N10-009 Network Implementation Practice Question
A network administrator needs to connect two buildings 2 km apart using single-mode fiber. Which transceiver type should be used?
⚠ Common exam trap
The N10-009 exam often tests the misconception that 1000BASE-SX can be used for long distances because it is a common Gigabit Ethernet standard, but the trap is that SX is strictly for multimode fiber and limited to 550 m, while LX is the correct choice for single-mode runs beyond that distance.
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
✓
1000BASE-LX
1000BASE-LX (Long Wavelength) operates at 1310 nm over single-mode fiber and supports distances up to 5 km (and often up to 10 km with proper link budgets), making it the correct choice for a 2 km link. Single-mode fiber is required for distances beyond 550 m, and 1000BASE-LX is the Gigabit Ethernet standard designed for such single-mode runs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
1000BASE-T
Why it's wrong here
1000BASE-T is an inappropriate choice because it operates exclusively over unshielded twisted-pair (UTP) copper cabling, specifically Category 5e or higher. This standard is designed for short-distance connections within a local area network, with a maximum segment length of only 100 meters. This distance limitation makes it entirely inadequate for connecting buildings 2 kilometers apart, irrespective of the fiber requirement.
When this WOULD be correct
A question asking for a transceiver to connect two switches within the same data center, less than 100 meters apart, using existing Cat6a cabling. 1000BASE-T would be correct for that scenario.
- ✗
1000BASE-SX
Why it's wrong here
1000BASE-SX is an unsuitable option as it is engineered for use with multimode fiber, not single-mode fiber as specified in the question. Furthermore, the "SX" (Short Wavelength) standard utilizes 850 nm lasers and is typically limited to a maximum distance of 550 meters over multimode fiber, which is significantly less than the required 2 kilometers for this connection.
When this WOULD be correct
A question specifying a link distance under 550 meters (e.g., within a data center) using multimode fiber would make 1000BASE-SX the correct choice.
- ✓
1000BASE-LX
Why this is correct
1000BASE-LX is the correct choice because it is specifically designed for Gigabit Ethernet over single-mode fiber optic cabling. The "LX" in its name signifies "Long Wavelength," indicating its use of longer wavelength lasers (1310 nm) suitable for extended distances. This standard supports reliable data transmission up to 5 kilometers, making it perfectly suitable for the 2 km distance between the two buildings using single-mode fiber.
- ✗
10GBASE-SR
Why it's wrong here
10GBASE-SR is an incorrect selection primarily because it is designed for 10 Gigabit Ethernet over multimode fiber, not single-mode fiber. The "SR" (Short Reach) designation indicates its use of 850 nm lasers and a typical maximum reach of 300 meters on OM3 or 400 meters on OM4 multimode fiber. This standard is incompatible with single-mode fiber and falls far short of the required 2 km distance.
When this WOULD be correct
When connecting devices within a data center using multimode fiber at distances up to 300 meters, 10GBASE-SR is the correct choice for 10 Gbps Ethernet.
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.
✓1000BASE-LXCorrect answer▾
Why this is correct
1000BASE-LX is the correct choice because it is specifically designed for Gigabit Ethernet over single-mode fiber optic cabling. The "LX" in its name signifies "Long Wavelength," indicating its use of longer wavelength lasers (1310 nm) suitable for extended distances. This standard supports reliable data transmission up to 5 kilometers, making it perfectly suitable for the 2 km distance between the two buildings using single-mode fiber.
✗1000BASE-TWrong answer — click to see why▾
Why this is wrong here
1000BASE-T uses twisted-pair copper cabling with a maximum distance of 100 meters, far short of the 2 km requirement. Single-mode fiber requires a different transceiver type.
★ When this WOULD be the correct answer
A question asking for a transceiver to connect two switches within the same data center, less than 100 meters apart, using existing Cat6a cabling. 1000BASE-T would be correct for that scenario.
Why candidates choose this
Candidates may confuse transceiver types or assume 'T' stands for fiber, or they might overlook the distance limitation and focus only on the speed requirement.
✗1000BASE-SXWrong answer — click to see why▾
Why this is wrong here
1000BASE-SX uses multimode fiber and has a maximum reach of about 550 meters, insufficient for a 2 km link.
★ When this WOULD be the correct answer
A question specifying a link distance under 550 meters (e.g., within a data center) using multimode fiber would make 1000BASE-SX the correct choice.
Why candidates choose this
Candidates may confuse SX with LX or assume 'S' stands for single-mode, not short wavelength, leading to incorrect selection for longer distances.
✗10GBASE-SRWrong answer — click to see why▾
Why this is wrong here
10GBASE-SR is designed for multimode fiber and supports distances up to 300 meters, insufficient for 2 km over single-mode fiber.
★ When this WOULD be the correct answer
When connecting devices within a data center using multimode fiber at distances up to 300 meters, 10GBASE-SR is the correct choice for 10 Gbps Ethernet.
Why candidates choose this
Candidates may confuse SR with LX, assuming both support long distances, or overlook the fiber type requirement (multimode vs. single-mode).
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
Ethernet Switching and VLANs
Key term
Single-mode fiber
Single-mode fiber is a type of optical fiber used in high-speed, long-distance networking that transmits a single light signal along a very thin core, minimizing signal loss and enabling data to travel many kilometers without repeaters.
Key term
Ethernet
Ethernet is a wired networking technology that connects devices like computers, printers, and servers to each other and to the internet using cables.
About these practice questions
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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.