On which OSI layer is the MAC address defined?

• A. Data Link Layer (Layer 2)
• B. Physical Layer (Layer 1)
• C. Network Layer (Layer 3)
• D. Transport Layer (Layer 4)

Answer: (A)

MAC addresses are defined at the Data Link Layer (Layer 2) because they identify devices on the local network segment and are used to deliver frames between network interfaces. When a frame traverses a local link, its header contains the destination and source MAC addresses, and switches use these addresses to forward frames and build forwarding tables. The physical layer handles the actual signaling on the medium, not addressing. The network layer handles routing and IP addresses across networks, which can change as packets move between segments. The transport layer deals with end-to-end communication and uses ports, not hardware addresses. So, the MAC address is a Layer 2 concept.