Editing Address Resolution Protocol (section)

=={{anchor|INARP}}Inverse ARP and Reverse ARP==
'''Inverse Address Resolution Protocol''' ('''Inverse ARP''' or '''InARP''') is used to obtain [[network layer]] addresses (for example, [[IP address]]es) of other nodes from [[data link layer]] (Layer 2) addresses. Since ARP translates layer-3 addresses to layer-2 addresses, InARP may be described as its inverse. In addition, InARP is implemented as a protocol extension to ARP: it uses the same packet format as ARP, but different operation codes.

InARP is primarily used in [[Frame Relay]] ([[DLCI]]) and ATM networks, in which layer-2 addresses of [[virtual circuit]]s are sometimes obtained from layer-2 signaling, and the corresponding layer-3 addresses must be available before those virtual circuits can be used.{{Ref RFC|2390}}

The [[Reverse Address Resolution Protocol]] (Reverse ARP or RARP), like InARP, translates layer-2 addresses to layer-3 addresses. However, in InARP the requesting station queries the layer-3 address of another node, whereas RARP is used to obtain the layer-3 address of the requesting station itself for address configuration purposes. RARP is obsolete; it was replaced by [[BOOTP]], which was later superseded by the [[Dynamic Host Configuration Protocol]] (DHCP).{{Ref RFC|903}}