- A
The user's computer firewall is blocking outbound web traffic.
Why wrong: If the firewall were blocking web traffic, the traceroute would still likely show the first hop, but the subsequent hops might fail due to the firewall dropping the ICMP packets? However, the traceroute uses ICMP or UDP which may be blocked by different rules. The pattern of first hop success and second hop timeout points to a routing issue beyond the gateway.
- B
The DNS server is not resolving domain names.
Why wrong: DNS resolution is not used in traceroute; traceroute uses IP addresses. The inability to reach external IPs indicates a routing problem, not DNS.
- C
The router's default route pointing to the ISP is missing or incorrectly configured.
This is the most likely cause. The router can forward packets to the default gateway, but without a valid default route to the next hop ISP router, traffic cannot leave the local network.
- D
The ISP's DNS server is unreachable.
Why wrong: Traceroute does not depend on DNS; it uses IP addresses. Even if DNS were unreachable, traceroute to an IP would still work. The failure occurs at the second hop, indicating a routing issue.
Quick Answer
The answer is a missing or incorrectly configured default route on the router. This is correct because the traceroute reveals that the user’s computer can reach its local default gateway (the first hop) with low latency, but the second hop—the ISP’s router—times out. Without a valid default route pointing to the ISP, the local router has no path for traffic destined outside the subnet, so packets to external addresses like 8.8.8.8 are dropped even though DHCP and local connectivity work fine. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of routing fundamentals and the difference between local and external reachability; a common trap is assuming the problem is with the user’s computer or DHCP since those work correctly. Remember the memory tip: “First hop works, second hop dies—check the default route to the skies.”
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's computer obtains an IP address from DHCP, can ping the default gateway, but cannot access any external websites. The technician runs 'tracert 8.8.8.8' from the user's computer. The first hop shows the default gateway with low latency, but the second hop shows a timeout. What 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:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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 router's default route pointing to the ISP is missing or incorrectly configured.
The traceroute shows that the user's computer can reach the default gateway (first hop) but times out at the second hop, which is the ISP's router. This indicates that the local router does not have a valid default route pointing to the ISP, so it cannot forward traffic beyond the local subnet. Without a correct default route, packets destined for external networks (like 8.8.8.8) are dropped, even though the user's computer can ping the gateway and obtain an IP via DHCP.
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 user's computer firewall is blocking outbound web traffic.
Why it's wrong here
If the firewall were blocking web traffic, the traceroute would still likely show the first hop, but the subsequent hops might fail due to the firewall dropping the ICMP packets? However, the traceroute uses ICMP or UDP which may be blocked by different rules. The pattern of first hop success and second hop timeout points to a routing issue beyond the gateway.
- ✗
The DNS server is not resolving domain names.
- ✓
The router's default route pointing to the ISP is missing or incorrectly configured.
Why this is correct
This is the most likely cause. The router can forward packets to the default gateway, but without a valid default route to the next hop ISP router, traffic cannot leave the local network.
Clue confirmation
The clue words "first", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The ISP's DNS server is unreachable.
Why it's wrong here
Traceroute does not depend on DNS; it uses IP addresses. Even if DNS were unreachable, traceroute to an IP would still work. The failure occurs at the second hop, indicating a routing issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a DNS resolution failure with a routing failure, but the traceroute to an IP address bypasses DNS entirely, so the timeout at the second hop isolates the issue to the router's default route rather than DNS or the local firewall.
Trap categories for this question
Command / output trap
If the firewall were blocking web traffic, the traceroute would still likely show the first hop, but the subsequent hops might fail due to the firewall dropping the ICMP packets? However, the traceroute uses ICMP or UDP which may be blocked by different rules. The pattern of first hop success and second hop timeout points to a routing issue beyond the gateway.
Detailed technical explanation
How to think about this question
Traceroute works by sending packets with incrementing TTL values; the first hop (TTL=1) elicits a response from the default gateway, but the second hop (TTL=2) times out because the router has no route to the destination and drops the packet, often sending an ICMP 'Destination Unreachable' (Type 3, Code 0) or simply timing out. In a typical home or small office setup, the router's default route (0.0.0.0/0) must point to the ISP's next-hop IP; if this route is missing or misconfigured (e.g., pointing to a wrong gateway), traffic cannot leave the local network. DHCP provides the client with an IP and gateway, but does not configure the router's default route—that is set manually or via PPPoE/static configuration.
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 router's default route pointing to the ISP is missing or incorrectly configured. — The traceroute shows that the user's computer can reach the default gateway (first hop) but times out at the second hop, which is the ISP's router. This indicates that the local router does not have a valid default route pointing to the ISP, so it cannot forward traffic beyond the local subnet. Without a correct default route, packets destined for external networks (like 8.8.8.8) are dropped, even though the user's computer can ping the gateway and obtain an IP via DHCP.
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: "first", "most likely". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a user's inability to access the internet. The user can successfully ping the default gateway and internal servers, but cannot ping a public IP address such as 8.8.8.8. The technician checks the firewall logs and confirms that outbound ICMP traffic to 8.8.8.8 is permitted. Which of the following is the most likely cause of the issue?
medium- A.Incorrect DNS server configuration on the workstation
- ✓ B.Missing default route on the router
- C.Incorrect subnet mask on the workstation
- D.Malware on the workstation is blocking ICMP traffic
Why B: The user can ping the default gateway and internal servers, which confirms that Layer 2 and Layer 3 connectivity within the local network is working. However, the inability to ping a public IP (8.8.8.8) indicates that traffic is not being forwarded beyond the local subnet. A missing default route on the router means the router does not know where to send packets destined for external networks, so it drops them. Since outbound ICMP is permitted on the firewall, the issue is routing, not filtering.
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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