220-1101 Question 90
Single answerDNSA technician is troubleshooting a Windows workstation that can reach websites by IP address, but users report that websites fail to load when they type names such as www.example.com. The technician verifies that the network cable is connected and the workstation has a valid IP address, subnet mask, and default gateway from DHCP. Which of the following is the MOST likely cause of the problem?
- A
The workstation has an incorrect DNS server address configured
- B
The default gateway is offline
- C
The workstation has a duplicate IP address on the network
- D
The DHCP lease duration is too short
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical DNS troubleshooting. A classic sign of a DNS issue is that a device can communicate using numeric IP addresses but cannot access resources using host names. That indicates Layer 3 connectivity is working, but name resolution is failing. On Windows and other client systems, technicians should check the configured DNS servers first, often with tools such as ipconfig /all, nslookup, or by reviewing adapter settings. This aligns with standard TCP/IP troubleshooting practices and common vendor documentation from Microsoft and networking best practices: verify physical connectivity, confirm IP addressing, then isolate whether the issue is routing or name resolution. Because the workstation already has valid addressing and can reach websites by IP, the most likely fault is incorrect DNS server configuration.
- A. Correct.
This is correct. If the PC can reach resources by IP address but not by host name, the problem is commonly DNS resolution. DNS translates human-readable names such as www.example.com into IP addresses. An incorrect DNS server entry, unreachable DNS server, or missing DNS configuration can cause name-based access to fail while direct IP connectivity still works.
- B. Incorrect.
This is incorrect. If the default gateway were offline, the workstation would typically have trouble reaching external websites by both name and IP address. Since the user can reach sites by IP address, routed connectivity is functioning, which makes the default gateway less likely to be the issue.
- C. Incorrect.
This is incorrect. A duplicate IP address usually causes intermittent or total connectivity problems, including dropped connections, ARP conflicts, and inconsistent communication. It would not specifically explain why IP-based browsing works while name-based browsing fails.
- D. Incorrect.
This is incorrect. A short DHCP lease might require frequent renewal, but it does not directly cause a system to fail only at name resolution. Unless DHCP provided bad DNS settings, lease duration itself is not the most likely cause of this symptom pattern.