Next Hop Resolution Protocol

The Next Hop Resolution Protocol (NHRP) is an extension of the ATM ARP routing mechanism^[1] that is sometimes used to improve the efficiency of routing computer network traffic over a non-broadcast, multiple access (NBMA) network.^[2] It is defined in IETF RFC 2332,^[3] and further described in RFC 2333.^[4] It can be used by a sender to determine a route with the fewest hops to a receiver.^[5] The protocol differs from ARP-type protocols in that it allows routing optimization across multiple IP subnets.^[6] NHRP is implemented by means of next-hop servers across IP subnets.^[7]

NHRP forms a part of the Multiprotocol Encapsulation over ATM (MPOA) protocol as described in RFC 2684.^[8][9] It also plays a role in Cisco's Dynamic Multipoint Virtual Private Network.^[2] A limitation of NHRP is its inability to improve^[clarify] multicast protocols.^[1]

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."