N10-009 Network Troubleshooting Practice Question
A user reports that they can access internal websites but cannot access any external websites. Other users in the same subnet can access external sites. The user's IP configuration shows a correct IP, subnet mask, and default gateway. What is the most likely cause?
⚠ Common exam trap
CompTIA often tests the distinction between network-layer issues (like default gateway or DNS) and application-layer issues (like proxy configuration), leading candidates to incorrectly choose DNS or gateway problems when the symptom is isolated to a single user with correct IP settings.
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 proxy server settings are incorrect.
The user can access internal websites but not external ones, while other users in the same subnet have no issues. This points to a client-specific configuration problem rather than a network-wide issue. Incorrect proxy server settings on the user's machine can prevent external HTTP/HTTPS traffic from being routed correctly, even though internal traffic (which may bypass the proxy) works fine.
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 DNS server is not reachable.
Why it's wrong here
If DNS were unreachable, the user would likely fail to resolve internal and external hostnames, but they can access internal sites, possibly by IP. However, the scenario states they can access internal websites (using names?) and others work, so DNS is probably fine.
When this WOULD be correct
A user cannot access any websites (internal or external) while other users on the same subnet can, and the IP configuration shows correct IP, subnet mask, and default gateway. This would indicate a DNS resolution failure, likely due to an unreachable or misconfigured DNS server.
- ✓
The proxy server settings are incorrect.
Why this is correct
If a client's web browser or operating system is configured to use a proxy server for internet access, but the proxy settings are incorrect (e.g., wrong IP address, port, or authentication), all external web requests will fail. However, many network configurations include exceptions or bypass rules for internal network addresses, allowing direct access to internal websites without going through the misconfigured proxy. This precise behavior, where internal access works but external fails, directly aligns with incorrect proxy server configuration.
- ✗
The default gateway is misconfigured.
Why it's wrong here
If the default gateway were misconfigured, the user would likely not be able to reach any destinations outside their subnet, including internal websites on other subnets. They would also have no external access, but internal access works, so this is unlikely.
When this WOULD be correct
A user cannot access any external websites, and other users in the same subnet also cannot access external sites. The user's IP configuration shows an incorrect default gateway address, such as a non-existent or wrong IP.
- ✗
The web browser has a corrupted cache.
Why it's wrong here
A corrupted web browser cache stores temporary files and data from previously visited websites. While a corrupted cache can lead to display issues, loading errors, or even prevent access to *specific* cached websites, it would not universally block *all* external websites while leaving *all* internal websites fully functional. Furthermore, if internal sites were cached, they could also be affected, which contradicts the scenario where internal access is unimpeded.
When this WOULD be correct
A user reports that a specific external website displays outdated content or fails to load correctly, while other websites work fine. Clearing the browser cache resolves the issue. In this scenario, a corrupted cache is the most likely cause.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓The proxy server settings are incorrect.Correct answer▾
Why this is correct
If a client's web browser or operating system is configured to use a proxy server for internet access, but the proxy settings are incorrect (e.g., wrong IP address, port, or authentication), all external web requests will fail. However, many network configurations include exceptions or bypass rules for internal network addresses, allowing direct access to internal websites without going through the misconfigured proxy. This precise behavior, where internal access works but external fails, directly aligns with incorrect proxy server configuration.
✗The DNS server is not reachable.Wrong answer — click to see why▾
Why this is wrong here
The user can access internal websites, which typically rely on internal DNS, and other users in the same subnet can access external sites, indicating the DNS server is reachable and functional. The issue is isolated to this user, not a network-wide DNS problem.
★ When this WOULD be the correct answer
A user cannot access any websites (internal or external) while other users on the same subnet can, and the IP configuration shows correct IP, subnet mask, and default gateway. This would indicate a DNS resolution failure, likely due to an unreachable or misconfigured DNS server.
Why candidates choose this
Candidates often associate internet access issues with DNS problems, but here the user can access internal sites, which typically use the same DNS server, so DNS is not the likely cause.
✗The default gateway is misconfigured.Wrong answer — click to see why▾
Why this is wrong here
The default gateway is correctly configured because the user can access internal websites, which require the gateway to route within the subnet, and other users in the same subnet can access external sites, indicating the gateway is functional.
★ When this WOULD be the correct answer
A user cannot access any external websites, and other users in the same subnet also cannot access external sites. The user's IP configuration shows an incorrect default gateway address, such as a non-existent or wrong IP.
Why candidates choose this
Candidates often associate external access issues with the default gateway, overlooking that internal access works and other users are unaffected, which rules out a gateway problem.
✗The web browser has a corrupted cache.Wrong answer — click to see why▾
Why this is wrong here
A corrupted browser cache typically causes issues like outdated content or display errors, but it would not prevent access to all external websites while internal sites remain accessible. The symptom of being unable to reach any external site points to a network or proxy configuration problem, not a local browser cache issue.
★ When this WOULD be the correct answer
A user reports that a specific external website displays outdated content or fails to load correctly, while other websites work fine. Clearing the browser cache resolves the issue. In this scenario, a corrupted cache is the most likely cause.
Why candidates choose this
Candidates may think that a corrupted cache can block website access entirely, confusing cache corruption with more severe connectivity issues. They might also recall that clearing the cache often fixes browsing problems, leading them to overestimate its impact.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
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Related to this question
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Troubleshoot: Network Connectivity
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
Key term
Proxy
A proxy is an intermediary server that sits between a client and a destination server, forwarding requests and responses while providing security, privacy, and control.
About these practice questions
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 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 N10-009 exam.