When configuring multiprotocol BGP extensions for IPv6, you must create the BGP routing process, configure peering relationships, and customize BGP for your particular network.

Note:The following sections describe the configuration tasks for creating an IPv6 multiprotocol BGP routing process and associating peers, peer groups, and networks to the routing process. The following sections do not provide in-depth information on customizing multiprotocol BGP because the protocol functions the same in IPv6 as it does in IPv4.

Command syntax:

Router(config)# router bgp autonomous-system-number

The command configures a BGP routing process, and enters router configuration mode for the specified routing process.

Router(config-router)# no bgp default ipv4-unicast

This command is used to disable the IPv4 unicast address family for the BGP routing process. Otherwise routing information for the IPv4 unicast address family is advertised by default.

As mentioned above usually an IPv4 address configured on one of the interfaces is used as BGP router id. You can optionally change/set this id with the following command:

Router(config-router)# bgp router-id ip-address

Note: Configuring a router id using the bgp router-id command resets all active BGP peering sessions.

As with IPv4 the next step is to configure BGP neighbors/peers. By default, neighbors that are defined using the neighbor remote-as command in router configuration mode exchange only IPv4 unicast address prefixes. To exchange other address prefix types, such as IPv6 prefixes, neighbors must also be activated using the neighbor activate command in address family configuration mode for the other prefix types, as shown for IPv6 prefixes.

The first step however is to add a neighbor in the context of previously created routing process:

Router(config-router)# neighbor ipv6-address remote-as \\
                                                                                     autonomous-system-number

The specified ipv6-address may be a unicast IPv6 address of any form, but configuring IPv6 multiprotocol BGP between two IPv6 routers (peers) using link-local addresses requires that the interface for the neighbor be identified by using the update-source router configuration command, and that a route map be configured to set an IPv6 global next hop. The update-source is defined in the global BGP configuration context, after the neighbour was created:

Router(config-router)# neighbor ipv6-address update-source \\
                                                                                     interface-type interface-number

If there are multiple connections to the neighbor and you do not specify the neighbor interface by using the interface-type and interface-number arguments in the neighbor update-source command, a TCP connection cannot be established with the neighbor using link-local addresses.

Now enter the IPv6 address family:

Router(config-router)# address-family ipv6 [unicast]

The unicast keyword specifies the IPv6 unicast address family. By default, the router is placed in configuration mode for the IPv6 unicast address family if the unicast keyword is not specified with the address-family ipv6 command.

Within this context one can enable the neighbor to exchange prefixes for the IPv6 address family with the local router.

Router(config-router-af)# neighbor ipv6-address activate