Every network card in a computer comes with its own built-in MAC address.
Every network card comes with a built-in address called a Media Access Control (MAC) address that can be used to identify it uniquely on a network. This address is used in most major networking protocols, including the common 802.11 Wi-Fi protocol and the wired Ethernet. It is also useful for security purposes, though not foolproof, since MAC addresses can be spoofed. You can find the MAC address on your Macintosh computer by looking in the Network System Preferences.
Instructions
Mac OS X Leopard
1. Click the "System Preferences" icon on your Dock. If you have removed it from your Dock, click the Spotlight icon (the magnifying glass) and type "System Preferences."
2. Click "Network."
3. Select your location and the network adapter you wish to view. For "wired" Internet, you will normally choose "Ethernet." For wireless, you will normally choose "Airport."
Mac OS X Snow Leopard
4. Click "System Preferences" > "Network."
5. Select your network adapter from the list.
6. Click "Advanced." Under the "Airport" tab, you will see the MAC address for your wireless internet. Under the "Ethernet" tab, you will see the MAC address for your wired Internet.
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