Overview#Media Access Control Address (MAC Address), also called a physical address, of a computer which is a Unique Identifier assigned to network interfaces for communications on the physical network segment.
Media Access Control Addresses are used as a network address for most IEEE 802 Network Technologies, including Ethernet and Wi-Fi. Logically, MAC Addresses are used in the Media Access Control sublayer of the OSI-Model.
Media Access Control Addresses are most often assigned by the manufacturer of a Network Interface Controller (NIC) and are stored in its hardware, such as the card's read-only memory or some other firmware mechanism. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number and may be referred to as the burned-in address (BIA).
Media Access Control Address may also be known as an Ethernet hardware address (EHA), hardware address or physical address. This can be contrasted to a programmed address, where the host device issues commands to the NIC to use an arbitrary address.
A network node may have multiple NICs and each NIC must have a unique MAC address.
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. The IEEE claims trademarks on the names EUI-48 and EUI-64, in which EUI is an abbreviation for Extended Unique Identifier.