200-301 Question 198
Single answerA network administrator is troubleshooting an issue where traffic from a trunk link is reaching the wrong VLAN. Upon investigation, it is identified that untagged traffic is being sent across the trunk link. What is the most likely cause of this issue?
- A
The native VLAN is mismatched on the two ends of the trunk link.
- B
The trunk link is not configured to allow any VLANs.
- C
The switchport on one side of the trunk is in access mode.
- D
The spanning-tree protocol is blocking the trunk port.
Show answer and explanation
Correct answer: A
Explanation
In a trunk link, untagged traffic is assigned to the native VLAN. If the native VLAN is mismatched on the two ends of the trunk link, the untagged traffic will be mapped to different VLANs on each side, causing the traffic to end up in an incorrect VLAN. Ensuring that the native VLAN is the same on both ends of the trunk resolves this issue.
- A. Correct.
If the native VLAN is mismatched on the two ends of the trunk link, untagged traffic will be mapped to different VLANs on each side, leading to traffic being sent to the wrong VLAN.
- B. Incorrect.
If the trunk link is not configured to allow any VLANs, no traffic would pass through the trunk, not just untagged traffic.
- C. Incorrect.
If the switchport on one side of the trunk is in access mode, the trunk link would not function at all, as one side would not be operating as a trunk.
- D. Incorrect.
The spanning-tree protocol blocking the trunk port would prevent all traffic from flowing through the port, not just untagged traffic.