MBGP—Capability Negotiation
BGP routers establish BGP sessions through the OPEN message
OPEN message contains  optional parameters
BGP session is terminated if OPEN parameters are not
recognised
New parameter: CAPABILITIES
Multiprotocol extension
Multiple routes for same destination
Configures router to negotiate either or both NLRI
If neighbor configures both or subset, common NRLI is used in both
directions
If there is no match, notification is sent and peering doesn’t come up
If neighbor doesn’t include the capability parameters in open, session
backs off and reopens with no capability parameters
Peering comes up in unicast-only mode