350-401 Question 122
Select 3An enterprise network administrator is troubleshooting a Layer 2 issue where traffic is not being forwarded between devices in the same VLAN across different switches. Upon reviewing the configuration, they discover that the trunk link between the switches is down. Which of the following actions could resolve the issue?
- A
Ensure the trunk link is set to the correct allowed VLANs on both switches.
- B
Verify that the trunk link is configured with the same native VLAN on both switches.
- C
Change the trunk link mode to 'access' to allow traffic for a single VLAN.
- D
Check for mismatched duplex or speed settings on the trunk link interfaces.
- E
Enable BPDU Guard on the trunk interfaces to prevent loops.
Show answer and explanation
Correct answers: A, B, D
Explanation
A trunk link is necessary to forward traffic for multiple VLANs between switches. To resolve the issue, the administrator must ensure the trunk link is configured correctly: the allowed VLANs must match, the native VLAN must be consistent, and the physical link settings (duplex and speed) must not conflict. Incorrect settings in any of these areas could cause the trunk link to fail.
- A. Correct.
Ensuring the trunk link allows the correct VLANs ensures traffic for the VLAN in question can be carried between switches.
- B. Correct.
Mismatched native VLANs can cause VLAN hopping issues or dropped traffic, so verifying they are consistent is critical.
- C. Incorrect.
Changing the trunk link to 'access' mode limits the link to a single VLAN, which does not resolve the issue of forwarding multiple VLANs across switches.
- D. Correct.
Mismatched duplex or speed settings can cause the trunk link to be down or unreliable, so verifying these settings is essential.
- E. Incorrect.
Enabling BPDU Guard on trunk links is not recommended as it may block legitimate BPDUs, impacting the spanning tree protocol and link operations.