In computer networking a Media Access Control address or MAC address is a identifier physically stored inside a network card or similar network interface and used to assign globally unique addresses in some OSI model Layer 2 networks. MAC addresses are assigned by the IEEE, and are used in many widely used network technologies, including (but not limiting to) the following:
Although MAC addresses are permanent by design, several mechanisms allow their modification. As an example, Internet gateway routers allow the network administrator to set the WAN interface MAC address, to fool ISPs that bind their service to a specific NIC. Also, running Linux, one can arbitrarily set the MAC address to fool software license keys tied to specific NICs using the command
ifconfig eth0 hw ether 00:01:02:03:04:05(This needs to be done before network initialization and is not permanent.)
See also: NSAP address for another endpoint addressing scheme.