200-301 Question 163
Select 3A network administrator is troubleshooting a switch in a LAN environment. They notice that a device connected to the switch is not reachable. Upon investigating, they find that the MAC address of the device is not present in the switch's MAC address table. Which of the following actions should the administrator take to resolve the issue?
- A
Verify that the device is powered on and connected to the correct switch port.
- B
Check for any VLAN mismatch on the switch port connected to the device.
- C
Manually add the MAC address of the device to the switch's MAC address table.
- D
Ensure that the switchport is configured as a trunk port.
- E
Inspect the switchport for any errors, such as being in an err-disabled state.
Show answer and explanation
Correct answers: A, B, E
Explanation
When a MAC address is missing from the switch's MAC address table, it indicates that the switch has not received any frames from the device. Common reasons include the device being powered off or disconnected, a VLAN mismatch causing dropped frames, or the switchport being in an error state. By verifying the device's connectivity, VLAN configuration, and switchport status, the administrator can identify and resolve the issue.
- A. Correct.
Correct. If the device is not powered on or connected, it will not send any frames, and the switch cannot learn its MAC address.
- B. Correct.
Correct. A VLAN mismatch could cause the switch to drop frames from the device, preventing the MAC address from being learned.
- C. Incorrect.
Incorrect. The MAC address table is dynamically populated by the switch; manually adding MAC addresses is not a standard troubleshooting step.
- D. Incorrect.
Incorrect. Configuring the switchport as a trunk port is irrelevant in this scenario unless the device is expected to handle VLAN tagging (e.g., a router or another switch).
- E. Correct.
Correct. If the switchport is in an err-disabled state, it will not forward traffic, and the MAC address of the device cannot be learned.