Also used in earlier Token Ring networks, the ID is assigned to vendors by the IEEE and 'burned into' the network circuit at the time of manufacture. The MAC address, which holds 256 trillion unique numbers, identifies that device from every other globally. This article is provided by FOLDOC - Free Online Dictionary of Computing ( ) MAC address( Media Access Control address) The unique 48-bit serial number in the network circuitry of every Ethernet and Wi-Fi device.