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What is a MAC Address?

written by: •edited by: Michael Dougherty•updated: 2/24/2010

A MAC address is an address that resides inside of a network device. It can be interesting to know what a MAC address does, how it is set up, and whether it is possible to change it. Read on to find out more about MAC addresses on your Mac.

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    MAC Address - Intro

    When we hear the term "MAC address", Mac (Macintosh) computers come to mind and it sounds like as if this is an address that is exclusively associated with a Mac computer.

    The fact is that a MAC address could relate to any computer whether it be a PC or Mac. Short for Media Access Control, also known as physical address or Ethernet address, the MAC address is an address that resides on a data link layer. The Data link layer is the second layer of the seven-layer OSI model of computer networking. Hubs, switches, Ethernet and network adapters operate at the data link layer. Each hardware device that works at the data link layer gets a unique address written into it at the time when the device is manufactured. The process of writing the address into hardware is also known as MAC addresses burning.

    The reason for burning an address into hardware is to ensure the device has a default address, which will help the device to operate without needing the user to do additional programming of an address.

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    What Does The MAC Address Do?

    The job of a MAC address is to help a node on a network get access to data and also helps to transmit the data as well. The same way network devices get IP addresses to communicate among each other, the devices also get a MAC address so that they can use it to pass data packets between devices on a network.

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    How is a MAC Address Set Up?

    A MAC address is 48 bits long. Being 48 bits long means there can be over 280 trillion MAC addresses. The large number of addresses ensures there will be no duplicates for many years to come.

    Take an example of this MAC Address: 03-0A-F1-45-69-AF. The first three bytes of the address (03-0A-F1) identifies the manufacturer. The rest of three bytes are assigned by the device manufacturer and these are always unique.

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    Is It possible To Change A MAC Address?

    Though MAC addresses are meant to remain unchanged forever, there are software packages available that can change an address in seconds. The software will determine and show the next logical configuration for the hardware and replace it with the original address upon user’s approval.

    Click here to find out the method to change a Mac address using different operating systems.

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    How To Find Your MAC Address

    To find out the MAC address of network devices installed on your Macintosh, follow these steps:

    1. Open the Apple menu and select System Preferences then click on Network.

    2. Depending on how you connect to Internet or local area network, double-click either on “AirPort" or “Built-in Ethernet".

    3. For Ethernet, click on “Advanced", and then select Ethernet (from the tabs). At the top, the MAC address of your Ethernet adapter will be shown.

    4. For AirPort, click on Advanced and your MAC address will be shown at the bottom of the page.

    You can also find MAC address by going to TCP/IP Control Panel. If your computer is running Open Transport, your MAC address will be shown under the “User Mode/Advanced" or “Info" screens. If the computer is running MacTCP, the MAC address is displayed under the Ethernet icon.