In switching, address learning updates the MAC address table based on what?

• A. It maps destination MAC addresses to specific ports
• B. It maps IP addresses to MAC addresses
• C. It disables unknown devices
• D. It updates the MAC address table based on the source MAC and port from arriving frames

Answer: (D)

In switching, learning happens by listening to the frames as they arrive. The switch records the source MAC address of each frame and the port on which that frame came in, then stores that pairing in its MAC address table. This means the table maps a MAC address to the specific port where the device is reachable. As more frames arrive, the switch updates or confirms these mappings so it can forward future frames directly to the correct port.

This approach is what lets the switch efficiently forward traffic: when a frame with a known destination MAC arrives, the switch uses the table to send it out only the port connected to that destination. Mapping destination MACs to ports is a consequence of the learned entries, but the learning trigger itself is based on the source MAC and the incoming port. IP-to-MAC mapping belongs to ARP and is a Layer 3 function, not how a switch learns its MAC table. Disabling unknown devices isn’t part of this learning process.