The Ethernet (or "MAC" or "hardware") address of a computer is set of six hexadecimal numbers strung together with colons that is unique to a single, particular, computer. It will only contain numbers (0-9) and the letters A-F. An ethernet address will look something like this:

It is the identifying mark that lets a networked computer communicate with the internet. The ethernet address is how we can associate an "IP address" to an individual computer. The IP address is necessary for communication on the internet.

Almost all laptops and some desktop computers have more than one network devices (Modems, Wireless adaptors, firewire adaptors, and the "normal one"), all of which have Hardware addresses. Please be sure to send the correct one. Without sending us the right ethernet adaptor address, the computer won't be able to connect to the network.

Modems nearly always id themselves as: 44:45:53:54:00:00. This is not the ethernet address. It's the modems's address. If you see 44:45:53:54:00:00, please keep looking.

So how do you find the Ethernet address?

• Windows XP, 2000, or NT
  1. From the start menu, go to the "Run" option. Type "cmd" in the text box and then click "Okay".
  2. In the window that pops up, type "ipconfig /all" and hit Enter.
  3. In the information that results, look for "Physical Address....:". The numbers on that line will be the Ethernet address.
• Macintosh Computers
  Mac OS X
  1. Go to System Preferences under the Apple Menu or click the light switch icon in the dock.
  2. Once the System Preferences are up, click on the Network icon.
  3. Make sure the "Show" dropdown menu is set to "Built-in Ethernet".
  4. The Ethernet Address will be listed in the lower left of the window
  Classic MacOS
  1. Go to the TCP/IP control panel under the Apple Menu.
  2. Make sure the "Connect via" dropdown menu is set to "Ethernet".
  3. Look for an "Info" button in the lower left. If you don't see one, go to "User Mode" under the Edit menu and switch from "Basic" to "advanced". Click okay, and then look for the "Info" button again.
  4. Click the "Info" button in the lower left. The "Hardware Address" will be displayed in a popup window.

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Last updated: Sep 15, 2005 (05:12:15 PM EDT)
URL: http://www.clasnet.ufl.edu/computers/ethernet.shtml