Media Access Control (MAC)

Definition: Media Access Control (MAC) technology provides unique identification and access control for computers on an Internet Protocol (IP) network. In wireless networking, MAC is the radio control protocol on the wireless network adapter. Media Access Control works at the lower sublayer of the data link layer (Layer 2) of the OSI model.

MAC Addresses

Media Access Control assigns a unique number to each IP network adapter called the MAC address. A MAC address is 48 bits long. The MAC address is commonly written as a sequence of 12 hexadecimal digits as follows:

48-3F-0A-91-00-BC

MAC addresses are uniquely set by the network adapter manufacturer and are sometimes called physical addresses. The first six hexadecimal digits of the address correspond to a manufacturer's unique identifier, while the last six digits correspond to the device's serial number. MAC addresses map to logical IP addresses through the Address Resolution Protocol (ARP).

Some Internet service providers track the MAC address of a home router for security purposes. Many routers support a process called cloning that allows the MAC address to be simulated so that it matches one the service provider is expecting. This allows households to change their router (and their real MAC address) without having to notify the provider.