CertiGuide to A+ (A+ 4 Real)  9  Chapter 13: Basic Networking Terminology       9  OSI Reference Model and Networking Protocols and Technologies            9  Layer 2 - Data Link Layer

Router 1 NIC

The MAC address is the layer 2 address that helps each computer identifies itself in a network. This address is built by the manufacturer and is installed in a microcircuit of the NIC. Each address is unique. The given address consists of 48 bits and is expressed in hexadecimal. IEEE (Institute of Electrical and Electronic Engineers) allocates the first 3 bytes for the manufacturer; then the manufacturer specifies the last three. This system ensures that a MAC address is unique. MAC addresses have one major disadvantage; they are unstructured and are considered flat address spaces¹⁸²

Router 1 NIC