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]
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."