How does a switch learn the MAC addresses of devices on its network?

A switch learns the MAC addresses of devices on its network by monitoring the source MAC addresses of incoming frames. When a device sends data over the network, it includes its own MAC address in the source field of the Ethernet frame. As the switch receives these frames, it inspects the source MAC address and records this information in its MAC address table along with the port through which the frame was received.

This process allows the switch to build a mapping of MAC addresses to specific ports over time, facilitating more efficient data transmission. When the switch needs to forward a frame to a specific device, it can look up the MAC address in its table rather than sending the frame to all ports (broadcasting), thus optimizing network performance and reducing unnecessary traffic.

Transmitting broadcast messages, examining the destination MAC addresses of outgoing frames, and inspecting IP headers of packets do not contribute directly to the switch's ability to learn and map MAC addresses to specific ports in the same way as monitoring incoming frames does.