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162 Appendix E: Understanding IP and IP addressing
297-8991-910 Standard 03.01 August 1999
Included in the family of address resolution protocols are reverse address
resolution protocol (RARP), proxy address resolution protocol (proxy ARP),
and inverse address resolution protocol (InARP).
ARP is defined in RFC826.
Reverse ARP
RARP is used to determine or assign a particular station IP address when only
the station LAN MAC address is known.
There are many reasons why an end system does not already have an IP
address. 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 a
pool of IP addresses with other itinerant users.
RFC903 defines RARP.
Proxy ARP
The proxy ARP is used to help an IP device locate a destination device, when
the destination device is on a remote IP network or wire. When a source station
broadcasts an ARP request on the local wire, and there is no station matching
the destination IP address on the wire, the source does not receive an ARP
response from the actual destination. Instead, the router derives the destination
IP 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 router
responds with its MAC address. This tells the source that the MAC address for
the router is the MAC address for the destination station. The source IP station
has no idea that the destination is on another wire.
Proxy ARP is defined in RFC1027.
Inverse ARP
The inverse address resolution protocol (InARP) determines the IP address for
a remote router on a particular frame relay data link connection identifier
(DLCI). This IP address is the local frame relay address of a permanent virtual
circuit (PVC) to a remote router.
Inverse ARP is defined in RFC2390.
Bootstrap Protocol
The bootstrap protocol (BOOTP) is a UDP/IP-based protocol that permits a
booting host to configure itself dynamically and without user supervision.
BOOTP provides a means to notify a host of the following:
• its assigned IP address