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. It is used as an address for most IEEE 802 network technologies, including Ethernet and Wi-Fi. It is embedded in the hardware of a device, which allows it to be uniquely identified on a network.
MAC addresses are most often assigned by the manufacturer of network interface controllers, using a globally-administered address range. The first octet of the MAC address is the priority code, which indicates the type of NIC. This allows network administrators to easily identify what type of device is connected to the network.
MAC addresses are increasingly being used for increasing network security. A host device can be identified by its MAC address, so access to a particular network can be restricted to certain MAC addresses. Likewise, the modem or router which controls access to the network can be set up to only allow devices with specific MAC addresses access to the network.
As the MAC address is embedded in the hardware of the NIC, it cannot be changed. This makes it a valuable security feature as it can be used to control access to the network and devices connected to it.
