This N10-009 practice question tests your understanding of network troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user reports that they cannot access a web server by its URL but can access it by IP address. A technician checks the DNS server and finds it is reachable. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DNS resolution failure for that specific record
The user can access the web server by IP address but not by URL, which indicates that the name-to-IP resolution is failing. Since the DNS server is reachable, the issue is not with network connectivity to the DNS server but rather with the specific DNS record for that web server. This is a classic DNS resolution failure for that specific record, often due to a missing or incorrect A or AAAA record.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Incorrect default gateway
Why it's wrong here
If the default gateway were incorrect, the user would not be able to reach the server by IP either.
✓
DNS resolution failure for that specific record
Why this is correct
The user can reach the server by IP, indicating connectivity is fine. The URL failure points to a DNS problem for that particular record.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Firewall blocking port 80
Why it's wrong here
If a firewall were blocking port 80, access by IP would also fail.
✗
IP conflict on the user's workstation
Why it's wrong here
An IP conflict would cause intermittent connectivity issues, but would not explain why only URL access fails.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a reachable DNS server means DNS is fully functional, but the question specifically tests the distinction between server reachability and record availability.
Detailed technical explanation
How to think about this question
DNS resolution relies on the client sending a query for the FQDN (e.g., www.example.com) to the configured DNS server, which returns the corresponding IP address via an A (IPv4) or AAAA (IPv6) record. If the record is missing, expired, or misconfigured (e.g., a CNAME pointing to a non-existent target), the resolver returns NXDOMAIN or SERVFAIL, causing the browser to fail while direct IP access works. Tools like `nslookup` or `dig` can confirm whether the specific record exists.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Troubleshooting — This question tests Network Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DNS resolution failure for that specific record — The user can access the web server by IP address but not by URL, which indicates that the name-to-IP resolution is failing. Since the DNS server is reachable, the issue is not with network connectivity to the DNS server but rather with the specific DNS record for that web server. This is a classic DNS resolution failure for that specific record, often due to a missing or incorrect A or AAAA record.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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