A Media Access Control address or MAC address is a unique code assigned to every piece of hardware that connects to the Internet. Internet capable phones, Network Interface Cards for desktop or notebook computers, Wireless Access Cards, and even some memory cards are among the devices that are assigned MAC addresses.

When a manufacturer creates a network capable piece of hardware they will assign the MAC address which will usually begin with a code that is tied to the manufacturer. The MAC address will be unique to every device, even two devices of the same type.

A device’s MAC address is composed of six pairs of hexadecimal numbers. The numbers are separated by colons as in the following example:

6E:51:F5:c1:11:00

MAC addresses are used at the data link layer of the OSI hardware model to allow packets to be passed directly between devices on a network. This helps to ensure that the data is sent to a physical device before being decoded and/or manipulated by a device.

A MAC address is similar to an IP address that the device also receives in that it ensures each device is unique and allows data to be passed among hardware devices. An IP address allows two devices to communicate across a LAN or network environment — normally IP addresses should also be unique and will allow the exchange of data.

Once assigned, the MAC address is used to ensure that each device connected to the LAN or other network is unique. With the recent advances in wireless networking technology, the MAC address from a wireless card can be entered into the configuration pages for a network’s wireless router. From there the router can either allow or deny the device to connect based on its MAC address. This can provide additional security for the network.

Many people who use network connected devices will not ever need the MAC address to use the device. Some service providers will require the MAC address of a device to be registered with them to ensure those who are paying for or are subscribed to the service are the only users who can connect. If this is the case, the MAC address can typically be found on a sticker on the device. If the device is portable, the MAC address may be printed inside the battery compartment.