What does ARP abbreviate for?
Address Resolution Protocol. When a host want to know the ethernet address corresponding to a certain IP, it send out a broadcast query for the IP address. Each receiving host compare it to its own IP address, and if it matches, returns a reply to the inquiring host.
How can we display all entries?
arp -an
arp -en
How can we display MAC address for a given IP?
arp -an 192.168.1.2
How can we delete ARP entries for a given IP?
arp -d 192.168.1.2
How can we create a static ARP table entry associating a particular IP address with a particular MAC address?
Create a static ARP table entry associating a particular IP address 1.1.1.1 with MAC address A123.ABCF.321A available through the eth0 interface:
arp -i eth0 -s 192.168.1.3 A123.ABCF.321A
For some reason, ARP queries for the remote host sometimes fail, for instance, when its ARP driver is buggy or there is another host in the network that erroneously identify itself with that host's IP address. This problem requires you to manually add an IP address to the ARP table. Hard-wiring IP addresses in the ARP table is a drastic measure to protect yourself from host on your network that pose as someone else.
