About this video
A MAC address is a six-octet hardware identifier assigned to a network interface card and used to direct traffic across an Ethernet LAN. When a device builds and transmits a frame, it encodes the destination MAC address before the source MAC address, a sequencing choice that allows switches to begin forwarding the frame toward its destination as quickly as possible without waiting to process the full header. Because MAC addresses are physically represented in binary, they carry the ones and zeros native to digital hardware, but working with long binary strings is impractical for humans, so MAC addresses are expressed in hexadecimal form instead. Hexadecimal works in four-bit groups rather than full eight-bit bytes, giving 16 possible values per group represented by the characters 0 through 9 and A through F, making the address far more concise and readable than its binary equivalent. A MAC address is divided into two three-octet halves. The first half is the Organizationally Unique Identifier, or OUI, a value registered with an industry authority and assigned to a specific hardware manufacturer. The second half, known as the universally administered address, is assigned by the manufacturer to each individual device it produces. Because MAC addresses are burned into hardware and must be unique on any given network, the manufacturer is responsible for ensuring no two devices ship with the same address, and can request additional OUI blocks from the registering authority when existing address space is exhausted.
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