200-301 Question 162
Single answerA network administrator observes that a switch is not forwarding traffic to a specific device in the network. Upon inspecting the MAC address table, the administrator notices the MAC address of the device is not listed. What action will the switch take when it receives a frame destined for this MAC address?
- A
The switch will drop the frame.
- B
The switch will flood the frame out of all ports except the one it was received on.
- C
The switch will forward the frame to the default gateway.
- D
The switch will send an ARP request to learn the MAC address.
Show answer and explanation
Correct answer: B
Explanation
When a switch receives a frame destined for a MAC address not present in its MAC address table, it uses a process called flooding. Flooding involves sending the frame out of all ports, except the port it was received on, in an attempt to locate the destination device. This ensures that the frame has the best chance of reaching its intended recipient even when the MAC address is unknown.
- A. Incorrect.
Incorrect: If the MAC address is not in the table, the frame is not dropped. The switch attempts to deliver the frame.
- B. Correct.
Correct: When a MAC address is unknown, the switch floods the frame out of all ports except the one it was received on. This is the default behavior to ensure the frame reaches its destination.
- C. Incorrect.
Incorrect: The switch does not forward unknown frames directly to the default gateway. This would only occur if there is specific routing logic in place.
- D. Incorrect.
Incorrect: Switches do not send ARP requests to learn MAC addresses. ARP requests are generated by hosts, not switches.