arp

arp

Synopsis
arp prints the ARP cache
arp -d clears the ARP cache
Details
ARP (the Address Resolution Protocol) is a low level protocol for discovering the MAC address of a network interface on the local network. MAC address are the low-level network addresses for routing IP (and other) network packets on a physical network.

When a host needs to comminutate with an unknown local IP address, it broadcasts an ARP request on the local network, asking for the MAC address for the IP address. The node with the IP address broadcasts a response giving the MAC address for the network interface corresponding to the IP address.

The ARP cache stores IP to MAC address mappings that have previously been discovered. This allows the network stack to send IP packets without repeatedly broadcasting for MAC addresses.

The arp command allows you to examine the contents of the ARP cache, and if necessary clear it to get rid of stale entries.