arp

     arp [-d] [ip-address] [dest-address]

     Without any parameters, the arp command will display the contents of the
     arp table.  With two parameters, arp can be used to add permanent arp
     entries to the table (permanent arp entries do not time out)

     -d           Delete the specified ARP entry.  If specified, ip-address
                  may be * to delete all entries.