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What is a MAC address?

A MAC address is a number that is unique to each network adapter. At a very low level, it is how computers communicate on a network. It is a critical part of how computers talk to each other, and an important piece of information when dealing with network security and network monitoring. A MAC address is a hexadecimal number that looks something like this: 00-01-02-2a-6b-31.

How to locate a MAC address on your computer

On Windows NT/2000/XP:

See if it is printed on the pcmcia card. If it isn't, open a command window [Start -> Run... -> cmd] and type

ipconfig /all

This will print out information for all of your network adapters. Your MAC address will be listed as the 'physical address.'


On a Macintosh:

If you are running Mac OS 9.x or previous, open the TCP/IP control panel. In the menus at the top of the screen there is an option to set the User Mode. Set your user mode to be either advanced or administrator. Click on the 'Info' button. Your MAC address should be listed in the window.

For Mac OS X or later, see instructions for Linux.


On a Linux machine:

Open a terminal window. Run the command

ifconfig -a

This should print out information about all of your network adapters. You may need to have root privileges to do this. If you do not have root access, try this:

arp -a | grep hostname

where hostname is the name of your computer.


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