Which Layer 2 device uses MAC address learning to forward frames to the correct port?

Which Layer 2 device uses MAC address learning to forward frames to the correct port?

• A. Switch
• B. Bridge
• C. Hub
• D. Router

Answer: (A)

MAC address learning is how a switch makes fast, accurate forwarding decisions at Layer 2. A switch watches the source MAC address of every frame that arrives on each port and records which port that MAC came from in a MAC address table. With this map, the switch can send future frames directly to the port that leads to the destination device, rather than blasting the frame to every port. If a frame’s destination MAC is known, the switch forwards it only to the corresponding port, which reduces unnecessary traffic and speeds up communication. If the destination MAC isn’t in the table yet, the switch floods the frame to all ports in the same broadcast domain so the destination can respond and the switch can learn where it lives. A hub simply repeats every incoming signal to all ports, so every device receives all frames. A router operates at the network layer and makes decisions based on IP addresses, not MAC addresses. A bridge can also learn MAC addresses, but in modern networks the device most associated with efficient Layer 2 forwarding via MAC learning is the switch.

MAC address learning is how a switch makes fast, accurate forwarding decisions at Layer 2. A switch watches the source MAC address of every frame that arrives on each port and records which port that MAC came from in a MAC address table. With this map, the switch can send future frames directly to the port that leads to the destination device, rather than blasting the frame to every port.

If a frame’s destination MAC is known, the switch forwards it only to the corresponding port, which reduces unnecessary traffic and speeds up communication. If the destination MAC isn’t in the table yet, the switch floods the frame to all ports in the same broadcast domain so the destination can respond and the switch can learn where it lives.

A hub simply repeats every incoming signal to all ports, so every device receives all frames. A router operates at the network layer and makes decisions based on IP addresses, not MAC addresses. A bridge can also learn MAC addresses, but in modern networks the device most associated with efficient Layer 2 forwarding via MAC learning is the switch.