220-1101 Question 108
Single answerDNSA technician is troubleshooting a Windows laptop that can reach websites by IP address, but users cannot browse to sites by name. For example, entering http://142.250.72.14 in a browser works, but entering www.google.com does not. The laptop can ping the default gateway successfully and has a valid IPv4 address from DHCP. Which of the following is the MOST likely cause of this issue?
- A
The laptop is configured with an incorrect DNS server address
- B
The default gateway is offline
- C
The laptop has a duplicate IP address
- D
The subnet mask is set incorrectly
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical DNS troubleshooting. A system that can communicate using IP addresses but not hostnames usually has a DNS resolution problem. In real support environments, technicians commonly verify this by testing connectivity to a known IP address and then comparing that with name-based access. If IP connectivity works, the network path is generally functional, and attention should shift to DNS settings, such as the configured DNS server address, DHCP-provided DNS information, or local DNS cache issues. This aligns with standard troubleshooting guidance from operating system and networking best practices: first verify basic connectivity, then isolate name resolution. For A+ Core 1, candidates should recognize DNS as the service that resolves names to IP addresses and identify incorrect DNS configuration as the most likely cause in this type of symptom pattern.
- A. Correct.
Correct. If the system can reach remote resources by IP address but not by hostname, name resolution is failing. DNS is responsible for translating hostnames such as www.google.com into IP addresses. An incorrect DNS server setting is a common real-world cause, especially on systems using manual network settings or receiving bad DHCP information.
- B. Incorrect.
Incorrect. If the default gateway were offline, the laptop would typically be unable to reach external IP addresses at all. In this scenario, the user can access a website by entering its IP address, which shows that routing to external networks is functioning.
- C. Incorrect.
Incorrect. A duplicate IP address usually causes intermittent or complete connectivity issues, not a problem isolated only to hostname resolution. The scenario specifically indicates that communication by IP works, which points away from an IP conflict as the primary issue.
- D. Incorrect.
Incorrect. An incorrect subnet mask can prevent communication with local or remote networks because the device may misidentify which addresses are local versus remote. However, since the laptop can reach the default gateway and external sites by IP address, the subnet mask is unlikely to be the root cause.