The answer is a faulty NAT configuration because the user can ping the default gateway and access the intranet, confirming Layer 3 connectivity to the local router, yet cannot reach the internet. This specific symptom isolates the issue to Network Address Translation, which is required to translate private RFC 1918 addresses like 192.168.1.x into a public IP for external routing; without it, packets reach the gateway but cannot be forwarded beyond the local network. On the CompTIA Network+ N10-009 exam, this scenario tests your ability to distinguish between local routing failures and NAT configuration issues—a common trap is assuming a gateway ping failure, but here the gateway works, so the problem lies in the router’s inability to perform address translation. Remember the memory tip: “Gateway ping, no internet? NAT’s the culprit.”
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 company's intranet but not the internet. The technician checks the IP configuration and finds that the default gateway is set to 192.168.1.1, and the user can ping that IP. Which of the following 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.
Why wrong: An incorrect DNS server would affect name resolution, but the user might still access the internet via IP; however, the question states intranet works, so DNS might be fine for internal names.
B
The router's NAT configuration is faulty.
NAT translates private IPs to public IPs. If it is misconfigured, internal hosts can reach the gateway but not the internet.
C
The DHCP server is not providing a default gateway.
Why wrong: Since the user has a manually set default gateway and can ping it, DHCP is not the issue.
D
The user's workstation has a static IP address.
Why wrong: Static IP is not inherently problematic; it simply means the address wasn't obtained via DHCP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router's NAT configuration is faulty.
Since the user can ping the default gateway (192.168.1.1) and access the intranet, Layer 3 connectivity to the local router is functional. The inability to reach the internet, despite having a valid gateway, points to a failure in the router's NAT (Network Address Translation) configuration. NAT is required to translate private RFC 1918 addresses (like 192.168.1.x) to a public IP for internet access; without it, packets are routed to the gateway but cannot be forwarded beyond the local network.
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 DNS server address is incorrect.
Why it's wrong here
An incorrect DNS server would affect name resolution, but the user might still access the internet via IP; however, the question states intranet works, so DNS might be fine for internal names.
✓
The router's NAT configuration is faulty.
Why this is correct
NAT translates private IPs to public IPs. If it is misconfigured, internal hosts can reach the gateway but not the internet.
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 DHCP server is not providing a default gateway.
Why it's wrong here
Since the user has a manually set default gateway and can ping it, DHCP is not the issue.
✗
The user's workstation has a static IP address.
Why it's wrong here
Static IP is not inherently problematic; it simply means the address wasn't obtained via DHCP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume internet access failure is always a DNS or gateway issue, but the ability to ping the gateway and access local resources isolates the problem to the router's NAT translation, not the workstation's IP configuration.
Detailed technical explanation
How to think about this question
NAT (specifically PAT, Port Address Translation, per RFC 2663) rewrites the source IP and port of outbound packets to the router's public IP. If NAT is misconfigured—e.g., missing 'ip nat inside' and 'ip nat outside' interface commands, or an empty access list for dynamic NAT—the router will drop packets destined for the internet after a successful routing table lookup. A common real-world scenario is a router that has a default route to the ISP but lacks NAT overload, causing traffic to reach the ISP but not return.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: The router's NAT configuration is faulty. — Since the user can ping the default gateway (192.168.1.1) and access the intranet, Layer 3 connectivity to the local router is functional. The inability to reach the internet, despite having a valid gateway, points to a failure in the router's NAT (Network Address Translation) configuration. NAT is required to translate private RFC 1918 addresses (like 192.168.1.x) to a public IP for internet access; without it, packets are routed to the gateway but cannot be forwarded beyond the local network.
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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