MACadres

MACadres is the term used in some languages to denote the MAC address, the unique hardware identifier assigned to a network interface controller (NIC). It is used to address devices at the data link layer (layer 2) of the OSI model and enables switches to forward frames within a local network.

Format and structure: Most MACadres are 48 bits long, displayed as six hexadecimal octets, for example 01:23:45:67:89:ab. The first three octets form the Organizationally Unique Identifier (OUI), assigned to the manufacturer, while the remaining three identify the specific NIC. The address is commonly written with colons or hyphens, and may appear in uppercase or lowercase depending on convention.

Two special bits in the first octet govern scope and administration: the least significant bit indicates multicast (I/G), and the second least significant bit indicates whether the address is locally administered (U/L) or globally unique. If the locally administered bit is set, the address may be changed by network administrators or software.

Management and usage: MACadres are typically burned into hardware at manufacture, but many systems allow software-based changes (MAC spoofing). In IPv4 networks, devices use ARP to map IP addresses to MACadres. In IPv6, interface identifiers can be derived from the MAC (EUI-64), though privacy practices often employ temporary random identifiers.

Privacy and security: Constant MACadres can be used to track devices across networks. To mitigate this, modern devices may randomize MACadres for certain operations, such as Wi‑Fi probe requests, and administrators may configure controls to limit tracking.

Standards and scope: IEEE 802 standards define MAC addressing for Ethernet (802.3) and wireless LAN (802.11). Related concepts include MACsec (IEEE 802.1AE), which provides data integrity and confidentiality at the MAC layer.