Concept Guide

The neighbors congured under CONFIGURATION-ROUTER-BGP mode and are dened using the neighbor remote-as command
exchange only IPv4 unicast address prexes. If you want a neighbor to exchange other prexes such as IPv4 multicast or IPv6 unicast, you
have to explicitly activate the respective neighbor using neighbor activate command in the respective IPv4 multicast or IPv6 unicast
address family conguration. In the above example conguration, activating the neighbor (20.20.20.2) under the IPv4 multicast address
family enables the neighbor to exchange IPv4 muticast prexes. Similarly, activating the neighbors (20.20.20.2 and 2001::2) under the IPv6
unicast address family enables the neighbor to exchange IPv6 unicast prexes. The neighbor (30.30.30.1) is activated by default for
exchanging IPv4 unicast address prexes, but will not exchange IPv4 multicast and IPv6 unicast address prexes since they are not
activated under the respective address family. If you want the neighbor (30.30.30.1) to exchange IPv4 multicast and/or IPv6 unicast
prexes, you have to explicitly active the neighbor using neighbor activate command.
If you do not want a neighbor to exchange IPv4 unicast prexes, you have to manually deactivate the peer with the no neighbor
activate command under the CONFIGURATION-ROUTER-BGP mode. If any neighbor is already activated to exchange IPv4 multicast
or IPv6 unicast prexes, exchanging of prexes can be deactivated using no neighbor activate command under the IPv4 multicast
or IPv6 unicast address family. In the above example conguration, the peer (3000::1) is deactivated from exchanging IPv4 unicast prexes.
The show ip bgp summary or show ip bgp ipv4 unicast summary displays IPv4 unicast address family conguration. In a
dual stack scenario, to view the specic IPv4 multicast or IPv6 unicast address family conguration, use show ip bgp ipv4
multicast summary or show ip bgp ipv6 unicast summary commands.
Following is the sample output for show ip bgp summary command.
R1#show ip bgp summary
BGP router identifier 1.1.1.1, local 10
BGP local RIB : Routes to be Added 0, Replaced 0, Withdrawn 0
3 neighbor(s) using 40960 bytes of memory
Neighbor AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/Pfx
20.20.20.2 200 10 20 0 0 0 00:06:11 0
30.30.30.1 20 0 0 0 0 0 00:00:00 0
2001::2 200 40 45 0 0 0 00:03:14 0
The same output will be displayed when using show ip bgp ipv4 unicast summary command.
Following is the sample output of show ip bgp ipv4 multicast summary command.
R1# show ip bgp ipv4 multicast summary
BGP router identifier 1.1.1.1, local AS number 10
BGP local RIB : Routes to be Added 0, Replaced 0, Withdrawn 0
1 neighbor(s) using 24576 bytes of memory
Neighbor AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/Pfx
20.20.20.2 200 10 20 0 0 0 00:06:11 0
R1#
Following is the output of show ip bgp ipv6 unicast summary command for the above conguration example.
R1#show ip bgp ipv6 unicast summary
BGP router identifier 1.1.1.1, local AS number 10
BGP local RIB : Routes to be Added 0, Replaced 0, Withdrawn 0
2 neighbor(s) using 24576 bytes of memory
Neighbor AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/Pfx
20.20.20.2 200 10 20 0 0 0 00:06:11 0
2001::2 200 40 45 0 0 0 00:03:14 0
R1#
Example of enabling BGP and address family conguration in router (R2)
Following is an example to enable BGP and address family conguration for the neighbor R1 (20.20.20.1) in the router R2.
R2(conf)# router bgp 200
R2(conf-router_bgp)# neighbor 20.20.20.1 remote-as 10
R2(conf-router_bgp)# neighbor 20.20.20.1 no shutdown
236
Border Gateway Protocol (BGP)