200-301 Question 199
Single answerA network administrator is troubleshooting a VLAN misconfiguration issue. One of the switches in the network is configured with a trunk port that uses the default Native VLAN (VLAN 1). The administrator notices that untagged traffic is not being delivered properly between switches. Which of the following could be the cause of the issue?
- A
The Native VLAN is not the same on both sides of the trunk link.
- B
The trunk port is configured to allow only tagged VLAN traffic.
- C
The Native VLAN is set to VLAN 1, which does not support untagged traffic.
- D
The switches are configured with different trunking encapsulation protocols.
Show answer and explanation
Correct answer: A
Explanation
In a trunk configuration, the Native VLAN must match on both ends of the trunk link for untagged traffic to traverse successfully. If the Native VLANs are mismatched, each switch will interpret untagged traffic differently, causing communication issues. This is a common misconfiguration that network administrators need to verify during troubleshooting.
- A. Correct.
If the Native VLAN is not the same on both sides of the trunk link, untagged traffic will not be properly handled, leading to communication issues.
- B. Incorrect.
Trunk ports support both tagged and untagged traffic, depending on the Native VLAN configuration. Blocking untagged traffic is not typical behavior unless explicitly configured.
- C. Incorrect.
VLAN 1 supports untagged traffic by default, as it is the default Native VLAN. The issue is not related to the specific VLAN being used as the Native VLAN.
- D. Incorrect.
While mismatched trunking encapsulation protocols (e.g., 802.1Q vs. ISL) can cause issues, this is unrelated to untagged traffic and Native VLAN configuration.