200-301 Question 189
Single answerYou are tasked with configuring interswitch connectivity between two switches, SW1 and SW2. Both switches are connected via a trunk link on interface GigabitEthernet0/1. After the configuration is complete, hosts in VLANs 10 and 20 cannot communicate across switches. Upon investigation, you find that VLAN 10 and VLAN 20 are configured on both switches. What could be the reason for this issue?
- A
The trunk port on SW1 is not configured to allow VLAN 10 and VLAN 20.
- B
The native VLAN is mismatched on the trunk link between SW1 and SW2.
- C
The trunk link is using Dynamic Trunking Protocol (DTP), and it has not negotiated into trunk mode.
- D
The VLANs are not assigned to any access ports on SW1 and SW2.
Show answer and explanation
Correct answer: A
Explanation
Interswitch connectivity requires the trunk link between switches to allow the VLANs that need to communicate. By default, trunk links allow all VLANs, but administrators often restrict VLANs for security or performance reasons. If VLAN 10 and VLAN 20 are not allowed on the trunk link, their traffic will not pass between SW1 and SW2, causing hosts in these VLANs to fail communication across switches.
- A. Correct.
If the trunk port is not explicitly configured to allow VLAN 10 and VLAN 20, traffic for these VLANs cannot pass across the trunk link, resulting in communication issues.
- B. Incorrect.
While a native VLAN mismatch can cause issues, it would not prevent VLAN 10 and VLAN 20 from communicating across the trunk link if they are explicitly allowed.
- C. Incorrect.
If the trunk link was not in trunk mode, the issue would be more severe, as no VLAN traffic would pass across the link. However, the question assumes the trunk link is active.
- D. Incorrect.
Even though the VLANs need to be assigned to access ports for host connectivity, this does not directly impact interswitch connectivity, which is the focus of the scenario.