What addressing information is recorded by a switch to build its MAC address table?

What addressing information is recorded by a switch to build its MAC address table?

• A. The source Layer 2 address of incoming frames
• B. The destination Layer 2 address of outgoing frames
• C. The IP address of the sender
• D. The VLAN ID of the frame

Answer: (A)

Switches build their MAC address table by learning from the source address of frames as they arrive on each port. When a frame comes into a port, the switch records the sender’s Layer 2 (MAC) address and the port it came from. This creates the mapping that the switch uses to forward future frames: if the destination MAC is known, the frame is sent only to the port associated with that MAC. The destination MAC address is used to forward the frame, not to build the table. IP addresses operate at a higher layer (Layer 3) and aren’t used to populate the MAC table. The VLAN ID affects traffic separation but doesn’t provide the addressing information used to populate the MAC table.

Switches build their MAC address table by learning from the source address of frames as they arrive on each port. When a frame comes into a port, the switch records the sender’s Layer 2 (MAC) address and the port it came from. This creates the mapping that the switch uses to forward future frames: if the destination MAC is known, the frame is sent only to the port associated with that MAC.

The destination MAC address is used to forward the frame, not to build the table. IP addresses operate at a higher layer (Layer 3) and aren’t used to populate the MAC table. The VLAN ID affects traffic separation but doesn’t provide the addressing information used to populate the MAC table.