MP-BGP
Traditional BGP-4 manages only IPv4 routing information. Inter-AS transmission of other network layer protocol packets (such as IPv6 and multicast packets) is limited. To support multiple network layer protocols, Multiprotocol BGP (MP-BGP) is designed in RFC 4760 as an extension to BGP-4. MP-BGP uses extended attributes and address families to support IPv6, multicast, and VPN, without changing the existing BGP packet forwarding or routing mechanism.
MP-BGP is called BGP4+ on IPv6 unicast networks or called Multicast BGP (MBGP) on IPv4 multicast networks. MP-BGP establishes separate topologies for IPv6 unicast networks and IPv4 multicast networks, and stores IPv6 unicast and IPv4 multicast routing information in different routing tables. This ensures that routing information of IPv6 unicast networks and IPv4 multicast networks is separated from each other, and allows routes of different networks to be maintained using different routing policies.
Extended Attributes
In BGP, an Update message carries three IPv4-related attributes: NLRI, Next_Hop, and Aggregator.
To support multiple network layer protocols, BGP requires NLRI and Next_Hop attributes to carry information about network layer protocols. Therefore, MP-BGP uses the following new optional non-transitive attributes:
MP_REACH_NLRI: indicates the multiprotocol reachable NLRI. It is used to advertise reachable routes and next hop information.
MP_UNREACH_NLRI: indicates the multiprotocol unreachable NLRI. It is used to withdraw unreachable routes.
Address Families
- BGP-IPv4 unicast address family view
- BGP-IPv4 multicast address family view
- BGP-VPN instance IPv4 address family view
- BGP-VPNv4 address family view
- BGP-IPv6 unicast address family view
- BGP-VPN instance IPv6 address family view
- BGP-VPNv6 address family view