N10-009 Network Troubleshooting Practice Question
Users in a branch office report that file transfers to the data center are slow. A technician runs a traceroute and sees consistently high latency on hop 5. The technician then pings hop 5 and gets replies with varying response times. There are no errors reported on the interface. What is the most likely cause?
⚠ Common exam trap
The N10-009 exam often tests the distinction between latency caused by congestion (queuing delay) versus packet loss or routing loops, and the trap here is that candidates may assume high latency always indicates a routing loop or firewall inspection, but the varying response times with no errors point specifically to interface congestion.
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
✓
Interface congestion causing queuing delays.
High latency on hop 5 with varying response times and no interface errors indicates that the router at hop 5 is experiencing congestion, causing packets to be queued before transmission. This queuing delay results in increased and variable round-trip times (RTT), which is a classic symptom of interface congestion. The absence of errors rules out physical-layer issues, and the consistent latency on that specific hop points to a bottleneck at that router's egress interface.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Routing loop causing packets to be dropped.
Why it's wrong here
A routing loop occurs when packets are continuously forwarded between two or more routers without ever reaching their destination, eventually causing their Time-To-Live (TTL) value to expire. This scenario would primarily result in significant packet loss and connection timeouts, rather than just high, variable latency at a specific hop. Traceroute would show asterisks (*) for unreachable hops or the same router IP address appearing multiple times before a timeout.
When this WOULD be correct
This would be correct if the traceroute showed packets timing out after a certain hop and then reappearing at earlier hops, or if the hop count increased indefinitely.
- ✓
Interface congestion causing queuing delays.
Why this is correct
When a network interface receives more traffic than it can transmit, packets are temporarily held in a buffer, or queue. This queuing introduces delays, and because the amount of traffic and buffer occupancy can fluctuate, these delays become highly variable. Such congestion directly leads to increased and inconsistent latency, significantly impacting the throughput and completion time of large file transfers as packets wait longer to be forwarded.
- ✗
DNS server misconfiguration causing lookup delays.
Why it's wrong here
DNS (Domain Name System) is responsible for resolving hostnames to IP addresses. A misconfiguration or delay in DNS would primarily affect the initial connection setup by preventing name resolution, leading to "host not found" errors or application-level delays before data transfer even begins. It would not typically manifest as increased latency on an established Layer 3 traceroute hop, which operates using IP addresses directly.
When this WOULD be correct
A user reports slow web browsing; a technician finds that name resolution takes several seconds while pinging IP addresses is fast. DNS server misconfiguration would be the likely cause.
- ✗
Firewall inspecting traffic and adding latency.
Why it's wrong here
Firewall inspection, particularly stateful packet inspection or deep packet inspection, inherently adds a processing overhead to each packet, resulting in a consistent amount of latency. While this overhead can be noticeable, it typically manifests as a stable, predictable increase in round-trip time, not the variable latency indicative of queuing. Variable response times suggest dynamic network conditions rather than a fixed processing delay from a security device.
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.
✓Interface congestion causing queuing delays.Correct answer▾
Why this is correct
When a network interface receives more traffic than it can transmit, packets are temporarily held in a buffer, or queue. This queuing introduces delays, and because the amount of traffic and buffer occupancy can fluctuate, these delays become highly variable. Such congestion directly leads to increased and inconsistent latency, significantly impacting the throughput and completion time of large file transfers as packets wait longer to be forwarded.
✗Routing loop causing packets to be dropped.Wrong answer — click to see why▾
Why this is wrong here
A routing loop typically causes packet loss or TTL expiration, not consistently high latency with varying response times and no interface errors.
★ When this WOULD be the correct answer
This would be correct if the traceroute showed packets timing out after a certain hop and then reappearing at earlier hops, or if the hop count increased indefinitely.
Why candidates choose this
Candidates may associate high latency with routing issues, but routing loops usually cause packet loss rather than just delay.
✗DNS server misconfiguration causing lookup delays.Wrong answer — click to see why▾
Why this is wrong here
DNS misconfiguration causes lookup delays before a connection is established, not high latency on a specific hop during a traceroute or ping after the connection is made.
★ When this WOULD be the correct answer
A user reports slow web browsing; a technician finds that name resolution takes several seconds while pinging IP addresses is fast. DNS server misconfiguration would be the likely cause.
Why candidates choose this
Candidates may confuse general network slowness with DNS issues, not realizing that traceroute and ping operate at the network layer and bypass DNS.
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?”
Go deeper
Related to this question
Learn chapter
Troubleshoot: Cable and Physical Layer
Key term
Traceroute
Traceroute is a network diagnostic tool that maps the route data packets take from your computer to a destination, showing each intermediate hop and the time taken.
Key term
Latency
Latency is the time delay between a request being sent over a network and the response being received, often measured in milliseconds.
About these practice questions
This N10-009 question is part of Courseiva's 464-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.