What is the MAC address?

The MAC address (Media Access Control, also the Hardware Address) is a unique identifier assigned to each unit of computer network equipment. Not all protocols use MAC addresses, and not all protocols using MAC addresses need such uniqueness of these addresses.

Definition of manufacturer by MAC address

for example: d4:3d:7e:9e:10:18, 00-18-0a-72-bd-a0, 000e.edce.ff2b, d404ff5dedf0, 186472

In broadcast networks (such as Ethernet-based networks), the MAC address allows you to uniquely identify each network node and deliver data only to that node. Thus, MAC addresses form the basis of networks at the link layer, which is used by protocols of a higher (network) level. To convert MAC addresses to network layer addresses and back, special protocols are used

Addresses such as MAC-48 are the most common, they are used in technologies such as Ethernet, Token ring, FDDI, WiMAX, etc. They consist of 48 bits, thus the MAC-48 address space amounts to 248 (or 281,474,976,710,656) addresses. According to the IEEE estimates, this stock of addresses will last at least until 2100.

EEE standards define a 48-bit (6 octets) MAC address, which is divided into four parts. The first 3 octets contain a 24-bit unique organization identifier (OUI), or (MFG code - Manufacturing, manufacturer) that the manufacturer receives in the IEEE. Only the lower 22 bits are used, the 2 senior ones have a special purpose: the first bit indicates whether the frame is destined for a single (0) or group (1) destination. The next bit indicates whether the MAC address is global (0) or locally ( 1) Administered.

Thus, the globally administered MAC address of the device is globally unique and is usually "stitched" into hardware.

The network administrator has the option, instead of using "wired", to assign the MAC address to the device at his discretion. Such a locally administered MAC address is selected arbitrarily and may not contain information about the OUI. The sign of the locally administered address is the corresponding bit of the first octet of the address.

In order to learn the MAC address of a network device, the following commands are used:

  • Windows — ipconfig /all — describes in more detail which MAC address to which network interface belongs
  • Linux — ifconfig -a | grep HWaddr
  • FreeBSD — ifconfig | grep ether
  • HP-UX — /usr/sbin/lanscan
  • Mac OS X — ifconfig, or in System Preferences> Network> select connection> Advanced> Ethernet> Ethernet identifier
  • QNX4 — netinfo -l
  • QNX6 — ifconfig or nicinfo