What happens when a switch receives an Ethernet frame with an unknown source MAC address and a destination MAC address of ff:ff:ff:ff:ff:ff?

When a switch receives an Ethernet frame with an unknown source MAC address and a destination MAC address of ff:ff:ff:ff:ff:ff, it identifies the frame as a broadcast since ff:ff:ff:ff:ff:ff is the broadcast MAC address that indicates all devices on the network.

In this scenario, the switch performs two key actions. First, it saves the source MAC address into its MAC Forwarding Database (FDB). This allows the switch to learn about that device's presence on the specific port, which is essential for future communications. By learning the source MAC address, the switch enhances its ability to make forwarding decisions for future frames destined for that MAC address.

Second, because the destination is a broadcast MAC address, the switch will flood the frame to all other ports except the one on which the frame was received. This flooding allows any device connected to the network to see the broadcast message, ensuring that all potential recipients have the chance to respond if they are intended to receive the information carried in the frame.

Thus, both actions are crucial for maintaining efficient communication within the network and allowing devices to dynamically learn where to send frames directed to each other.