BGP - multiprotocol BGP

The original version of BGP only supported IPv4 unicast prefixes. Since then, BGP has been required to support additional protocols. That's where multiprotocol or MP-BGP comes in.

MP-BGP is an extension to the standard BGP, which allows it to carry routing information for multiple network protocols.

The "protocols" it supports are the following:

Each of the above is considered an address family in the context of MP-BGP. MP-BGP is also able to support the following fields which are necessary to enable it to support these various protocols:

  • Address Family Identifier (AFI): specifies the address family.
  • Subsequent Address Family Identifier (SAFI): Has additional information for some address families.
  • Multiprotocol Unreachable Network Layer Reachability Information (MP_UNREACH_NLRI): This is an attribute used to transport networks that are unreachable.
  • BGP Capabilities Advertisement: This is used by a BGP router to announce to the other BGP router what capabilities it supports. MP-BGP and BGP-4 are compatible, the BGP-4 router can ignore the messages that it doesn’t understand.