- A
The file server has an incorrect default gateway configured.
Why wrong: As the user and file server are on the same subnet, a default gateway is not needed for local communication. A misconfigured gateway would not affect local ping or file access.
- B
The user's workstation has an incorrect DNS server configured.
Why wrong: The user is connecting via IP address, so DNS resolution is not involved. An incorrect DNS server would not prevent a direct IP connection.
- C
The file server's firewall is blocking the file-sharing protocol while allowing ICMP.
This is the most likely cause. The file server's firewall may permit ping (ICMP) but block the specific application port (e.g., TCP 445), which stops the file share connection while allowing ping to succeed.
- D
The user's workstation has a duplicate IP address assigned.
Why wrong: A duplicate IP address would cause network conflicts and typically disrupt all network communication, including ping. Since ping works, a duplicate IP is highly unlikely.
Quick Answer
The answer is the file server’s host firewall blocking the application traffic while allowing ICMP. This is correct because the technician’s successful ping proves network-layer connectivity is working—ICMP Echo Requests are reaching the server and returning—but the user’s inability to access the file server indicates the application-layer protocol, such as SMB on TCP/445, is being filtered. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how host-based firewalls can selectively permit or deny traffic by protocol, a common misconfiguration where administrators enable ping for troubleshooting but forget to allow file-sharing rules. The trap here is assuming a successful ping guarantees full service availability; in reality, ICMP and application traffic are handled separately by the firewall. Remember the memory tip: “Ping works, service fails? Check the host firewall’s protocol rules.”
N10-009 Network Troubleshooting Practice Question
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 can access the internet but cannot connect to an internal file server at IP address 192.168.1.50. The technician successfully pings the file server's IP address from the user's workstation. The file server is on the same subnet as the user. What is the most likely cause of this issue?
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 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 file server's firewall is blocking the file-sharing protocol while allowing ICMP.
The technician can ping the file server (ICMP success) but the user cannot connect to it using the file-sharing protocol (e.g., SMB on TCP/445). This indicates network-layer reachability is fine, but the application-layer service is blocked. The most likely cause is the file server's host-based firewall (e.g., Windows Defender Firewall) allowing ICMP Echo Requests while blocking inbound SMB traffic, which is a common misconfiguration.
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.
- ✗
The file server has an incorrect default gateway configured.
Why it's wrong here
As the user and file server are on the same subnet, a default gateway is not needed for local communication. A misconfigured gateway would not affect local ping or file access.
- ✗
The user's workstation has an incorrect DNS server configured.
Why it's wrong here
The user is connecting via IP address, so DNS resolution is not involved. An incorrect DNS server would not prevent a direct IP connection.
- ✓
The file server's firewall is blocking the file-sharing protocol while allowing ICMP.
Why this is correct
This is the most likely cause. The file server's firewall may permit ping (ICMP) but block the specific application port (e.g., TCP 445), which stops the file share connection while allowing ping to succeed.
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.
- ✗
The user's workstation has a duplicate IP address assigned.
Why it's wrong here
A duplicate IP address would cause network conflicts and typically disrupt all network communication, including ping. Since ping works, a duplicate IP is highly unlikely.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a successful ping guarantees full connectivity, but ICMP and application traffic use different protocols and ports, so a firewall can block one while allowing the other.
Detailed technical explanation
How to think about this question
ICMP (ping) operates at the network layer (Layer 3) and is often permitted by default in host firewalls, while file-sharing protocols like SMB use TCP port 445 (or NetBIOS over TCP/IP on ports 137-139) at the transport layer (Layer 4). A host firewall can selectively allow ICMP while blocking specific TCP/UDP ports. In real-world scenarios, administrators may inadvertently leave ICMP enabled for troubleshooting while forgetting to permit necessary application ports.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this N10-009 question test?
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: The file server's firewall is blocking the file-sharing protocol while allowing ICMP. — The technician can ping the file server (ICMP success) but the user cannot connect to it using the file-sharing protocol (e.g., SMB on TCP/445). This indicates network-layer reachability is fine, but the application-layer service is blocked. The most likely cause is the file server's host-based firewall (e.g., Windows Defender Firewall) allowing ICMP Echo Requests while blocking inbound SMB traffic, which is a common misconfiguration.
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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Last reviewed: Jun 11, 2026
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