100-150 Question 188
Single answerA network administrator notices that devices connected to a switch are unable to communicate with each other, even though they are on the same VLAN. Upon investigation, the administrator realizes that the MAC address table is not being populated. Which switching concept is most likely causing this issue?
- A
The switch's port security feature is enabled, blocking traffic.
- B
The switch is operating on Layer 1, not Layer 2.
- C
The switch's spanning tree protocol (STP) is disabled.
- D
The switch has not learned the MAC addresses of connected devices.
Show answer and explanation
Correct answer: D
Explanation
The MAC address table is a critical component of a switch's operation at Layer 2. It maps MAC addresses to specific switch ports, enabling the switch to forward traffic efficiently. If the table is not being populated, the switch cannot correctly forward frames to connected devices, resulting in communication issues even within the same VLAN.
- A. Incorrect.
Port security can block traffic if a violation occurs, but it would not prevent the MAC address table from being populated. This is not the cause of the issue.
- B. Incorrect.
Switches operate at Layer 2 of the OSI model by default. A switch operating at Layer 1 would behave like a hub, which is not the situation here.
- C. Incorrect.
Disabling STP could lead to loop issues, but it does not directly impact the MAC address table population.
- D. Correct.
The MAC address table is essential for Layer 2 switching. If it is not populated, the switch cannot forward frames to the correct destination, causing communication failure.