Final answer:
A switch decides to forward a frame destined for a known unicast MAC address by examining the destination MAC address in the frame's header and checking its forwarding table. If the MAC address is found, the switch forwards the frame to the corresponding port. If not, it broadcasts the frame to all ports.
Step-by-step explanation:
When a switch receives a frame, it examines the destination MAC address in the frame's header. If the MAC address is in the switch's forwarding table, the switch forwards the frame to the corresponding port.
A forwarding table is created through a process called MAC learning. As the switch receives frames, it learns the MAC addresses and associates them with the corresponding ports. If a destination MAC address is not found in the forwarding table, the switch broadcasts the frame to all ports except the one it was received on, in case the destination device is connected to one of those ports.
The switch determines whether a MAC address is a unicast (a specific device) or broadcast (all devices) address by examining the least significant bit of the MAC address. If the bit is set to 0, it's a unicast address and the switch uses the forwarding process described above. If the bit is set to 1, it's a broadcast address and the switch broadcasts the frame to all ports.