Editing Reverse Address Resolution Protocol

{{Short description|Obsolete computer networking protocol}}
{{Internet protocol suite|link=[[Reverse Address Resolution Protocol|Reverse ARP]]}}

The '''Reverse Address Resolution Protocol''' ('''RARP''') is an obsolete computer [[communication protocol]] used by a [[client computer]] to request its Internet Protocol ([[IPv4]]) address from a [[computer network]], when all it has available is its [[link layer]] or hardware address, such as a [[MAC address]].{{Ref RFC|903}} The client broadcasts the request and does not need prior knowledge of the network topology or the identities of servers capable of fulfilling its request.

RARP has been rendered obsolete by the [[Bootstrap Protocol]] (BOOTP) and the modern [[Dynamic Host Configuration Protocol]] (DHCP), which both support a much greater feature set than RARP.

RARP requires one or more server hosts to maintain a database of mappings of [[link layer]] addresses to their respective protocol addresses. MAC addresses need to be individually configured on the servers by an administrator. RARP is limited to serving only [[IP address]]es.

Reverse ARP differs from the [[Inverse Address Resolution Protocol]] (InARP), which is designed to obtain the IP address associated with a local [[Frame Relay]] data link connection identifier.{{Ref RFC|2390}} InARP is not used in [[Ethernet]].

==Modern Day Uses==

Although the original uses for RARP have been superseded by different protocols, some modern-day protocols use RARP to handle MAC migration, particularly in virtual machines, using a technique originating in [[QEMU]].

Examples include:
* Cisco's [[Overlay Transport Virtualization]] (OTV).  RARP is used to update the layer 2 forwarding tables when a MAC address moves between data centers.
* [[VMware vSphere]]'s vMotion.<ref>{{Cite web |last=Deshpande |first=Venky |date=22 July 2013 |title=VXLAN Series – How vMotion impacts the forwarding table – Part 6 |url=http://www.soviet-empire.com/ussr/viewtopic.php?t=50411 |access-date=15 March 2023 |website=vmware}}</ref>  RARP is used when a VM MAC moves between hosts.

==See also==
*[[Maintenance Operations Protocol]] (MOP)

==References==
{{reflist}}

[[Category:Internet protocols]]
[[Category:Internet Standards]]
[[Category:Link protocols]]