N10-009 Network Troubleshooting Practice Question
Users in a small office can access external websites normally, but they cannot reach the internal company wiki server at 192.168.10.25. A technician can successfully ping the server's IP address from a user's workstation. The DNS resolution for the wiki's hostname (wiki.company.local) returns the correct IP. The company's firewall permits HTTP traffic to the server. What is the most likely cause of the issue?
⚠ Common exam trap
Many exam-takers assume a successful ping implies full application-layer connectivity, but ping uses ICMP (Layer 3) while HTTP uses TCP (Layer 4), so a working ping does not guarantee that the web service is running or reachable on the correct port.
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 web server service is not running or is listening on a different port
Since the technician can successfully ping the server's IP address from the user's workstation, Layer 3 connectivity is confirmed, ruling out routing or gateway issues. DNS resolution returns the correct IP, so name resolution is not the problem. The firewall permits HTTP traffic, so access control is not blocking the connection. The most likely cause is that the web server service (e.g., Apache, IIS) is not running or is listening on a non-standard port (e.g., 8080 instead of 80), preventing the HTTP request from reaching the service even though the host is reachable.
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 web server service is not running or is listening on a different port
Why this is correct
This is the correct answer because a successful ping only verifies basic IP-level connectivity (Layer 3) to the server. If the web server application (e.g., Apache, Nginx, IIS) is not actively running, or if it's configured to listen on a non-standard TCP port (e.g., not 80 for HTTP or 443 for HTTPS) without the client specifying it, the client's browser cannot complete the TCP three-way handshake required to establish a connection to the web service. Consequently, even with network reachability, the application-layer service remains inaccessible, resulting in a connection refused or timeout error for web requests.
- ✗
The default gateway on the server is misconfigured
Why it's wrong here
If the default gateway on the server were misconfigured, the server would struggle to send traffic to devices outside its local subnet, or to respond to requests originating from different subnets. While the problem states users can access external websites normally, implying the workstation's gateway is fine, a server-side gateway issue would likely manifest as ping replies failing or being asymmetric, especially if the workstation is on a different subnet. Since ping to the server works, its ability to route traffic to the local network is confirmed, making a gateway misconfiguration improbable.
When this WOULD be correct
A question where users cannot access any external websites but can access internal resources, and a server cannot be pinged from outside its subnet. For example: 'Users in a remote office can access internal servers but not the internet. A technician can ping the remote office's router but not the company's web server. What is the most likely cause?'
- ✗
The user's workstation has a duplicate IP address
Why it's wrong here
A duplicate IP address on the user's workstation would cause widespread and intermittent network connectivity issues, not just an isolated problem accessing a specific internal web server. The Address Resolution Protocol (ARP) would experience conflicts, leading to unpredictable routing of traffic and dropped packets for all network communications, including ping, DNS lookups, and access to external websites. Since external websites are accessible normally and ping to the server works, a duplicate IP is highly unlikely to be the root cause.
- ✗
The DNS cache on the workstation is poisoned
Why it's wrong here
DNS cache poisoning would involve the workstation's local DNS resolver storing incorrect IP address mappings for domain names, causing connection attempts to be directed to the wrong server. However, the problem statement implicitly indicates that the technician has already confirmed that the DNS resolution for the internal web server's hostname correctly returns its expected IP address (e.g., 192.168.10.25). Since the name-to-IP resolution is accurate, DNS is functioning correctly for this specific target, eliminating cache poisoning as the cause of the connection failure.
When this WOULD be correct
A user cannot access a website by its hostname but can access it by IP address. DNS resolution returns a wrong IP (or fails), and flushing the DNS cache resolves the issue. This indicates DNS cache poisoning.
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 web server service is not running or is listening on a different portCorrect answer▾
Why this is correct
This is the correct answer because a successful ping only verifies basic IP-level connectivity (Layer 3) to the server. If the web server application (e.g., Apache, Nginx, IIS) is not actively running, or if it's configured to listen on a non-standard TCP port (e.g., not 80 for HTTP or 443 for HTTPS) without the client specifying it, the client's browser cannot complete the TCP three-way handshake required to establish a connection to the web service. Consequently, even with network reachability, the application-layer service remains inaccessible, resulting in a connection refused or timeout error for web requests.
✗The default gateway on the server is misconfiguredWrong answer — click to see why▾
Why this is wrong here
The default gateway on the server is misconfigured would prevent the server from reaching external networks, but here users can access external websites normally and can ping the server's IP, indicating the server is reachable. The issue is that users cannot reach the wiki server's web service, which is a higher-layer problem.
★ When this WOULD be the correct answer
A question where users cannot access any external websites but can access internal resources, and a server cannot be pinged from outside its subnet. For example: 'Users in a remote office can access internal servers but not the internet. A technician can ping the remote office's router but not the company's web server. What is the most likely cause?'
Why candidates choose this
Candidates often associate connectivity issues with gateway misconfiguration because it's a common cause of network unreachability, but they overlook that the ping succeeds, which rules out layer 3 problems between the workstation and the server.
✗The DNS cache on the workstation is poisonedWrong answer — click to see why▾
Why this is wrong here
DNS cache poisoning would cause incorrect IP resolution, but the question states that DNS returns the correct IP and ping to the server succeeds, so the issue is not DNS-related.
★ When this WOULD be the correct answer
A user cannot access a website by its hostname but can access it by IP address. DNS resolution returns a wrong IP (or fails), and flushing the DNS cache resolves the issue. This indicates DNS cache poisoning.
Why candidates choose this
Candidates may assume that any name resolution issue is due to DNS cache poisoning, especially when external access works but internal fails, without verifying that DNS actually returns the correct IP.
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?”
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Troubleshoot: Cable and Physical Layer
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.
Key term
Fully Qualified Domain Name
A Fully Qualified Domain Name is the complete and unambiguous website or server name that includes the host, domain, and top-level domain, leaving no room for guesswork.
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.