Next Hop Resolution Protocol: Difference between revisions

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The '''Next Hop Resolution Protocol''' (NHRP) is an extension of the ATM ARP routing mechanism<ref name="White">{{cite journal|last1=White|first1=P.P.|title=ATM switching and IP routing integration: the next stage in Internet evolution?|journal=IEEE Communications Magazine|date=April 1998|volume=36|issue=4|pages=79–83|doi=10.1109/35.667418|url=http://www.cl.cam.ac.uk/~jac22/otalks/atmipint.pdf|accessdate=18 June 2016}}</ref> that is sometimes used to improve the efficiency of routing computer network traffic over a [[Nonbroadcast Multiple Access Network|non-broadcast, multiple access (NBMA) network]].<ref name="Cisco">{{cite web|title=NHRP|url=http://www.cisco.com/c/en/us/td/docs/ios/12_4/ip_addr/configuration/guide/hadnhrp.html#wp1054887|website=Cisco|accessdate=17 June 2016}}</ref> It is defined in [[IETF]] RFC 2332,<ref>{{cite journal|last1=B.|first1=Cole|last2=J.|first2=Luciani|last3=N.|first3=Doraswamy|last4=D.|first4=Piscitello|last5=D.|first5=Katz|title=NBMA Next Hop Resolution Protocol (NHRP)|url=https://tools.ietf.org/html/rfc2332|website=tools.ietf.org|date=April 1998 |accessdate=17 June 2016}}</ref> and further described in RFC 2333.<ref>{{cite journal|last1=Cansever|first1=Derya H.|title=NHRP Protocol Applicability Statement|url=https://tools.ietf.org/html/rfc2333|website=tools.ietf.org|date=April 1998 |accessdate=17 June 2016}}</ref> It can be used by a sender to determine a route with the fewest hops to a receiver.<ref>{{cite web|last1=Rouse|first1=Margaret|title=What is Next Hop Resolution Protocol (NHRP)? - Definition from WhatIs.com|url=http://searchnetworking.techtarget.com/definition/Next-Hop-Resolution-Protocol|website=SearchNetworking|accessdate=17 June 2016}}</ref> The protocol differs from [[Address Resolution Protocol|ARP]]-type protocols in that it allows routing optimization across multiple IP subnets.<ref>{{cite journal|last1=Luciani|first1=James V.|editor-first1=Seyhan |editor-first2=Indra |editor-last1=Civanlar |editor-last2=Widjaja |title=Next-hop resolution protocol|date=1 January 1997|journal=SPIE Proceedings|series=Broadband Networking Technologies |volume=3233|pages=161–165|doi=10.1117/12.290456|bibcode=1997SPIE.3233..161L |s2cid=21461973|url=http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=933004|url-access=subscription}}</ref> NHRP is implemented by means of next-hop servers across IP subnets.<ref>{{cite book|last1=Ahmad|first1=Khalid|title=Sourcebook of ATM and IP Internetworking|date=2 April 2004|publisher=John Wiley & Sons|isbn=9780471660941|page=360|url=https://books.google.com/books?id=BjeG2uAaNK4C&q=%22Next+Hop+Resolution+Protocol%22&pg=PA360|accessdate=18 June 2016|language=en}}</ref>

Next Hop Resolution Protocol is used for Layer 3 switching. An NHRP client on a NBMA (Non-Broadcast Multi-Access network) routes a request through traditional routers to obtain destination's network layer address as well as the Next Hop IP address. If the destination lies on the same subnet as the client itself, then the destination IP would be the Next Hop IP address as well.

NHRP forms a part of the [[Multiprotocol Encapsulation over ATM]] (MPOA) protocol as described in RFC 2684.<ref>{{cite journal|last1=Dan|first1=Grossman|last2=Juha|first2=Heinanen|title=Multiprotocol Encapsulation over ATM Adaptation Layer 5|url=https://tools.ietf.org/html/rfc2684|website=tools.ietf.org|date=September 1999 }}</ref><ref>{{cite book|last1=Newman|first1=P.|last2=Lyon|first2=T.|last3=Minshall|first3=G.|title=Proceedings of IEEE INFOCOM '96. Conference on Computer Communications |chapter=Flow labelled IP: A connectionless approach to ATM |date=1 March 1996|volume=3|pages=1251–1260 vol.3|doi=10.1109/INFCOM.1996.493071|isbn=0-8186-7293-5|s2cid=5482472|chapter-url=https://www.researchgate.net/publication/2615390|accessdate=18 June 2016}}</ref> It also plays a role in Cisco's [[Dynamic Multipoint Virtual Private Network]].<ref name="Cisco" /> A limitation of NHRP is its inability to improve{{Clarify span||date=October 2023}} [[multicast]] protocols.<ref name="White" />

==Description==

From RFC 2332: "[NHRP] allows a source station (a [[Host (network)|host]] or [[Router (computing)|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."

== References ==

<references />

== External links==

*[https://sourceforge.net/projects/opennhrp OpenNHRP project page]

[[Category:Routing protocols]]

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