N10-009 Network Troubleshooting Practice Question
A user reports that they cannot access the internal web server by its fully qualified domain name (intranet.company.com). The workstation's IP configuration shows a DNS server of 8.8.8.8, but the internal DNS server is 10.0.0.10. The user can successfully ping the server's IP address (10.0.0.50). What is the MOST likely cause of the issue?
⚠ Common exam trap
Test-takers frequently confuse a DNS resolution failure with a network connectivity issue, but the ability to ping the IP address proves the problem is strictly name resolution, not layer 2 or layer 3 problems.
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: The workstation is using the wrong DNS server address
The workstation's DNS server is set to 8.8.8.8 (a public Google DNS server), which cannot resolve the internal domain name 'intranet.company.com' because that zone is only hosted on the internal DNS server at 10.0.0.10. Since the user can ping the server's IP address (10.0.0.50), network connectivity is fine, confirming the issue is name resolution. The most likely cause is that the workstation is using the wrong DNS server address.
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: The workstation is using the wrong DNS server address
Why this is correct
If the workstation is configured to use an external DNS server (e.g., a public internet DNS resolver), it will be unable to resolve internal hostnames like "internalwebserver.local" because external DNS servers lack records for private network zones. While IP-based connectivity is confirmed by the successful ping to the server's IP address, the failure to access it by hostname indicates a breakdown in the name resolution process specifically for internal resources. This prevents accessing the web server by its friendly name, even though it is physically reachable.
- ✗
B: The subnet mask on the workstation is incorrect
Why it's wrong here
An incorrect subnet mask would cause the workstation to miscalculate its local network segment, potentially preventing communication with other devices on its own subnet. If the subnet mask were wrong, the workstation might incorrectly classify the web server's IP as remote, requiring a gateway, or fail to communicate locally. However, the ability to ping the server's IP address directly indicates that the workstation correctly identifies the server as being within its reachable local network segment, ruling out a subnet mask issue.
When this WOULD be correct
A user cannot access any network resources, including pinging the default gateway or other hosts on the same subnet. The workstation's IP configuration shows an incorrect subnet mask (e.g., 255.255.255.0 instead of 255.255.0.0), causing the workstation to believe remote hosts are on a different subnet and failing to send traffic to the default gateway.
- ✗
C: The network cable is faulty
Why it's wrong here
A faulty network cable at the physical layer would disrupt all network communication, leading to complete connectivity failure. Such an issue would prevent any data transmission, making it impossible to even ping the server's IP address. Since the user can successfully ping the server by its IP, the physical cabling and connection are demonstrably functional, ruling out a cable fault as the root cause of the inability to access the web server by its hostname.
When this WOULD be correct
A user cannot access any network resources, and pinging both IP addresses and hostnames fails. The workstation shows a link light but no network activity. In that scenario, a faulty cable would be a likely cause.
- ✗
D: The default gateway is misconfigured
Why it's wrong here
The default gateway is crucial for routing traffic to destinations outside the local subnet. If the default gateway were misconfigured or unreachable, the workstation would be unable to communicate with any resources located on different network segments. However, the successful ping to the internal web server's IP address confirms that either the server is on the same local subnet (not requiring the gateway for direct communication) or the gateway is correctly configured and operational for internal routing purposes.
When this WOULD be correct
A user reports they cannot access an external website (e.g., www.example.com) but can ping the internal server by IP. The workstation's default gateway is set to an incorrect address, preventing traffic from leaving the local subnet. In that scenario, a misconfigured default gateway would be 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.
✓A: The workstation is using the wrong DNS server addressCorrect answer▾
Why this is correct
If the workstation is configured to use an external DNS server (e.g., a public internet DNS resolver), it will be unable to resolve internal hostnames like "internalwebserver.local" because external DNS servers lack records for private network zones. While IP-based connectivity is confirmed by the successful ping to the server's IP address, the failure to access it by hostname indicates a breakdown in the name resolution process specifically for internal resources. This prevents accessing the web server by its friendly name, even though it is physically reachable.
✗B: The subnet mask on the workstation is incorrectWrong answer — click to see why▾
Why this is wrong here
The user can successfully ping the server's IP address (10.0.0.50), which indicates that the network cable is functional and the subnet mask is correct for local communication. An incorrect subnet mask would typically prevent communication with hosts on the same subnet, but pinging the server's IP works, so the subnet mask is not the issue.
★ When this WOULD be the correct answer
A user cannot access any network resources, including pinging the default gateway or other hosts on the same subnet. The workstation's IP configuration shows an incorrect subnet mask (e.g., 255.255.255.0 instead of 255.255.0.0), causing the workstation to believe remote hosts are on a different subnet and failing to send traffic to the default gateway.
Why candidates choose this
Candidates may think that an incorrect subnet mask could cause DNS resolution failures because it affects routing decisions, but in this scenario, the ability to ping the server's IP confirms that layer 3 connectivity is intact, isolating the issue to DNS.
✗C: The network cable is faultyWrong answer — click to see why▾
Why this is wrong here
The user can successfully ping the server's IP address, which rules out a faulty network cable. A faulty cable would cause connectivity issues at the IP level, making pings fail.
★ When this WOULD be the correct answer
A user cannot access any network resources, and pinging both IP addresses and hostnames fails. The workstation shows a link light but no network activity. In that scenario, a faulty cable would be a likely cause.
Why candidates choose this
Candidates may think any network issue could be due to a physical cable problem, especially when they overlook that successful IP pings confirm Layer 1 and Layer 2 are functioning.
✗D: The default gateway is misconfiguredWrong answer — click to see why▾
Why this is wrong here
The user can successfully ping the server's IP address (10.0.0.50), which indicates that the network path is functional. A misconfigured default gateway would prevent communication with external networks, but internal traffic within the same subnet does not require a gateway. Since the server is on the same network (10.0.0.x), the gateway is not needed for this access.
★ When this WOULD be the correct answer
A user reports they cannot access an external website (e.g., www.example.com) but can ping the internal server by IP. The workstation's default gateway is set to an incorrect address, preventing traffic from leaving the local subnet. In that scenario, a misconfigured default gateway would be the most likely cause.
Why candidates choose this
Candidates may confuse general network connectivity issues with DNS resolution problems. They might think that if DNS fails, the default gateway could be at fault, but the ability to ping the server's IP proves the gateway is not the issue here.
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 |
Go deeper
Related to this question
Learn chapter
Troubleshoot: Network Connectivity
Key term
FQDN
A complete domain name that specifies the exact location of a host in the DNS hierarchy, ending with a trailing dot.
Key term
Name Server
A name server is a specialized server that translates human-readable domain names into machine-readable IP addresses so that computers can find each other on a network.
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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.