MAC address

A 'Media Access Control address' or MAC address is a 48-bit identifier used to assign addresses in some OSI Layer 2 networks. MAC addresses are assigned by the IEEE, and are used in the following network technologies:

• Ethernet
• Token Ring
• 802.11? wireless networks
• ATM (switched virtual connections only, as part of an NSAP address)

add more technologies here...

Since the original designers of Ethernet had the foresight to use a 48 bit address space, there are potentially 2⁴⁸ or 281 million million possible MAC addresses. The IEEE hands out 24-bit OUI prefixes to organizations, effectively allocating blocks of 2²⁴ (around 16 million) MAC addresses at a time.

See also: NSAP address for another endpoint addressing scheme.

External links:

• http://standards.ieee.org/regauth/oui/index.shtml