200-301 Question 193
Single answerA network engineer is configuring a trunk link between two switches (Switch A and Switch B). After completing the configuration, only VLAN 10 traffic is successfully flowing across the trunk, while traffic from other VLANs is being dropped. Which of the following is the most likely cause of the issue?
- A
The native VLANs on Switch A and Switch B are mismatched.
- B
The trunk port on Switch A is configured to allow only VLAN 10.
- C
The trunk port on Switch B is set to access mode.
- D
The spanning-tree protocol is blocking VLANs other than VLAN 10.
Show answer and explanation
Correct answer: B
Explanation
The most likely cause of the issue is that the trunk port on Switch A is configured to allow only VLAN 10. By default, a trunk port carries traffic for all VLANs unless it is explicitly configured to allow specific VLANs using the 'switchport trunk allowed vlan' command. In this case, the configuration restricts the trunk to carry only VLAN 10, resulting in other VLAN traffic being dropped.
- A. Incorrect.
While native VLAN mismatches can cause issues, they do not limit traffic to a single VLAN. Instead, they create inconsistent behavior for untagged traffic.
- B. Correct.
If the trunk port is configured to allow only VLAN 10, traffic from other VLANs will be dropped, which matches the described scenario.
- C. Incorrect.
If the trunk port on Switch B is in access mode, no VLAN trunking would occur, and all VLAN traffic would be impacted, not just traffic from specific VLANs.
- D. Incorrect.
Spanning-tree protocol (STP) may block certain ports to prevent loops, but it would not selectively block traffic from specific VLANs like VLAN 10.