The address for a machine as it is identified at the Media Access Control (MAC) layer in the network structure. MAC address is generally stored in ROM on the network adapter card and is distinct. A Media Access Control address (MAC address) is a unique identifier given to network interfaces for communications on the physical layer segment. MAC addresses are needed for numerous network technologies and most IEEE 802 network methodologies, adding Ethernet. MAC addresses are needed in the Media Access Control protocol sub-layer of the OSI architecture.