N10-009 Question 295
Single answerVerify full system functionality and implement preventive measures if applicableA network administrator replaced a failed access switch in a small branch office after hours. The new switch has been configured with the correct VLANs, trunk settings, and management IP. The next morning, users report that they can reach internal file shares and print to network printers, but they cannot access internet websites or the company VPN concentrator at headquarters. A quick check shows client PCs are receiving the correct IP addresses from DHCP. Which action should the administrator take NEXT to verify full system functionality and prevent this issue from recurring after future switch replacements?
- A
Test end-to-end connectivity from multiple VLANs to the default gateway and external destinations, then save and back up the switch configuration
- B
Replace all user patch cables connected to the new switch and reboot every client workstation
- C
Increase the DHCP lease time so clients keep their current addresses during future maintenance windows
- D
Disable spanning tree on the uplink ports so traffic can pass immediately after a switch replacement
Show answer and explanation
Correct answer: A
Explanation
This scenario tests the ability to verify full system functionality after a network change, not just confirm partial connectivity. Because users can reach internal resources and receive correct DHCP addresses, the switch is at least partially operational at Layers 1 and 2, and local VLAN membership is likely working. However, inability to reach internet sites or the VPN concentrator suggests that upstream connectivity or routing-related functionality has not been fully validated. The best next step is to perform end-to-end testing from affected VLANs to the default gateway and beyond, such as ping or traceroute tests to the gateway, WAN edge, and external destinations, while also checking trunk operation and any gateway-facing links. After confirming the switch is functioning correctly, saving and backing up the configuration is an important preventive measure. This follows common operational best practices in vendor documentation and change-management guidance: validate critical business services after implementation, document the final working state, and maintain configuration backups for rapid recovery during future hardware replacements.
- A. Correct.
Correct. Verifying full system functionality means confirming more than local resource access. The administrator should test gateway reachability, routing to external destinations, and access to critical services from affected VLANs to identify whether the uplink, default route path, ACLs, or trunk/native VLAN settings are still preventing full connectivity. Saving and backing up the validated configuration is an appropriate preventive measure so future replacements can be restored consistently and quickly. This aligns with post-change validation and configuration management best practices.
- B. Incorrect.
Incorrect. Patch cables and client reboots are not the most logical next step because users can already reach local file shares and printers, which indicates local Layer 2 connectivity is functioning. Replacing all cables and rebooting endpoints would add unnecessary disruption and does not specifically verify upstream or end-to-end functionality.
- C. Incorrect.
Incorrect. DHCP lease duration is unrelated to the reported symptom. Clients are already receiving the correct IP configuration, so address retention is not the problem. This option reflects a common misconception that any client connectivity issue is DHCP-related, when the evidence points instead to incomplete path validation beyond the local network.
- D. Incorrect.
Incorrect. Disabling spanning tree is not an appropriate fix or preventive measure. Spanning Tree Protocol helps prevent Layer 2 loops and is a standard best practice on switched networks. Disabling it on uplinks could create broadcast storms and major outages. If convergence timing were a concern, features such as PortFast are used carefully on edge ports, not by disabling STP on inter-switch uplinks.