MPBGP

MP-BGP, short for Multi-Protocol Border Gateway Protocol, is an extension of the Border Gateway Protocol designed to carry routing information for multiple address families within a single BGP session. It enables the exchange of IPv4 and IPv6 routes, as well as VPN, multicast, and other protocol families, over the same peering relationship. MP-BGP is widely used in service provider and large enterprise networks, particularly to implement VPNs over MPLS and to enable diverse routing domains to interoperate.

The mechanism of MP-BGP relies on a framework of address family identifiers. Each route is associated with an address family identifier (AFI) and a subsequent address family identifier (SAFI) that specify the type of prefix being carried, such as unicast IPv4, unicast IPv6, or VPN-specific NLRI. MP_REACH_NLRI and MP_UNREACH_NLRI attributes transport the reachability information for the selected AFI/SAFI. In VPN contexts, the use of Route Distinguishers (RD) and Route Targets (RT) provides separation of customer VPN routes within a common BGP framework, enabling multiple VRFs to share the same routing backbone without conflict. Regular IPv4 or IPv6 unicast routes can co-exist with VPN routes in the same session.

Common use cases include BGP/MPLS IP VPNs (VPNv4 and VPNv6), L2 and L3 VPNs, and multicast VPNs, which benefit from MP-BGP’s ability to consolidate multiple route families over a single control plane. Deployment considerations emphasize proper AFI/SAFI support, careful RD/RT administration, and route filtering to prevent leaks, along with scalability and interoperability with route reflectors and VRF import/export policies. MP-BGP thus provides a flexible, scalable mechanism for diverse routing needs in modern networks.