The answer is an optical power meter because the link lights are green, confirming Layer 1 signal presence, yet intermittent connectivity points to marginal or fluctuating signal strength that a simple LED cannot reveal. An optical power meter measures the exact light level in dBm, allowing you to verify whether the received power falls within the receiver’s sensitivity range—a critical check when troubleshooting fiber link issues where the link is up but performance is unreliable. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding that a green link LED only indicates carrier detect, not signal quality; the common trap is choosing a cable tester or OTDR, which are overkill for basic power verification. Remember the memory tip: “Green light means alive, but power meter tells if it thrives.”
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 technician is troubleshooting intermittent connectivity issues on a fiber link between two switches. The link light on both switches is green. Which of the following tools should the technician use to further investigate the issue?
Why wrong: A multimeter is used for electrical measurements on copper cables, not for fiber optic signals.
B
Tone generator
Why wrong: A tone generator is used to trace copper cables, not for fiber optic troubleshooting.
C
Optical power meter
An optical power meter measures the light power in a fiber link, helping to identify signal loss that could cause intermittent issues.
D
Cable certifier
Why wrong: A cable certifier is used for certification testing of copper or fiber, but an optical power meter is more direct for troubleshooting signal strength.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Optical power meter
The correct tool is an optical power meter because the link lights are green, indicating Layer 1 signal presence, but intermittent connectivity suggests the signal strength may be marginal or fluctuating. An optical power meter measures the exact light level in dBm to verify it falls within the receiver's sensitivity range, which a simple link LED cannot detect.
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.
✗
Multimeter
Why it's wrong here
A multimeter is used for electrical measurements on copper cables, not for fiber optic signals.
✗
Tone generator
Why it's wrong here
A tone generator is used to trace copper cables, not for fiber optic troubleshooting.
✓
Optical power meter
Why this is correct
An optical power meter measures the light power in a fiber link, helping to identify signal loss that could cause intermittent issues.
Related concept
Read the scenario before looking for a memorised answer.
✗
Cable certifier
Why it's wrong here
A cable certifier is used for certification testing of copper or fiber, but an optical power meter is more direct for troubleshooting signal strength.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a green link light guarantees a healthy connection, but Cisco often tests that Layer 1 indicators only confirm signal presence, not signal quality, so an optical power meter is required to diagnose marginal power levels causing intermittent errors.
Detailed technical explanation
How to think about this question
Fiber optic receivers have a minimum and maximum input power range (e.g., -3 dBm to -20 dBm for 1000BASE-LX); if the power is too low (attenuation) or too high (saturation), bit errors occur even though the link LED shows green. An optical power meter measures the actual received power, and a fiber inspection microscope would also be needed to check for dirty or damaged end faces, a common cause of intermittent issues.
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: Optical power meter — The correct tool is an optical power meter because the link lights are green, indicating Layer 1 signal presence, but intermittent connectivity suggests the signal strength may be marginal or fluctuating. An optical power meter measures the exact light level in dBm to verify it falls within the receiver's sensitivity range, which a simple link LED cannot detect.
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.
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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