination peer address.
.. code-block:: frr
router bgp 64555
neighbor foo update-source 192.168.0.1
neighbor bar update-source lo0
.. clicmd:: neighbor PEER default-originate [route-map WORD]
*bgpd*'s default is to not announce the default route (0.0.0.0/0) even if it
is in routing table. When you want to announce default routes to the peer,
use this command.
If ``route-map`` keyword is specified, then the default route will be
originated only if route-map conditions are met. For example, announce
the default route only if ``10.10.10.10/32`` route exists and set an
arbitrary community for a default route.
.. code-block:: frr
router bgp 64555
address-family ipv4 unicast
neighbor 192.168.255.1 default-originate route-map default
!
ip prefix-list p1 seq 5 permit 10.10.10.10/32
!
route-map default permit 10
match ip address prefix-list p1
set community 123:123
!
.. clicmd:: neighbor PEER port PORT
.. clicmd:: neighbor PEER password PASSWORD
Set a MD5 password to be used with the tcp socket that is being used
to connect to the remote peer. Please note if you are using this
command with a large number of peers on linux you should consider
modifying the `net.core.optmem_max` sysctl to a larger value to
avoid out of memory errors from the linux kernel.
.. clicmd:: neighbor PEER send-community <both|all|extended|standard|large>
Send the communities to the peer.
Default: enabled.
.. clicmd:: neighbor PEER send-community extended rpki
Send the extended RPKI communities to the peer. RPKI extended community
can be send only to iBGP and eBGP-OAD peers.
Default: enabled.
.. clicmd:: neighbor PEER weight WEIGHT
This command specifies a default `weight` value for the neighbor's routes.
.. clicmd:: neighbor PEER maximum-prefix NUMBER [force]
Sets a maximum number of prefixes we can receive from a given peer. If this
number is exceeded, the BGP session will be destroyed.
In practice, it is generally preferable to use a prefix-list to limit what
prefixes are received from the peer instead of using this knob. Tearing down
the BGP session when a limit is exceeded is far more destructive than merely
rejecting undesired prefixes. The prefix-list method is also much more
granular and offers much smarter matching criterion than number of received
prefixes, making it more suited to implementing policy.
If ``force`` is set, then ALL prefixes are counted for maximum instead of
accepted only. This is useful for cases where an inbound filter is applied,
but you want maximum-prefix to act on ALL (including filtered) prefixes. This
option requires `soft-reconfiguration inbound` to be enabled for the peer.
.. clicmd:: neighbor PEER maximum-prefix-out NUMBER
Sets a maximum number of prefixes we can send to a given peer.
Since sent prefix count is managed by update-groups, this option
creates a separate update-group for outgoing updates.
.. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend [replace-as [dual-as]]]
Specify an alternate AS for this BGP process when interacting with the
specified peer. With no modifiers, the specified local-as is prepended to
the received AS_PATH when receiving routing updates from the peer, and
prepended to the outgoing AS_PATH (after the process local AS) when
transmitting local routes to the peer.
If the no-prepend attribute is specified, then the supplied local-as is not
prepended to the received AS_PATH.
If the replace-as attribute is specified, then only the supplied local-as is
prepended to the AS_PATH when transmitting local-route updates to this peer.
Note that replace-as can only be specified if no-prepend is.
The ``dual-as`` keyword is used to configure the neighbor to establish a peering
session using the real autonomous-system number (``router bgp ASN``) or by using
the autonomous system number configured with the ``local-as``.
This command is only allowed for eBGP peers.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> as-override
Override AS number of the originating router with the local AS number.
Usually this configuration is used in PEs (Provider Edge) to replace
the incoming customer AS number so the connected CE (Customer Edge)
can use the same AS number as the other customer sites. This allows
customers of the provider network to use the same AS number across
their sites.
This command is only allowed for eBGP peers.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> allowas-in [<(1-10)|origin>]
Accept incoming routes with AS path containing AS number with the same value
as the current system AS.
This is used when you want to use the same AS number in your sites, but you
can't connect them directly. This is an alternative to
`neighbor WORD as-override`.
The parameter `(1-10)` configures the amount of accepted occurrences of the
system AS number in AS path.
The parameter `origin` configures BGP to only accept routes originated with
the same AS number as the system.
This command is only allowed for eBGP peers.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-all-paths
Configure BGP to send all known paths to neighbor in order to preserve multi
path capabilities inside a network.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-bestpath-per-AS
Configure BGP to send best known paths to neighbor in order to preserve multi
path capabilities inside a network.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-tx-best-selected (1-6)
Configure BGP to calculate and send N best known paths to the neighbor.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> disable-addpath-rx
Do not accept additional paths from this neighbor.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> addpath-rx-paths-limit (1-65535)
Limit the maximum number of paths a BGP speaker can receive from a peer, optimizing
the transmission of BGP routes by selectively relaying pertinent routes instead of
the entire set.
If this command is configured, the sender will only send the number of paths specified
in PATHS-LIMIT capability.
To exchange this limit, both peers must support the PATHS-LIMIT capability.
.. clicmd:: neighbor PEER ttl-security hops NUMBER
This command enforces Generalized TTL Security Mechanism (GTSM), as
specified in RFC 5082. With this command, only neighbors that are the
specified number of hops away will be allowed to become neighbors. This
command is mutually exclusive with *ebgp-multihop*.
.. clicmd:: neighbor PEER capability extended-nexthop
Allow bgp to negotiate the extended-nexthop capability with it's peer.
If you are peering over a v6 LL address then this capability is turned
on automatically. If you are peering over a v6 Global Address then
turning on this command will allow BGP to install v4 routes with
v6 nexthops if you do not have v4 configured on interfaces.
.. clicmd:: neighbor PEER capability dynamic
Allow BGP to negotiate the Dynamic Capability with its peers.
Dynamic Capability defines a new BGP message (CAPABILITY) that can be used
to set/unset BGP capabilities without bringing down a BGP session.
This includes changing graceful-restart (LLGR also) timers,
enabling/disabling add-path, and other supported capabilities.
.. clicmd:: neighbor PEER capability fqdn
Allow BGP to negotiate the FQDN Capability with its peers.
FQDN Capability defines a new BGP message (CAPABILITY) allowing the
use of peer's name and domain name.
This capability is activated by default. The ``no neighbor PEER capability
fqdn`` avoid negotiation of that capability. This is useful for peers who
are not supporting this capability or supporting BGP Capabilities
Negotiation RFC 2842.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> accept-own
Enable handling of self-originated VPN routes containing ``accept-own`` community.
This feature allows you to handle self-originated VPN routes, which a BGP speaker
receives from a route-reflector. A 'self-originated' route is one that was
originally advertised by the speaker itself. As per :rfc:`4271`, a BGP speaker rejects
advertisements that originated the speaker itself. However, the BGP ACCEPT_OWN
mechanism enables a router to accept the prefixes it has advertised, when reflected
from a route-reflector that modifies certain attributes of the prefix.
A special community called ``accept-own`` is attached to the prefix by the
route-reflector, which is a signal to the receiving router to bypass the ORIGINATOR_ID
and NEXTHOP/MP_REACH_NLRI check.
Default: disabled.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> path-attribute discard (1-255)...
Drops specified path attributes from BGP UPDATE messages from the specified neighbor.
If you do not want specific attributes, you can drop them using this command, and
let the BGP proceed by ignoring those attributes.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> path-attribute treat-as-withdraw (1-255)...
Received BGP UPDATES that contain specified path attributes are treat-as-withdraw. If
there is an existing prefix in the BGP routing table, it will be removed.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> graceful-shutdown
Mark all routes from this neighbor as less preferred by setting ``graceful-shutdown``
community, and local-preference to 0.
.. clicmd:: bgp fast-external-failover
This command causes bgp to take down ebgp peers immediately
when a link flaps. `bgp fast-external-failover` is the default
and will not be displayed as part of a `show run`. The no form
of the command turns off this ability.
.. clicmd:: bgp default-originate timer (0-65535)
Set the period to rerun the default-originate route-map scanner process. The
default is 5 seconds. With a full routing table, it might be useful to increase
this setting to avoid scanning the whole BGP table aggressively.
Setting to 0 turns off the scanning at all.
.. clicmd:: bgp default ipv4-unicast
This command allows the user to specify that the IPv4 Unicast address
family is turned on by default or not. This command defaults to on
and is not displayed.
The `no bgp default ipv4-unicast` form of the command is displayed.
.. clicmd:: bgp default ipv4-multicast
This command allows the user to specify that the IPv4 Multicast address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv4-multicast` form of the command is displayed.
.. clicmd:: bgp default ipv4-vpn
This command allows the user to specify that the IPv4 MPLS VPN address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv4-vpn` form of the command is displayed.
.. clicmd:: bgp default ipv4-flowspec
This command allows the user to specify that the IPv4 Flowspec address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv4-flowspec` form of the command is displayed.
.. clicmd:: bgp default ipv6-unicast
This command allows the user to specify that the IPv6 Unicast address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv6-unicast` form of the command is displayed.
.. clicmd:: bgp default ipv6-multicast
This command allows the user to specify that the IPv6 Multicast address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv6-multicast` form of the command is displayed.
.. clicmd:: bgp default ipv6-vpn
This command allows the user to specify that the IPv6 MPLS VPN address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv6-vpn` form of the command is displayed.
.. clicmd:: bgp default ipv6-flowspec
This command allows the user to specify that the IPv6 Flowspec address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default ipv6-flowspec` form of the command is displayed.
.. clicmd:: bgp default l2vpn-evpn
This command allows the user to specify that the L2VPN EVPN address
family is turned on by default or not. This command defaults to off
and is not displayed.
The `bgp default l2vpn-evpn` form of the command is displayed.
.. clicmd:: bgp default show-hostname
This command shows the hostname of the peer in certain BGP commands
outputs. It's easier to troubleshoot if you have a number of BGP peers.
.. clicmd:: bgp default show-nexthop-hostname
This command shows the hostname of the next-hop in certain BGP commands
outputs. It's easier to troubleshoot if you have a number of BGP peers
and a number of routes to check.
.. clicmd:: bgp default dynamic-capability
This command enables dynamic capability advertisement by default
for all the neighbors.
For ``datacenter`` profile, this is enabled by default.
.. clicmd:: bgp default software-version-capability
This command enables software version capability advertisement by default
for all the neighbors.
For ``datacenter`` profile, this is enabled by default.
.. code-block:: frr
IPv4 Unicast Summary:
BGP router identifier 10.0.0.6, local AS number 65001 VRF default vrf-id 0
BGP table version 12
RIB entries 23, using 4600 bytes of memory
Peers 3, using 2174 KiB of memory
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
10.0.0.4 4 65001 20 22 12 0 0 00:00:11 5 12 FRRouting/8.5.1
10.0.0.5 4 65001 21 22 12 0 0 00:00:11 5 12 FRRouting/9.0
192.168.67.7 4 65001 27 31 12 0 0 00:00:23 2 10 FRRouting/9.1-dev-MyOwnFRRVersion-g3c8c08dcd9
Total number of neighbors 3
.. clicmd:: neighbor PEER advertisement-interval (0-600)
Setup the minimum route advertisement interval(mrai) for the
peer in question. This number is between 0 and 600 seconds,
with the default advertisement interval being 0.
.. clicmd:: neighbor PEER timers (0-65535) (0-65535)
Set keepalive and hold timers for a neighbor. The first value is keepalive
and the second is hold time.
.. clicmd:: neighbor PEER timers connect (1-65535)
Set connect timer for a neighbor. The connect timer controls how long BGP
waits between connection attempts to a neighbor.
.. clicmd:: neighbor PEER timers delayopen (1-240)
This command allows the user enable the
`RFC 4271 <https://tools.ietf.org/html/rfc4271/>` DelayOpenTimer with the
specified interval or disable it with the negating command for the peer. By
default, the DelayOpenTimer is disabled. The timer interval may be set to a
duration of 1 to 240 seconds.
.. clicmd:: bgp minimum-holdtime (1-65535)
This command allows user to prevent session establishment with BGP peers
with lower holdtime less than configured minimum holdtime.
When this command is not set, minimum holdtime does not work.
.. clicmd:: bgp tcp-keepalive (1-65535) (1-65535) (1-30)
This command allows user to configure TCP keepalive with new BGP peers.
Each parameter respectively stands for TCP keepalive idle timer (seconds),
interval (seconds), and maximum probes. By default, TCP keepalive is
disabled.
Displaying Information about Peers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: show bgp <afi> <safi> neighbors WORD bestpath-routes [detail] [json] [wide]
For the given neighbor, WORD, that is specified list the routes selected
by BGP as having the best path.
If ``detail`` option is specified, the detailed version of all routes
will be displayed. The same format as ``show [ip] bgp [afi] [safi] PREFIX``
will be used, but for the whole table of received, advertised or filtered
prefixes.
If ``json`` option is specified, output is displayed in JSON format.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
.. _bgp-peer-filtering:
Peer Filtering
^^^^^^^^^^^^^^
.. clicmd:: neighbor PEER distribute-list NAME [in|out]
This command specifies a distribute-list for the peer. `direct` is
``in`` or ``out``.
.. clicmd:: neighbor PEER prefix-list NAME [in|out]
.. clicmd:: neighbor PEER filter-list NAME [in|out]
.. clicmd:: neighbor PEER route-map NAME [in|out]
Apply a route-map on the neighbor. `direct` must be `in` or `out`.
.. clicmd:: bgp route-reflector allow-outbound-policy
By default, attribute modification via route-map policy out is not reflected
on reflected routes. This option allows the modifications to be reflected as
well. Once enabled, it affects all reflected routes.
.. clicmd:: neighbor PEER sender-as-path-loop-detection
Enable the detection of sender side AS path loops and filter the
bad routes before they are sent.
This setting is disabled by default.
.. _bgp-peer-group:
Peer Groups
^^^^^^^^^^^
Peer groups are used to help improve scaling by generating the same
update information to all members of a peer group. Note that this means
that the routes generated by a member of a peer group will be sent back
to that originating peer with the originator identifier attribute set to
indicated the originating peer. All peers not associated with a
specific peer group are treated as belonging to a default peer group,
and will share updates.
.. clicmd:: neighbor WORD peer-group
This command defines a new peer group.
.. clicmd:: neighbor PEER peer-group PGNAME
This command bind specific peer to peer group WORD.
.. clicmd:: neighbor PEER solo
This command is used to indicate that routes advertised by the peer
should not be reflected back to the peer.
.. clicmd:: show [ip] bgp peer-group [json]
This command displays configured BGP peer-groups.
.. code-block:: frr
exit1-debian-9# show bgp peer-group
BGP peer-group test1, remote AS 65001
Peer-group type is external
Configured address-families: IPv4 Unicast; IPv6 Unicast;
1 IPv4 listen range(s)
192.168.100.0/24
2 IPv6 listen range(s)
2001:db8:1::/64
2001:db8:2::/64
Peer-group members:
192.168.200.1 Active
2001:db8::1 Active
BGP peer-group test2
Peer-group type is external
Configured address-families: IPv4 Unicast;
Optional ``json`` parameter is used to display JSON output.
.. code-block:: frr
{
"test1":{
"remoteAs":65001,
"type":"external",
"addressFamiliesConfigured":[
"IPv4 Unicast",
"IPv6 Unicast"
],
"dynamicRanges":{
"IPv4":{
"count":1,
"ranges":[
"192.168.100.0\/24"
]
},
"IPv6":{
"count":2,
"ranges":[
"2001:db8:1::\/64",
"2001:db8:2::\/64"
]
}
},
"members":{
"192.168.200.1":{
"status":"Active"
},
"2001:db8::1":{
"status":"Active"
}
}
},
"test2":{
"type":"external",
"addressFamiliesConfigured":[
"IPv4 Unicast"
]
}
}
Capability Negotiation
^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: neighbor PEER strict-capability-match
Strictly compares remote capabilities and local capabilities. If
capabilities are different, send Unsupported Capability error then reset
connection.
You may want to disable sending Capability Negotiation OPEN message optional
parameter to the peer when remote peer does not implement Capability
Negotiation. Please use *dont-capability-negotiate* command to disable the
feature.
.. clicmd:: neighbor PEER dont-capability-negotiate
Suppress sending Capability Negotiation as OPEN message optional parameter
to the peer. This command only affects the peer is configured other than
IPv4 unicast configuration.
When remote peer does not have capability negotiation feature, remote peer
will not send any capabilities at all. In that case, bgp configures the peer
with configured capabilities.
You may prefer locally configured capabilities more than the negotiated
capabilities even though remote peer sends capabilities. If the peer is
configured by *override-capability*, *bgpd* ignores received capabilities
then override negotiated capabilities with configured values.
Additionally the operator should be reminded that this feature fundamentally
disables the ability to use widely deployed BGP features. BGP unnumbered,
hostname support, AS4, Addpath, Route Refresh, ORF, Dynamic Capabilities,
and graceful restart.
.. clicmd:: neighbor PEER override-capability
Override the result of Capability Negotiation with local configuration.
Ignore remote peer's capability value.
.. clicmd:: neighbor PEER capability software-version
Send the software version in the BGP OPEN message to the neighbor. This is
very useful in environments with a large amount of peers with different
versions of FRR or any other vendor.
Disabled by default.
.. clicmd:: neighbor PEER aigp
Send and receive AIGP attribute for this neighbor. This is valid only for
eBGP neighbors.
Disabled by default. iBGP neighbors have this option enabled implicitly.
.. _bgp-as-path-access-lists:
AS Path Access Lists
--------------------
AS path access list is user defined AS path.
.. clicmd:: bgp as-path access-list WORD [seq (0-4294967295)] permit|deny LINE
This command defines a new AS path access list.
.. clicmd:: show bgp as-path-access-list [json]
Display all BGP AS Path access lists.
If the ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show bgp as-path-access-list WORD [json]
Display the specified BGP AS Path access list.
If the ``json`` option is specified, output is displayed in JSON format.
.. _bgp-bogon-filter-example:
Bogon ASN filter policy configuration example
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. code-block:: frr
bgp as-path access-list 99 permit _0_
bgp as-path access-list 99 permit _23456_
bgp as-path access-list 99 permit _1310[0-6][0-9]_|_13107[0-1]_
bgp as-path access-list 99 seq 20 permit ^65
.. _bgp-using-as-path-in-route-map:
Using AS Path in Route Map
--------------------------
.. clicmd:: match as-path WORD
For a given as-path, WORD, match it on the BGP as-path given for the prefix
and if it matches do normal route-map actions. The no form of the command
removes this match from the route-map.
.. clicmd:: set as-path prepend AS-PATH
Prepend the given string of AS numbers to the AS_PATH of the BGP path's NLRI.
The no form of this command removes this set operation from the route-map.
.. clicmd:: set as-path prepend last-as NUM
Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
The no form of this command removes this set operation from the route-map.
.. clicmd:: set as-path replace <any|ASN> [<ASN>]
Replace a specific AS number to local AS number or a configured AS number.
``any`` replaces each AS number in the AS-PATH with either the local AS
number or the configured AS number.
.. clicmd:: set as-path replace as-path-access-list WORD [<ASN>]
Replace some AS numbers from the AS_PATH of the BGP path's NLRI. Substituted
AS numbers are conformant with the regex defined in as-path access-list
WORD. Changed AS numbers are replaced either by the local AS number or the
configured AS number.
The no form of this command removes this set operation from the route-map.
.. clicmd:: set as-path exclude all
Remove all AS numbers from the AS_PATH of the BGP path's NLRI. The no form of
this command removes this set operation from the route-map.
.. clicmd:: set as-path exclude as-path-access-list WORD
Remove some AS numbers from the AS_PATH of the BGP path's NLRI. Removed AS
numbers are conformant with the regex defined in as-path access-list WORD.
The no form of this command removes this set operation from the route-map.
.. _bgp-communities-attribute:
Communities Attribute
---------------------
The BGP communities attribute is widely used for implementing policy routing.
Network operators can manipulate BGP communities attribute based on their
network policy. BGP communities attribute is defined in :rfc:`1997` and
:rfc:`1998`. It is an optional transitive attribute, therefore local policy can
travel through different autonomous system.
The communities attribute is a set of communities values. Each community value
is 4 octet long. The following format is used to define the community value.
``AS:VAL``
This format represents 4 octet communities value. ``AS`` is high order 2
octet in digit format. ``VAL`` is low order 2 octet in digit format. This
format is useful to define AS oriented policy value. For example,
``7675:80`` can be used when AS 7675 wants to pass local policy value 80 to
neighboring peer.
``graceful-shutdown``
``graceful-shutdown`` represents well-known communities value
``GRACEFUL_SHUTDOWN`` ``0xFFFF0000`` ``65535:0``. :rfc:`8326` implements
the purpose Graceful BGP Session Shutdown to reduce the amount of
lost traffic when taking BGP sessions down for maintenance. The use
of the community needs to be supported from your peers side to
actually have any effect.
``accept-own``
``accept-own`` represents well-known communities value ``ACCEPT_OWN``
``0xFFFF0001`` ``65535:1``. :rfc:`7611` implements a way to signal
to a router to accept routes with a local nexthop address. This
can be the case when doing policing and having traffic having a
nexthop located in another VRF but still local interface to the
router. It is recommended to read the RFC for full details.
``route-filter-translated-v4``
``route-filter-translated-v4`` represents well-known communities value
``ROUTE_FILTER_TRANSLATED_v4`` ``0xFFFF0002`` ``65535:2``.
``route-filter-v4``
``route-filter-v4`` represents well-known communities value
``ROUTE_FILTER_v4`` ``0xFFFF0003`` ``65535:3``.
``route-filter-translated-v6``
``route-filter-translated-v6`` represents well-known communities value
``ROUTE_FILTER_TRANSLATED_v6`` ``0xFFFF0004`` ``65535:4``.
``route-filter-v6``
``route-filter-v6`` represents well-known communities value
``ROUTE_FILTER_v6`` ``0xFFFF0005`` ``65535:5``.
``llgr-stale``
``llgr-stale`` represents well-known communities value ``LLGR_STALE``
``0xFFFF0006`` ``65535:6``.
Assigned and intended only for use with routers supporting the
Long-lived Graceful Restart Capability as described in
[Draft-IETF-uttaro-idr-bgp-persistence]_.
Routers receiving routes with this community may (depending on
implementation) choose allow to reject or modify routes on the
presence or absence of this community.
``no-llgr``
``no-llgr`` represents well-known communities value ``NO_LLGR``
``0xFFFF0007`` ``65535:7``.
Assigned and intended only for use with routers supporting the
Long-lived Graceful Restart Capability as described in
[Draft-IETF-uttaro-idr-bgp-persistence]_.
Routers receiving routes with this community may (depending on
implementation) choose allow to reject or modify routes on the
presence or absence of this community.
``accept-own-nexthop``
``accept-own-nexthop`` represents well-known communities value
``accept-own-nexthop`` ``0xFFFF0008`` ``65535:8``.
[Draft-IETF-agrewal-idr-accept-own-nexthop]_ describes
how to tag and label VPN routes to be able to send traffic between VRFs
via an internal layer 2 domain on the same PE device. Refer to
[Draft-IETF-agrewal-idr-accept-own-nexthop]_ for full details.
``blackhole``
``blackhole`` represents well-known communities value ``BLACKHOLE``
``0xFFFF029A`` ``65535:666``. :rfc:`7999` documents sending prefixes to
peers and upstream for the purpose of blackholing traffic.
Prefixes tagged with the this community should normally not be
re-advertised from neighbors of the originating network. Upon receiving
``BLACKHOLE`` community from a BGP speaker, ``NO_ADVERTISE`` community
is added automatically.
``no-export``
``no-export`` represents well-known communities value ``NO_EXPORT``
``0xFFFFFF01``. All routes carry this value must not be advertised to
outside a BGP confederation boundary. If neighboring BGP peer is part of BGP
confederation, the peer is considered as inside a BGP confederation
boundary, so the route will be announced to the peer.
``no-advertise``
``no-advertise`` represents well-known communities value ``NO_ADVERTISE``
``0xFFFFFF02``. All routes carry this value must not be advertise to other
BGP peers.
``local-AS``
``local-AS`` represents well-known communities value ``NO_EXPORT_SUBCONFED``
``0xFFFFFF03``. All routes carry this value must not be advertised to
external BGP peers. Even if the neighboring router is part of confederation,
it is considered as external BGP peer, so the route will not be announced to
the peer.
``no-peer``
``no-peer`` represents well-known communities value ``NOPEER``
``0xFFFFFF04`` ``65535:65284``. :rfc:`3765` is used to communicate to
another network how the originating network want the prefix propagated.
When the communities attribute is received duplicate community values in the
attribute are ignored and value is sorted in numerical order.
.. [Draft-IETF-uttaro-idr-bgp-persistence] <https://tools.ietf.org/id/draft-uttaro-idr-bgp-persistence-04.txt>
.. [Draft-IETF-agrewal-idr-accept-own-nexthop] <https://tools.ietf.org/id/draft-agrewal-idr-accept-own-nexthop-00.txt>
.. _bgp-community-lists:
Community Lists
^^^^^^^^^^^^^^^
Community lists are user defined lists of community attribute values. These
lists can be used for matching or manipulating the communities attribute in
UPDATE messages.
There are two types of community list:
standard
This type accepts an explicit value for the attribute.
expanded
This type accepts a regular expression. Because the regex must be
interpreted on each use expanded community lists are slower than standard
lists.
.. clicmd:: bgp community-list standard NAME permit|deny COMMUNITY
This command defines a new standard community list. ``COMMUNITY`` is
communities value. The ``COMMUNITY`` is compiled into community structure.
We can define multiple community list under same name. In that case match
will happen user defined order. Once the community list matches to
communities attribute in BGP updates it return permit or deny by the
community list definition. When there is no matched entry, deny will be
returned. When ``COMMUNITY`` is empty it matches to any routes.
.. clicmd:: bgp community-list expanded NAME permit|deny COMMUNITY
This command defines a new expanded community list. ``COMMUNITY`` is a
string expression of communities attribute. ``COMMUNITY`` can be a regular
expression (:ref:`bgp-regular-expressions`) to match the communities
attribute in BGP updates. The expanded community is only used to filter,
not `set` actions.
.. deprecated:: 5.0
It is recommended to use the more explicit versions of this command.
.. clicmd:: bgp community-list NAME permit|deny COMMUNITY
When the community list type is not specified, the community list type is
automatically detected. If ``COMMUNITY`` can be compiled into communities
attribute, the community list is defined as a standard community list.
Otherwise it is defined as an expanded community list. This feature is left
for backward compatibility. Use of this feature is not recommended.
Note that all community lists share the same namespace, so it's not
necessary to specify ``standard`` or ``expanded``; these modifiers are
purely aesthetic.
.. clicmd:: show bgp community-list [NAME detail]
Displays community list information. When ``NAME`` is specified the
specified community list's information is shown.
::
# show bgp community-list
Named Community standard list CLIST
permit 7675:80 7675:100 no-export
deny internet
Named Community expanded list EXPAND
permit :
# show bgp community-list CLIST detail
Named Community standard list CLIST
permit 7675:80 7675:100 no-export
deny internet
.. _bgp-numbered-community-lists:
Numbered Community Lists
^^^^^^^^^^^^^^^^^^^^^^^^
When number is used for BGP community list name, the number has
special meanings. Community list number in the range from 1 to 99 is
standard community list. Community list number in the range from 100
to 500 is expanded community list. These community lists are called
as numbered community lists. On the other hand normal community lists
is called as named community lists.
.. clicmd:: bgp community-list (1-99) permit|deny COMMUNITY
This command defines a new community list. The argument to (1-99) defines
the list identifier.
.. clicmd:: bgp community-list (100-500) permit|deny COMMUNITY
This command defines a new expanded community list. The argument to
(100-500) defines the list identifier.
.. _bgp-community-alias:
Community alias
^^^^^^^^^^^^^^^
BGP community aliases are useful to quickly identify what communities are set
for a specific prefix in a human-readable format. Especially handy for a huge
amount of communities. Accurately defined aliases can help you faster spot
things on the wire.
.. clicmd:: bgp community alias NAME ALIAS
This command creates an alias name for a community that will be used
later in various CLI outputs in a human-readable format.
.. code-block:: frr
~# vtysh -c 'show run' | grep 'bgp community alias'
bgp community alias 65001:14 community-1
bgp community alias 65001:123:1 lcommunity-1
~# vtysh -c 'show ip bgp 172.16.16.1/32'
BGP routing table entry for 172.16.16.1/32, version 21
Paths: (2 available, best #2, table default)
Advertised to non peer-group peers:
65030
192.168.0.2 from 192.168.0.2 (172.16.16.1)
Origin incomplete, metric 0, valid, external, best (Neighbor IP)
Community: 65001:12 65001:13 community-1 65001:65534
Large Community: lcommunity-1 65001:123:2
Last update: Fri Apr 16 12:51:27 2021
.. clicmd:: show bgp [afi] [safi] [all] alias WORD [wide|json]
Display prefixes with matching BGP community alias.
.. _bgp-using-communities-in-route-map:
Using Communities in Route Maps
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In :ref:`route-map` we can match on or set the BGP communities attribute. Using
this feature network operator can implement their network policy based on BGP
communities attribute.
The following commands can be used in route maps:
.. clicmd:: match alias WORD
This command performs match to BGP updates using community alias WORD. When
the one of BGP communities value match to the one of community alias value in
community alias, it is match.
.. clicmd:: match community WORD exact-match [exact-match]
This command perform match to BGP updates using community list WORD. When
the one of BGP communities value match to the one of communities value in
community list, it is match. When `exact-match` keyword is specified, match
happen only when BGP updates have completely same communities value
specified in the community list.
.. clicmd:: set community <none|COMMUNITY> additive
This command sets the community value in BGP updates. If the attribute is
already configured, the newly provided value replaces the old one unless the
``additive`` keyword is specified, in which case the new value is appended
to the existing value.
If ``none`` is specified as the community value, the communities attribute
is not sent.
It is not possible to set an expanded community list.
.. clicmd:: set comm-list WORD delete
This command remove communities value from BGP communities attribute. The
``word`` is community list name. When BGP route's communities value matches
to the community list ``word``, the communities value is removed. When all
of communities value is removed eventually, the BGP update's communities
attribute is completely removed.
.. _bgp-communities-example:
Example Configuration
^^^^^^^^^^^^^^^^^^^^^
The following configuration is exemplary of the most typical usage of BGP
communities attribute. In the example, AS 7675 provides an upstream Internet
connection to AS 100. When the following configuration exists in AS 7675, the
network operator of AS 100 can set local preference in AS 7675 network by
setting BGP communities attribute to the updates.
.. code-block:: frr
router bgp 7675
neighbor 192.168.0.1 remote-as 100
address-family ipv4 unicast
neighbor 192.168.0.1 route-map RMAP in
exit-address-family
!
bgp community-list 70 permit 7675:70
bgp community-list 80 permit 7675:80
bgp community-list 90 permit 7675:90
!
route-map RMAP permit 10
match community 70
set local-preference 70
!
route-map RMAP permit 20
match community 80
set local-preference 80
!
route-map RMAP permit 30
match community 90
set local-preference 90
The following configuration announces ``10.0.0.0/8`` from AS 100 to AS 7675.
The route has communities value ``7675:80`` so when above configuration exists
in AS 7675, the announced routes' local preference value will be set to 80.
.. code-block:: frr
router bgp 100
network 10.0.0.0/8
neighbor 192.168.0.2 remote-as 7675
address-family ipv4 unicast
neighbor 192.168.0.2 route-map RMAP out
exit-address-family
!
ip prefix-list PLIST permit 10.0.0.0/8
!
route-map RMAP permit 10
match ip address prefix-list PLIST
set community 7675:80
The following configuration is an example of BGP route filtering using
communities attribute. This configuration only permit BGP routes which has BGP
communities value (``0:80`` and ``0:90``) or ``0:100``. The network operator can
set special internal communities value at BGP border router, then limit the
BGP route announcements into the internal network.
.. code-block:: frr
router bgp 7675
neighbor 192.168.0.1 remote-as 100
address-family ipv4 unicast
neighbor 192.168.0.1 route-map RMAP in
exit-address-family
!
bgp community-list 1 permit 0:80 0:90
bgp community-list 1 permit 0:100
!
route-map RMAP permit in
match community 1
The following example filters BGP routes which have a community value of
``1:1``. When there is no match community-list returns ``deny``. To avoid
filtering all routes, a ``permit`` line is set at the end of the
community-list.
.. code-block:: frr
router bgp 7675
neighbor 192.168.0.1 remote-as 100
address-family ipv4 unicast
neighbor 192.168.0.1 route-map RMAP in
exit-address-family
!
bgp community-list standard FILTER deny 1:1
bgp community-list standard FILTER permit
!
route-map RMAP permit 10
match community FILTER
The following configuration is an example of communities value deletion. With
this configuration the community values ``100:1`` and ``100:2`` are removed
from BGP updates. For communities value deletion, only ``permit``
community-list is used. ``deny`` community-list is ignored.
.. code-block:: frr
router bgp 7675
neighbor 192.168.0.1 remote-as 100
address-family ipv4 unicast
neighbor 192.168.0.1 route-map RMAP in
exit-address-family
!
bgp community-list standard DEL permit 100:1 100:2
!
route-map RMAP permit 10
set comm-list DEL delete
.. _bgp-extended-communities-attribute:
Extended Communities Attribute
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
BGP extended communities attribute is introduced with MPLS VPN/BGP technology.
MPLS VPN/BGP expands capability of network infrastructure to provide VPN
functionality. At the same time it requires a new framework for policy routing.
With BGP Extended Communities Attribute we can use Route Target or Site of
Origin for implementing network policy for MPLS VPN/BGP.
BGP Extended Communities Attribute is similar to BGP Communities Attribute. It
is an optional transitive attribute. BGP Extended Communities Attribute can
carry multiple Extended Community value. Each Extended Community value is
eight octet length.
BGP Extended Communities Attribute provides an extended range compared with BGP
Communities Attribute. Adding to that there is a type field in each value to
provides community space structure.
There are two format to define Extended Community value. One is AS based format
the other is IP address based format.
``AS:VAL``
This is a format to define AS based Extended Community value. ``AS`` part
is 2 octets Global Administrator subfield in Extended Community value.
``VAL`` part is 4 octets Local Administrator subfield. ``7675:100``
represents AS 7675 policy value 100.
``IP-Address:VAL``
This is a format to define IP address based Extended Community value.
``IP-Address`` part is 4 octets Global Administrator subfield. ``VAL`` part
is 2 octets Local Administrator subfield.
.. _bgp-extended-community-lists:
Extended Community Lists
^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: bgp extcommunity-list standard NAME permit|deny EXTCOMMUNITY
This command defines a new standard extcommunity-list. `extcommunity` is
extended communities value. The `extcommunity` is compiled into extended
community structure. We can define multiple extcommunity-list under same
name. In that case match will happen user defined order. Once the
extcommunity-list matches to extended communities attribute in BGP updates
it return permit or deny based upon the extcommunity-list definition. When
there is no matched entry, deny will be returned. When `extcommunity` is
empty it matches to any routes.
.. clicmd:: bgp extcommunity-list expanded NAME permit|deny LINE
This command defines a new expanded extcommunity-list. `line` is a string
expression of extended communities attribute. `line` can be a regular
expression (:ref:`bgp-regular-expressions`) to match an extended communities
attribute in BGP updates.
Note that all extended community lists shares a single name space, so it's
not necessary to specify their type when creating or destroying them.
.. clicmd:: show bgp extcommunity-list [NAME detail]
This command displays current extcommunity-list information. When `name` is
specified the community list's information is shown.
.. _bgp-extended-communities-in-route-map:
BGP Extended Communities in Route Map
"""""""""""""""""""""""""""""""""""""
.. clicmd:: match extcommunity WORD
.. clicmd:: set extcommunity none
This command resets the extended community value in BGP updates. If the attribute is
already configured or received from the peer, the attribute is discarded and set to
none. This is useful if you need to strip incoming extended communities.
.. clicmd:: set extcommunity rt EXTCOMMUNITY
This command sets Route Target value.
.. clicmd:: set extcommunity nt EXTCOMMUNITY
This command sets Node Target value.
If the receiving BGP router supports Node Target Extended Communities,
it will install the route with the community that contains it's own
local BGP Identifier. Otherwise, it's not installed.
.. clicmd:: set extcommunity soo EXTCOMMUNITY
This command sets Site of Origin value.
.. clicmd:: set extcomumnity color EXTCOMMUNITY
This command sets colors values.
.. clicmd:: set extcommunity bandwidth <(1-25600) | cumulative | num-multipaths> [non-transitive]
This command sets the BGP link-bandwidth extended community for the prefix
(best path) for which it is applied. The link-bandwidth can be specified as
an ``explicit value`` (specified in Mbps), or the router can be told to use
the ``cumulative bandwidth`` of all multipaths for the prefix or to compute
it based on the ``number of multipaths``. The link bandwidth extended
community is encoded as ``transitive`` unless the set command explicitly
configures it as ``non-transitive``.
.. seealso:: :ref:`wecmp_linkbw`
Note that the extended expanded community is only used for `match` rule, not for
`set` actions.
.. _bgp-large-communities-attribute:
Large Communities Attribute
^^^^^^^^^^^^^^^^^^^^^^^^^^^
The BGP Large Communities attribute was introduced in Feb 2017 with
:rfc:`8092`.
The BGP Large Communities Attribute is similar to the BGP Communities Attribute
except that it has 3 components instead of two and each of which are 4 octets
in length. Large Communities bring additional functionality and convenience
over traditional communities, specifically the fact that the ``GLOBAL`` part
below is now 4 octets wide allowing seamless use in networks using 4-byte ASNs.
``GLOBAL:LOCAL1:LOCAL2``
This is the format to define Large Community values. Referencing :rfc:`8195`
the values are commonly referred to as follows:
- The ``GLOBAL`` part is a 4 octet Global Administrator field, commonly used
as the operators AS number.
- The ``LOCAL1`` part is a 4 octet Local Data Part 1 subfield referred to as
a function.
- The ``LOCAL2`` part is a 4 octet Local Data Part 2 field and referred to
as the parameter subfield.
As an example, ``65551:1:10`` represents AS 65551 function 1 and parameter
10. The referenced RFC above gives some guidelines on recommended usage.
.. _bgp-large-community-lists:
Large Community Lists
"""""""""""""""""""""
Two types of large community lists are supported, namely `standard` and
`expanded`.
.. clicmd:: bgp large-community-list standard NAME permit|deny LARGE-COMMUNITY
This command defines a new standard large-community-list. `large-community`
is the Large Community value. We can add multiple large communities under
same name. In that case the match will happen in the user defined order.
Once the large-community-list matches the Large Communities attribute in BGP
updates it will return permit or deny based upon the large-community-list
definition. When there is no matched entry, a deny will be returned. When
`large-community` is empty it matches any routes.
.. clicmd:: bgp large-community-list expanded NAME permit|deny LINE
This command defines a new expanded large-community-list. Where `line` is a
string matching expression, it will be compared to the entire Large
Communities attribute as a string, with each large-community in order from
lowest to highest. `line` can also be a regular expression which matches
this Large Community attribute.
Note that all community lists share the same namespace, so it's not
necessary to specify ``standard`` or ``expanded``; these modifiers are
purely aesthetic.
.. clicmd:: show bgp large-community-list
.. clicmd:: show bgp large-community-list NAME detail
This command display current large-community-list information. When
`name` is specified the community list information is shown.
.. clicmd:: show ip bgp large-community-info
This command displays the current large communities in use.
.. _bgp-large-communities-in-route-map:
Large Communities in Route Map
""""""""""""""""""""""""""""""
.. clicmd:: match large-community LINE [exact-match]
Where `line` can be a simple string to match, or a regular expression. It
is very important to note that this match occurs on the entire
large-community string as a whole, where each large-community is ordered
from lowest to highest. When `exact-match` keyword is specified, match
happen only when BGP updates have completely same large communities value
specified in the large community list.
.. clicmd:: set large-community LARGE-COMMUNITY
.. clicmd:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
.. clicmd:: set large-community LARGE-COMMUNITY additive
These commands are used for setting large-community values. The first
command will overwrite any large-communities currently present.
The second specifies two large-communities, which overwrites the current
large-community list. The third will add a large-community value without
overwriting other values. Multiple large-community values can be specified.
Note that the large expanded community is only used for `match` rule, not for
`set` actions.
.. _bgp-roles-and-only-to-customers:
BGP Roles and Only to Customers
-------------------------------
BGP roles are defined in :rfc:`9234` and provide an easy way to route leaks
prevention, detection and mitigation.
To enable its mechanics, you must set your local role to reflect your type of
peering relationship with your neighbor. Possible values of ``LOCAL-ROLE`` are:
- provider
- rs-server
- rs-client
- customer
- peer
The local Role value is negotiated with the new BGP Role capability with a
built-in check of the corresponding value. In case of mismatch the new OPEN
Roles Mismatch Notification <2, 11> would be sent.
The correct Role pairs are:
* Provider - Customer
* Peer - Peer
* RS-Server - RS-Client
.. code-block:: shell
~# vtysh -c 'show bgp neighbor' | grep 'Role'
Local Role: customer
Neighbor Role: provider
Role: advertised and received
If strict-mode is set BGP session won't become established until BGP neighbor
set local Role on its side. This configuration parameter is defined in
:rfc:`9234` and used to enforce corresponding configuration at your
counter-part side. Default value - disabled.
Routes that sent from provider, rs-server, or peer local-role (or if received
by customer, rs-clinet, or peer local-role) will be marked with a new
Only to Customer (OTC) attribute.
Routes with this attribute can only be sent to your neighbor if your
local-role is provider or rs-server. Routes with this attribute can be
received only if your local-role is customer or rs-client.
In case of peer-peer relationship routes can be received only if
OTC value is equal to your neighbor AS number.
All these rules with OTC help to detect and mitigate route leaks and
happened automatically if local-role is set.
.. clicmd:: neighbor PEER local-role LOCAL-ROLE [strict-mode]
This command set your local-role to ``LOCAL-ROLE``:
<provider|rs-server|rs-client|customer|peer>.
This role helps to detect and prevent route leaks.
If ``strict-mode`` is set, your neighbor must send you Capability with the
value of his role (by setting local-role on his side). Otherwise, a Role
Mismatch Notification will be sent.
Labeled unicast
---------------
*bgpd* supports labeled information, as per :rfc:`3107`.
.. clicmd:: bgp labeled-unicast <explicit-null|ipv4-explicit-null|ipv6-explicit-null>
By default, locally advertised prefixes use the `implicit-null` label to
encode in the outgoing NLRI. The following command uses the `explicit-null`
label value for all the BGP instances.
.. _bgp-l3vpn-vrfs:
L3VPN VRFs
----------
*bgpd* supports :abbr:`L3VPN (Layer 3 Virtual Private Networks)` :abbr:`VRFs
(Virtual Routing and Forwarding)` for IPv4 :rfc:`4364` and IPv6 :rfc:`4659`.
L3VPN routes, and their associated VRF MPLS labels, can be distributed to VPN
SAFI neighbors in the *default*, i.e., non VRF, BGP instance. VRF MPLS labels
are reached using *core* MPLS labels which are distributed using LDP or BGP
labeled unicast. *bgpd* also supports inter-VRF route leaking.
L3VPN over GRE interfaces
^^^^^^^^^^^^^^^^^^^^^^^^^
In MPLS-VPN or SRv6-VPN, an L3VPN next-hop entry requires that the path
chosen respectively contains a labelled path or a valid SID IPv6 address.
Otherwise the L3VPN entry will not be installed. It is possible to ignore
that check when the path chosen by the next-hop uses a GRE interface, and
there is a route-map configured at inbound side of ipv4-vpn or ipv6-vpn
address family with following syntax:
.. clicmd:: set l3vpn next-hop encapsulation gre
The incoming BGP L3VPN entry is accepted, provided that the next hop of the
L3VPN entry uses a path that takes the GRE tunnel as outgoing interface. The
remote endpoint should be configured just behind the GRE tunnel; remote
device configuration may vary depending whether it acts at edge endpoint or
not: in any case, the expectation is that incoming MPLS traffic received at
this endpoint should be considered as a valid path for L3VPN.
.. _bgp-vrf-route-leaking:
VRF Route Leaking
-----------------
BGP routes may be leaked (i.e. copied) between a unicast VRF RIB and the VPN
SAFI RIB of the default VRF for use in MPLS-based L3VPNs. Unicast routes may
also be leaked between any VRFs (including the unicast RIB of the default BGP
instanced). A shortcut syntax is also available for specifying leaking from one
VRF to another VRF using the default instance's VPN RIB as the intermediary. A
common application of the VRF-VRF feature is to connect a customer's private
routing domain to a provider's VPN service. Leaking is configured from the
point of view of an individual VRF: ``import`` refers to routes leaked from VPN
to a unicast VRF, whereas ``export`` refers to routes leaked from a unicast VRF
to VPN.
Required parameters
^^^^^^^^^^^^^^^^^^^
Routes exported from a unicast VRF to the VPN RIB must be augmented by two
parameters:
- an :abbr:`RD (Route Distinguisher)`
- an :abbr:`RTLIST (Route-target List)`
Configuration for these exported routes must, at a minimum, specify these two
parameters.
Routes imported from the VPN RIB to a unicast VRF are selected according to
their RTLISTs. Routes whose RTLIST contains at least one route-target in
common with the configured import RTLIST are leaked. Configuration for these
imported routes must specify an RTLIST to be matched.
The RD, which carries no semantic value, is intended to make the route unique
in the VPN RIB among all routes of its prefix that originate from all the
customers and sites that are attached to the provider's VPN service.
Accordingly, each site of each customer is typically assigned an RD that is
unique across the entire provider network.
The RTLIST is a set of route-target extended community values whose purpose is
to specify route-leaking policy. Typically, a customer is assigned a single
route-target value for import and export to be used at all customer sites. This
configuration specifies a simple topology wherein a customer has a single
routing domain which is shared across all its sites. More complex routing
topologies are possible through use of additional route-targets to augment the
leaking of sets of routes in various ways.
When using the shortcut syntax for vrf-to-vrf leaking, the RD and RT are
auto-derived.
General configuration
^^^^^^^^^^^^^^^^^^^^^
Configuration of route leaking between a unicast VRF RIB and the VPN SAFI RIB
of the default VRF is accomplished via commands in the context of a VRF
address-family:
.. clicmd:: rd vpn export AS:NN|IP:nn
Specifies the route distinguisher to be added to a route exported from the
current unicast VRF to VPN.
.. clicmd:: rt vpn import|export|both RTLIST...
Specifies the route-target list to be attached to a route (export) or the
route-target list to match against (import) when exporting/importing between
the current unicast VRF and VPN. The `rt vpn export RTLIST` command is not
mandatory and can be replaced or completed by the `set extcommunity rt`
command in the route-map attached with the `route-map vpn export`. The below
configuration illustrates how the route target is selected based on the
prefixes, and not solely on vrf criterium:
.. code-block:: frr
access-list acl1 permit 192.0.2.0/24
access-list acl2 permit 192.0.3.0/24
route-map rmap permit 10
match address acl1
set extcommunity rt 65001:10
!
route-map rmap permit 20
match address acl1
set extcommunity rt 65001:20
!
router bgp 65001 vrf vrf1
!
address-family ipv4 unicast
rd vpn export 65001:1
import vpn
export vpn
rt vpn import 65001:1
route-map vpn export rmap
The RTLIST is a space-separated list of route-targets, which are BGP
extended community values as described in
:ref:`bgp-extended-communities-attribute`.
.. clicmd:: label vpn export allocation-mode per-vrf|per-nexthop
Select how labels are allocated in the given VRF. By default, the `per-vrf`
mode is selected, and one label is used for all prefixes from the VRF. The
`per-nexthop` will use a unique label for all prefixes that are reachable
via the same nexthop.
.. clicmd:: label vpn export (0..1048575)|auto
Enables an MPLS label to be attached to a route exported from the current
unicast VRF to VPN. If the value specified is ``auto``, the label value is
automatically assigned from a pool maintained by the Zebra daemon. If Zebra
is not running, or if this command is not configured, automatic label
assignment will not complete, which will block corresponding route export.
.. clicmd:: nexthop vpn export A.B.C.D|X:X::X:X
Specifies an optional nexthop value to be assigned to a route exported from
the current unicast VRF to VPN. If left unspecified, the nexthop will be set
to 0.0.0.0 or 0:0::0:0 (self).
.. clicmd:: route-map vpn import|export MAP
Specifies an optional route-map to be applied to routes imported or exported
between the current unicast VRF and VPN.
.. clicmd:: import|export vpn
Enables import or export of routes between the current unicast VRF and VPN.
.. clicmd:: import vrf VRFNAME
Shortcut syntax for specifying automatic leaking from vrf VRFNAME to
the current VRF using the VPN RIB as intermediary. The RD and RT
are auto derived and should not be specified explicitly for either the
source or destination VRF's.
This shortcut syntax mode is not compatible with the explicit
`import vpn` and `export vpn` statements for the two VRF's involved.
The CLI will disallow attempts to configure incompatible leaking
modes.
.. clicmd:: bgp retain route-target all
It is possible to retain or not VPN prefixes that are not imported by local
VRF configuration. This can be done via the following command in the context
of the global VPNv4/VPNv6 family. This command defaults to on and is not
displayed.
The `no bgp retain route-target all` form of the command is displayed.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> soo EXTCOMMUNITY
Without this command, SoO extended community attribute is configured using
an inbound route map that sets the SoO value during the update process.
With the introduction of the new BGP per-neighbor Site-of-Origin (SoO) feature,
two new commands configured in sub-modes under router configuration mode
simplify the SoO value configuration.
If we configure SoO per neighbor at PEs, the SoO community is automatically
added for all routes from the CPEs. Routes are validated and prevented from
being sent back to the same CPE (e.g.: multi-site). This is especially needed
when using ``as-override`` or ``allowas-in`` to prevent routing loops.
.. clicmd:: mpls bgp forwarding
It is possible to permit BGP install VPN prefixes without transport labels,
by issuing the following command under the interface configuration context.
This configuration will install VPN prefixes originated from an e-bgp session,
and with the next-hop directly connected.
.. clicmd:: mpls bgp l3vpn-multi-domain-switching
Redistribute labeled L3VPN routes from AS to neighboring AS (RFC-4364 option
B, or within the same AS when the iBGP peer uses ``next-hop-self`` to rewrite
the next-hop attribute). The labeled L3VPN routes received on this interface are
re-advertised with local labels and an MPLS table swap entry is set to bind
the local label to the received label.
.. _bgp-l3vpn-srv6:
L3VPN SRv6
----------
.. clicmd:: segment-routing srv6
Use SRv6 backend with BGP L3VPN, and go to its configuration node.
.. clicmd:: locator NAME
Specify the SRv6 locator to be used for SRv6 L3VPN. The Locator name must
be set in zebra, but user can set it in any order.
L3VPN SRv6 SID reachability
---------------------------
In the context of IPv4 L3VPN over SRv6 specific usecase, 2001:db8:12::2
is the peer IPv6 address of r2, and 2001:db8:2:2:: is the SRv6 SID
advertised by router r2 for prefix P. On r1, the SID reachability is
checked in order to install the prefix P. The below output indicates
that the 2001:db8:2:2:: prefix is valid.
.. code-block:: frr
r1# show bgp nexthop detail
Current BGP nexthop cache:
2001:db8:2:2:: valid [IGP metric 0], #paths 4
gate 2001:db8:12::2, if eth0
Last update: Tue Nov 14 10:36:28 2023
Paths:
1/1 192.168.2.0/24 VRF vrf10 flags 0x4018
1/3 192.168.2.0/24 RD 65002:10 VRF default flags 0x418
2001:db8:12::2 valid [IGP metric 0], #paths 0, peer 2001:db8:12::2
if eth0
Last update: Tue Nov 14 10:36:26 2023
Paths:
General configuration
^^^^^^^^^^^^^^^^^^^^^
Configuration of the SRv6 SID used to advertise a L3VPN for both IPv4 and IPv6
is accomplished via the following command in the context of a VRF:
.. clicmd:: sid vpn per-vrf export (1..1048575)|auto
Enables a SRv6 SID to be attached to a route exported from the current
unicast VRF to VPN. A single SID is used for both IPv4 and IPv6 address
families. If you want to set a SID for only IPv4 address family or IPv6
address family, you need to use the command ``sid vpn export (1..1048575)|auto``
in the context of an address-family. If the value specified is ``auto``,
the SID value is automatically assigned from a pool maintained by the Zebra
daemon. If Zebra is not running, or if this command is not configured, automatic
SID assignment will not complete, which will block corresponding route export.
.. _bgp-evpn:
Ethernet Virtual Network - EVPN
-------------------------------
Note: When using EVPN features and if you have a large number of hosts, make
sure to adjust the size of the arp neighbor cache to avoid neighbor table
overflow and/or excessive garbage collection. On Linux, the size of the table
and garbage collection frequency can be controlled via the following
sysctl configurations:
.. code-block:: shell
net.ipv4.neigh.default.gc_thresh1
net.ipv4.neigh.default.gc_thresh2
net.ipv4.neigh.default.gc_thresh3
net.ipv6.neigh.default.gc_thresh1
net.ipv6.neigh.default.gc_thresh2
net.ipv6.neigh.default.gc_thresh3
For more information, see ``man 7 arp``.
.. _bgp-enabling-evpn:
Enabling EVPN
^^^^^^^^^^^^^
EVPN should be enabled on the BGP instance corresponding to the VRF acting as
the underlay for the VXLAN tunneling. In most circumstances this will be the
default VRF. The command to enable EVPN for a BGP instance is
``advertise-all-vni`` which lives under ``address-family l2vpn evpn``:
.. code-block:: frr
router bgp 65001
!
address-family l2vpn evpn
advertise-all-vni
A more comprehensive configuration example can be found in the :ref:`evpn` page.
.. _bgp-evpn-l3-route-targets:
EVPN L3 Route-Targets
^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: route-target <import|export|both> <RTLIST|auto>
Modify the route-target set for EVPN advertised type-2/type-5 routes.
RTLIST is a list of any of matching
``(A.B.C.D:MN|EF:OPQR|GHJK:MN|*:OPQR|*:MN)`` where ``*`` indicates wildcard
matching for the AS number. It will be set to match any AS number. This is
useful in datacenter deployments with Downstream VNI. ``auto`` is used to
retain the autoconfigure that is default behavior for L3 RTs.
.. _bgp-evpn-advertise-pip:
EVPN advertise-PIP
^^^^^^^^^^^^^^^^^^
In a EVPN symmetric routing MLAG deployment, all EVPN routes advertised
with anycast-IP as next-hop IP and anycast MAC as the Router MAC (RMAC - in
BGP EVPN Extended-Community).
EVPN picks up the next-hop IP from the VxLAN interface's local tunnel IP and
the RMAC is obtained from the MAC of the L3VNI's SVI interface.
Note: Next-hop IP is used for EVPN routes whether symmetric routing is
deployed or not but the RMAC is only relevant for symmetric routing scenario.
Current behavior is not ideal for Prefix (type-5) and self (type-2)
routes. This is because the traffic from remote VTEPs routed sub optimally
if they land on the system where the route does not belong.
The advertise-pip feature advertises Prefix (type-5) and self (type-2)
routes with system's individual (primary) IP as the next-hop and individual
(system) MAC as Router-MAC (RMAC), while leaving the behavior unchanged for
other EVPN routes.
To support this feature there needs to have ability to co-exist a
(system-MAC, system-IP) pair with a (anycast-MAC, anycast-IP) pair with the
ability to terminate VxLAN-encapsulated packets received for either pair on
the same L3VNI (i.e associated VLAN). This capability is needed per tenant
VRF instance.
To derive the system-MAC and the anycast MAC, there must be a
separate/additional MAC-VLAN interface corresponding to L3VNI’s SVI.
The SVI interface’s MAC address can be interpreted as system-MAC
and MAC-VLAN interface's MAC as anycast MAC.
To derive system-IP and anycast-IP, the default BGP instance's router-id is used
as system-IP and the VxLAN interface’s local tunnel IP as the anycast-IP.
User has an option to configure the system-IP and/or system-MAC value if the
auto derived value is not preferred.
Note: By default, advertise-pip feature is enabled and user has an option to
disable the feature via configuration CLI. Once the feature is disabled under
bgp vrf instance or MAC-VLAN interface is not configured, all the routes follow
the same behavior of using same next-hop and RMAC values.
.. clicmd:: advertise-pip [ip <addr> [mac <addr>]]
Enables or disables advertise-pip feature, specify system-IP and/or system-MAC
parameters.
EVPN advertise-svi-ip
^^^^^^^^^^^^^^^^^^^^^
Typically, the SVI IP address is reused on VTEPs across multiple racks. However,
if you have unique SVI IP addresses that you want to be reachable you can use the
advertise-svi-ip option. This option advertises the SVI IP/MAC address as a type-2
route and eliminates the need for any flooding over VXLAN to reach the IP from a
remote VTEP.
.. clicmd:: advertise-svi-ip
Note that you should not enable both the advertise-svi-ip and the advertise-default-gw
at the same time.
.. _bgp-evpn-overlay-index-gateway-ip:
EVPN Overlay Index Gateway IP
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RFC https://datatracker.ietf.org/doc/html/rfc9136 explains the use of overlay
indexes for recursive route resolution for EVPN type-5 route.
We support gateway IP overlay index.
A gateway IP, advertised with EVPN prefix route, is used to find an EVPN MAC/IP
route with its IP field same as the gateway IP. This MAC/IP entry provides the
nexthop VTEP and the tunnel information required for the VxLAN encapsulation.
Functionality:
::
. +--------+ BGP +--------+ BGP +--------+ +--------+
SN1 | | IPv4 | | EVPN | | | |
======+ Host1 +------+ PE1 +------+ PE2 +------+ Host2 +
| | | | | | | |
+--------+ +--------+ +--------+ +--------+
Consider above topology where prefix SN1 is connected behind host1. Host1
advertises SN1 to PE1 over BGP IPv4 session. PE1 advertises SN1 to PE2 using
EVPN type-5 route with host1 IP as the gateway IP. PE1 also advertises
Host1 MAC/IP as type-2 route which is used to resolve host1 gateway IP.
PE2 receives this type-5 route and imports it into the vrf based on route
targets. BGP prefix imported into the vrf uses gateway IP as its BGP nexthop.
This route is installed into zebra if following conditions are satisfied:
1. Gateway IP nexthop is L3 reachable.
2. PE2 has received EVPN type-2 route with IP field set to gateway IP.
Topology requirements:
1. This feature is supported for asymmetric routing model only. While
sending packets to SN1, ingress PE (PE2) performs routing and
egress PE (PE1) performs only bridging.
2. This feature supports only traditional(non vlan-aware) bridge model. Bridge
interface associated with L2VNI is an L3 interface. i.e., this interface is
configured with an address in the L2VNI subnet. Note that the gateway IP
should also have an address in the same subnet.
3. As this feature works in asymmetric routing model, all L2VNIs and corresponding
VxLAN and bridge interfaces should be present at all the PEs.
4. L3VNI configuration is required to generate and import EVPN type-5 routes.
L3VNI VxLAN and bridge interfaces also should be present.
A PE can use one of the following two mechanisms to advertise an EVPN type-5
route with gateway IP.
1. CLI to add gateway IP while generating EVPN type-5 route from a BGP IPv4/IPv6
prefix:
.. clicmd:: advertise <ipv4|ipv6> unicast [gateway-ip]
When this CLI is configured for a BGP vrf under L2VPN EVPN address family, EVPN
type-5 routes are generated for BGP prefixes in the vrf. Nexthop of the BGP
prefix becomes the gateway IP of the corresponding type-5 route.
If the above command is configured without the "gateway-ip" keyword, type-5
routes are generated without overlay index.
2. Add gateway IP to EVPN type-5 route using a route-map:
.. clicmd:: set evpn gateway-ip <ipv4|ipv6> <addr>
When route-map with above set clause is applied as outbound policy in BGP, it
will set the gateway-ip in EVPN type-5 NLRI.
Example configuration:
.. code-block:: frr
router bgp 100
neighbor 192.168.0.1 remote-as 101
!
address-family ipv4 l2vpn evpn
neighbor 192.168.0.1 route-map RMAP out
exit-address-family
!
route-map RMAP permit 10
set evpn gateway-ip 10.0.0.1
set evpn gateway-ip 10::1
A PE that receives a type-5 route with gateway IP overlay index should have
"enable-resolve-overlay-index" configuration enabled to recursively resolve the
overlay index nexthop and install the prefix into zebra.
.. clicmd:: enable-resolve-overlay-index
Example configuration:
.. code-block:: frr
router bgp 65001
bgp router-id 192.168.100.1
no bgp ebgp-requires-policy
neighbor 10.0.1.2 remote-as 65002
!
address-family l2vpn evpn
neighbor 10.0.1.2 activate
advertise-all-vni
enable-resolve-overlay-index
exit-address-family
!
.. _bgp-evpn-mac-vrf-site-of-origin:
EVPN MAC-VRF Site-of-Origin
^^^^^^^^^^^^^^^^^^^^^^^^^^^
In some EVPN deployments it is useful to associate a logical VTEP's Layer 2
domain (MAC-VRF) with a Site-of-Origin "site" identifier. This provides a
BGP topology-independent means of marking and import-filtering EVPN routes
originated from a particular L2 domain. One situation where this is valuable
is when deploying EVPN using anycast VTEPs, i.e. Active/Active MLAG, as it
can be used to avoid ownership conflicts between the two control planes
(EVPN vs MLAG).
Example Use Case (MLAG Anycast VTEPs):
During normal operation, an MLAG VTEP will advertise EVPN routes for attached
hosts using a shared anycast IP as the BGP next-hop. It is expected for its
MLAG peer to drop routes originated by the MLAG Peer since they have a Martian
(self) next-hop. However, prior to the anycast IP being assigned to the local
system, the anycast BGP next-hop will not be considered a Martian (self) IP.
This results in a timing window where hosts that are locally attached to the
MLAG pair's L2 domain can be learned both as "local" (via MLAG) or "remote"
(via an EVPN route with a non-local next-hop). This can trigger erroneous MAC
Mobility events, as the host "moves" between one MLAG Peer's Unique VTEP-IP
and the shared anycast VTEP-IP, which causes unnecessary control plane and
data plane events to propagate throughout the EVPN domain.
By associating the MAC-VRF of both MLAG VTEPs with the same site identifier,
EVPN routes originated by one MLAG VTEP will ignored by its MLAG peer, ensuring
that only the MLAG control plane attempts to take ownership of local hosts.
The EVPN MAC-VRF Site-of-Origin feature works by influencing two behaviors:
1. All EVPN routes originating from the local MAC-VRF will have a
Site-of-Origin extended community added to the route, matching the
configured value.
2. EVPN routes will be subjected to a "self SoO" check during MAC-VRF
or IP-VRF import processing. If the EVPN route is found to carry a
Site-of-Origin extended community whose value matches the locally
configured MAC-VRF Site-of-Origin, the route will be maintained in
the global EVPN RIB ("show bgp l2vpn evpn route") but will not be
imported into the corresponding MAC-VRF ("show bgp vni") or IP-VRF
("show bgp [vrf <vrfname>] [ipv4 | ipv6 [unicast]]").
The import filtering described in item (2) is constrained just to Type-2
(MAC-IP) and Type-3 (IMET) EVPN routes.
The EVPN MAC-VRF Site-of-Origin can be configured using a single CLI command
under ``address-family l2vpn evpn`` of the EVPN underlay BGP instance.
.. clicmd:: mac-vrf soo <site-of-origin-string>
Example configuration:
.. code-block:: frr
router bgp 100
neighbor 192.168.0.1 remote-as 101
!
address-family ipv4 l2vpn evpn
neighbor 192.168.0.1 activate
advertise-all-vni
mac-vrf soo 100.64.0.0:777
exit-address-family
This configuration ensures:
1. EVPN routes originated from a local L2VNI will have a Site-of-Origin
extended community with the value ``100.64.0.0:777``
2. Received EVPN routes carrying a Site-of-Origin extended community with the
value ``100.64.0.0:777`` will not be imported into a local MAC-VRF (L2VNI)
or IP-VRF (L3VNI).
.. _bgp-evpn-mh:
EVPN Multihoming
^^^^^^^^^^^^^^^^
All-Active Multihoming is used for redundancy and load sharing. Servers
are attached to two or more PEs and the links are bonded (link-aggregation).
This group of server links is referred to as an Ethernet Segment.
Ethernet Segments
"""""""""""""""""
An Ethernet Segment can be configured by specifying a system-MAC and a
local discriminator or a complete ESINAME against the bond interface on the
PE (via zebra) -
.. clicmd:: evpn mh es-id <(1-16777215)|ESINAME>
.. clicmd:: evpn mh es-sys-mac X:X:X:X:X:X
The sys-mac and local discriminator are used for generating a 10-byte,
Type-3 Ethernet Segment ID. ESINAME is a 10-byte, Type-0 Ethernet Segment ID -
"00:AA:BB:CC:DD:EE:FF:GG:HH:II".
Type-1 (EAD-per-ES and EAD-per-EVI) routes are used to advertise the locally
attached ESs and to learn off remote ESs in the network. Local Type-2/MAC-IP
routes are also advertised with a destination ESI allowing for MAC-IP syncing
between Ethernet Segment peers.
Reference: RFC 7432, RFC 8365
EVPN-MH is intended as a replacement for MLAG or Anycast VTEPs. In
multihoming each PE has an unique VTEP address which requires the introduction
of a new dataplane construct, MAC-ECMP. Here a MAC/FDB entry can point to a
list of remote PEs/VTEPs.
BUM handling
""""""""""""
Type-4 (ESR) routes are used for Designated Forwarder (DF) election. DFs
forward BUM traffic received via the overlay network. This implementation
uses a preference based DF election specified by draft-ietf-bess-evpn-pref-df.
The DF preference is configurable per-ES (via zebra) -
.. clicmd:: evpn mh es-df-pref (1-16777215)
BUM traffic is rxed via the overlay by all PEs attached to a server but
only the DF can forward the de-capsulated traffic to the access port. To
accommodate that non-DF filters are installed in the dataplane to drop
the traffic.
Similarly traffic received from ES peers via the overlay cannot be forwarded
to the server. This is split-horizon-filtering with local bias.
Knobs for interop
"""""""""""""""""
Some vendors do not send EAD-per-EVI routes. To interop with them we
need to relax the dependency on EAD-per-EVI routes and activate a remote
ES-PE based on just the EAD-per-ES route.
Note that by default we advertise and expect EAD-per-EVI routes.
.. clicmd:: disable-ead-evi-rx
.. clicmd:: disable-ead-evi-tx
Fast failover
"""""""""""""
As the primary purpose of EVPN-MH is redundancy keeping the failover efficient
is a recurring theme in the implementation. Following sub-features have
been introduced for the express purpose of efficient ES failovers.
- Layer-2 Nexthop Groups and MAC-ECMP via L2NHG.
- Host routes (for symmetric IRB) via L3NHG.
On dataplanes that support layer3 nexthop groups the feature can be turned
on via the following BGP config -
.. clicmd:: use-es-l3nhg
- Local ES (MAC/Neigh) failover via ES-redirect.
On dataplanes that do not have support for ES-redirect the feature can be
turned off via the following zebra config -
.. clicmd:: evpn mh redirect-off
Uplink/Core tracking
""""""""""""""""""""
When all the underlay links go down the PE no longer has access to the VxLAN
+overlay. To prevent blackholing of traffic the server/ES links are
protodowned on the PE. A link can be setup for uplink tracking via the
following zebra configuration -
.. clicmd:: evpn mh uplink
Proxy advertisements
""""""""""""""""""""
To handle hitless upgrades support for proxy advertisement has been added
as specified by draft-rbickhart-evpn-ip-mac-proxy-adv. This allows a PE
(say PE1) to proxy advertise a MAC-IP rxed from an ES peer (say PE2). When
the ES peer (PE2) goes down PE1 continues to advertise hosts learnt from PE2
for a holdtime during which it attempts to establish local reachability of
the host. This holdtime is configurable via the following zebra commands -
.. clicmd:: evpn mh neigh-holdtime (0-86400)
.. clicmd:: evpn mh mac-holdtime (0-86400)
Startup delay
"""""""""""""
When a switch is rebooted we wait for a brief period to allow the underlay
and EVPN network to converge before enabling the ESs. For this duration the
ES bonds are held protodown. The startup delay is configurable via the
following zebra command -
.. clicmd:: evpn mh startup-delay (0-3600)
EAD-per-ES fragmentation
""""""""""""""""""""""""
The EAD-per-ES route carries the EVI route targets for all the broadcast
domains associated with the ES. Depending on the EVI scale the EAD-per-ES
route maybe fragmented.
The number of EVIs per-EAD route can be configured via the following
BGP command -
.. clicmd:: ead-es-frag evi-limit (1-1000)
Sample Configuration
^^^^^^^^^^^^^^^^^^^^^
.. code-block:: frr
!
router bgp 5556
!
address-family l2vpn evpn
ead-es-frag evi-limit 200
exit-address-family
!
!
EAD-per-ES route-target
"""""""""""""""""""""""
The EAD-per-ES route by default carries all the EVI route targets. Depending
on EVI scale that can result in route fragmentation. In some cases it maybe
necessary to avoid this fragmentation and that can be done via the following
workaround -
1. Configure a single supplementary BD per-tenant VRF. This SBD needs to
be provisioned on all EVPN PEs associated with the tenant-VRF.
2. Config the SBD's RT as the EAD-per-ES route's export RT.
Sample Configuration
^^^^^^^^^^^^^^^^^^^^^
.. code-block:: frr
!
router bgp 5556
!
address-family l2vpn evpn
ead-es-route-target export 5556:1001
ead-es-route-target export 5556:1004
ead-es-route-target export 5556:1008
exit-address-family
!
Support with VRF network namespace backend
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It is possible to separate overlay networks contained in VXLAN interfaces from
underlay networks by using VRFs. VRF-lite and VRF-netns backends can be used for
that. In the latter case, it is necessary to set both bridge and vxlan interface
in the same network namespace, as below example illustrates:
.. code-block:: shell
# linux shell
ip netns add vrf1
ip link add name vxlan101 type vxlan id 101 dstport 4789 dev eth0 local 10.1.1.1
ip link set dev vxlan101 netns vrf1
ip netns exec vrf1 ip link set dev lo up
ip netns exec vrf1 brctl addbr bridge101
ip netns exec vrf1 brctl addif bridge101 vxlan101
This makes it possible to separate not only layer 3 networks like VRF-lite networks.
Also, VRF netns based make possible to separate layer 2 networks on separate VRF
instances.
.. _bgp-conditional-advertisement:
BGP Conditional Advertisement
-----------------------------
The BGP conditional advertisement feature uses the ``non-exist-map`` or the
``exist-map`` and the ``advertise-map`` keywords of the neighbor advertise-map
command in order to track routes by the route prefix.
``non-exist-map``
1. If a route prefix is not present in the output of non-exist-map command,
then advertise the route specified by the advertise-map command.
2. If a route prefix is present in the output of non-exist-map command,
then do not advertise the route specified by the addvertise-map command.
``exist-map``
1. If a route prefix is present in the output of exist-map command,
then advertise the route specified by the advertise-map command.
2. If a route prefix is not present in the output of exist-map command,
then do not advertise the route specified by the advertise-map command.
This feature is useful when some prefixes are advertised to one of its peers
only if the information from the other peer is not present (due to failure in
peering session or partial reachability etc).
The conditional BGP announcements are sent in addition to the normal
announcements that a BGP router sends to its peer.
The conditional advertisement process is triggered by the BGP scanner process,
which runs every 60 by default. This means that the maximum time for the
conditional advertisement to take effect is the value of the process timer.
As an optimization, while the process always runs on each timer expiry, it
determines whether or not the conditional advertisement policy or the routing
table has changed; if neither have changed, no processing is necessary and the
scanner exits early.
.. clicmd:: neighbor A.B.C.D advertise-map NAME [exist-map|non-exist-map] NAME
This command enables BGP scanner process to monitor routes specified by
exist-map or non-exist-map command in BGP table and conditionally advertises
the routes specified by advertise-map command.
.. clicmd:: bgp conditional-advertisement timer (5-240)
Set the period to rerun the conditional advertisement scanner process. The
default is 60 seconds.
Sample Configuration
^^^^^^^^^^^^^^^^^^^^^
.. code-block:: frr
interface enp0s9
ip address 10.10.10.2/24
!
interface enp0s10
ip address 10.10.20.2/24
!
interface lo
ip address 203.0.113.1/32
!
router bgp 2
bgp log-neighbor-changes
no bgp ebgp-requires-policy
neighbor 10.10.10.1 remote-as 1
neighbor 10.10.20.3 remote-as 3
!
address-family ipv4 unicast
neighbor 10.10.10.1 soft-reconfiguration inbound
neighbor 10.10.20.3 soft-reconfiguration inbound
neighbor 10.10.20.3 advertise-map ADV-MAP non-exist-map EXIST-MAP
exit-address-family
!
ip prefix-list DEFAULT seq 5 permit 192.0.2.5/32
ip prefix-list DEFAULT seq 10 permit 192.0.2.1/32
ip prefix-list EXIST seq 5 permit 10.10.10.10/32
ip prefix-list DEFAULT-ROUTE seq 5 permit 0.0.0.0/0
ip prefix-list IP1 seq 5 permit 10.139.224.0/20
!
bgp community-list standard DC-ROUTES seq 5 permit 64952:3008
bgp community-list standard DC-ROUTES seq 10 permit 64671:501
bgp community-list standard DC-ROUTES seq 15 permit 64950:3009
bgp community-list standard DEFAULT-ROUTE seq 5 permit 65013:200
!
route-map ADV-MAP permit 10
match ip address prefix-list IP1
!
route-map ADV-MAP permit 20
match community DC-ROUTES
!
route-map EXIST-MAP permit 10
match community DEFAULT-ROUTE
match ip address prefix-list DEFAULT-ROUTE
!
Sample Output
^^^^^^^^^^^^^
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.
.. code-block:: frr
Router2# show ip bgp
BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0/0 10.10.10.1 0 0 1 i
*> 10.139.224.0/20 10.10.10.1 0 0 1 ?
*> 192.0.2.1/32 10.10.10.1 0 0 1 i
*> 192.0.2.5/32 10.10.10.1 0 0 1 i
Displayed 4 routes and 4 total paths
Router2# show ip bgp neighbors 10.10.20.3
!--- Output suppressed.
For address family: IPv4 Unicast
Update group 7, subgroup 7
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Withdraw
0 accepted prefixes
!--- Output suppressed.
Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
BGP table version is 20, local router ID is 203.0.113.1, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*> 0.0.0.0/0 0.0.0.0 0 1 i
*> 192.0.2.5/32 0.0.0.0 0 1 i
Total number of prefixes 2
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.
.. code-block:: frr
Router2# show ip bgp
BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*> 10.139.224.0/20 10.10.10.1 0 0 1 ?
*> 192.0.2.1/32 10.10.10.1 0 0 1 i
*> 192.0.2.5/32 10.10.10.1 0 0 1 i
Displayed 3 routes and 3 total paths
Router2# show ip bgp neighbors 10.10.20.3
!--- Output suppressed.
For address family: IPv4 Unicast
Update group 7, subgroup 7
Packet Queue length 0
Inbound soft reconfiguration allowed
Community attribute sent to this neighbor(all)
Condition NON_EXIST, Condition-map *EXIST-MAP, Advertise-map *ADV-MAP, status: Advertise
0 accepted prefixes
!--- Output suppressed.
Router2# show ip bgp neighbors 10.10.20.3 advertised-routes
BGP table version is 21, local router ID is 203.0.113.1, vrf id 0
Default local pref 100, local AS 2
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*> 10.139.224.0/20 0.0.0.0 0 1 ?
*> 192.0.2.1/32 0.0.0.0 0 1 i
*> 192.0.2.5/32 0.0.0.0 0 1 i
Total number of prefixes 3
Router2#
.. _bgp-debugging:
Debugging
---------
.. clicmd:: show debug
Show all enabled debugs.
.. clicmd:: show bgp listeners
Display Listen sockets and the vrf that created them. Useful for debugging of when
listen is not working and this is considered a developer debug statement.
.. clicmd:: debug bgp allow-martian
Enable or disable BGP accepting martian nexthops from a peer. Please note
this is not an actual debug command and this command is also being deprecated
and will be removed soon. The new command is :clicmd:`bgp allow-martian-nexthop`
.. clicmd:: debug bgp bfd
Enable or disable debugging for BFD events. This will show BFD integration
library messages and BGP BFD integration messages that are mostly state
transitions and validation problems.
.. clicmd:: debug bgp conditional-advertisement
Enable or disable debugging of BGP conditional advertisement.
.. clicmd:: debug bgp neighbor-events
Enable or disable debugging for neighbor events. This provides general
information on BGP events such as peer connection / disconnection, session
establishment / teardown, and capability negotiation.
.. clicmd:: debug bgp updates [detail]
Enable or disable debugging for BGP updates. This provides information on
BGP UPDATE messages transmitted and received between local and remote
instances.
If ``detail`` is specified, the output will include the full BGP UPDATE with
detailed information such as attribute length, withdraw length, and more.
.. clicmd:: debug bgp updates <in|out> [<A.B.C.D|X:X::X:X|WORD> [prefix-list WORD]]
Enable or disable debugging for BGP updates. Optionally, you can specify
a prefix-list to filter the updates for an arbitrary neighbor.
.. clicmd:: debug bgp keepalives
Enable or disable debugging for BGP keepalives. This provides information on
BGP KEEPALIVE messages transmitted and received between local and remote
instances.
.. clicmd:: debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
Enable or disable debugging for bestpath selection on the specified prefix.
.. clicmd:: debug bgp nht
Enable or disable debugging of BGP nexthop tracking.
.. clicmd:: debug bgp update-groups
Enable or disable debugging of dynamic update groups. This provides general
information on group creation, deletion, join and prune events.
.. clicmd:: debug bgp zebra
Enable or disable debugging of communications between *bgpd* and *zebra*.
Dumping Messages and Routing Tables
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. clicmd:: dump bgp all PATH [INTERVAL]
.. clicmd:: dump bgp all-et PATH [INTERVAL]
Dump all BGP packet and events to `path` file.
If `interval` is set, a new file will be created for echo `interval` of
seconds. The path `path` can be set with date and time formatting
(strftime). The type ‘all-et’ enables support for Extended Timestamp Header
(:ref:`packet-binary-dump-format`).
.. clicmd:: dump bgp updates PATH [INTERVAL]
.. clicmd:: dump bgp updates-et PATH [INTERVAL]
Dump only BGP updates messages to `path` file.
If `interval` is set, a new file will be created for echo `interval` of
seconds. The path `path` can be set with date and time formatting
(strftime). The type ‘updates-et’ enables support for Extended Timestamp
Header (:ref:`packet-binary-dump-format`).
.. clicmd:: dump bgp routes-mrt PATH
.. clicmd:: dump bgp routes-mrt PATH INTERVAL
Dump whole BGP routing table to `path`. This is heavy process. The path
`path` can be set with date and time formatting (strftime). If `interval` is
set, a new file will be created for echo `interval` of seconds.
Note: the interval variable can also be set using hours and minutes: 04h20m00.
.. _bgp-other-commands:
Other BGP Commands
------------------
The following are available in the top level *enable* mode:
.. clicmd:: clear bgp \*
Clear all peers.
.. clicmd:: clear bgp ipv4|ipv6 ASNUM
Clear peers with the AS number in plain or dotted format.
.. clicmd:: clear bgp ipv4|ipv6 \*
Clear all peers with this address-family activated.
.. clicmd:: clear bgp ipv4|ipv6 unicast \*
Clear all peers with this address-family and sub-address-family activated.
.. clicmd:: clear bgp ipv4|ipv6 PEER
Clear peers with address of X.X.X.X and this address-family activated.
.. clicmd:: clear bgp ipv4|ipv6 unicast PEER
Clear peer with address of X.X.X.X and this address-family and sub-address-family activated.
.. clicmd:: clear bgp ipv4|ipv6 PEER soft|in|out
Clear peer using soft reconfiguration in this address-family.
.. clicmd:: clear bgp ipv4|ipv6 unicast PEER soft|in|out
Clear peer using soft reconfiguration in this address-family and sub-address-family.
.. clicmd:: clear bgp [ipv4|ipv6] [unicast] PEER|\* message-stats
Clear BGP message statistics for a specified peer or for all peers,
optionally filtered by activated address-family and sub-address-family.
.. clicmd:: clear bgp [ipv4|ipv6] [unicast] PEER|\* capabilities
Clear specific BGP capabilities for a specified peer or for all peers. This
includes such capabilities like FQDN capability, that can't be controlled by
any other configuration knob.
For example, if you want to change the FQDN, you MUST reset the BGP session
in order to send a new FQDN capability to the peer. This command allows you
to resend FQDN capability without resetting the session.
.. code-block:: frr
hostname bgp-new.example.com
clear bgp 10.10.10.1 capabilities
.. note::
Changing the hostname is possible only when connected to the specific daemon.
If you change the hostname via ``vtysh``, it won't be changed.
The following are available in the ``router bgp`` mode:
.. clicmd:: write-quanta (1-64)
BGP message Tx I/O is vectored. This means that multiple packets are written
to the peer socket at the same time each I/O cycle, in order to minimize
system call overhead. This value controls how many are written at a time.
Under certain load conditions, reducing this value could make peer traffic
less 'bursty'. In practice, leave this settings on the default (64) unless
you truly know what you are doing.
.. clicmd:: read-quanta (1-10)
Unlike Tx, BGP Rx traffic is not vectored. Packets are read off the wire one
at a time in a loop. This setting controls how many iterations the loop runs
for. As with write-quanta, it is best to leave this setting on the default.
The following command is available in ``config`` mode as well as in the
``router bgp`` mode:
.. clicmd:: bgp graceful-shutdown
The purpose of this command is to initiate BGP Graceful Shutdown which
is described in :rfc:`8326`. The use case for this is to minimize or
eliminate the amount of traffic loss in a network when a planned
maintenance activity such as software upgrade or hardware replacement
is to be performed on a router. The feature works by re-announcing
routes to eBGP peers with the GRACEFUL_SHUTDOWN community included.
Peers are then expected to treat such paths with the lowest preference.
This happens automatically on a receiver running FRR; with other
routing protocol stacks, an inbound policy may have to be configured.
In FRR, triggering graceful shutdown also results in announcing a
LOCAL_PREF of 0 to iBGP peers.
Graceful shutdown can be configured per BGP instance or globally for
all of BGP. These two options are mutually exclusive. The no form of
the command causes graceful shutdown to be stopped, and routes will
be re-announced without the GRACEFUL_SHUTDOWN community and/or with
the usual LOCAL_PREF value. Note that if this option is saved to
the startup configuration, graceful shutdown will remain in effect
across restarts of *bgpd* and will need to be explicitly disabled.
.. clicmd:: bgp input-queue-limit (1-4294967295)
Set the BGP Input Queue limit for all peers when messaging parsing. Increase
this only if you have the memory to handle large queues of messages at once.
.. clicmd:: bgp output-queue-limit (1-4294967295)
Set the BGP Output Queue limit for all peers when messaging parsing. Increase
this only if you have the memory to handle large queues of messages at once.
.. _bgp-displaying-bgp-information:
Displaying BGP Information
==========================
The following four commands display the IPv6 and IPv4 routing tables, depending
on whether or not the ``ip`` keyword is used.
Actually, :clicmd:`show ip bgp` command was used on older `Quagga` routing
daemon project, while :clicmd:`show bgp` command is the new format. The choice
has been done to keep old format with IPv4 routing table, while new format
displays IPv6 routing table.
.. clicmd:: show ip bgp [all] [wide|json [detail]]
.. clicmd:: show ip bgp A.B.C.D [json]
.. clicmd:: show bgp [all] [wide|json [detail]]
.. clicmd:: show bgp X:X::X:X [json]
These commands display BGP routes. When no route is specified, the default
is to display all BGP routes.
::
BGP table version is 0, local router ID is 10.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
\*> 1.1.1.1/32 0.0.0.0 0 32768 i
Total number of prefixes 1
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
This is especially handy dealing with IPv6 prefixes and
if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
If ``all`` option is specified, ``ip`` keyword is ignored, show bgp all and
show ip bgp all commands display routes for all AFIs and SAFIs.
If ``json`` option is specified, output is displayed in JSON format.
If ``detail`` option is specified after ``json``, more verbose JSON output
will be displayed.
Some other commands provide additional options for filtering the output.
.. clicmd:: show [ip] bgp regexp LINE
This command displays BGP routes using AS path regular expression
(:ref:`bgp-regular-expressions`).
.. clicmd:: show [ip] bgp [all] summary [wide] [json]
Show a bgp peer summary for the specified address family.
The old command structure :clicmd:`show ip bgp` may be removed in the future
and should no longer be used. In order to reach the other BGP routing tables
other than the IPv6 routing table given by :clicmd:`show bgp`, the new command
structure is extended with :clicmd:`show bgp [afi] [safi]`.
``wide`` option gives more output like ``LocalAS`` and extended ``Desc`` to
64 characters.
.. code-block:: frr
exit1# show ip bgp summary wide
IPv4 Unicast Summary:
BGP router identifier 192.168.100.1, local AS number 65534 VRF default vrf-id 0
BGP table version 3
RIB entries 5, using 920 bytes of memory
Peers 1, using 27 KiB of memory
Neighbor V AS LocalAS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
192.168.0.2 4 65030 123 15 22 0 0 0 00:07:00 0 1 us-east1-rs1.frrouting.org
Total number of neighbors 1
exit1#
If PfxRcd and/or PfxSnt is shown as ``(Policy)``, that means that the EBGP
default policy is turned on, but you don't have any filters applied for
incoming/outgoing directions.
.. seealso:: :ref:`bgp-requires-policy`
.. clicmd:: show bgp [afi] [safi] [all] [wide|json]
.. clicmd:: show bgp vrfs [<VRFNAME$vrf_name>] [json]
The command displays all bgp vrf instances basic info like router-id,
configured and established neighbors,
evpn related basic info like l3vni, router-mac, vxlan-interface.
User can get that information as JSON format when ``json`` keyword
at the end of cli is presented.
.. code-block:: frr
torc-11# show bgp vrfs
Type Id routerId #PeersCfg #PeersEstb Name
L3-VNI RouterMAC Interface
DFLT 0 17.0.0.6 3 3 default
0 00:00:00:00:00:00 unknown
VRF 21 17.0.0.6 0 0 sym_1
8888 34:11:12:22:22:01 vlan4034_l3
VRF 32 17.0.0.6 0 0 sym_2
8889 34:11:12:22:22:01 vlan4035_l3
Total number of VRFs (including default): 3
.. clicmd:: show bgp [<ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast|flowspec> | l2vpn evpn]
These commands display BGP routes for the specific routing table indicated by
the selected afi and the selected safi. If no afi and no safi value is given,
the command falls back to the default IPv6 routing table.
.. clicmd:: show bgp l2vpn evpn route [type <macip|2|multicast|3|es|4|prefix|5>]
EVPN prefixes can also be filtered by EVPN route type.
.. clicmd:: show bgp l2vpn evpn route [detail] [type <ead|1|macip|2|multicast|3|es|4|prefix|5>] self-originate [json]
Display self-originated EVPN prefixes which can also be filtered by EVPN route type.
.. clicmd:: show bgp vni <all|VNI> [vtep VTEP] [type <ead|1|macip|2|multicast|3>] [<detail|json>]
Display per-VNI EVPN routing table in bgp. Filter route-type, vtep, or VNI.
.. clicmd:: show bgp [afi] [safi] [all] summary [json]
Show a bgp peer summary for the specified address family, and subsequent
address-family.
.. clicmd:: show bgp [afi] [safi] [all] summary failed [json]
Show a bgp peer summary for peers that are not successfully exchanging routes
for the specified address family, and subsequent address-family.
.. clicmd:: show bgp [afi] [safi] [all] summary established [json]
Show a bgp peer summary for peers that are successfully exchanging routes
for the specified address family, and subsequent address-family.
.. clicmd:: show bgp [afi] [safi] [all] summary neighbor [PEER] [json]
Show a bgp summary for the specified peer, address family, and
subsequent address-family. The neighbor filter can be used in combination
with the failed, established filters.
.. clicmd:: show bgp [afi] [safi] [all] summary remote-as <internal|external|ASN> [json]
Show a bgp peer summary for the specified remote-as ASN or type (``internal``
for iBGP and ``external`` for eBGP sessions), address family, and subsequent
address-family. The remote-as filter can be used in combination with the
failed, established filters.
.. clicmd:: show bgp [afi] [safi] [all] summary terse [json]
Shorten the output. Do not show the following information about the BGP
instances: the number of RIB entries, the table version and the used memory.
The ``terse`` option can be used in combination with the remote-as, neighbor,
failed and established filters, and with the ``wide`` option as well.
.. clicmd:: show bgp [afi] [safi] [neighbor [PEER] [routes|advertised-routes|received-routes] [<A.B.C.D/M|X:X::X:X/M> | detail] [json]
This command shows information on a specific BGP peer of the relevant
afi and safi selected.
The ``routes`` keyword displays only routes in this address-family's BGP
table that were received by this peer and accepted by inbound policy.
The ``advertised-routes`` keyword displays only the routes in this
address-family's BGP table that were permitted by outbound policy and
advertised to to this peer.
The ``received-routes`` keyword displays all routes belonging to this
address-family (prior to inbound policy) that were received by this peer.
If a specific prefix is specified, the detailed version of that prefix will
be displayed.
If ``detail`` option is specified, the detailed version of all routes
will be displayed. The same format as ``show [ip] bgp [afi] [safi] PREFIX``
will be used, but for the whole table of received, advertised or filtered
prefixes.
If ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show bgp [<view|vrf> VIEWVRFNAME] [afi] [safi] neighbors PEER received prefix-filter [json]
Display Address Prefix ORFs received from this peer.
.. clicmd:: show bgp [afi] [safi] [all] dampening dampened-paths [wide|json]
Display paths suppressed due to dampening of the selected afi and safi
selected.
.. clicmd:: show bgp [afi] [safi] [all] dampening flap-statistics [wide|json]
Display flap statistics of routes of the selected afi and safi selected.
.. clicmd:: show bgp [afi] [safi] [all] dampening parameters [json]
Display details of configured dampening parameters of the selected afi and
safi.
If the ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show bgp [afi] [safi] [all] version (1-4294967295) [wide|json]
Display prefixes with matching version numbers. The version number and
above having prefixes will be listed here.
It helps to identify which prefixes were installed at some point.
Here is an example of how to check what prefixes were installed starting
with an arbitrary version:
.. code-block:: shell
# vtysh -c 'show bgp ipv4 unicast json' | jq '.tableVersion'
9
# vtysh -c 'show ip bgp version 9 json' | jq -r '.routes | keys[]'
192.168.3.0/24
# vtysh -c 'show ip bgp version 8 json' | jq -r '.routes | keys[]'
192.168.2.0/24
192.168.3.0/24
.. clicmd:: show bgp [afi] [safi] statistics
Display statistics of routes of the selected afi and safi.
.. clicmd:: show bgp statistics-all
Display statistics of routes of all the afi and safi.
.. clicmd:: show [ip] bgp [afi] [safi] [all] cidr-only [wide|json]
Display routes with non-natural netmasks.
.. clicmd:: show [ip] bgp [afi] [safi] [all] prefix-list WORD [wide|json]
Display routes that match the specified prefix-list.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
If the ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show [ip] bgp [afi] [safi] [all] access-list WORD [wide|json]
Display routes that match the specified access-list.
.. clicmd:: show [ip] bgp [afi] [safi] [all] filter-list WORD [wide|json]
Display routes that match the specified AS-Path filter-list.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
If the ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show [ip] bgp [afi] [safi] [all] route-map WORD [wide|json]
Display routes that match the specified route-map.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
If the ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show [ip] bgp [afi] [safi] [all] <A.B.C.D/M|X:X::X:X/M> longer-prefixes [wide|json]
Displays the specified route and all more specific routes.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
If the ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show [ip] bgp [afi] [safi] [all] self-originate [wide|json]
Display self-originated routes.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
If the ``json`` option is specified, output is displayed in JSON format.
.. 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]
Display the routes advertised to a BGP neighbor or received routes
from neighbor or filtered routes received from neighbor based on the
option specified.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
This is especially handy dealing with IPv6 prefixes and
if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
If ``all`` option is specified, ``ip`` keyword is ignored and,
routes displayed for all AFIs and SAFIs.
if afi is specified, with ``all`` option, routes will be displayed for
each SAFI in the selcted AFI
If a specific prefix is specified, the detailed version of that prefix will
be displayed.
If ``detail`` option is specified, the detailed version of all routes
will be displayed. The same format as ``show [ip] bgp [afi] [safi] PREFIX``
will be used, but for the whole table of received, advertised or filtered
prefixes.
If ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show [ip] bgp [afi] [safi] [all] detail-routes
Display the detailed version of all routes. The same format as using
``show [ip] bgp [afi] [safi] PREFIX``, but for the whole BGP table.
If ``all`` option is specified, ``ip`` keyword is ignored and,
routes displayed for all AFIs and SAFIs.
If ``afi`` is specified, with ``all`` option, routes will be displayed for
each SAFI in the selected AFI.
.. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] [afi] [safi] detail [json]
Display the detailed version of all routes from the specified bgp vrf table
for a given afi + safi.
If no vrf is specified, then it is assumed as a default vrf and routes
are displayed from default vrf table.
If ``all`` option is specified as vrf name, then all bgp vrf tables routes
from a given afi+safi are displayed in the detailed output of routes.
If ``json`` option is specified, detailed output is displayed in JSON format.
Following are sample output for few examples of how to use this command.
.. code-block:: frr
torm-23# sh bgp ipv4 unicast detail (OR) sh bgp vrf default ipv4 unicast detail
!--- Output suppressed.
BGP routing table entry for 172.16.16.1/32
Paths: (1 available, best #1, table default)
Not advertised to any peer
Local, (Received from a RR-client)
172.16.16.1 (metric 20) from torm-22(172.16.16.1) (192.168.0.10)
Origin IGP, metric 0, localpref 100, valid, internal
Last update: Fri May 8 12:54:05 2023
BGP routing table entry for 172.16.16.2/32
Paths: (1 available, best #1, table default)
Not advertised to any peer
Local
0.0.0.0 from 0.0.0.0 (172.16.16.2)
Origin incomplete, metric 0, weight 32768, valid, sourced, bestpath-from-AS Local, best (First path received)
Last update: Wed May 8 12:54:41 2023
Displayed 2 routes and 2 total paths
.. code-block:: frr
torm-23# sh bgp vrf all detail
Instance default:
!--- Output suppressed.
BGP routing table entry for 172.16.16.1/32
Paths: (1 available, best #1, table default)
Not advertised to any peer
Local, (Received from a RR-client)
172.16.16.1 (metric 20) from torm-22(172.16.16.1) (192.168.0.10)
Origin IGP, metric 0, localpref 100, valid, internal
Last update: Fri May 8 12:44:05 2023
BGP routing table entry for 172.16.16.2/32
Paths: (1 available, best #1, table default)
Not advertised to any peer
Local
0.0.0.0 from 0.0.0.0 (172.16.16.2)
Origin incomplete, metric 0, weight 32768, valid, sourced, bestpath-from-AS Local, best (First path received)
Last update: Wed May 8 12:45:01 2023
Displayed 2 routes and 2 total paths
Instance vrf3:
!--- Output suppressed.
BGP routing table entry for 192.168.0.2/32
Paths: (1 available, best #1, vrf vrf3)
Not advertised to any peer
Imported from 172.16.16.1:12:[2]:[0]:[48]:[00:02:00:00:00:58]:[32]:[192.168.0.2], VNI 1008/4003
Local
172.16.16.1 from torm-22(172.16.16.1) (172.16.16.1) announce-nh-self
Origin IGP, localpref 100, valid, internal, bestpath-from-AS Local, best (First path received)
Extended Community: RT:65000:1008 ET:8 Rmac:00:02:00:00:00:58
Last update: Fri May 8 02:41:55 2023
BGP routing table entry for 192.168.1.2/32
Paths: (1 available, best #1, vrf vrf3)
Not advertised to any peer
Imported from 172.16.16.1:13:[2]:[0]:[48]:[00:02:00:00:00:58]:[32]:[192.168.1.2], VNI 1009/4003
Local
172.16.16.1 from torm-22(172.16.16.1) (172.16.16.1) announce-nh-self
Origin IGP, localpref 100, valid, internal, bestpath-from-AS Local, best (First path received)
Extended Community: RT:65000:1009 ET:8 Rmac:00:02:00:00:00:58
Last update: Fri May 8 02:41:55 2023
Displayed 2 routes and 2 total paths
.. code-block:: frr
torm-23# sh bgp vrf vrf3 ipv4 unicast detail
!--- Output suppressed.
BGP routing table entry for 192.168.0.2/32
Paths: (1 available, best #1, vrf vrf3)
Not advertised to any peer
Imported from 172.16.16.1:12:[2]:[0]:[48]:[00:02:00:00:00:58]:[32]:[192.168.0.2], VNI 1008/4003
Local
172.16.16.1 from torm-22(172.16.16.1) (172.16.16.1) announce-nh-self
Origin IGP, localpref 100, valid, internal, bestpath-from-AS Local, best (First path received)
Extended Community: RT:65000:1008 ET:8 Rmac:00:02:00:00:00:58
Last update: Fri May 8 02:23:35 2023
BGP routing table entry for 192.168.1.2/32
Paths: (1 available, best #1, vrf vrf3)
Not advertised to any peer
Imported from 172.16.16.1:13:[2]:[0]:[48]:[00:02:00:00:00:58]:[32]:[192.168.1.2], VNI 1009/4003
Local
172.16.16.1 from torm-22(172.16.16.1) (172.16.16.1) announce-nh-self
Origin IGP, localpref 100, valid, internal, bestpath-from-AS Local, best (First path received)
Extended Community: RT:65000:1009 ET:8 Rmac:00:02:00:00:00:58
Last update: Fri May 8 02:23:55 2023
Displayed 2 routes and 2 total paths
.. _bgp-display-routes-by-community:
Displaying Routes by Community Attribute
----------------------------------------
The following commands allow displaying routes based on their community
attribute.
.. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community [wide|json]
.. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY [wide|json]
.. clicmd:: show [ip] bgp <ipv4|ipv6> [all] community COMMUNITY exact-match [wide|json]
These commands display BGP routes which have the community attribute.
attribute. When ``COMMUNITY`` is specified, BGP routes that match that
community are displayed. When `exact-match` is specified, it display only
routes that have an exact match.
.. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD [json]
.. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match [json]
These commands display BGP routes for the address family specified that
match the specified community list. When `exact-match` is specified, it
displays only routes that have an exact match.
If ``wide`` option is specified, then the prefix table's width is increased
to fully display the prefix and the nexthop.
This is especially handy dealing with IPv6 prefixes and
if :clicmd:`[no] bgp default show-nexthop-hostname` is enabled.
If ``all`` option is specified, ``ip`` keyword is ignored and,
routes displayed for all AFIs and SAFIs.
if afi is specified, with ``all`` option, routes will be displayed for
each SAFI in the selcted AFI
If ``json`` option is specified, output is displayed in JSON format.
.. clicmd:: show bgp labelpool <chunks|inuse|ledger|requests|summary> [json]
These commands display information about the BGP labelpool used for
the association of MPLS labels with routes for L3VPN and Labeled Unicast
If ``chunks`` option is specified, output shows the current list of label
chunks granted to BGP by Zebra, indicating the start and end label in
each chunk
If ``inuse`` option is specified, output shows the current inuse list of
label to prefix mappings
If ``ledger`` option is specified, output shows ledger list of all
label requests made per prefix
If ``requests`` option is specified, output shows current list of label
requests which have not yet been fulfilled by the labelpool
If ``summary`` option is specified, output is a summary of the counts for
the chunks, inuse, ledger and requests list along with the count of
outstanding chunk requests to Zebra and the number of zebra reconnects
that have happened
If ``json`` option is specified, output is displayed in JSON format.
.. _bgp-display-routes-by-lcommunity:
Displaying Routes by Large Community Attribute
----------------------------------------------
The following commands allow displaying routes based on their
large community attribute.
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY exact-match
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community LARGE-COMMUNITY json
These commands display BGP routes which have the large community attribute.
attribute. When ``LARGE-COMMUNITY`` is specified, BGP routes that match that
large community are displayed. When `exact-match` is specified, it display
only routes that have an exact match. When `json` is specified, it display
routes in json format.
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD exact-match
.. clicmd:: show [ip] bgp <ipv4|ipv6> large-community-list WORD json
These commands display BGP routes for the address family specified that
match the specified large community list. When `exact-match` is specified,
it displays only routes that have an exact match. When `json` is specified,
it display routes in json format.
.. _bgp-display-routes-by-as-path:
Displaying Routes by AS Path
----------------------------
.. clicmd:: show bgp ipv4|ipv6 regexp LINE
This commands displays BGP routes that matches a regular
expression `line` (:ref:`bgp-regular-expressions`).
.. clicmd:: show [ip] bgp ipv4 vpn
.. clicmd:: show [ip] bgp ipv6 vpn
Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
.. clicmd:: show bgp ipv4 vpn summary
.. clicmd:: show bgp ipv6 vpn summary
Print a summary of neighbor connections for the specified AFI/SAFI combination.
Displaying Routes by Route Distinguisher
----------------------------------------
.. clicmd:: show bgp [<ipv4|ipv6> vpn | l2vpn evpn [route]] rd <all|RD>
For L3VPN and EVPN address-families, routes can be displayed on a per-RD
(Route Distinguisher) basis or for all RD's.
.. clicmd:: show bgp l2vpn evpn rd <all|RD> [overlay | tags]
Use the ``overlay`` or ``tags`` keywords to display the overlay/tag
information about the EVPN prefixes in the selected Route Distinguisher.
.. clicmd:: show bgp l2vpn evpn route rd <all|RD> mac <MAC> [ip <MAC>] [json]
For EVPN Type 2 (macip) routes, a MAC address (and optionally an IP address)
can be supplied to the command to only display matching prefixes in the
specified RD.
Displaying Update Group Information
-----------------------------------
.. clicmd:: show bgp update-groups [advertise-queue|advertised-routes|packet-queue]
Display Information about each individual update-group being used.
If SUBGROUP-ID is specified only display about that particular group. If
advertise-queue is specified the list of routes that need to be sent
to the peers in the update-group is displayed, advertised-routes means
the list of routes we have sent to the peers in the update-group and
packet-queue specifies the list of packets in the queue to be sent.
.. clicmd:: show bgp update-groups statistics
Display Information about update-group events in FRR.
Displaying Nexthop Information
------------------------------
.. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] nexthop ipv4 [A.B.C.D] [detail] [json]
.. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] nexthop ipv6 [X:X::X:X] [detail] [json]
.. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] nexthop [<A.B.C.D|X:X::X:X>] [detail] [json]
.. clicmd:: show [ip] bgp <view|vrf> all nexthop [json]
Display information about nexthops to bgp neighbors. If a certain nexthop is
specified, also provides information about paths associated with the nexthop.
With detail option provides information about gates of each nexthop.
.. clicmd:: show [ip] bgp [<view|vrf> VIEWVRFNAME] import-check-table [detail] [json]
Display information about nexthops from table that is used to check network's
existence in the rib for network statements.
Segment-Routing IPv6
--------------------
.. clicmd:: show bgp segment-routing srv6
This command displays information about SRv6 L3VPN in bgpd. Specifically,
what kind of Locator is being used, and its Locator chunk information.
And the SID of the SRv6 Function that is actually managed on bgpd.
In the following example, bgpd is using a Locator named loc1, and two SRv6
Functions are managed to perform VPNv6 VRF redirect for vrf10 and vrf20.
::
router# show bgp segment-routing srv6
locator_name: loc1
locator_chunks:
- 2001:db8:1:1::/64
functions:
- sid: 2001:db8:1:1::100
locator: loc1
- sid: 2001:db8:1:1::200
locator: loc1
bgps:
- name: default
vpn_policy[AFI_IP].tovpn_sid: none
vpn_policy[AFI_IP6].tovpn_sid: none
- name: vrf10
vpn_policy[AFI_IP].tovpn_sid: none
vpn_policy[AFI_IP6].tovpn_sid: 2001:db8:1:1::100
- name: vrf20
vpn_policy[AFI_IP].tovpn_sid: none
vpn_policy[AFI_IP6].tovpn_sid: 2001:db8:1:1::200
AS-notation support
-------------------
By default, the ASN value output follows how the BGP ASN instance is
expressed in the configuration. Three as-notation outputs are available:
- plain output: both AS4B and AS2B use a single number.
` router bgp 65536`.
- dot output: AS4B values are using two numbers separated by a period.
`router bgp 1.1` means that the AS number is 65536.
- dot+ output: AS2B and AS4B values are using two numbers separated by a
period. `router bgp 0.5` means that the AS number is 5.
The below option permits forcing the as-notation output:
.. clicmd:: router bgp ASN as-notation dot|dot+|plain
The chosen as-notation format will override the BGP ASN output.
.. _bgp-route-reflector:
Route Reflector
===============
BGP routers connected inside the same AS through BGP belong to an internal
BGP session, or IBGP. In order to prevent routing table loops, IBGP does not
advertise IBGP-learned routes to other routers in the same session. As such,
IBGP requires a full mesh of all peers. For large networks, this quickly becomes
unscalable. Introducing route reflectors removes the need for the full-mesh.
When route reflectors are configured, these will reflect the routes announced
by the peers configured as clients. A route reflector client is configured
with:
.. clicmd:: neighbor PEER route-reflector-client
To avoid single points of failure, multiple route reflectors can be configured.
A cluster is a collection of route reflectors and their clients, and is used
by route reflectors to avoid looping.
.. clicmd:: bgp cluster-id A.B.C.D
.. clicmd:: bgp no-rib
To set and unset the BGP daemon ``-n`` / ``--no_kernel`` options during runtime
to disable BGP route installation to the RIB (Zebra), the ``[no] bgp no-rib``
commands can be used;
Please note that setting the option during runtime will withdraw all routes in
the daemons RIB from Zebra and unsetting it will announce all routes in the
daemons RIB to Zebra. If the option is passed as a command line argument when
starting the daemon and the configuration gets saved, the option will persist
unless removed from the configuration with the negating command prior to the
configuration write operation. At this point in time non SAFI_UNICAST BGP
data is not properly withdrawn from zebra when this command is issued.
.. clicmd:: bgp allow-martian-nexthop
When a peer receives a martian nexthop as part of the NLRI for a route
permit the nexthop to be used as such, instead of rejecting and resetting
the connection.
.. clicmd:: bgp send-extra-data zebra
This command turns on the ability of BGP to send extra data to zebra. Currently,
it's the AS-Path, communities, and the path selection reason. The default
behavior in BGP is not to send this data. If the routes were sent to zebra and
the option is changed, bgpd doesn't reinstall the routes to comply with the new
setting.
.. clicmd:: bgp session-dscp (0-63)
This command allows the BGP daemon to control, at a global level, the DSCP value
used in outgoing packets for each BGP connection.
.. _bgp-suppress-fib:
Suppressing routes not installed in FIB
=======================================
The FRR implementation of BGP advertises prefixes learnt from a peer to other
peers even if the routes do not get installed in the FIB. There can be
scenarios where the hardware tables in some of the routers (along the path from
the source to destination) is full which will result in all routes not getting
installed in the FIB. If these routes are advertised to the downstream routers
then traffic will start flowing and will be dropped at the intermediate router.
The solution is to provide a configurable option to check for the FIB install
status of the prefixes and advertise to peers if the prefixes are successfully
installed in the FIB. The advertisement of the prefixes are suppressed if it is
not installed in FIB.
The following conditions apply will apply when checking for route installation
status in FIB:
1. The advertisement or suppression of routes based on FIB install status
applies only for newly learnt routes from peer (routes which are not in
BGP local RIB).
2. If the route received from peer already exists in BGP local RIB and route
attributes have changed (best path changed), the old path is deleted and
new path is installed in FIB. The FIB install status will not have any
effect. Therefore only when the route is received first time the checks
apply.
3. The feature will not apply for routes learnt through other means like
redistribution to bgp from other protocols. This is applicable only to
peer learnt routes.
4. If a route is installed in FIB and then gets deleted from the dataplane,
then routes will not be withdrawn from peers. This will be considered as
dataplane issue.
5. The feature will slightly increase the time required to advertise the routes
to peers since the route install status needs to be received from the FIB
6. If routes are received by the peer before the configuration is applied, then
the bgp sessions need to be reset for the configuration to take effect.
7. If the route which is already installed in dataplane is removed for some
reason, sending withdraw message to peers is not currently supported.
.. clicmd:: bgp suppress-fib-pending
This command is applicable at the global level and at an individual
bgp level. If applied at the global level all bgp instances will
wait for fib installation before announcing routes and there is no
way to turn it off for a particular bgp vrf.
.. _routing-policy:
Routing Policy
==============
You can set different routing policy for a peer. For example, you can set
different filter for a peer.
.. code-block:: frr
!
router bgp 1 view 1
neighbor 10.0.0.1 remote-as 2
address-family ipv4 unicast
neighbor 10.0.0.1 distribute-list 1 in
exit-address-family
!
router bgp 1 view 2
neighbor 10.0.0.1 remote-as 2
address-family ipv4 unicast
neighbor 10.0.0.1 distribute-list 2 in
exit-address-family
This means BGP update from a peer 10.0.0.1 goes to both BGP view 1 and view 2.
When the update is inserted into view 1, distribute-list 1 is applied. On the
other hand, when the update is inserted into view 2, distribute-list 2 is
applied.
.. _bgp-regular-expressions:
BGP Regular Expressions
=======================
BGP regular expressions are based on :t:`POSIX 1003.2` regular expressions. The
following description is just a quick subset of the POSIX regular expressions.
.\*
Matches any single character.
\*
Matches 0 or more occurrences of pattern.
\+
Matches 1 or more occurrences of pattern.
?
Match 0 or 1 occurrences of pattern.
^
Matches the beginning of the line.
$
Matches the end of the line.
_
The ``_`` character has special meanings in BGP regular expressions. It
matches to space and comma , and AS set delimiter ``{`` and ``}`` and AS
confederation delimiter ``(`` and ``)``. And it also matches to the
beginning of the line and the end of the line. So ``_`` can be used for AS
value boundaries match. This character technically evaluates to
``(^|[,{}()]|$)``.
.. _bgp-configuration-examples:
Miscellaneous Configuration Examples
====================================
Example of a session to an upstream, advertising only one prefix to it.
.. code-block:: frr
router bgp 64512
bgp router-id 10.236.87.1
neighbor upstream peer-group
neighbor upstream remote-as 64515
neighbor upstream capability dynamic
neighbor 10.1.1.1 peer-group upstream
neighbor 10.1.1.1 description ACME ISP
address-family ipv4 unicast
network 10.236.87.0/24
neighbor upstream prefix-list pl-allowed-adv out
exit-address-family
!
ip prefix-list pl-allowed-adv seq 5 permit 82.195.133.0/25
ip prefix-list pl-allowed-adv seq 10 deny any
A more complex example including upstream, peer and customer sessions
advertising global prefixes and NO_EXPORT prefixes and providing actions for
customer routes based on community values. Extensive use is made of route-maps
and the 'call' feature to support selective advertising of prefixes. This
example is intended as guidance only, it has NOT been tested and almost
certainly contains silly mistakes, if not serious flaws.
.. code-block:: frr
router bgp 64512
bgp router-id 10.236.87.1
neighbor upstream capability dynamic
neighbor cust capability dynamic
neighbor peer capability dynamic
neighbor 10.1.1.1 remote-as 64515
neighbor 10.1.1.1 peer-group upstream
neighbor 10.2.1.1 remote-as 64516
neighbor 10.2.1.1 peer-group upstream
neighbor 10.3.1.1 remote-as 64517
neighbor 10.3.1.1 peer-group cust-default
neighbor 10.3.1.1 description customer1
neighbor 10.4.1.1 remote-as 64518
neighbor 10.4.1.1 peer-group cust
neighbor 10.4.1.1 description customer2
neighbor 10.5.1.1 remote-as 64519
neighbor 10.5.1.1 peer-group peer
neighbor 10.5.1.1 description peer AS 1
neighbor 10.6.1.1 remote-as 64520
neighbor 10.6.1.1 peer-group peer
neighbor 10.6.1.1 description peer AS 2
address-family ipv4 unicast
network 10.123.456.0/24
network 10.123.456.128/25 route-map rm-no-export
neighbor upstream route-map rm-upstream-out out
neighbor cust route-map rm-cust-in in
neighbor cust route-map rm-cust-out out
neighbor cust send-community both
neighbor peer route-map rm-peer-in in
neighbor peer route-map rm-peer-out out
neighbor peer send-community both
neighbor 10.3.1.1 prefix-list pl-cust1-network in
neighbor 10.4.1.1 prefix-list pl-cust2-network in
neighbor 10.5.1.1 prefix-list pl-peer1-network in
neighbor 10.6.1.1 prefix-list pl-peer2-network in
exit-address-family
!
ip prefix-list pl-default permit 0.0.0.0/0
!
ip prefix-list pl-upstream-peers permit 10.1.1.1/32
ip prefix-list pl-upstream-peers permit 10.2.1.1/32
!
ip prefix-list pl-cust1-network permit 10.3.1.0/24
ip prefix-list pl-cust1-network permit 10.3.2.0/24
!
ip prefix-list pl-cust2-network permit 10.4.1.0/24
!
ip prefix-list pl-peer1-network permit 10.5.1.0/24
ip prefix-list pl-peer1-network permit 10.5.2.0/24
ip prefix-list pl-peer1-network permit 192.168.0.0/24
!
ip prefix-list pl-peer2-network permit 10.6.1.0/24
ip prefix-list pl-peer2-network permit 10.6.2.0/24
ip prefix-list pl-peer2-network permit 192.168.1.0/24
ip prefix-list pl-peer2-network permit 192.168.2.0/24
ip prefix-list pl-peer2-network permit 172.16.1/24
!
bgp as-path access-list seq 5 asp-own-as permit ^$
bgp as-path access-list seq 10 asp-own-as permit _64512_
!
! #################################################################
! Match communities we provide actions for, on routes receives from
! customers. Communities values of <our-ASN>:X, with X, have actions:
!
! 100 - blackhole the prefix
! 200 - set no_export
! 300 - advertise only to other customers
! 400 - advertise only to upstreams
! 500 - set no_export when advertising to upstreams
! 2X00 - set local_preference to X00
!
! blackhole the prefix of the route
bgp community-list standard cm-blackhole permit 64512:100
!
! set no-export community before advertising
bgp community-list standard cm-set-no-export permit 64512:200
!
! advertise only to other customers
bgp community-list standard cm-cust-only permit 64512:300
!
! advertise only to upstreams
bgp community-list standard cm-upstream-only permit 64512:400
!
! advertise to upstreams with no-export
bgp community-list standard cm-upstream-noexport permit 64512:500
!
! set local-pref to least significant 3 digits of the community
bgp community-list standard cm-prefmod-100 permit 64512:2100
bgp community-list standard cm-prefmod-200 permit 64512:2200
bgp community-list standard cm-prefmod-300 permit 64512:2300
bgp community-list standard cm-prefmod-400 permit 64512:2400
bgp community-list expanded cme-prefmod-range permit 64512:2...
!
! Informational communities
!
! 3000 - learned from upstream
! 3100 - learned from customer
! 3200 - learned from peer
!
bgp community-list standard cm-learnt-upstream permit 64512:3000
bgp community-list standard cm-learnt-cust permit 64512:3100
bgp community-list standard cm-learnt-peer permit 64512:3200
!
! ###################################################################
! Utility route-maps
!
! These utility route-maps generally should not used to permit/deny
! routes, i.e. they do not have meaning as filters, and hence probably
! should be used with 'on-match next'. These all finish with an empty
! permit entry so as not interfere with processing in the caller.
!
route-map rm-no-export permit 10
set community additive no-export
route-map rm-no-export permit 20
!
route-map rm-blackhole permit 10
description blackhole, up-pref and ensure it cannot escape this AS
set ip next-hop 127.0.0.1
set local-preference 10
set community additive no-export
route-map rm-blackhole permit 20
!
! Set local-pref as requested
route-map rm-prefmod permit 10
match community cm-prefmod-100
set local-preference 100
route-map rm-prefmod permit 20
match community cm-prefmod-200
set local-preference 200
route-map rm-prefmod permit 30
match community cm-prefmod-300
set local-preference 300
route-map rm-prefmod permit 40
match community cm-prefmod-400
set local-preference 400
route-map rm-prefmod permit 50
!
! Community actions to take on receipt of route.
route-map rm-community-in permit 10
description check for blackholing, no point continuing if it matches.
match community cm-blackhole
call rm-blackhole
route-map rm-community-in permit 20
match community cm-set-no-export
call rm-no-export
on-match next
route-map rm-community-in permit 30
match community cme-prefmod-range
call rm-prefmod
route-map rm-community-in permit 40
!
! #####################################################################
! Community actions to take when advertising a route.
! These are filtering route-maps,
!
! Deny customer routes to upstream with cust-only set.
route-map rm-community-filt-to-upstream deny 10
match community cm-learnt-cust
match community cm-cust-only
route-map rm-community-filt-to-upstream permit 20
!
! Deny customer routes to other customers with upstream-only set.
route-map rm-community-filt-to-cust deny 10
match community cm-learnt-cust
match community cm-upstream-only
route-map rm-community-filt-to-cust permit 20
!
! ###################################################################
! The top-level route-maps applied to sessions. Further entries could
! be added obviously..
!
! Customers
route-map rm-cust-in permit 10
call rm-community-in
on-match next
route-map rm-cust-in permit 20
set community additive 64512:3100
route-map rm-cust-in permit 30
!
route-map rm-cust-out permit 10
call rm-community-filt-to-cust
on-match next
route-map rm-cust-out permit 20
!
! Upstream transit ASes
route-map rm-upstream-out permit 10
description filter customer prefixes which are marked cust-only
call rm-community-filt-to-upstream
on-match next
route-map rm-upstream-out permit 20
description only customer routes are provided to upstreams/peers
match community cm-learnt-cust
!
! Peer ASes
! outbound policy is same as for upstream
route-map rm-peer-out permit 10
call rm-upstream-out
!
route-map rm-peer-in permit 10
set community additive 64512:3200
Example of how to set up a 6-Bone connection.
.. code-block:: frr
! bgpd configuration
! ==================
!
! MP-BGP configuration
!
router bgp 7675
bgp router-id 10.0.0.1
neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 remote-as `as-number`
!
address-family ipv6
network 3ffe:506::/32
neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 activate
neighbor 3ffe:1cfa:0:2:2a0:c9ff:fe9e:f56 route-map set-nexthop out
neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 remote-as `as-number`
neighbor 3ffe:1cfa:0:2:2c0:4fff:fe68:a231 route-map set-nexthop out
exit-address-family
!
ipv6 access-list all permit any
!
! Set output nexthop address.
!
route-map set-nexthop permit 10
match ipv6 address all
set ipv6 nexthop global 3ffe:1cfa:0:2:2c0:4fff:fe68:a225
set ipv6 nexthop local fe80::2c0:4fff:fe68:a225
!
log file bgpd.log
!
.. _bgp-tcp-mss:
BGP tcp-mss support
===================
TCP provides a mechanism for the user to specify the max segment size.
setsockopt API is used to set the max segment size for TCP session. We
can configure this as part of BGP neighbor configuration.
This document explains how to avoid ICMP vulnerability issues by limiting
TCP max segment size when you are using MTU discovery. Using MTU discovery
on TCP paths is one method of avoiding BGP packet fragmentation.
TCP negotiates a maximum segment size (MSS) value during session connection
establishment between two peers. The MSS value negotiated is primarily based
on the maximum transmission unit (MTU) of the interfaces to which the
communicating peers are directly connected. However, due to variations in
link MTU on the path taken by the TCP packets, some packets in the network
that are well within the MSS value might be fragmented when the packet size
exceeds the link's MTU.
This feature is supported with TCP over IPv4 and TCP over IPv6.
CLI Configuration:
------------------
Below configuration can be done in router bgp mode and allows the user to
configure the tcp-mss value per neighbor. The configuration gets applied
only after hard reset is performed on that neighbor. If we configure tcp-mss
on both the neighbors then both neighbors need to be reset.
The configuration takes effect based on below rules, so there is a configured
tcp-mss and a synced tcp-mss value per TCP session.
By default if the configuration is not done then the TCP max segment size is
set to the Maximum Transmission unit (MTU) – (IP/IP6 header size + TCP header
size + ethernet header). For IPv4 its MTU – (20 bytes IP header + 20 bytes TCP
header + 12 bytes ethernet header) and for IPv6 its MTU – (40 bytes IPv6 header
+ 20 bytes TCP header + 12 bytes ethernet header).
If the config is done then it reduces 12-14 bytes for the ether header and
uses it after synchronizing in TCP handshake.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> tcp-mss (1-65535)
When tcp-mss is configured kernel reduces 12-14 bytes for ethernet header.
E.g. if tcp-mss is configured as 150 the synced value will be 138.
Note: configured and synced value is different since TCP module will reduce
12 bytes for ethernet header.
Running config:
---------------
.. code-block:: frr
frr# show running-config
Building configuration...
Current configuration:
!
router bgp 100
bgp router-id 192.0.2.1
neighbor 198.51.100.2 remote-as 100
neighbor 198.51.100.2 tcp-mss 150 => new entry
neighbor 2001:DB8::2 remote-as 100
neighbor 2001:DB8::2 tcp-mss 400 => new entry
Show command:
-------------
.. code-block:: frr
frr# show bgp neighbors 198.51.100.2
BGP neighbor is 198.51.100.2, remote AS 100, local AS 100, internal link
Hostname: frr
BGP version 4, remote router ID 192.0.2.2, local router ID 192.0.2.1
BGP state = Established, up for 02:15:28
Last read 00:00:28, Last write 00:00:28
Hold time is 180, keepalive interval is 60 seconds
Configured tcp-mss is 150, synced tcp-mss is 138 => new display
.. code-block:: frr
frr# show bgp neighbors 2001:DB8::2
BGP neighbor is 2001:DB8::2, remote AS 100, local AS 100, internal link
Hostname: frr
BGP version 4, remote router ID 192.0.2.2, local router ID 192.0.2.1
BGP state = Established, up for 02:16:34
Last read 00:00:34, Last write 00:00:34
Hold time is 180, keepalive interval is 60 seconds
Configured tcp-mss is 400, synced tcp-mss is 388 => new display
Show command json output:
-------------------------
.. code-block:: frr
frr# show bgp neighbors 2001:DB8::2 json
{
"2001:DB8::2":{
"remoteAs":100,
"localAs":100,
"nbrInternalLink":true,
"hostname":"frr",
"bgpVersion":4,
"remoteRouterId":"192.0.2.2",
"localRouterId":"192.0.2.1",
"bgpState":"Established",
"bgpTimerUpMsec":8349000,
"bgpTimerUpString":"02:19:09",
"bgpTimerUpEstablishedEpoch":1613054251,
"bgpTimerLastRead":9000,
"bgpTimerLastWrite":9000,
"bgpInUpdateElapsedTimeMsecs":8347000,
"bgpTimerHoldTimeMsecs":180000,
"bgpTimerKeepAliveIntervalMsecs":60000,
"bgpTcpMssConfigured":400, => new entry
"bgpTcpMssSynced":388, => new entry
.. code-block:: frr
frr# show bgp neighbors 198.51.100.2 json
{
"198.51.100.2":{
"remoteAs":100,
"localAs":100,
"nbrInternalLink":true,
"hostname":"frr",
"bgpVersion":4,
"remoteRouterId":"192.0.2.2",
"localRouterId":"192.0.2.1",
"bgpState":"Established",
"bgpTimerUpMsec":8370000,
"bgpTimerUpString":"02:19:30",
"bgpTimerUpEstablishedEpoch":1613054251,
"bgpTimerLastRead":30000,
"bgpTimerLastWrite":30000,
"bgpInUpdateElapsedTimeMsecs":8368000,
"bgpTimerHoldTimeMsecs":180000,
"bgpTimerKeepAliveIntervalMsecs":60000,
"bgpTcpMssConfigured":150, => new entry
"bgpTcpMssSynced":138, => new entry
.. include:: routeserver.rst
.. include:: rpki.rst
.. include:: wecmp_linkbw.rst
.. include:: flowspec.rst
.. [#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)
.. [bgp-route-osci-cond] McPherson, D. and Gill, V. and Walton, D., "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", IETF RFC3345
.. [stable-flexible-ibgp] Flavel, A. and M. Roughan, "Stable and flexible iBGP", ACM SIGCOMM 2009
.. [ibgp-correctness] Griffin, T. and G. Wilfong, "On the correctness of IBGP configuration", ACM SIGCOMM 2002
.. _bgp-fast-convergence:
BGP fast-convergence support
============================
Whenever BGP peer address becomes unreachable we must bring down the BGP
session immediately. Currently only single-hop EBGP sessions are brought
down immediately.IBGP and multi-hop EBGP sessions wait for hold-timer
expiry to bring down the sessions.
This new configuration option helps user to teardown BGP sessions immediately
whenever peer becomes unreachable.
.. clicmd:: bgp fast-convergence
This configuration is available at the bgp level. When enabled, configuration
is applied to all the neighbors configured in that bgp instance.
.. code-block:: frr
router bgp 64496
neighbor 10.0.0.2 remote-as 64496
neighbor fd00::2 remote-as 64496
bgp fast-convergence
!
address-family ipv4 unicast
redistribute static
exit-address-family
!
address-family ipv6 unicast
neighbor fd00::2 activate
exit-address-family
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