MAC OUI
The OUI (Organizationally Unique Identifier) is the first three bytes (24 bits) of a network interface's MAC address, assigned by the IEEE Registration Authority to the manufacturer that requested it. Because every Ethernet or Wi-Fi interface ships with a vendor-assigned MAC address, looking up its OUI against the IEEE's public registry often reveals the maker of a device, useful for spotting an unexpected device type on a network even without a hostname. The OUI's second-least-significant bit also marks whether an address is "locally administered" rather than factory-assigned, which is how randomized or privacy-focused MAC addresses, such as those modern phones use per network, can be distinguished from a real vendor-issued address.
By AdminKit team, Netbase JSC · Updated