MAC addresses
Every network adapter has a Media Access Control address (usually shortened to MAC address). A MAC address is a six-byte identifying number permanently embedded in the firmware of the adapter, and is readable by the network and the operating system of the device on which the adapter is installed. All modems and Ethernet cards have a MAC address. The address must follow the standards set by the Institute of Electrical and Electronics Engineers (IEEE), which sets computer networking standards. The IPv4 address is a six-pair set of hexadecimal numbers, for example, a1-c2-e3-44-5f-6d.
The purpose of the MAC address is to uniquely identify every node on a network; nodes include workstations and devices like printers. Every adapter has a unique MAC address. Even two identical models from the same manufacturer will have distinct MAC addresses.
The IPv6 protocol uses the MAC address of a network node to generate its IPv6 IP address. This is accomplished by expanding the 48-bit MAC address into a 64-bit portion of an 128-bit IPv6 IP address. This represents a change from the practice of IPv4, where the MAC address was entirely distinct from the IP address.
Note: Some literature calls the MAC address the physical address, the hardware address, or the adapter address for various reasons. While that's not wrong or inaccurate, the proper way to refer to that address is to call it the MAC address.
