N10-009 Question 289
Single answerA network technician is troubleshooting reports that users in one office suite cannot reach a file server in another VLAN. The users can reach local resources and the default gateway, but pings to the remote file server fail. The technician suspects an ACL on the Layer 3 switch is blocking traffic between the two VLANs. To test this theory, the technician reviews the ACL and sees an explicit deny statement for the users' subnet to the server subnet. What should the technician do NEXT according to best-practice troubleshooting methodology?
- A
Remove the deny statement immediately and close the ticket because the root cause has been identified
- B
Verify that the ACL deny is the actual cause by checking hit counts or performing a controlled test, then modify the ACL through the change process if confirmed
- C
Replace the Layer 3 switch because inter-VLAN routing is failing
- D
Escalate the issue immediately to the ISP because the remote server is unreachable
Show answer and explanation
Correct answer: B
Explanation
The key skill being tested is the ability to follow a disciplined troubleshooting process rather than jumping straight to remediation. In Network+ methodology, after forming a theory, the technician must test that theory to confirm causation. In this scenario, the ACL deny entry is a strong clue, but best practice is to validate it with evidence such as ACL hit counts, logging, packet captures, or a controlled test. If the theory is confirmed, the next step is to determine and implement the appropriate fix, typically through change management to avoid unintended security exposure. If the theory were not confirmed, the technician would need to establish a new theory or escalate appropriately. This approach aligns with standard troubleshooting frameworks used in CompTIA Network+ and common enterprise operational practices such as documented testing, least-impact changes, and change control.
- A. Incorrect.
This is incorrect because identifying a possible cause is not the same as confirming it. In the troubleshooting process, the technician should test the theory before making changes. Immediately removing the deny statement also bypasses standard change control and could introduce a security issue if the ACL was intentional.
- B. Correct.
This is correct because it follows the CompTIA troubleshooting methodology: test the theory to determine the cause, and if the theory is confirmed, determine the next steps to resolve the problem. Checking ACL hit counters, reviewing logs, or performing a controlled test helps confirm whether the deny statement is blocking the traffic. If confirmed, the technician should proceed with an approved ACL modification or documented exception through normal change-management procedures.
- C. Incorrect.
This is incorrect because the evidence does not indicate a hardware failure. Users can reach their default gateway, which suggests local switching and routing are functioning. Replacing hardware before confirming the cause is costly and does not align with structured troubleshooting.
- D. Incorrect.
This is incorrect because the symptoms point to an internal inter-VLAN communication issue, not an ISP problem. The users can reach local resources and their gateway, and the suspected ACL is on the internal Layer 3 switch. Escalating externally without validating the internal theory would be premature.