220-1102 Question 177
Single answerGatewayA small office user reports that their Windows laptop can open internal file shares on 192.168.10.0/24 and can ping other local devices, but websites and cloud apps do not load. The technician runs ipconfig and sees the laptop has IP address 192.168.10.45, subnet mask 255.255.255.0, DNS server 192.168.10.20, and default gateway 192.168.10.254. The office router that provides internet access is actually configured as 192.168.10.1. Which action should the technician take FIRST to restore internet access?
- A
Change the default gateway on the laptop to 192.168.10.1
- B
Change the DNS server on the laptop to 8.8.8.8
- C
Change the subnet mask on the laptop to 255.255.0.0
- D
Renew the laptop's IP address lease
Show answer and explanation
Correct answer: A
Explanation
This question tests practical understanding of the default gateway in host networking. A device uses its subnet mask to determine whether a destination is local or remote. Traffic for remote networks is sent to the default gateway, typically the LAN IP address of the router. In this scenario, local communication works, which strongly indicates the IP address and subnet mask are usable on the local subnet. The failure occurs only when trying to reach external resources, which points to an incorrect default gateway. This aligns with standard TCP/IP troubleshooting practices used in operating systems such as Windows and in vendor documentation from Microsoft and major networking vendors: verify IP configuration, confirm the default gateway, and ensure the host can route traffic off the local subnet.
- A. Correct.
Correct. The default gateway is the path a host uses to reach networks outside its local subnet, including the internet. Because the laptop can reach local devices, its IP address and subnet mask are functioning well enough for local communication. However, the configured gateway does not match the actual router address, so traffic destined for external networks is being sent to the wrong device or to a nonexistent address. Setting the gateway to 192.168.10.1 is the most direct and appropriate first step.
- B. Incorrect.
Incorrect. A DNS problem can prevent name resolution, but it would not explain a known incorrect default gateway when the symptom is inability to reach internet resources beyond the local subnet. Also, many cloud app failures can result from lack of routing, not just DNS. Since the scenario identifies the router's correct IP and shows the gateway is wrong, fixing the gateway should come first.
- C. Incorrect.
Incorrect. The current subnet mask of 255.255.255.0 matches the 192.168.10.0/24 network described in the scenario. Changing it to 255.255.0.0 would incorrectly enlarge the local network range and could create additional routing issues. This distractor reflects the common misconception that any connectivity issue is caused by the subnet mask.
- D. Incorrect.
Incorrect. Renewing the lease may help if the system received bad DHCP information, but the question asks what to do first, and the root problem has already been identified: the default gateway is incorrect. If DHCP is providing the wrong gateway, renewing might simply reapply the same bad setting unless the DHCP scope is fixed. The immediate corrective action on the laptop is to set the proper gateway.