N10-009 Network Implementation Practice Question
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?
⚠ Common exam trap
The N10-009 exam 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.
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
✓
Multimode fiber with 1000BASE-SX transceivers
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.
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
While 1000BASE-LX transceivers can operate over single-mode fiber for distances up to 5 kilometers (or 550m over multimode with a mode-conditioning patch cable), deploying single-mode fiber for a relatively short 400-meter link is an over-specification. Single-mode fiber infrastructure and its associated transceivers are considerably more expensive than multimode alternatives. This choice introduces unnecessary capital expenditure for a distance that can be more economically and efficiently covered by multimode fiber solutions.
When this WOULD be correct
A question requiring a link longer than 550 meters (e.g., 2 km) with high EMI, where cost is less of a concern. Single-mode fiber with 1000BASE-LX would be correct for distances up to 5 km.
- ✓
Multimode fiber with 1000BASE-SX transceivers
Why this is correct
1000BASE-SX is a Gigabit Ethernet standard specifically designed for short-wavelength (850 nm) transmission over multimode fiber. It reliably supports distances up to 550 meters when using OM3 or OM4 fiber, making it an ideal and highly suitable choice for a 400-meter link. This option provides the necessary 1Gbps bandwidth at the most cost-effective price point for the specified distance, avoiding unnecessary expenses associated with longer-reach or higher-speed solutions.
- ✗
Multimode fiber with 10GBASE-SR transceivers
Why it's wrong here
10GBASE-SR transceivers are designed for 10 Gigabit Ethernet over multimode fiber, typically supporting distances up to 300 meters on OM3 fiber or 400 meters on OM4 fiber. Although it could potentially cover the 400m distance with the correct multimode fiber grade, the question implies a standard connection, not necessarily 10Gbps. Opting for 10GBASE-SR is significantly more expensive than a 1Gbps solution like 1000BASE-SX, representing an unnecessary cost if 1Gbps bandwidth is sufficient for the switch interconnection.
When this WOULD be correct
A network engineer needs to connect two switches 300 meters apart with 10 Gbps throughput in a data center environment using OM3 multimode fiber. The question specifies high bandwidth requirements and a distance within 10GBASE-SR's reach, making it the correct choice.
- ✗
Single-mode fiber with 1000BASE-EX transceivers
Why it's wrong here
1000BASE-EX is a long-reach Gigabit Ethernet standard specifically engineered for single-mode fiber, capable of transmitting data up to 40 kilometers (25 miles). Utilizing such an extended-reach solution for a mere 400-meter connection is grossly excessive and economically unsound. The transceivers and associated single-mode fiber infrastructure for 1000BASE-EX are substantially more expensive than what is required for this relatively short distance, making it an impractical and wasteful choice.
When this WOULD be correct
A question requiring a link distance of 10 km or more, such as connecting two buildings across a campus, where single-mode fiber and 1000BASE-EX transceivers provide the necessary reach and cost-efficiency for long distances.
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.
✓Multimode fiber with 1000BASE-SX transceiversCorrect answer▾
Why this is correct
1000BASE-SX is a Gigabit Ethernet standard specifically designed for short-wavelength (850 nm) transmission over multimode fiber. It reliably supports distances up to 550 meters when using OM3 or OM4 fiber, making it an ideal and highly suitable choice for a 400-meter link. This option provides the necessary 1Gbps bandwidth at the most cost-effective price point for the specified distance, avoiding unnecessary expenses associated with longer-reach or higher-speed solutions.
✗Single-mode fiber with 1000BASE-LX transceiversWrong answer — click to see why▾
Why this is wrong here
Single-mode fiber with 1000BASE-LX can reach 400 meters, but multimode fiber with 1000BASE-SX is more cost-effective for this distance and is designed for shorter runs with high EMI. Single-mode fiber and transceivers are more expensive, making option A less cost-effective.
★ When this WOULD be the correct answer
A question requiring a link longer than 550 meters (e.g., 2 km) with high EMI, where cost is less of a concern. Single-mode fiber with 1000BASE-LX would be correct for distances up to 5 km.
Why candidates choose this
Candidates may think single-mode fiber is always better for longer distances and EMI resistance, overlooking that 400 meters is well within multimode's range and that multimode is cheaper.
✗Multimode fiber with 10GBASE-SR transceiversWrong answer — click to see why▾
Why this is wrong here
10GBASE-SR transceivers are designed for 10 Gbps speeds, which is overkill for a 400-meter link and more expensive than 1000BASE-SX. Additionally, multimode fiber with 10GBASE-SR typically supports distances up to 300 meters (OM3) or 400 meters (OM4) at 10 Gbps, but the question asks for a cost-effective solution, and 10GBASE-SR is not cost-effective for 1 Gbps needs.
★ When this WOULD be the correct answer
A network engineer needs to connect two switches 300 meters apart with 10 Gbps throughput in a data center environment using OM3 multimode fiber. The question specifies high bandwidth requirements and a distance within 10GBASE-SR's reach, making it the correct choice.
Why candidates choose this
Candidates may confuse the distance capabilities of 10GBASE-SR (up to 400 meters with OM4) and think it is suitable for the 400-meter distance, while overlooking that the question requires cost-effectiveness and does not specify 10 Gbps speed.
✗Single-mode fiber with 1000BASE-EX transceiversWrong answer — click to see why▾
Why this is wrong here
1000BASE-EX transceivers are designed for single-mode fiber and support distances up to 40 km, which is overkill and more expensive for a 400-meter link. Multimode fiber with 1000BASE-SX is more cost-effective for this distance.
★ When this WOULD be the correct answer
A question requiring a link distance of 10 km or more, such as connecting two buildings across a campus, where single-mode fiber and 1000BASE-EX transceivers provide the necessary reach and cost-efficiency for long distances.
Why candidates choose this
Candidates may assume that single-mode fiber is always better for longer distances and overlook the cost factor, or they might confuse 1000BASE-EX with 1000BASE-LX, which is also single-mode but for shorter distances.
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
Physical Network Infrastructure
Key term
Transceiver
A transceiver is a device that both transmits and receives signals, combining a transmitter and a receiver into a single unit for communication over a network medium.
Key term
Multimode fiber
A type of optical fiber that carries multiple light signals simultaneously over short to medium distances, commonly used in local area networks and data centers.
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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.