Next Hop Resolution Protocol

The Next Hop Resolution Protocol (NHRP) is an extension of the ATM ARP routing mechanism that is sometimes used to improve the efficiency of routing computer network traffic over a non-broadcast, multiple access (NBMA) network. It is defined in IETF RFC 2332, and further described in RFC 2333. It can be used by a sender to determine a route with the fewest hops to a receiver. The protocol differs from ARP-type protocols in that it allows routing optimization across multiple IP subnets. NHRP is implemented by means of next-hop servers across IP subnets.

NHRP forms a part of the Multiprotocol Encapsulation over ATM (MPOA) protocol as described in RFC 2684. It also plays a role in Cisco's Dynamic Multipoint Virtual Private Network. A limitation of NHRP is its inability to improve multicast protocols.

Description
From RFC 2332: "[NHRP] allows a source station (a host or router), wishing to communicate over [an NBMA] subnetwork, to determine the internetworking layer addresses and NBMA addresses of suitable 'NBMA next hops' toward a destination station."