The correct choice is multimode fiber with 1000BASE-SX transceivers, as this combination delivers cost-effective 1 Gbps connectivity for the 400-meter run while resisting high electromagnetic interference. Multimode fiber’s larger core allows cheaper VCSEL-based SX optics to transmit reliably over distances up to 550 meters, making it ideal for short-to-medium links where budget matters. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding that 1000BASE-SX is the affordable option for runs under 550 meters, while 1000BASE-LX (single-mode) is overkill and more expensive for this distance. A common trap is choosing single-mode fiber for longer reach, but remember: SX stands for “short wavelength” and is paired with multimode for shorter, cost-sensitive links. Memory tip: “SX for Short, LX for Long” — and for runs under half a kilometer, keep it SX.
N10-009 Network Implementation Practice Question
This N10-009 practice question tests your understanding of network implementation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 network engineer needs to connect two switches located 400 meters apart. The cable run includes high electromagnetic interference from nearby machinery. The engineer decides to use fiber optic cabling. Which transceiver type and fiber combination should be used to ensure the link reaches 400 meters while remaining cost-effective?
Why wrong: Single-mode fiber can reach 400m, but it is overkill and more expensive than multimode for this distance.
B
Multimode fiber with 1000BASE-SX transceivers
1000BASE-SX over multimode fiber supports distances up to 550 meters, making it suitable and cost-effective for 400m.
C
Multimode fiber with 10GBASE-SR transceivers
Why wrong: 10GBASE-SR can also work over multimode fiber but typically supports shorter distances (300m for OM3) and is more expensive than 1Gbps options if 1Gbps is sufficient.
D
Single-mode fiber with 1000BASE-EX transceivers
Why wrong: 1000BASE-EX is designed for longer distances (up to 40km), which is excessive and costly for 400m.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Multimode fiber with 1000BASE-SX transceivers
Option B is correct because 1000BASE-SX transceivers over multimode fiber (typically OM2 or OM3) can reliably reach 400 meters at 1 Gbps, and this combination is cost-effective for short-to-medium distances. Multimode fiber uses a larger core that is cheaper to terminate and pair with lower-cost VCSEL-based SX optics, making it ideal for runs under 550 meters in environments with high EMI.
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.
✗
Single-mode fiber with 1000BASE-LX transceivers
Why it's wrong here
Single-mode fiber can reach 400m, but it is overkill and more expensive than multimode for this distance.
✓
Multimode fiber with 1000BASE-SX transceivers
Why this is correct
1000BASE-SX over multimode fiber supports distances up to 550 meters, making it suitable and cost-effective for 400m.
Related concept
Read the scenario before looking for a memorised answer.
✗
Multimode fiber with 10GBASE-SR transceivers
Why it's wrong here
10GBASE-SR can also work over multimode fiber but typically supports shorter distances (300m for OM3) and is more expensive than 1Gbps options if 1Gbps is sufficient.
✗
Single-mode fiber with 1000BASE-EX transceivers
Why it's wrong here
1000BASE-EX is designed for longer distances (up to 40km), which is excessive and costly for 400m.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that single-mode fiber is always superior or necessary for any distance over 100 meters, but the trap here is ignoring the cost-effectiveness requirement and assuming LX is the only option for 400 meters, when SX over multimode is both sufficient and cheaper.
Detailed technical explanation
How to think about this question
Multimode fiber (e.g., OM3 with 850 nm VCSELs) supports 1000BASE-SX up to 550 meters, so 400 meters is well within spec. The key differentiator is cost: multimode transceivers use cheaper VCSEL lasers and larger-core fiber that allows looser alignment tolerances, reducing installation and component costs. In real-world deployments, high EMI from machinery does not affect fiber, but the choice between single-mode and multimode often hinges on distance and budget—here, 400 meters is the sweet spot for cost-effective multimode.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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 Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Multimode fiber with 1000BASE-SX transceivers — Option B is correct because 1000BASE-SX transceivers over multimode fiber (typically OM2 or OM3) can reliably reach 400 meters at 1 Gbps, and this combination is cost-effective for short-to-medium distances. Multimode fiber uses a larger core that is cheaper to terminate and pair with lower-cost VCSEL-based SX optics, making it ideal for runs under 550 meters in environments with high EMI.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer needs to connect two buildings that are 200 meters apart with a 1 Gbps link. The path is outdoors and susceptible to lightning strikes. Which cable type is the most appropriate for this scenario?
easy
A.Cat6a UTP
✓ B.Multimode fiber optic
C.Cat5e UTP
D.Single-mode fiber optic
Why B: Multimode fiber optic cable is the most appropriate choice because it supports 1 Gbps over distances up to 550 meters (using OM2/OM3 fiber) and is completely immune to electromagnetic interference (EMI) from lightning strikes. Unlike copper cabling, fiber uses light pulses for transmission, so it does not conduct electricity, making it ideal for outdoor runs between buildings where lightning is a risk.
Variation 2. A network engineer is planning to connect two switches that are 150 meters apart. The link must support at least 1 Gbps and the budget is limited. Which cable type should be used?
medium
A.Cat6a twisted-pair copper
✓ B.Multimode fiber optic
C.Single-mode fiber optic
D.Cat5e twisted-pair copper
Why B: Multimode fiber optic cable supports 1 Gbps over distances up to 550 meters (OM2) or more, easily covering the 150-meter requirement at a lower cost than single-mode fiber. It is the best choice for this distance and budget because twisted-pair copper (Cat5e/Cat6a) is limited to 100 meters for 1 Gbps, and single-mode fiber is more expensive due to laser-based transceivers.
Last reviewed: Jun 11, 2026
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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.
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