Sets the administrative distance for a particular route.
+.. _bgp-requires-policy:
+
+Require policy on EBGP
+-------------------------------
+
+.. index:: [no] bgp ebgp-requires-policy
+.. clicmd:: [no] bgp ebgp-requires-policy
+
+ This command requires incoming and outgoing filters to be applied for eBGP sessions. Without the incoming filter, no routes will be accepted. Without the outgoing filter, no routes will be announced.
+
.. _bgp-route-flap-dampening:
Route Flap Dampening
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
-route-reflection topologies. However, any route-hiding technologies potentially
-could also exacerbate oscillation with MED.
+: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 -
Redistribute OSPF route to BGP process.
-.. index:: redistribute vpn
-.. clicmd:: redistribute vpn
+.. index:: redistribute vnc
+.. clicmd:: redistribute vnc
Redistribute VNC routes to BGP process.
+.. index:: redistribute vnc-direct
+.. clicmd:: redistribute vnc-direct
+
+ Redistribute VNC direct (not via zebra) routes to BGP process.
+
.. index:: update-delay MAX-DELAY
.. clicmd:: update-delay MAX-DELAY
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 maximum-prefix NUMBER
.. clicmd:: [no] neighbor PEER maximum-prefix NUMBER
-.. index:: [no] neighbor PEER local-as AS-NUMBER no-prepend
-.. clicmd:: [no] neighbor PEER local-as AS-NUMBER no-prepend
+ Sets a maximum number of prefixes we can receive from a given peer. If this
+ number is exceeded, the BGP session will be destroyed.
-.. index:: [no] neighbor PEER local-as AS-NUMBER no-prepend replace-as
-.. clicmd:: [no] neighbor PEER local-as AS-NUMBER no-prepend replace-as
+ 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
-.. clicmd:: [no] neighbor PEER local-as AS-NUMBER
+.. 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
This command defines a new peer group.
-.. index:: neighbor PEER peer-group WORD
-.. clicmd:: neighbor PEER peer-group WORD
+.. index:: neighbor PEER peer-group PGNAME
+.. clicmd:: neighbor PEER peer-group PGNAME
This command bind specific peer to peer group WORD.
Using AS Path in Route Map
--------------------------
-.. index:: match as-path WORD
-.. clicmd:: match as-path WORD
+.. index:: [no] match as-path WORD
+.. clicmd:: [no] match as-path WORD
+ For a given as-path, WORD, match it on the BGP as-path given for the prefix
+ and if it matches do normal route-map actions. The no form of the command
+ removes this match from the route-map.
-.. index:: set as-path prepend AS-PATH
-.. clicmd:: set as-path prepend AS-PATH
+.. index:: [no] set as-path prepend AS-PATH
+.. clicmd:: [no] set as-path prepend AS-PATH
- Prepend the given string of AS numbers to the AS_PATH.
+ Prepend the given string of AS numbers to the AS_PATH of the BGP path's NLRI.
+ The no form of this command removes this set operation from the route-map.
-.. index:: set as-path prepend last-as NUM
-.. clicmd:: set as-path prepend last-as NUM
+.. index:: [no] set as-path prepend last-as NUM
+.. clicmd:: [no] set as-path prepend last-as NUM
Prepend the existing last AS number (the leftmost ASN) to the AS_PATH.
+ The no form of this command removes this set operation from the route-map.
.. _bgp-communities-attribute:
``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 maintainance. The use
+ 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.
``llgr-stale``
``llgr-stale`` represents well-known communities value ``LLGR_STALE``
``0xFFFF0006`` ``65535:6``.
- Assigned and intented only for use with routers supporting the
+ 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 recieving routes with this community may (depending on
+ 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 intented only for use with routers supporting the
+ 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 recieving routes with this community may (depending on
+ 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.
There are two types of community list:
standard
- This type accepts an explicit value for the atttribute.
+ This type accepts an explicit value for the attribute.
expanded
This type accepts a regular expression. Because the regex must be
Route Reflector
===============
-.. note:: This documentation is woefully incomplete.
+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.
-.. index:: bgp cluster-id A.B.C.D
-.. clicmd:: bgp cluster-id A.B.C.D
+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:
route-map rm-no-export permit 20
!
route-map rm-blackhole permit 10
- description blackhole, up-pref and ensure it cant escape this AS
+ 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
projects / mirror_frr.git / blobdiff