Every device on a TCP/IP network has a unique number assigned to it called the MAC (Media Access Control) address. The MAC address is used by the network hardware such as routers, switches, etc. to send traffic from one device to another device on your network.
Your computer uses a service called ARP (Address Resolution Protocol) to resolve and track the TCP/IP and MAC address of the remote devices that you're communicating with. This information is handy for doing semi-low level network troubleshooting. It can also be used for granting or denying permissions to a network segment or device on that network.

To determine the MAC address of a remote device:

  • Open the MS-DOS prompt (From the Run... command, type "CMD" and press Enter).
  • Ping a remote device that you want to find the MAC address (for example: PING
  • Type "ARP -A", and press Enter.

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\WINDOWS>arp -a

Interface: --- 0x10004
Internet Address Physical Address Type aa-fb-c8-34-da-7a dynamic