162 Appendix E: Understanding IP and IP addressing297-8991-910 Standard 03.01 August 1999Included in the family of address resolution protocols are reverse addressresolution protocol (RARP), proxy address resolution protocol (proxy ARP),and inverse address resolution protocol (InARP).ARP is defined in RFC826.Reverse ARPRARP is used to determine or assign a particular station IP address when onlythe station LAN MAC address is known.There are many reasons why an end system does not already have an IPaddress. The end-system could be a diskless workstation homed off a server.Or, it could be a portable computer belonging to an itinerant user, sharing apool of IP addresses with other itinerant users.RFC903 defines RARP.Proxy ARPThe proxy ARP is used to help an IP device locate a destination device, whenthe destination device is on a remote IP network or wire. When a source stationbroadcasts an ARP request on the local wire, and there is no station matchingthe destination IP address on the wire, the source does not receive an ARPresponse from the actual destination. Instead, the router derives the destinationIP wire address and searches for a match in its IP routing table.If the destination IP wire address is present in the routing table, the routerresponds with its MAC address. This tells the source that the MAC address forthe router is the MAC address for the destination station. The source IP stationhas no idea that the destination is on another wire.Proxy ARP is defined in RFC1027.Inverse ARPThe inverse address resolution protocol (InARP) determines the IP address fora remote router on a particular frame relay data link connection identifier(DLCI). This IP address is the local frame relay address of a permanent virtualcircuit (PVC) to a remote router.Inverse ARP is defined in RFC2390.Bootstrap ProtocolThe bootstrap protocol (BOOTP) is a UDP/IP-based protocol that permits abooting host to configure itself dynamically and without user supervision.BOOTP provides a means to notify a host of the following:• its assigned IP address
