If your computer has an Ethernet or Wi-Fi network adapter card installed and is connected to a TCP/IP network, the Address Resolution Protocol is used to map IP addresses of systems you are communicating with on the local network to their network card’s physical MAC address. The ARP command allows you to view the MAC addresses of systems with which your system is communicating, such as your local router interface. This information can be useful when troubleshooting connection problems, or when a duplicate IP address is configured on your network.
To view the contents of the ARP cache on your system, issue the ARP –a command. If your ARP cache contains no entries, ping another computer on your network, and issue the command again.