220-1101 Question 151
Single answerGatewayA technician is troubleshooting a Windows laptop in a small office. The user can open shared folders on another PC at 192.168.10.25 and can ping the local printer at 192.168.10.50, but cannot browse the web or ping 8.8.8.8. Running ipconfig shows the laptop has IP address 192.168.10.42, subnet mask 255.255.255.0, and default gateway 192.168.20.1. The office router that provides internet access is 192.168.10.1. Which change should the technician make first to restore internet connectivity?
- A
Change the default gateway to 192.168.10.1
- B
Change the subnet mask to 255.255.0.0
- C
Change the IP address to 192.168.20.42
- D
Change the DNS server to 8.8.8.8
Show answer and explanation
Correct answer: A
Explanation
A default gateway is the router a host uses to reach destinations outside its local subnet. In this scenario, the laptop can reach local devices on 192.168.10.0/24, proving local Layer 2 and local IP communication are working. However, the configured default gateway is 192.168.20.1, which is not on the host's local subnet and therefore is not the correct next hop for internet-bound traffic. The correct fix is to set the default gateway to the office router at 192.168.10.1. This aligns with standard TCP/IP host configuration practices documented by operating system and networking vendors: local traffic stays on the local subnet, while remote traffic is sent to the configured default gateway. A good troubleshooting best practice is to test connectivity in order: local host, local subnet, default gateway, then external IP, and finally DNS-based name resolution.
- A. Correct.
Correct. The laptop can communicate with devices on its local subnet, which shows the NIC, IP address, and local switching are functioning. It cannot reach external networks because the configured default gateway is on a different subnet and is incorrect for this network. The default gateway should be the router interface on the same local subnet, which in this case is 192.168.10.1.
- B. Incorrect.
Incorrect. The current subnet mask of 255.255.255.0 correctly matches the 192.168.10.0/24 network used by the laptop, printer, and router. Changing to 255.255.0.0 would expand the local network definition unnecessarily and would not fix the fact that the configured gateway is wrong. This is a common misconception when users confuse subnetting issues with routing issues.
- C. Incorrect.
Incorrect. Changing the laptop's IP address to 192.168.20.42 would move it off the working 192.168.10.0 network where the other local devices reside. That would likely break the currently working access to shared folders and the printer. The problem is not the host IP; it is the misconfigured gateway.
- D. Incorrect.
Incorrect. DNS is not the first issue to address here because the laptop cannot even ping 8.8.8.8, which is a direct IP test and does not require DNS resolution. If the system cannot reach external IP addresses, the technician should first verify routing, especially the default gateway.