Q: What's a MAC address and why do I need it?

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Answer

A MAC (Media Access Control) address is the unique hardware address of a network device such as an Ethernet card or a Wireless card. At MIT, the MAC address is registered and used to 'certify' users that want to use DHCP or Wireless on their computers. The MAC address information is kept in different locations depending on the operating system you are using. The address, sometimes called the physical or hardware address, is in the form of six pairs of digits separated by a colon or dash (e.g., 00:1A:22:3B:44:CD)

Macintosh OS X 10.6.x

1. Launch System Profiler found in the Utilities folder
2. Select the entry Network from the left column with the title Contents
3. Highlight the appropriate entry (typically Ethernet or Airport) from the listings in the right hand side of the pane
4. The MAC address will be found listed in the lower half of the window

Macintosh OS X 10.5.x

1. Open System Preferences (Apple menu > System Preferences).
2. Click Network.
3. In the left-hand panel, select a network device (for example Built-in Ethernet or AirPort).
4. In the right-hand panel of information for the device, click Advanced.
5. In the subsequent window:
   • For Ethernet, click the Ethernet tab; the Ethernet ID is the MAC address.
   • For AirPort, click the AirPort tab; the AirPort ID is the MAC address.

Macintosh OS X 10.4.x

1. Open System Preferences (Apple menu > System Preferences).
2. Click Network.
3. From the Show list, choose your network device.
4. Select the appropriate tab for the device:
   • For Ethernet, click the Ethernet tab; the Ethernet ID is the MAC address.
   • For AirPort, click the AirPort tab; the AirPort ID is the MAC address.

Windows XP/Vista/7

1. Select Start > Run.
2. Type cmd and click OK.
3. In the DOS window, type ipconfig /all (with a space between 'ipconfig' and '/all').
   Result: All your Ethernet devices should be listed, usually by vendor and some type of description. Your MAC address is listed as Physical Address.