MAC addresses

A Media Access Control (MAC) address is a physical address in contrast to, say, an IP address which is logical.

Each device on a local network has a MAC as a unique identifier. It is a hardware-based, physical attribute of the device, typically permanently encoded onto a non-volatile memory chip attached to the network_card.

MAC addresses consist of 6 bytes (48-bits) represented as 12 hexadecimal_digits.