MACaadresse

MAC address, short for Media Access Control address, is a unique identifier assigned to network interfaces for communications at the data-link layer of a network. It is typically embedded in hardware, such as the ROM or firmware of a network interface card, and is intended to be globally unique to the manufacturer and device. MAC addresses are used on local networks to deliver frames and are generally not routable beyond the local link. When data traverses multiple hops, each link segment uses its own MAC addressing.

A MAC address is 48 bits (6 octets) and is commonly formatted as six hexadecimal numbers separated by colons or hyphens, for example 00:1A:2B:3C:4D:5E. The first three octets form the Organizationally Unique Identifier (OUI), assigned by IEEE to a manufacturer; the last three identify the specific device. The first octet contains two special bits: the least significant bit indicates multicast (1) or unicast (0); the second least significant bit indicates locally administered (1) or globally unique (0).

In operation, devices may use a specific MAC address or may randomly generate one for privacy. Some users can spoof a MAC address in software. On IPv4 networks, ARP translates IP addresses to MAC addresses on the local link; IPv6 uses Neighbor Discovery for similar mappings. Because MAC addresses operate on the local network segment, they do not convey identifying information across the Internet.