CCNA Network Infrastructure and Connectivity Practice Question
Which TWO statements about SFP transceivers and interface diagnostics are true?
⚠ Common exam trap
Cisco often tests the distinction between copper and fiber SFP distance limits, and the trap here is assuming that a copper SFP can achieve fiber-like distances, when in reality 1000BASE-T is strictly limited to 100 meters.
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
✓
SFP modules are hot-swappable, meaning they can be inserted or removed without powering off the switch.
Option A is correct because SFP (Small Form-factor Pluggable) transceivers are designed to be hot-swappable, so they can be inserted into or removed from an SFP port while the switch remains powered on, which is a key operational advantage for maintenance and upgrades. Option C is correct because the show interfaces transceiver command on Cisco switches reads the transceiver's digital diagnostic monitoring (DOM/DDM) data and reports real-time values such as temperature, supply voltage, bias current, and transmit/receive optical power levels. Option B is incorrect because 1000BASE-T copper SFPs are limited to about 100 meters over Category 5e/6 cabling, not 10 km; 10 km distances are achieved with single-mode fiber optics such as 1000BASE-LX/LH. Option D is incorrect because it reverses the fiber types: single-mode fiber has a core of about 9 microns, while multi-mode fiber has a larger core, typically 50 or 62.5 microns. Option E is incorrect because Cisco switches generally require Cisco-branded or Cisco-compatible SFPs; third-party or uncoded transceivers are often rejected with an 'unsupported transceiver' error unless the switch is specifically configured to allow them.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
SFP modules are hot-swappable, meaning they can be inserted or removed without powering off the switch.
Why this is correct
SFP modules are hot-swappable by design, meaning they can be inserted or removed from an active switch port without powering down the chassis or rebooting the device. This field-replaceable feature allows network administrators to change media types or replace faulty optics while maintaining uptime, though care must be taken to follow electrostatic discharge (ESD) precautions during handling.
- ✗
Copper 1000BASE-T SFP modules can transmit data up to 10 km over Category 5e cabling.
Why it's wrong here
Copper 1000BASE-T SFP modules are designed for a maximum reach of only 100 meters over Category 5e or better twisted-pair cabling, not 10 km. The 10 km distance is typical for long-haul fiber optic transceivers using single-mode fiber, because copper-based Ethernet at gigabit speeds suffers from high-frequency attenuation and crosstalk that severely limit its transmission distance.
- ✓
The show interfaces transceiver command provides diagnostic details such as temperature, voltage, and optical power levels.
Why this is correct
The show interfaces transceiver command reads Digital Optical Monitoring (DOM) data from the SFP module, reporting real-time parameters such as internal temperature, supply voltage, laser bias current, and transmit/receive optical power levels. This is essential for verifying that a fiber link is operating within specified thresholds and for predicting failures due to degrading optics.
- ✗
Multi-mode fiber uses a smaller core diameter, about 9 microns, compared to single-mode fiber.
Why it's wrong here
Multi-mode fiber actually has a larger core diameter—either 50 or 62.5 microns—compared to single-mode fiber, which uses a 9-micron core. The smaller core of single-mode fiber allows only a single light path, reducing modal dispersion and enabling longer transmission distances, whereas the larger core of multi-mode fiber supports multiple propagation modes but limits distance due to modal dispersion.
- ✗
Any SFP transceiver, regardless of vendor, will operate in a Cisco switch by default.
Why it's wrong here
By default, a Cisco switch rejects third-party SFP transceivers because they lack the Cisco-specific encoded vendor ID and part number. The switch may disable the port and log an error message unless the global configuration command 'service unsupported-transceiver' is used, and even then, not all platforms or software versions will guarantee operation with non-Cisco optics.
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.
✓SFP modules are hot-swappable, meaning they can be inserted or removed without powering off the switch.Correct answer▾
Why this is correct
SFP modules are hot-swappable by design, meaning they can be inserted or removed from an active switch port without powering down the chassis or rebooting the device. This field-replaceable feature allows network administrators to change media types or replace faulty optics while maintaining uptime, though care must be taken to follow electrostatic discharge (ESD) precautions during handling.
✗Copper 1000BASE-T SFP modules can transmit data up to 10 km over Category 5e cabling.Wrong answer — click to see why▾
Why this is wrong here
1000BASE-T SFPs (such as the GLC-T) have a maximum reach of 100 m, not 10 km. 10 km is typical for 1000BASE-LX/LH single-mode fiber SFPs.
✗Multi-mode fiber uses a smaller core diameter, about 9 microns, compared to single-mode fiber.Wrong answer — click to see why▾
Why this is wrong here
Multi-mode fibers have larger cores to allow multiple light paths, while single-mode’s narrow core supports only one path. The 9-micron core is characteristic of single-mode.
✗Any SFP transceiver, regardless of vendor, will operate in a Cisco switch by default.Wrong answer — click to see why▾
Why this is wrong here
Cisco IOS checks the SFP EEPROM for vendor coding. Third-party SFPs might not be recognized, causing an error or link failure until unsupported transceiver mode is enabled.
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?”
Go deeper
Related to this question
Learn chapter
Cisco IOS Clock and Calendar
Key term
Small Form-factor Pluggable
A Small Form-factor Pluggable (SFP) is a compact, hot-swappable transceiver module used to connect networking devices to fiber optic or copper cables, converting electrical signals into light signals for data transmission.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
About these practice questions
This 200-301 question is part of Courseiva's 1,450-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco 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 200-301 exam.