The Reverse Address Resolution Protocol (RARP) is an obsolete computer

communication protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

used by a client computer to request its Internet Protocol (

IPv4 Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. ...

) address from a

computer network A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or b ...

, when all it has available is its link layer or hardware address, such as a

MAC address A MAC address (short for medium access control address or media access control address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use i ...

. 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 The Bootstrap Protocol (BOOTP) is a computer networking protocol used in Internet Protocol networks to automatically assign an IP address to network devices from a configuration server. The BOOTP was originally defined in published in 1985. Whi ...

(BOOTP) and the modern

Dynamic Host Configuration Protocol The Dynamic Host Configuration Protocol (DHCP) is a network protocol, network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the netw ...

(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 An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface i ...

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 Frame Relay (FR) is a standardized wide area network (WAN) technology that specifies the Physical layer, physical and data link layers of digital telecommunications channels using a packet switching methodology. Frame Relay was originally devel ...

data link connection identifier. InARP is not used in

Ethernet Ethernet ( ) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

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 The Quick Emulator (QEMU) is a free and open-source emulator that uses dynamic binary translation to emulate a computer's processor; that is, it translates the emulated binary codes to an equivalent binary format which is executed by the mach ...

. 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 VMware vSphere (formerly VMware Infrastructure 4) is VMware's cloud computing virtualization platform. It includes vCenter Configuration Manager, as well as vCenter Application Discovery Manager, and the ability of vMotion to move more than o ...

's vMotion. RARP is used when a VM MAC moves between hosts.

References

{{reflist Internet protocols Internet Standards Link protocols

Modern Day Uses

See also

References