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11.5.2 BGP Peer commands

In a router bgp clause there are neighbor specific configurations required.

BGP: neighbor peer shutdown
BGP: no neighbor peer shutdown

Shutdown the peer. We can delete the neighbor’s configuration by no neighbor peer remote-as as-number 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.

BGP: neighbor peer ebgp-multihop
BGP: no neighbor peer ebgp-multihop
BGP: neighbor peer description ...
BGP: no neighbor peer description ...

Set description of the peer.

BGP: 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.

BGP: neighbor peer interface ifname
BGP: 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.

BGP: neighbor peer next-hop-self [all]
BGP: 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 modifiation is done also for routes learned via iBGP.

BGP: neighbor peer update-source <ifname|address>
BGP: no neighbor peer update-source

Specify the IPv4 source address to use for the 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).

router bgp 64555
 neighbor foo update-source
 neighbor bar update-source lo0
BGP: neighbor peer default-originate
BGP: no neighbor peer default-originate

bgpd’s default is to not announce the default route ( even it is in routing table. When you want to announce default routes to the peer, use this command.

BGP: neighbor peer port port
BGP: neighbor peer port port
BGP: neighbor peer send-community
BGP: neighbor peer send-community
BGP: neighbor peer weight weight
BGP: no neighbor peer weight weight

This command specifies a default weight value for the neighbor’s routes.

BGP: neighbor peer maximum-prefix number
BGP: no neighbor peer maximum-prefix number
BGP: neighbor peer local-as as-number
BGP: neighbor peer local-as as-number no-prepend
BGP: neighbor peer local-as as-number no-prepend replace-as
BGP: no neighbor peer local-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.

BGP: neighbor peer ttl-security hops number
BGP: 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 mututally exclusive with ebgp-multihop.

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