How does MAC address learning operate?

MAC address learning is a fundamental function of Ethernet switches, enabled by default on all VLANs and interfaces. When a switch receives a frame, it inspects the source MAC address and records it, along with the ingress port, in its MAC address table. This allows the switch to efficiently forward future frames destined for that MAC address out the correct port. If a MAC address is already in the table but is seen on a different port, the entry is updated, overwriting the old entry. This process is crucial for basic network operation, not primarily for DoS protection or forwarding via CDP.