In networking a Media Access Control address (MAC address) is a unique identifier attached to most network adapters. It is a number that acts like a name for a particular network adapter or node. Each node on the network must have its own unique identifier or MAC address.  MAC addresses are sourced from the IEEE organization. There are two types that can be purchased including Organizational Unique Identifiers and Individual Address Blocks.  Each requires an on-line application that can be downloaded from standards.ieee.org. The OUI address blocks are for large volume requirements. IAB address blocks, on the other hand: are for people who need less than 4,096 unique 48-bit numbers and thus find it hard to justify buying their own OUI. Customers can purchase an Individual Address Block which will give them a block of 4,096 MAC addresses.