How do bridges and Layer 2 switches filter traffic?

Bridges and Layer 2 switches use the destination MAC address to filter traffic effectively. When a frame arrives at a bridge or switch, it reads the destination MAC address contained in the Ethernet frame header. This address indicates where the frame should be forwarded within the network.

The device then compares this destination MAC address against its MAC address table, which maintains a list of known devices within the network and their associated ports. If the destination MAC address corresponds to a device that is connected to a specific port, the switch or bridge forwards the frame only to that port. This targeted forwarding reduces unnecessary traffic on other ports and enhances network efficiency.

The ability to filter based on MAC addresses allows these devices to create a more efficient network by minimizing collisions and optimizing bandwidth usage, as only the intended recipient receives the frame instead of broadcasting it to all ports. This capability is fundamental to how LANs operate and is a key function of Layer 2 devices.