N10-009 Network Operations Practice Question
A network administrator is troubleshooting an intermittent connectivity issue between two buildings. The administrator suspects a physical layer problem and wants to measure the signal loss on a fiber optic cable run. Which tool should the administrator use?
⚠ Common exam trap
Many exam-takers confuse a cable tester with an OTDR; a cable tester is for copper continuity, while an OTDR measures optical loss and distance on fiber.
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
✓
Optical time-domain reflectometer (OTDR)
An OTDR is specifically designed to measure signal loss and characterize fiber optic cables. It can identify attenuation, breaks, and other issues along the fiber run. A cable tester, toner probe, and multimeter are suitable for copper cabling or electrical measurements, not for measuring optical loss on fiber.
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 measures electrical properties such as voltage, current, and resistance on copper conductors. It is not designed for fiber optic testing and cannot measure optical signal loss. Using a multimeter on fiber could damage the fiber or the meter, and it would not provide any useful attenuation data.
- ✗
Cable tester
Why it's wrong here
A cable tester verifies continuity and correct pinout on copper cables, such as twisted-pair Ethernet. It does not measure optical signal loss or attenuation on fiber optic cabling. For fiber, a cable tester may only confirm basic continuity, but it cannot provide the dB loss measurements needed to identify attenuation issues over distance.
- ✓
Optical time-domain reflectometer (OTDR)
Why this is correct
An OTDR sends light pulses into a fiber and measures the reflected light to characterize the fiber's condition. It can measure attenuation, splice loss, connector loss, and locate breaks or bends along the entire length. This makes it the appropriate tool for measuring signal loss on a fiber optic cable run between buildings.
- ✗
Toner probe
Why it's wrong here
A toner probe is used to trace and identify cables within a bundle or at a patch panel. It does not measure signal loss or attenuation on fiber optic cables. While useful for locating the correct cable, it provides no quantitative data about optical power loss or fiber integrity.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
Go deeper
Related to this question
Learn chapter
Network Diagram Types: Physical, Logical, Wiring
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
Key term
Toner probe
A toner probe is a two-part tool used in networking to trace and identify specific cables within a bundle of wires, often by sending an audio signal down the wire and detecting it with a wand.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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.