(Media Access Control address) The unique 48-bit serial number in the network circuitry of Ethernet and Wi-Fi devices that identifies that machine from every other globally. Also used in earlier Token Ring networks, the ID is assigned to vendors by the IEEE and "burned into" most network adapters (NICs) at the time of manufacture. However, some NICs are programmable, and the possibility of having the same MAC address is theoretically therefore not impossible. See MAC layer, OUI and binary values.
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