MAC Address

The Media Access Control (MAC) Address is a unique value that serves as an identifier of network adapters (Network Interface Card). A MAC address exists on Layer 2 of the Open Systems Interconnection (OSI) model. It uniquely recognizes an adapter on a Local Area Network (LAN) or Metropolitan Area Network (MAN).

The OSI model is a reference model used to describe the layered communications design and network applications. The Layer 2, out of the 7 layers of the OSI model, is the Data Link Layer. It consists of two sub-layers: the Logical Link Control (LCC) and the MAC layer. The MAC sublayer controls how a network node gets an access to the data and the approval to send the data. Together, they enable computers to distinctively recognize themselves on a network at this comparatively low level.

A MAC address is also known as physical addresser hardware address. At the time of manufacture of the hardware, a MAC address with a globally unique value is written into the hardware. Because of this, a MAC address is at times called Burned-In Address (BIA). In many cases, it is possible to change the MAC address of a device once the software is manufactured.

A MAC address is composed of 12-digit numbers (48 bits in length). The first half of a MAC address represents the adapter manufacturer’s ID number regulated by an Internet standard body. The other half contains the serial number assigned by the manufacturer to the adapter. There are more than 281 trillion possible MAC addresses.

MAC addresses are used by several Layer 2 technologies such as Ethernet, Bluetooth, Fibre Channel, ATM, 802.11, Token Ring, SCSI, and FDDI. MAC addresses originated in the Ethernet specification. This is why MAC addresses are also referred to as Ethernet addresses.

In computer networking, a MAC address is every bit as important as an IP address. While MAC addresses function on the Data Link layer (Layer 2), IP addresses work on the Network Layer (Layer 3). The Network Layer controls the paths for data transfer through the network.

MAC addresses support hardware implementation of the network stack. IP addresses support the software implementation. MAC addresses follow the network device and typically remain fixed. IP addresses change as the network device moves from one network to another.