arp - manipulate the system ARP cache.
Display all entries in arp cache / table:
arp -a
Display entry for specific address:
arp 192.168.0.1
Display arp entries for specific interface:
arp -i eth0
Delete an entry in arp cache:
arp -d 192.168.0.2
Add an entry to the arp cache:
arp -s 192.168.1.1 -i eth0 00:99:21:1f:1e:77