Information Technology Reference
In-Depth Information
The BGP router ID should be manually set for every router. This ensures
that if IPv4 is ever removed from the network, the IPv6 BGP sessions
will remain active. While IPv4 addresses are configured on the router,
this does not cause a problem. However, the removal of IPv4 can result
in a failure of all IPv6 BGP sessions if the BGP router ID is not set. The
command is
bgp router-id
x.x.x.x
under the BGP router configuration.
Step 2
Configure a loopback with an IPv6 address. This addressing is used to
form the MP-BGP sessions, just like the IPv4 sessions. It is not required
to configure addressing on all the internal links, because link-local
addressing can be used for forwarding. To use link-local addressing on
the physical links, configure the command
ipv6 enable
under each
interface to initiate the autocreation of link-local addresses. Global
addressing is used for external-facing links to provide a reachable next-
hop address.
Step 3
Enable the IPv6 IGP. This step provides reachability across the entire
network for IPv6 packets, which allows the IPv6 BGP sessions to form
after they have been configured. In this case study, because IS-IS is used,
you can do this by configuring
ipv6 router isis
under each interface,
including the loopback interface.
Step 4
With the foundation in place, you can configure the IPv6 BGP sessions.
You do this under the main BGP configuration. After you configure the
BGP sessions, you must activate them in the IPv6 address family
configuration mode.
Step 5
The IPv6 BGP network is now ready to advertise prefix information. IPv6 prefix informa-
tion should be injected under IPv6 address family configuration mode using redistribution
or network statements. Also, BGP synchronization must be disabled for IPv6 and IPv4 if
synchronization is not being used.
IPv6 Network Topology
The IPv6 loopback addresses configured on each router are in the form of 2001:0400:0:
1234::
X
/128, where
X
is the router number. IPv6 prefixes are injected into BGP on each of
the edge routers for IPv6 reachability testing.
The output from
show bgp ipv6 summary
on R1 is shown in Example 12-5. The output
should be familiar to you from working with IPv4.
Example 12-5
show bgp ipv6 summary
Output
R1#show bgp ipv6 summary
BGP router identifier 10.1.1.1, local AS number 65000
BGP table version is 5, main routing table version 5
4 network entries and 6 paths using 948 bytes of memory
