The answer is CPU overload on the router. High latency with varying values, known as jitter, on a specific hop combined with clean interface error counters points directly to a router whose processor is overwhelmed. When a router’s CPU is saturated, it must queue packets for processing, introducing variable delays even though the physical layer—checked via error counters—shows no CRC or framing issues. On the CompTIA Network+ N10-009 exam, this scenario tests your ability to distinguish between layer 1/2 problems (which show interface errors) and layer 3 processing bottlenecks. A common trap is to blame bandwidth or cabling when the interface counters are clean; instead, remember that CPU overload causes latency without errors. Memory tip: “Clean counters, crazy latency? Check the CPU.”
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.
Users in a remote office are experiencing slow file transfers to the data center. The network technician runs a traceroute and discovers high latency on a specific hop. The technician pings that hop and gets replies with varying latency. The technician also checks the interface error counters on the router at that hop and finds no errors. 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: "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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
CPU overload on the router
High latency with varying values (jitter) combined with clean interface error counters points to a router that is overwhelmed by processing demands. When a router's CPU is overloaded, it queues packets for processing, introducing variable delays even though the physical layer shows no errors. This matches the symptom of a specific hop showing latency spikes without CRC or framing errors.
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.
✗
Duplex mismatch
Why it's wrong here
A duplex mismatch typically results in CRC errors and collisions, which are not present here.
✗
Incorrect MTU
Why it's wrong here
An MTU mismatch would cause fragmentation or packet drops, but the ping replies suggest the link is working with variable latency.
✗
Route flapping
Why it's wrong here
Route flapping would cause intermittent connectivity and unreachability, not consistently high latency.
✓
CPU overload on the router
Why this is correct
High CPU utilization can cause packet queuing delays, leading to variable latency without interface errors.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see 'no errors' on the interface and assume the problem must be at a higher layer, but CompTIA often tests that CPU overload can cause latency without any interface errors, misleading those who think clean counters always mean a healthy router.
Detailed technical explanation
How to think about this question
CPU overload on a router can stem from excessive routing protocol processing, ACL logging, or high packet rates requiring process-switching instead of fast-switching or CEF. This forces packets into the router's process-level queues, introducing queuing delays that vary with CPU load. In real-world scenarios, a sudden spike in BGP updates or a misconfigured SNMP polling interval can cause this symptom without any physical-layer errors.
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 practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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: CPU overload on the router — High latency with varying values (jitter) combined with clean interface error counters points to a router that is overwhelmed by processing demands. When a router's CPU is overloaded, it queues packets for processing, introducing variable delays even though the physical layer shows no errors. This matches the symptom of a specific hop showing latency spikes without CRC or framing errors.
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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