MAC Address, short for Media Access Control Address is an identity code burnt in to a device, such as a network card (Ethernet card), when it is manufactured. A MAC address is a 48-bit defined number which uniquely identifies that card from all others in the world. This unique hardware address is represented by six octets, separated by colons, such as CO:3C:4E:00:10:8F. Layer 2 of the OSI reference model uses the MAC address to deliver the frames to the destination host.
A MAC address Addresses can either be "universally administered addresses" or "locally administered addresses."
A universally administered address is uniquely assigned to a device by its manufacturer. These are sometimes called "burned-in addresses." The first three octets (in transmission order) identify the organization that issued the identifier and are known as the Organizationally Unique Identifier (OUI). The following three octets are assigned by that organization in nearly any manner, subject to the constraint of uniqueness.
A locally administered address is assigned to a device by a network administrator, overriding the burned-in address.
