How does a switch react when it does not recognize a source MAC address in its bridge table?

When a switch encounters a source MAC address that is not yet in its bridge table, it takes the action of adding that MAC address to its bridge table. This occurs during the process of learning, where the switch examines the source MAC address of incoming frames on its ports. By learning and recording the MAC address, the switch can then more effectively forward future frames destined for that MAC address directly to the correct port, enhancing network efficiency.

This behavior is vital for maintaining the overall connectivity within a switched network, particularly in environments with dynamic traffic patterns. As devices come and go, or as they change their locations on the network, the switch adapts by updating its bridge table accordingly. This allows for a responsive network design that can efficiently direct packets to their intended destinations based on the source MAC addresses of the devices communicating on the network.