arp -a
arp -d hostname
arp -s hostname ether_address [ temp ] [ pub ]
With no flags, arp displays the current ARP entry for hostname. The host may be specified by name or by number, using Internet dot notation.
-a Displays all of the current ARP entries.
-d Deletes an entry for the host called hostname.
-s Creates an ARP entry for the host called hostname with the Ethernet address ether_address. The Ethernet address is given as six hex bytes separated by colons. The entry will be permanent if the words following -s includes the keyword temp. Temporary entries that consist of a complete Internet address and a matching Ethernet address are flushed from the arp table if they haven't been referenced in the past 20 minutes. A permanent entry is not flushed.
If the words following -s include the keyword pub, the entry will be "published"; i.e., this system will act as an ARP server, responding to requests for hostname even though the host address is not its own.