In MAC address 00-20-60-CE-2B-28, which part is the Organisationally Unique Identifier (OUI)?

A MAC address (Media Access Control address) is a 48-bit identifier typically expressed in six groups

of two hexadecimal digits (e.g., 00-20-60-CE-2B-28). It consists of two key parts:

OUI (Organizationally Unique Identifier) – The first 24 bits (or first 3 octets, e.g., 00-20-60) are

assigned by the IEEE to hardware manufacturers. This identifies the vendor or manufacturer.

Device Identifier (NIC Specific) – The remaining 24 bits (e.g., CE-2B-28) are assigned uniquely by the

vendor to each device/interface.

So in the address 00-20-60-CE-2B-28:

00-20-60 is the OUI

CE-2B-28 is the device-specific portion

Thus, the correct answer is D. 00-20-60.

Reference:

IEEE MAC Address Standard (IEEE 802)

Nokia IP Networking Fundamentals Study Guide – Chapter: "Ethernet Addressing"