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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
============
The default configuration file of *bgpd* is :file:`bgpd.conf`. *bgpd* searches
the current directory first, followed by |INSTALL_PREFIX_ETC|/bgpd.conf. All of
*bgpd*'s commands must be configured in :file:`bgpd.conf` when the integrated
config is not being used.
*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 a specific IP address 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.
.. _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.
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 BGP
protocol uses the AS number for detecting whether the BGP connection is
internal or external.
.. index:: router bgp ASN
.. clicmd:: router bgp ASN
Enable a BGP protocol process with the specified ASN. After
this statement you can input any `BGP Commands`.
.. index:: no router bgp ASN
.. clicmd:: no router bgp ASN
Destroy a BGP protocol process with the specified ASN.
.. index:: bgp router-id A.B.C.D
.. 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:
.. index:: router bgp ASN vrf VRFNAME
.. 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
...
In the past this feature done differently and the following commands were
required to enable the functionality. They are now deprecated.
.. deprecated:: 5.0
This command is deprecated and may be safely removed from the config.
.. index:: bgp multiple-instance
.. clicmd:: bgp multiple-instance
Enable BGP multiple instance feature. Because this is now the default
configuration this command will not be displayed in the running
configuration.
.. deprecated:: 5.0
This command is deprecated and may be safely removed from the config.
.. index:: no bgp multiple-instance
.. clicmd:: no bgp multiple-instance
In previous versions of FRR, this command disabled the BGP multiple instance
feature. This functionality is automatically turned on when BGP multiple
instances or views exist so this command no longer does anything.
.. 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.
.. index:: router bgp AS-NUMBER view NAME
.. 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
.. index:: show [ip] bgp view NAME
.. clicmd:: show [ip] bgp view NAME
Display the routing table of BGP view ``NAME``.
Route Selection
---------------
.. index:: bgp bestpath as-path confed
.. 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.
.. index:: bgp bestpath as-path multipath-relax
.. 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.
.. _bgp-distance:
Administrative Distance Metrics
-------------------------------
.. index:: distance bgp (1-255) (1-255) (1-255)
.. clicmd:: distance bgp (1-255) (1-255) (1-255)
This command change distance value of BGP. The arguments are the distance
values for for external routes, internal routes and local routes
respectively.
.. index:: distance (1-255) A.B.C.D/M
.. clicmd:: distance (1-255) A.B.C.D/M
.. index:: distance (1-255) A.B.C.D/M WORD
.. clicmd:: distance (1-255) A.B.C.D/M WORD
Sets the administrative distance for a particular route.
.. _bgp-route-flap-dampening:
Route Flap Dampening
--------------------
.. clicmd:: bgp dampening (1-45) (1-20000) (1-20000) (1-255)
This command enables BGP route-flap dampening and specifies dampening parameters.
half-life
Half-life time for the penalty
reuse-threshold
Value to start reusing a route
suppress-threshold
Value to start suppressing a route
max-suppress
Maximum duration to suppress a stable route
The route-flap damping algorithm is compatible with :rfc:`2439`. The use of
this command is not recommended nowadays.
.. 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.
.. index:: bgp deterministic-med
.. 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`.
.. index:: bgp always-compare-med
.. 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-network:
Networks
--------
.. index:: network A.B.C.D/M
.. 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.
.. index:: no network A.B.C.D/M
.. clicmd:: no network A.B.C.D/M
.. _bgp-route-aggregation:
Route Aggregation
-----------------
.. _bgp-route-aggregation-ipv4:
Route Aggregation-IPv4 Address Family
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. index:: aggregate-address A.B.C.D/M
.. clicmd:: aggregate-address A.B.C.D/M
This command specifies an aggregate address.
.. index:: aggregate-address A.B.C.D/M as-set
.. clicmd:: aggregate-address A.B.C.D/M as-set
This command specifies an aggregate address. Resulting routes include
AS set.
.. index:: aggregate-address A.B.C.D/M summary-only
.. clicmd:: aggregate-address A.B.C.D/M summary-only
This command specifies an aggregate address. Aggregated routes will
not be announce.
.. index:: no aggregate-address A.B.C.D/M
.. clicmd:: no aggregate-address A.B.C.D/M
This command removes an aggregate address.
This configuration example setup the aggregate-address under
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
exit-address-family
.. _bgp-route-aggregation-ipv6:
Route Aggregation-IPv6 Address Family
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. index:: aggregate-address X:X::X:X/M
.. clicmd:: aggregate-address X:X::X:X/M
This command specifies an aggregate address.
.. index:: aggregate-address X:X::X:X/M as-set
.. clicmd:: aggregate-address X:X::X:X/M as-set
This command specifies an aggregate address. Resulting routes include
AS set.
.. index:: aggregate-address X:X::X:X/M summary-only
.. clicmd:: aggregate-address X:X::X:X/M summary-only
This command specifies an aggregate address. Aggregated routes will
not be announce.
.. index:: no aggregate-address X:X::X:X/M
.. clicmd:: no aggregate-address X:X::X:X/M
This command removes an aggregate address.
This configuration example setup the aggregate-address under
ipv4 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
exit-address-family
.. _bgp-redistribute-to-bgp:
Redistribution
--------------
.. index:: redistribute kernel
.. clicmd:: redistribute kernel
Redistribute kernel route to BGP process.
.. index:: redistribute static
.. clicmd:: redistribute static
Redistribute static route to BGP process.
.. index:: redistribute connected
.. clicmd:: redistribute connected
Redistribute connected route to BGP process.
.. index:: redistribute rip
.. clicmd:: redistribute rip
Redistribute RIP route to BGP process.
.. index:: redistribute ospf
.. clicmd:: redistribute ospf
Redistribute OSPF route to BGP process.
.. index:: redistribute vpn
.. clicmd:: redistribute vpn
Redistribute VNC routes to BGP process.
.. index:: update-delay MAX-DELAY
.. clicmd:: update-delay MAX-DELAY
.. index:: update-delay MAX-DELAY ESTABLISH-WAIT
.. clicmd:: update-delay MAX-DELAY ESTABLISH-WAIT
This feature is used to enable read-only mode on BGP process restart or when
BGP process is cleared using 'clear ip bgp \*'. 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.
.. index:: table-map ROUTE-MAP-NAME
.. 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
^^^^^^^^^^^^^^
.. index:: neighbor PEER remote-as ASN
.. 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
.. index:: neighbor PEER remote-as internal
.. 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.
.. index:: neighbor PEER remote-as external
.. 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.
.. index:: [no] bgp listen range <A.B.C.D/M|X:X::X:X/M> peer-group PGNAME
.. clicmd:: [no] 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.
.. _bgp-configuring-peers:
Configuring Peers
^^^^^^^^^^^^^^^^^
.. index:: [no] neighbor PEER shutdown
.. clicmd:: [no] neighbor PEER shutdown
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.
.. index:: [no] neighbor PEER disable-connected-check
.. clicmd:: [no] neighbor PEER disable-connected-check
Allow peerings between directly connected eBGP peers using loopback
addresses.
.. index:: [no] neighbor PEER ebgp-multihop
.. clicmd:: [no] neighbor PEER ebgp-multihop
.. index:: [no] neighbor PEER description ...
.. clicmd:: [no] neighbor PEER description ...
Set description of the peer.
.. index:: [no] neighbor PEER version VERSION
.. clicmd:: [no] neighbor PEER version VERSION
Set up the neighbor's BGP version. `version` can be `4`, `4+` or `4-`. BGP
version `4` is the default value used for BGP peering. BGP version `4+`
means that the neighbor supports Multiprotocol Extensions for BGP-4. BGP
version `4-` is similar but the neighbor speaks the old Internet-Draft
revision 00's Multiprotocol Extensions for BGP-4. Some routing software is
still using this version.
.. index:: [no] neighbor PEER interface IFNAME
.. clicmd:: [no] 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.
This command is deprecated and may be removed in a future release. Its use
should be avoided.
.. index:: [no] neighbor PEER next-hop-self [all]
.. clicmd:: [no] neighbor PEER next-hop-self [all]
This command specifies an announced route's nexthop as being equivalent to
the address of the bgp router if it is learned via eBGP. If the optional
keyword `all` is specified the modification is done also for routes learned
via iBGP.
.. index:: [no] neighbor PEER update-source <IFNAME|ADDRESS>
.. clicmd:: [no] neighbor PEER update-source <IFNAME|ADDRESS>
Specify the IPv4 source address to use for the :abbr:`BGP` session to this
neighbour, may be specified as either an IPv4 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).
.. code-block:: frr
router bgp 64555
neighbor foo update-source 192.168.0.1
neighbor bar update-source lo0
.. index:: [no] neighbor PEER default-originate
.. clicmd:: [no] neighbor PEER default-originate
*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.
.. index:: neighbor PEER port PORT
.. clicmd:: neighbor PEER port PORT
.. index:: neighbor PEER send-community
.. clicmd:: neighbor PEER send-community
.. index:: [no] neighbor PEER weight WEIGHT
.. clicmd:: [no] neighbor PEER weight WEIGHT
This command specifies a default `weight` value for the neighbor's routes.
.. index:: [no] neighbor PEER maximum-prefix NUMBER
.. clicmd:: [no] neighbor PEER maximum-prefix NUMBER
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.
.. index:: [no] neighbor PEER local-as AS-NUMBER [no-prepend] [replace-as]
.. clicmd:: [no] neighbor PEER local-as AS-NUMBER [no-prepend] [replace-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.
This command is only allowed for eBGP peers.
.. index:: [no] neighbor PEER ttl-security hops NUMBER
.. clicmd:: [no] 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*.
.. index:: [no] neighbor PEER capability extended-nexthop
.. clicmd:: [no] 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.
.. index:: [no] bgp fast-external-failover
.. clicmd:: [no] bgp fast-external-failover
This command causes bgp to not 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.
.. index:: [no] bgp default ipv4-unicast
.. clicmd:: [no] bgp default ipv4-unicast
This command allows the user to specify that v4 peering 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.
.. _bgp-peer-filtering:
Peer Filtering
^^^^^^^^^^^^^^
.. index:: neighbor PEER distribute-list NAME [in|out]
.. clicmd:: neighbor PEER distribute-list NAME [in|out]
This command specifies a distribute-list for the peer. `direct` is
``in`` or ``out``.
.. index:: neighbor PEER prefix-list NAME [in|out]
.. clicmd:: neighbor PEER prefix-list NAME [in|out]
.. index:: neighbor PEER filter-list NAME [in|out]
.. clicmd:: neighbor PEER filter-list NAME [in|out]
.. index:: neighbor PEER route-map NAME [in|out]
.. clicmd:: neighbor PEER route-map NAME [in|out]
Apply a route-map on the neighbor. `direct` must be `in` or `out`.
.. index:: bgp route-reflector allow-outbound-policy
.. 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.
.. _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.
.. index:: neighbor WORD peer-group
.. clicmd:: neighbor WORD peer-group
This command defines a new peer group.
.. index:: neighbor PEER peer-group PGNAME
.. clicmd:: neighbor PEER peer-group PGNAME
This command bind specific peer to peer group WORD.
.. index:: neighbor PEER solo
.. clicmd:: neighbor PEER solo
This command is used to indicate that routes advertised by the peer
should not be reflected back to the peer. This command only is only
meaningful when there is a single peer defined in the peer-group.
Capability Negotiation
^^^^^^^^^^^^^^^^^^^^^^
.. index:: neighbor PEER strict-capability-match
.. clicmd:: neighbor PEER strict-capability-match
.. index:: no neighbor PEER strict-capability-match
.. clicmd:: no 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.
.. index:: neighbor PEER dont-capability-negotiate
.. clicmd:: neighbor PEER dont-capability-negotiate
.. index:: no neighbor PEER dont-capability-negotiate
.. clicmd:: no 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.
.. index:: neighbor PEER override-capability
.. clicmd:: neighbor PEER override-capability
.. index:: no neighbor PEER override-capability
.. clicmd:: no neighbor PEER override-capability
Override the result of Capability Negotiation with local configuration.
Ignore remote peer's capability value.
.. _bgp-as-path-access-lists:
AS Path Access Lists
--------------------
AS path access list is user defined AS path.
.. index:: ip as-path access-list WORD permit|deny LINE
.. clicmd:: ip as-path access-list WORD permit|deny LINE
This command defines a new AS path access list.
.. index:: no ip as-path access-list WORD
.. clicmd:: no ip as-path access-list WORD
.. index:: no ip as-path access-list WORD permit|deny LINE
.. clicmd:: no ip as-path access-list WORD permit|deny LINE
.. _bgp-using-as-path-in-route-map:
Using AS Path in Route Map
--------------------------
.. index:: match as-path WORD
.. clicmd:: match as-path WORD
.. index:: set as-path prepend AS-PATH
.. clicmd:: set as-path prepend AS-PATH
Prepend the given string of AS numbers to the AS_PATH.
.. index:: set as-path prepend last-as NUM
.. clicmd:: set as-path prepend last-as NUM
Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
.. _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.
``internet``
``internet`` represents well-known communities value 0.
``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
EBGP 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. It is
recommended upon receiving prefixes tagged with this community to
add ``NO_EXPORT`` and ``NO_ADVERTISE``.
``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.
.. index:: ip community-list standard NAME permit|deny COMMUNITY
.. clicmd:: ip 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.
.. index:: ip community-list expanded NAME permit|deny COMMUNITY
.. clicmd:: ip 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.
.. index:: ip community-list NAME permit|deny COMMUNITY
.. clicmd:: ip 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.
.. index:: no ip community-list [standard|expanded] NAME
.. clicmd:: no ip community-list [standard|expanded] NAME
Deletes the community list specified by ``NAME``. All community lists share
the same namespace, so it's not necessary to specify ``standard`` or
``expanded``; these modifiers are purely aesthetic.
.. index:: show ip community-list [NAME]
.. clicmd:: show ip community-list [NAME]
Displays community list information. When ``NAME`` is specified the
specified community list's information is shown.
::
# show ip community-list
Named Community standard list CLIST
permit 7675:80 7675:100 no-export
deny internet
Named Community expanded list EXPAND
permit :
# show ip community-list CLIST
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 and 99 is
standard community list. Community list number in the range from 100
to 199 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.
.. index:: ip community-list (1-99) permit|deny COMMUNITY
.. clicmd:: ip community-list (1-99) permit|deny COMMUNITY
This command defines a new community list. The argument to (1-99) defines
the list identifier.
.. index:: ip community-list (100-199) permit|deny COMMUNITY
.. clicmd:: ip community-list (100-199) permit|deny COMMUNITY
This command defines a new expanded community list. The argument to
(100-199) defines the list identifier.
.. _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 ollowing commands can be used in route maps:
.. index:: match community WORD exact-match [exact-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.
.. index:: set community <none|COMMUNITY> additive
.. 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.
.. index:: set comm-list WORD delete
.. 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
!
ip community-list 70 permit 7675:70
ip community-list 70 deny
ip community-list 80 permit 7675:80
ip community-list 80 deny
ip community-list 90 permit 7675:90
ip community-list 90 deny
!
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`` or ``0:90``. 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
!
ip community-list 1 permit 0:80 0:90
!
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
!
ip community-list standard FILTER deny 1:1
ip community-list standard FILTER permit
!
route-map RMAP permit 10
match community FILTER
The communities value keyword ``internet`` has special meanings in standard
community lists. In the below example ``internet`` matches all BGP routes even
if the route does not have communities attribute at all. So community list
``INTERNET`` is the same as ``FILTER`` in the previous example.
.. code-block:: frr
ip community-list standard INTERNET deny 1:1
ip community-list standard INTERNET permit internet
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
!
ip 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
^^^^^^^^^^^^^^^^^^^^^^^^
.. index:: ip extcommunity-list standard NAME permit|deny EXTCOMMUNITY
.. clicmd:: ip 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.
.. index:: ip extcommunity-list expanded NAME permit|deny LINE
.. clicmd:: ip 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.
.. index:: no ip extcommunity-list NAME
.. clicmd:: no ip extcommunity-list NAME
.. index:: no ip extcommunity-list standard NAME
.. clicmd:: no ip extcommunity-list standard NAME
.. index:: no ip extcommunity-list expanded NAME
.. clicmd:: no ip extcommunity-list expanded NAME
These commands delete extended community lists specified by `name`. All of
extended community lists shares a single name space. So extended community
lists can be removed simply specifying the name.
.. index:: show ip extcommunity-list
.. clicmd:: show ip extcommunity-list
.. index:: show ip extcommunity-list NAME
.. clicmd:: show ip extcommunity-list NAME
This command displays current extcommunity-list information. When `name` is
specified the community list's information is shown.::
# show ip extcommunity-list
.. _bgp-extended-communities-in-route-map:
BGP Extended Communities in Route Map
"""""""""""""""""""""""""""""""""""""
.. index:: match extcommunity WORD
.. clicmd:: match extcommunity WORD
.. index:: set extcommunity rt EXTCOMMUNITY
.. clicmd:: set extcommunity rt EXTCOMMUNITY
This command set Route Target value.
.. index:: set extcommunity soo EXTCOMMUNITY
.. clicmd:: set extcommunity soo EXTCOMMUNITY
This command set Site of Origin value.
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`.
.. index:: ip large-community-list standard NAME permit|deny LARGE-COMMUNITY
.. clicmd:: ip 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.
.. index:: ip large-community-list expanded NAME permit|deny LINE
.. clicmd:: ip 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.
.. index:: no ip large-community-list NAME
.. clicmd:: no ip large-community-list NAME
.. index:: no ip large-community-list standard NAME
.. clicmd:: no ip large-community-list standard NAME
.. index:: no ip large-community-list expanded NAME
.. clicmd:: no ip large-community-list expanded NAME
These commands delete Large Community lists specified by `name`. All Large
Community lists share a single namespace. This means Large Community lists
can be removed by simply specifying the name.
.. index:: show ip large-community-list
.. clicmd:: show ip large-community-list
.. index:: show ip large-community-list NAME
.. clicmd:: show ip large-community-list NAME
This command display current large-community-list information. When
`name` is specified the community list information is shown.
.. index:: show ip bgp large-community-info
.. 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
""""""""""""""""""""""""""""""
.. index:: match large-community LINE [exact-match]
.. 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.
.. index:: set large-community LARGE-COMMUNITY
.. clicmd:: set large-community LARGE-COMMUNITY
.. index:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
.. clicmd:: set large-community LARGE-COMMUNITY LARGE-COMMUNITY
.. index:: set large-community LARGE-COMMUNITY additive
.. 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-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.
.. _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 intemediary. 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:
.. index:: rd vpn export AS:NN|IP:nn
.. 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.
.. index:: no rd vpn export [AS:NN|IP:nn]
.. clicmd:: no rd vpn export [AS:NN|IP:nn]
Deletes any previously-configured export route distinguisher.
.. index:: rt vpn import|export|both RTLIST...
.. 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 RTLIST is a space-separated list of route-targets, which are BGP
extended community values as described in
:ref:`bgp-extended-communities-attribute`.
.. index:: no rt vpn import|export|both [RTLIST...]
.. clicmd:: no rt vpn import|export|both [RTLIST...]
Deletes any previously-configured import or export route-target list.
.. index:: label vpn export (0..1048575)|auto
.. 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.
.. index:: no label vpn export [(0..1048575)|auto]
.. clicmd:: no label vpn export [(0..1048575)|auto]
Deletes any previously-configured export label.
.. index:: nexthop vpn export A.B.C.D|X:X::X:X
.. 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).
.. index:: no nexthop vpn export [A.B.C.D|X:X::X:X]
.. clicmd:: no nexthop vpn export [A.B.C.D|X:X::X:X]
Deletes any previously-configured export nexthop.
.. index:: route-map vpn import|export MAP
.. 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.
.. index:: no route-map vpn import|export [MAP]
.. clicmd:: no route-map vpn import|export [MAP]
Deletes any previously-configured import or export route-map.
.. index:: import|export vpn
.. clicmd:: import|export vpn
Enables import or export of routes between the current unicast VRF and VPN.
.. index:: no import|export vpn
.. clicmd:: no import|export vpn
Disables import or export of routes between the current unicast VRF and VPN.
.. index:: import vrf VRFNAME
.. 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.
.. index:: no import vrf VRFNAME
.. clicmd:: no import vrf VRFNAME
Disables automatic leaking from vrf VRFNAME to the current VRF using
the VPN RIB as intermediary.
.. _bgp-cisco-compatibility:
Cisco Compatibility
-------------------
FRR has commands that change some configuration syntax and default behavior to
behave more closely to Cisco conventions. These are deprecated and will be
removed in a future version of FRR.
.. deprecated:: 5.0
Please transition to using the FRR specific syntax for your configuration.
.. index:: bgp config-type cisco
.. clicmd:: bgp config-type cisco
Cisco compatible BGP configuration output.
When this configuration line is specified:
- ``no synchronization`` is displayed. This command does nothing and is for
display purposes only.
- ``no auto-summary`` is displayed.
- The ``network`` and ``aggregate-address`` arguments are displayed as:
::
A.B.C.D M.M.M.M
FRR: network 10.0.0.0/8
Cisco: network 10.0.0.0
FRR: aggregate-address 192.168.0.0/24
Cisco: aggregate-address 192.168.0.0 255.255.255.0
Community attribute handling is also different. If no configuration is
specified community attribute and extended community attribute are sent to
the neighbor. If a user manually disables the feature, the community
attribute is not sent to the neighbor. When ``bgp config-type cisco`` is
specified, the community attribute is not sent to the neighbor by default.
To send the community attribute user has to specify
:clicmd:`neighbor A.B.C.D send-community` like so:
.. code-block:: frr
!
router bgp 1
neighbor 10.0.0.1 remote-as 1
address-family ipv4 unicast
no neighbor 10.0.0.1 send-community
exit-address-family
!
router bgp 1
neighbor 10.0.0.1 remote-as 1
address-family ipv4 unicast
neighbor 10.0.0.1 send-community
exit-address-family
!
.. deprecated:: 5.0
Please transition to using the FRR specific syntax for your configuration.
.. index:: bgp config-type zebra
.. clicmd:: bgp config-type zebra
FRR style BGP configuration. This is the default.
.. _bgp-debugging:
Debugging
---------
.. index:: show debug
.. clicmd:: show debug
Show all enabled debugs.
.. index:: [no] debug bgp neighbor-events
.. clicmd:: [no] 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.
.. index:: [no] debug bgp updates
.. clicmd:: [no] debug bgp updates
Enable or disable debugging for BGP updates. This provides information on
BGP UPDATE messages transmitted and received between local and remote
instances.
.. index:: [no] debug bgp keepalives
.. clicmd:: [no] 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.
.. index:: [no] debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
.. clicmd:: [no] debug bgp bestpath <A.B.C.D/M|X:X::X:X/M>
Enable or disable debugging for bestpath selection on the specified prefix.
.. index:: [no] debug bgp nht
.. clicmd:: [no] debug bgp nht
Enable or disable debugging of BGP nexthop tracking.
.. index:: [no] debug bgp update-groups
.. clicmd:: [no] debug bgp update-groups
Enable or disable debugging of dynamic update groups. This provides general
information on group creation, deletion, join and prune events.
.. index:: [no] debug bgp zebra
.. clicmd:: [no] debug bgp zebra
Enable or disable debugging of communications between *bgpd* and *zebra*.
Dumping Messages and Routing Tables
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. index:: dump bgp all PATH [INTERVAL]
.. clicmd:: dump bgp all PATH [INTERVAL]
.. index:: dump bgp all-et PATH [INTERVAL]
.. clicmd:: dump bgp all-et PATH [INTERVAL]
.. index:: no dump bgp all [PATH] [INTERVAL]
.. clicmd:: no dump bgp all [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`).
.. index:: dump bgp updates PATH [INTERVAL]
.. clicmd:: dump bgp updates PATH [INTERVAL]
.. index:: dump bgp updates-et PATH [INTERVAL]
.. clicmd:: dump bgp updates-et PATH [INTERVAL]
.. index:: no dump bgp updates [PATH] [INTERVAL]
.. clicmd:: no dump bgp updates [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`).
.. index:: dump bgp routes-mrt PATH
.. clicmd:: dump bgp routes-mrt PATH
.. index:: dump bgp routes-mrt PATH INTERVAL
.. clicmd:: dump bgp routes-mrt PATH INTERVAL
.. index:: no dump bgp route-mrt [PATH] [INTERVAL]
.. clicmd:: no dump bgp route-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
------------------
.. index:: clear bgp ipv4|ipv6 \*
.. clicmd:: clear bgp ipv4|ipv6 \*
Clear all address family peers.
.. index:: clear bgp ipv4|ipv6 PEER
.. clicmd:: clear bgp ipv4|ipv6 PEER
Clear peers which have addresses of X.X.X.X
.. index:: clear bgp ipv4|ipv6 PEER soft in
.. clicmd:: clear bgp ipv4|ipv6 PEER soft in
Clear peer using soft reconfiguration.
.. _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.
.. index:: show ip bgp
.. clicmd:: show ip bgp
.. index:: show ip bgp A.B.C.D
.. clicmd:: show ip bgp A.B.C.D
.. index:: show bgp
.. clicmd:: show bgp
.. index:: show bgp X:X::X:X
.. clicmd:: show bgp X:X::X:X
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
Some other commands provide additional options for filtering the output.
.. index:: show [ip] bgp regexp LINE
.. clicmd:: show [ip] bgp regexp LINE
This command displays BGP routes using AS path regular expression
(:ref:`bgp-regular-expressions`).
.. index:: show [ip] bgp summary
.. clicmd:: show [ip] bgp summary
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]`.
.. index:: show bgp [afi] [safi]
.. clicmd:: show bgp [afi] [safi]
.. index:: show bgp <ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast>
.. clicmd:: show bgp <ipv4|ipv6> <unicast|multicast|vpn|labeled-unicast>
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
.. index:: show bgp [afi] [safi] summary
.. clicmd:: show bgp [afi] [safi] summary
Show a bgp peer summary for the specified address family, and subsequent
address-family.
.. index:: show bgp [afi] [safi] neighbor [PEER]
.. clicmd:: show bgp [afi] [safi] neighbor [PEER]
This command shows information on a specific BGP peer of the relevant
afi and safi selected.
.. index:: show bgp [afi] [safi] dampening dampened-paths
.. clicmd:: show bgp [afi] [safi] dampening dampened-paths
Display paths suppressed due to dampening of the selected afi and safi
selected.
.. index:: show bgp [afi] [safi] dampening flap-statistics
.. clicmd:: show bgp [afi] [safi] dampening flap-statistics
Display flap statistics of routes of the selected afi and safi selected.
.. _bgp-display-routes-by-community:
Displaying Routes by Community Attribute
----------------------------------------
The following commands allow displaying routes based on their community
attribute.
.. index:: show [ip] bgp <ipv4|ipv6> community
.. clicmd:: show [ip] bgp <ipv4|ipv6> community
.. index:: show [ip] bgp <ipv4|ipv6> community COMMUNITY
.. clicmd:: show [ip] bgp <ipv4|ipv6> community COMMUNITY
.. index:: show [ip] bgp <ipv4|ipv6> community COMMUNITY exact-match
.. clicmd:: show [ip] bgp <ipv4|ipv6> community COMMUNITY exact-match
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.
.. index:: show [ip] bgp <ipv4|ipv6> community-list WORD
.. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD
.. index:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match
.. clicmd:: show [ip] bgp <ipv4|ipv6> community-list WORD exact-match
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.
.. _bgp-display-routes-by-as-path:
Displaying Routes by AS Path
----------------------------
.. index:: show bgp ipv4|ipv6 regexp LINE
.. clicmd:: show bgp ipv4|ipv6 regexp LINE
This commands displays BGP routes that matches a regular
expression `line` (:ref:`bgp-regular-expressions`).
.. index:: show [ip] bgp ipv4 vpn
.. clicmd:: show [ip] bgp ipv4 vpn
.. index:: show [ip] bgp ipv6 vpn
.. clicmd:: show [ip] bgp ipv6 vpn
Print active IPV4 or IPV6 routes advertised via the VPN SAFI.
.. index:: show bgp ipv4 vpn summary
.. clicmd:: show bgp ipv4 vpn summary
.. index:: show bgp ipv6 vpn summary
.. clicmd:: show bgp ipv6 vpn summary
Print a summary of neighbor connections for the specified AFI/SAFI combination.
.. _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:
.. index:: neighbor PEER route-reflector-client
.. clicmd:: neighbor PEER route-reflector-client
.. index:: no neighbor PEER route-reflector-client
.. clicmd:: no 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.
.. index:: bgp cluster-id A.B.C.D
.. clicmd:: bgp cluster-id A.B.C.D
.. _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
bgp multiple-instance
!
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
!
ip as-path access-list asp-own-as permit ^$
ip as-path access-list 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
ip community-list standard cm-blackhole permit 64512:100
!
! set no-export community before advertising
ip community-list standard cm-set-no-export permit 64512:200
!
! advertise only to other customers
ip community-list standard cm-cust-only permit 64512:300
!
! advertise only to upstreams
ip community-list standard cm-upstream-only permit 64512:400
!
! advertise to upstreams with no-export
ip community-list standard cm-upstream-noexport permit 64512:500
!
! set local-pref to least significant 3 digits of the community
ip community-list standard cm-prefmod-100 permit 64512:2100
ip community-list standard cm-prefmod-200 permit 64512:2200
ip community-list standard cm-prefmod-300 permit 64512:2300
ip community-list standard cm-prefmod-400 permit 64512:2400
ip community-list expanded cme-prefmod-range permit 64512:2...
!
! Informational communities
!
! 3000 - learned from upstream
! 3100 - learned from customer
! 3200 - learned from peer
!
ip community-list standard cm-learnt-upstream permit 64512:3000
ip community-list standard cm-learnt-cust permit 64512:3100
ip 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
!
.. include:: routeserver.rst
.. include:: rpki.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
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