5.5 Summary

5.5 Summary

RARP is used by many diskless systems to obtain their IP address when bootstrapped. The RARP packet format is nearly identical to the ARP packet. An RARP request is broadcast, identifying the sender's hardware address, asking for anyone to respond with the sender's IP address. The reply is normally unicast.

Problems with RARP include its use of a link-layer broadcast, preventing most routers from forwarding an RARP request, and the minimal information returned: just the system's IP address. In Chapter 16 we'll see that BOOTP returns more information for the diskless system that is bootstrapping: its IP address, the name of a host to bootstrap from, and so on.

While the RARP concept is simple, the implementation of an RARP server is system dependent. Hence not all TCP/IP implementations provide an RARP server.