<P> A media access control address (MAC address) of a device is a unique identifier assigned to network interfaces for communications at the data link layer of a network segment . MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and Wi - Fi . Logically, MAC addresses are used in the media access control protocol sublayer of the OSI reference model . </P> <P> MAC addresses are most often assigned by the manufacturer of a network interface controller (NIC) and are stored in its hardware, such as the card's read - only memory or some other firmware mechanism . If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number and may be referred to as the burned - in address (BIA). It may also be known as an Ethernet hardware address (EHA), hardware address or physical address (not to be confused with a memory physical address). This can be contrasted to a programmed address, where the host device issues commands to the NIC to use an arbitrary address . </P> <P> A network node may have multiple NICs and each NIC must have a unique MAC address . Sophisticated network equipment such as a multilayer switch or router may require one or more permanently assigned MAC addresses . </P>

Who assigns the first six digits of the mac address