220-1101 Hardware and Network Troubleshooting Practice Question
A technician is troubleshooting a desktop workstation that can successfully ping other local devices and the default gateway by IP address, but cannot access any websites when browsing with a web browser. The workstation obtains its IP configuration automatically via DHCP. The technician confirms that the DHCP server is providing a valid DNS server address and that other workstations on the same network can browse the internet normally. Which of the following is the MOST likely cause of the issue?
⚠ Common exam trap
CompTIA often tests the distinction between Layer 3 connectivity (ping by IP) and application-layer issues (DNS, proxy, browser settings); the trap here is that candidates assume DNS is the problem because web browsing fails, but the workstation can ping by IP, and DHCP provides a valid DNS server, so the real issue is a misconfigured proxy server that blocks HTTP/HTTPS traffic.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The workstation is configured to use a proxy server that is not available
The workstation can ping local devices and the default gateway by IP address, confirming that Layer 2/3 connectivity (ARP, IP routing) is functional. However, it cannot browse websites, which requires DNS resolution (UDP/TCP port 53) and HTTP/HTTPS traffic (TCP ports 80/443). Since other workstations on the same network browse normally, the issue is isolated to this workstation. A misconfigured proxy server (e.g., set in browser or system proxy settings) can intercept or block web traffic, preventing access to websites even when DNS and IP connectivity are working.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Duplicate IP address on the network
Why it's wrong here
A duplicate IP address on the network would cause intermittent, chaotic behavior: multiple NICs answering ARP requests for the same IP, leading to dropped packets, address conflict warnings, and unreliable pings even to local gateways. Since the technician successfully and consistently pings local devices, a duplicate IP is unlikely—it typically makes all IP communications flaky, not just web browsing.
- ✗
Incorrect subnet mask configured by DHCP
Why it's wrong here
If DHCP assigned an incorrect subnet mask, the client's view of what is 'local' would change, but the user can ping the gateway, which is on the same subnet. A mask that is too narrow might make the gateway appear remote, but the ping success proves the mask is not causing that issue. Also, an incorrect mask would affect all non-local traffic—not selectively web traffic—so it does not explain why only browsing fails.
- ✗
The workstation's DNS client cache is corrupted
Why it's wrong here
A corrupted DNS cache would prevent name resolution for all applications, including ping by domain name. The technician only mentioned pinging by IP, but web browsing uses domain names. However, the most likely cause is a proxy setting, not cache corruption, and the user could try 'ipconfig /flushdns' to test.
- ✓
The workstation is configured to use a proxy server that is not available
Why this is correct
A proxy server configured in the browser or at the system level intercepts HTTP/HTTPS requests and forwards them through that proxy. If the proxy is unreachable or down, web requests fail, but `ping` uses ICMP and bypasses proxy settings entirely, so local IP connectivity appears normal. This perfectly matches the symptom: the workstation can ping on the LAN but cannot browse the web. Checking browser/system proxy settings or PAC file should be a high-priority next step.
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Key term
Fully Qualified Domain Name
A Fully Qualified Domain Name is the complete and unambiguous website or server name that includes the host, domain, and top-level domain, leaving no room for guesswork.
Key term
User Datagram Protocol
User Datagram Protocol (UDP) is a fast, connectionless network protocol that sends data without first checking if the receiver is ready or if the data arrived safely.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.