220-1101 Networking Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  The laptop is configured with a static IP address outside the DHCP scope.

  Why it's wrong here

  A static IP address that falls outside the DHCP scope is not inherently problematic—DHCP scopes define the pool of addresses the router hands out, not the valid usable addresses on a subnet. As long as the laptop's IP is within the same subnet as the router, the gateway is reachable, and the laptop could still ping it and possibly route traffic. The fact that the laptop can ping the gateway proves it has a valid, in-subnet address, so an out-of-scope static IP alone cannot explain a complete loss of internet access; the failure must lie elsewhere, such as DNS or upstream routing.

• ✗

  The router's WAN port is disconnected.

  Why it's wrong here

  If the router's WAN port were disconnected, the router would not have a public IP address and would be unable to send or receive traffic to the internet. The router's successful ping to 8.8.8.8—a Google public DNS server—definitively demonstrates that the WAN link is up, the router has internet connectivity, and that packets are transiting the ISP's network. Therefore, a disconnected WAN port directly contradicts the observed evidence and cannot be the cause of the laptop's inability to access the internet.

• ✓

  The laptop's DNS settings are pointing to an invalid DNS server.

  Why this is correct

  The laptop can connect to the Wi-Fi network and reach the local gateway, confirming that layer 1, 2, and 3 connectivity to the router is intact. However, the router's ability to ping 8.8.8.8 by IP address proves the internet connection is up, but it does not help the laptop resolve domain names if its configured DNS server is unreachable or invalid. For example, if the laptop is configured with a DNS server IP that doesn't exist or is not responding, attempts to resolve hostnames fail, resulting in an inability to load websites even though IP-based communication like pinging the gateway or even 8.8.8.8 would still work. This is the classic symptom of misconfigured DNS settings for a client that otherwise has full IP connectivity.

• ✗

  The ISP has a service outage affecting only web traffic.

  Why it's wrong here

  A service outage at the ISP that only affected web traffic would be extremely unusual and would also impact the router's own ability to reach web servers; however, the router successfully pinged 8.8.8.8, which is a Google public DNS server, demonstrating that the ISP connection is functioning for ICMP traffic. While it is theoretically possible for an ISP to block or throttle specific protocols like HTTP/HTTPS, the scenario provides no evidence of such selective filtering. In practice, an ISP outage that breaks only web traffic would still require the router to have full connectivity, and the fact that the router can ping an external IP strongly suggests the WAN path is healthy. Thus, the evidence points away from an ISP problem and toward a client-side configuration issue such as DNS.

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