200-301 Question 186
Single answerYou are configuring the interswitch connectivity between two Cisco switches, SwitchA and SwitchB, using trunking. After configuring the trunk ports, the devices are not exchanging VLAN traffic as expected. Upon reviewing the configuration, you find the trunk mode on SwitchA is set to 'dynamic auto' and on SwitchB is set to 'dynamic auto'. What action should you take to resolve the issue?
- A
Manually set the trunk mode on both switches to 'trunk'.
- B
Change the trunk mode on SwitchA to 'dynamic desirable'.
- C
Change the trunk mode on SwitchB to 'access'.
- D
Enable VLAN pruning on both switches.
Show answer and explanation
Correct answer: B
Explanation
When both switches are set to 'dynamic auto', neither initiates the trunking process, and the trunk does not form. Changing one side to 'dynamic desirable' allows it to initiate trunk negotiation, resulting in a successful trunk link. This approach is preferred as it aligns with dynamic negotiation protocols and minimizes manual configuration.
- A. Incorrect.
This would resolve the issue, but it is not the most efficient solution as it forces both ports into trunk mode unnecessarily.
- B. Correct.
Changing one side to 'dynamic desirable' will allow the two switches to negotiate the trunk successfully, as 'dynamic desirable' initiates the trunking process.
- C. Incorrect.
Changing the trunk mode to 'access' will disable trunking and prevent interswitch VLAN traffic, which is not the goal.
- D. Incorrect.
VLAN pruning is used to limit unnecessary VLAN traffic on a trunk, but it does not resolve trunk negotiation issues.