ARP and RARP

ARP and RARP operate between the Network Interface and Internet layers of the TCP/IP model. The features of ARP are

• Maps a 32-bit IP address to a 48-bit Ethernet address.

• Solicited messages are where a specific Ethernet address was asked for by a host and unsolicited messages contain information about a host that issued an ARP request.

• ARP maintains a cache in memory, responses are held for 20 minutes by default ”the variable ip_ire_arp_interval holds the value in microseconds. Use ndd to inspect, or modify, the variable.

• The arp command manages cache entries. Options are: -a (display all entries), -d (delete an entry), -s (add a static entry) and “f (add multiple entries from a file).

The features of RARP are

• Maps a 48-bit Ethernet address to a 32-bit IP address. RARP uses /etc/ethers and /etc/inet/ hosts to provide mapping.

• in.rarpd is started at bootup by the /etc/rc3.d/S16boot.server script. Use the “d option to run the daemon in debug mode.

• If the message Timeout waiting for ARP/RARP packet is received by a client booting with RARP, the cause could be a missing or incorrect entry in /etc/ethers or /etc/inet/hosts , or that in.rarpd is not running.