Next Hop Resolution Protocol (NHRP)

References:
http://en.wikipedia.org/wiki/Next_Hop_Resolution_Protocol
http://www.cisco.com/en/US/docs/ios/12_4/ip_addr/configuration/guide/hadnhrp.html#wp1054887
http://www.netcraftsmen.net/resources/archived-articles/433.html
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_white_paper09186a008018983e.shtml