Question 53 of 464
N10-009 Network Troubleshooting Practice Question
A user reports that they can access a website by its IP address but not by its domain name. Which of the following is most likely the issue?
⚠ Common exam trap
Many candidates confuse DNS failure with a gateway or routing issue, but the ability to reach the server by IP proves Layer 3 connectivity is working, isolating the problem to the application layer name resolution process.
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
✓
A) DNS resolution failure
Accessing a website by IP address but not by domain name indicates that the client can reach the web server over the network, but the name-to-IP translation process is failing. This is a classic symptom of a DNS resolution failure, where the client cannot query or receive a valid A or AAAA record for the domain from its configured DNS server.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A) DNS resolution failure
Why this is correct
A DNS resolution failure is the correct diagnosis because the Domain Name System (DNS) is solely responsible for translating human-readable domain names (like example.com) into numerical IP addresses. If DNS is not functioning correctly, the system cannot resolve the name to an IP, preventing access by name. However, since direct IP address access bypasses the DNS lookup process entirely, it would continue to work without issue.
- ✗
B) Incorrect default gateway
Why it's wrong here
An incorrect default gateway would prevent any traffic from leaving the local network segment to reach external destinations, regardless of whether the destination is specified by name or IP address. The default gateway is crucial for routing packets to networks beyond the local subnet. If the user can access the website by its IP address, it confirms that outbound communication to external networks is indeed working, thus ruling out an incorrect gateway.
When this WOULD be correct
A user reports they cannot access any external websites or services, but can access local network resources. In this scenario, an incorrect default gateway would be the most likely issue because it prevents traffic from leaving the local subnet.
- ✗
C) Duplicate IP address
Why it's wrong here
A duplicate IP address on a network causes intermittent connectivity issues, packet loss, and potential network conflicts as devices contend for the same address. While this would severely disrupt network communication, it would not selectively prevent name resolution while allowing direct IP access. The problem would affect all traffic attempting to use that IP, not just DNS lookups.
When this WOULD be correct
A user reports that they cannot access any network resources, and an IP conflict is detected in the logs. The correct answer would be 'Duplicate IP address' because the conflict disrupts all IP communication.
- ✗
D) Corrupted TCP/IP stack
Why it's wrong here
A corrupted TCP/IP stack implies fundamental damage to the operating system's core networking protocols, which are essential for all network communication. This would manifest as a complete inability to establish network connections, affecting both name-based and direct IP-based access. Since the user can still access the website via its IP address, the TCP/IP stack is likely functional.
When this WOULD be correct
A user cannot access any network resources, and ipconfig /all shows an invalid IP address (e.g., 169.254.x.x). In that scenario, a corrupted TCP/IP stack could prevent proper IP configuration.
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.
✓A) DNS resolution failureCorrect answer▾
Why this is correct
A DNS resolution failure is the correct diagnosis because the Domain Name System (DNS) is solely responsible for translating human-readable domain names (like example.com) into numerical IP addresses. If DNS is not functioning correctly, the system cannot resolve the name to an IP, preventing access by name. However, since direct IP address access bypasses the DNS lookup process entirely, it would continue to work without issue.
✗B) Incorrect default gatewayWrong answer — click to see why▾
Why this is wrong here
The issue is that the user can access the website by IP address but not by domain name, which points to a name resolution problem, not a routing issue. An incorrect default gateway would prevent access to any external IP addresses, not just domain names.
★ When this WOULD be the correct answer
A user reports they cannot access any external websites or services, but can access local network resources. In this scenario, an incorrect default gateway would be the most likely issue because it prevents traffic from leaving the local subnet.
Why candidates choose this
Candidates may confuse network connectivity issues with DNS issues, assuming that if a website is unreachable, it must be a gateway problem. They might not realize that successful access via IP address rules out gateway and routing problems.
✗C) Duplicate IP addressWrong answer — click to see why▾
Why this is wrong here
A duplicate IP address would cause intermittent connectivity or complete loss of network access, but it would not specifically prevent domain name resolution while allowing access by IP address.
★ When this WOULD be the correct answer
A user reports that they cannot access any network resources, and an IP conflict is detected in the logs. The correct answer would be 'Duplicate IP address' because the conflict disrupts all IP communication.
Why candidates choose this
Candidates may confuse symptoms of IP conflicts with DNS issues, thinking that a duplicate IP could cause name resolution failures, but DNS operates independently of IP uniqueness.
✗D) Corrupted TCP/IP stackWrong answer — click to see why▾
Why this is wrong here
A corrupted TCP/IP stack would cause connectivity issues regardless of whether the destination is accessed by IP or domain name, but the user can access the website by IP, so the stack is functioning correctly.
★ When this WOULD be the correct answer
A user cannot access any network resources, and ipconfig /all shows an invalid IP address (e.g., 169.254.x.x). In that scenario, a corrupted TCP/IP stack could prevent proper IP configuration.
Why candidates choose this
Candidates may think that any network problem could be due to a corrupted TCP/IP stack, especially when they cannot immediately identify the DNS issue, leading them to choose a more generic 'system-level' cause.
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
Quick reference
Common DNS Record Types
| Record | Purpose | Example |
|---|---|---|
| A | IPv4 address mapping | example.com → 93.184.216.34 |
| AAAA | IPv6 address mapping | example.com → 2606:2800::1 |
| CNAME | Alias to another hostname | www → example.com |
| MX | Mail server for domain | example.com → mail.example.com (priority 10) |
| TXT | Text data (SPF, DKIM, verification) | v=spf1 include:_spf.example.com ~all |
| NS | Authoritative name servers | example.com NS ns1.example.com |
| PTR | Reverse DNS (IP → hostname) | 34.216.184.93.in-addr.arpa → example.com |
| SOA | Zone authority record | Primary NS, admin email, serial, TTL defaults |
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Last reviewed: Jun 11, 2026
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.
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