- A
Single-mode fiber (SMF) typically uses a larger core diameter than multimode fiber (MMF).
Why wrong: This is incorrect; SMF has a much smaller core (about 9 microns) compared to MMF (50 or 62.5 microns).
- B
Multimode fiber (MMF) is generally preferred for longer-distance links, such as between buildings on a campus network.
Why wrong: This is incorrect; MMF is used for shorter distances (up to a few hundred meters for high data rates), while SMF is preferred for longer links.
- C
A 1000BASE-LX SFP transceiver operating over single-mode fiber can support distances up to 10 km.
Why wrong: 1000BASE-LX uses a long-wavelength laser (1300 nm) and is specified for single-mode fiber distances up to 10 km (and up to 550 m over multimode fiber with mode conditioning patch cables).
- D
When using a 10GBASE-SR SFP+ transceiver over OM3 multimode fiber, the maximum supported distance is 300 meters.
10GBASE-SR over OM3 fiber (50/125 µm, 2000 MHz*km bandwidth) supports distances up to 300 meters. Over OM4 fiber, the distance increases to 400 meters.
- E
Fiber optic cabling is immune to electromagnetic interference (EMI), making it ideal for environments with high electrical noise.
Fiber uses light to transmit data, so EMI does not affect the signal, making it suitable for noisy industrial environments.
Quick Answer
The correct answer identifies that fiber optic cabling is immune to electromagnetic interference (EMI), making it ideal for electrically noisy environments, and that 10GBASE-SR over OM3 multimode fiber supports distances up to 300 meters. This immunity to EMI is a fundamental advantage over copper cabling, which can suffer from signal degradation in industrial settings or near heavy machinery, while the 300-meter reach for 10GBASE-SR on OM3 reflects the practical balance between cost and performance in modern enterprise networks. On the CCNA 200-301 v2 exam, this question tests your understanding of fiber types and their deployment scenarios, often appearing as a trap where single-mode fiber is incorrectly described as having a larger core or where multimode is said to support longer distances. A common memory tip is to remember that single-mode has a smaller core and longer reach, while multimode has a larger core and shorter reach—think “small core, long haul; big core, short hop.”
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. 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.
Which TWO statements accurately describe the characteristics and deployment considerations for fiber optic cabling in a modern enterprise network?
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
When using a 10GBASE-SR SFP+ transceiver over OM3 multimode fiber, the maximum supported distance is 300 meters.
The correct statements are that 10GBASE-SR over OM3 multimode fiber supports up to 300 meters and that fiber optic cabling is immune to electromagnetic interference (EMI), making it ideal for electrically noisy environments. Single-mode fiber actually has a smaller core diameter than multimode, making option A incorrect. Multimode fiber is designed for shorter links, so option B is wrong. Standard 1000BASE-LX SFP transceivers over single-mode fiber are limited to 5 km, not 10 km, so option C is inaccurate.
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 (SMF) typically uses a larger core diameter than multimode fiber (MMF).
Why it's wrong here
This is incorrect; SMF has a much smaller core (about 9 microns) compared to MMF (50 or 62.5 microns).
- ✗
Multimode fiber (MMF) is generally preferred for longer-distance links, such as between buildings on a campus network.
Why it's wrong here
This is incorrect; MMF is used for shorter distances (up to a few hundred meters for high data rates), while SMF is preferred for longer links.
- ✗
A 1000BASE-LX SFP transceiver operating over single-mode fiber can support distances up to 10 km.
Why it's wrong here
1000BASE-LX uses a long-wavelength laser (1300 nm) and is specified for single-mode fiber distances up to 10 km (and up to 550 m over multimode fiber with mode conditioning patch cables).
When this WOULD be correct
In enterprise networks, 1000BASE-LX SFP transceivers are commonly used for long-haul links over single-mode fiber, supporting distances up to 10 km. This makes them ideal for connecting geographically separated buildings or campus backbones where cost-effective gigabit connectivity over several kilometers is required.
- ✓
When using a 10GBASE-SR SFP+ transceiver over OM3 multimode fiber, the maximum supported distance is 300 meters.
Why this is correct
10GBASE-SR over OM3 fiber (50/125 µm, 2000 MHz*km bandwidth) supports distances up to 300 meters. Over OM4 fiber, the distance increases to 400 meters.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Fiber optic cabling is immune to electromagnetic interference (EMI), making it ideal for environments with high electrical noise.
Why this is correct
Fiber uses light to transmit data, so EMI does not affect the signal, making it suitable for noisy industrial environments.
Related concept
Read the scenario before looking for a memorised answer.
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 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓When using a 10GBASE-SR SFP+ transceiver over OM3 multimode fiber, the maximum supported distance is 300 meters.Correct answer▾
Why this is correct
10GBASE-SR over OM3 fiber (50/125 µm, 2000 MHz*km bandwidth) supports distances up to 300 meters. Over OM4 fiber, the distance increases to 400 meters.
✗Single-mode fiber (SMF) typically uses a larger core diameter than multimode fiber (MMF).Wrong answer — click to see why▾
Why this is wrong here
Single-mode fiber (SMF) has a much smaller core diameter (about 9 microns) compared to multimode fiber (MMF) which typically has a core of 50 or 62.5 microns. This statement reverses the actual core sizes.
Why candidates choose this
Students may confuse the terms 'single-mode' and 'multimode', incorrectly assuming that single-mode implies a larger core to carry a single light path, whereas the opposite is true.
✗Multimode fiber (MMF) is generally preferred for longer-distance links, such as between buildings on a campus network.Wrong answer — click to see why▾
Why this is wrong here
Multimode fiber (MMF) is designed for shorter distances (typically up to a few hundred meters at high data rates) due to modal dispersion, while single-mode fiber (SMF) is preferred for longer-distance links such as between buildings on a campus network.
Why candidates choose this
Test-takers might think that because MMF supports multiple light modes, it can transmit over longer distances, but in reality, modal dispersion limits its reach.
✗A 1000BASE-LX SFP transceiver operating over single-mode fiber can support distances up to 10 km.Wrong answer — click to see why▾
Why this is wrong here
The standard 1000BASE-LX (IEEE 802.3) over single-mode fiber supports up to 5 km, not 10 km; extended reach is not covered in CCNA.
★ When this WOULD be the correct answer
In enterprise networks, 1000BASE-LX SFP transceivers are commonly used for long-haul links over single-mode fiber, supporting distances up to 10 km. This makes them ideal for connecting geographically separated buildings or campus backbones where cost-effective gigabit connectivity over several kilometers is required.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that single-mode fiber has a larger core diameter than multimode fiber, when in fact the opposite is true, and that multimode fiber is suitable for long-haul links, whereas it is actually limited to shorter distances due to modal dispersion.
Detailed technical explanation
How to think about this question
The key difference between SMF and MMF lies in core size and light propagation: SMF uses a narrow core that forces light to travel in a single mode, virtually eliminating modal dispersion and enabling distances beyond 10 km. In contrast, MMF allows multiple light paths (modes), which cause pulse spreading over distance, limiting reach to typically 550 m for 1000BASE-SX. Real-world campus deployments often use SMF for inter-building links and MMF for intra-building horizontal cabling.
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 200-301 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: When using a 10GBASE-SR SFP+ transceiver over OM3 multimode fiber, the maximum supported distance is 300 meters. — The correct statements are that 10GBASE-SR over OM3 multimode fiber supports up to 300 meters and that fiber optic cabling is immune to electromagnetic interference (EMI), making it ideal for electrically noisy environments. Single-mode fiber actually has a smaller core diameter than multimode, making option A incorrect. Multimode fiber is designed for shorter links, so option B is wrong. Standard 1000BASE-LX SFP transceivers over single-mode fiber are limited to 5 km, not 10 km, so option C is inaccurate.
What should I do if I get this 200-301 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 →
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Last reviewed: Jun 11, 2026
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