Media Access Control Address (MAC address)

A Media Access Control Address (MAC address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. As typically represented, MAC addresses are recognizable as six groups of two hexadecimal digits, separated by hyphens, colons, or without a separator. MAC addresses are primarily assigned by device manufacturers and are therefore often referred to as the burned-in address, or as an Ethernet hardware address, hardware address, or physical address. Each address can be stored in hardware, such as the card's Read-Only Memory (ROM), or by a firmware mechanism. Network nodes with multiple network interfaces, such as routers and multilayer switches, must have a unique MAC address for each NIC in the same network. However, two NICs connected to two different networks can share the same MAC address.