MP-BGP Extensions for IPv6 NLRI

The deployment of IPv6 in a global network requires an Exterior Gateway Protocol (EGP) to provide full global reachability. The decision was to include support for IPv6 NLRI and to allow IPv6 transport for MP-BGP. This allowed the reuse of operational experience gained through years of work with BGP. The BGP extension to carry various types of routing information is called multiprotocol BGP, or MP-BGP. This functionality is discussed in Chapter 2, “Understanding BGP Building Blocks,” in the section “BGP Capabilities.”

The difference between BGPv4 and MP-BGP is the ability to carry prefix information for multiple protocols, such as IP multicast, CLNS, MPLS labels, IPv4 VPN, and IPv6. This information is advertised using address families. Prefix information is advertised using the BGP attribute MP_REACH_NLRI and is withdrawn using the MP_UNREACH_NLRI attribute.