What is a MAC Address?⌗

A media access control (MAC) address is a unique identification number assigned to every network interface controller (NIC).

MAC addresses are assigned by the device manufacturer and are burned-in to the NIC.

MAC Addresses are also called

  • Burned-in address: as the address is burned into the Read-only Memory (ROM) of the NIC,
  • Physical address: The MAC address is the unique hardware address of every NIC,
  • Hardware address
  • Ethernet hardware address

Structure of MAC Address⌗

A MAC address is a 48-bit address. It has 6 groups of 2 hexadecimal digits.

MAC Address format

The 6 octets are separated by colons (:), hyphens (-), or left without a separator.

Organizationally Unique Identifier⌗

The first 3 octets of a MAC address represent the manufacturer of the NIC.

The OUI are assigned by the IEEE Registration Authority.

For example,

OUIOrganization
AC:ED:5CIntel Corporate
CC:46:D6Cisco Systems, Inc
F8:8F:CAGoogle, Inc.
C4:2A:D0Apple, Inc.

Manufacturers usually have multiple OUIs. The full list of OUIs is here.

Some virtualisation softwares have their own OUIs, such as VMware (00:50:56), QEMU (52:54:00), etc.

Network Interface Controller⌗

The NIC is the hardware component that connects a device to the network, such an adapter or card.

The last 3 octets of the MAC address identify the NIC.