Organisationally Unique Identifier
The Organisationally Unique Identifier, or OUI is an IEEE-assigned organisation identifier that resides in the first six bytes of each MAC address. The first bit of the most significant byte (MSB) of an OUI specifies whether the frame being sent is a unicast address or a group address. If this bit is set to binary 0, then it is a unicast address, while if it is a binary 1 then the address is either a broadcast, multicast or functional address. The second bit of the MSB of an OUI identifies whether the second half of the frame's MAC address (or BIA) is the one originally assigned by the makers of the network interface card (NIC) or whether is a Locally Administered Address (LAA), which is an overriding address configured by the NIC's administrator.
External links
IEEE OUI and Company_id assignments
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