MAC Address

Media Access Control Address

A media access control address (MAC address) of a device is a unique identifier assigned to a network interface controller (NIC) for communications at the data link layer of a network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and Wi-Fi. In this context, MAC addresses are used in the medium access control protocol sublayer.

A MAC may be referred to as the burned-in address (BIA). It may also be known as an Ethernet hardware address (EHA), hardware address or physical address (not to be confused with a memory physical address).

A network node may have multiple NICs and each NIC must have a unique MAC address. Sophisticated network equipment such as a multilayer switch or router may require one or more permanently assigned MAC addresses.

MAC addresses are most often assigned by the manufacturer of a NIC and are stored in its hardware, such as the card's read-only memory or some other firmware mechanism. A MAC address may include the manufacturer's organizationally unique identifier (OUI). MAC addresses are formed according to the rules of one of three numbering name spaces managed by the Institute of Electrical and Electronics Engineers (IEEE): MAC-48, EUI-48, and EUI-64.[1][2] EUI is an abbreviation for Extended Unique Identifier.