A 24-bit identifier uniquely identifying a vendor or organization is known as?

• A. OUI
• B. IP Address
• C. MAC Address
• D. Domain Name

Answer: (A)

The Organizationally Unique Identifier is a 24-bit identifier assigned to a vendor by IEEE. It identifies the manufacturer in hardware addresses, and in a MAC address the first three octets (the 24-bit portion) encode this OUI, linking the address to the specific vendor. The remaining three octets identify a particular NIC from that vendor, making the whole MAC address unique to that device.

An IP address is 32 bits and identifies a device on an IP network, not a vendor. A MAC address is 48 bits total, consisting of the OUI plus a NIC-specific portion, but the 24-bit term that designates the vendor itself is the OUI. A domain name is a human-readable label used in DNS, not a numeric hardware identifier.