CCNA Network Infrastructure and Connectivity Practice Question
Which TWO statements accurately describe cabling and SFP transceiver diagnostics?
⚠ Common exam trap
Cisco often tests the distinction between copper and fiber SFP product IDs (e.g., 'GLC-T' is copper, not fiber) and the correct diagnostic commands for each media type, leading candidates to confuse TDR (copper) with fiber optical power monitoring.
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
✓
The 'show interfaces transceiver' command displays optical power levels for both Tx and Rx on fiber SFPs.
Option C is correct because the 'show interfaces transceiver' command (and its variants like 'show interfaces transceiver detail') reports diagnostic optical parameters on fiber SFPs, including transmit (Tx) and receive (Rx) optical power levels in dBm, which is exactly how you verify link budget and signal integrity. Option E is correct because multimode fiber SFPs with LC connectors (e.g., 1000BASE-SX) are designed for short-reach campus/distribution links, typically supporting up to 550 meters over OM2 multimode fiber (and 220-550 m depending on fiber grade and modal bandwidth). Option A is wrong because copper SFPs such as 1000BASE-T have a 100-meter reach over standard Cat5e or better, not requiring Cat6a. Option B is wrong because 'GLC-T' and 'SFP-GE-T' are copper (1000BASE-T) SFP product IDs, not fiber module identifiers. Option D is wrong because 'show cable-diagnostics tdr interface' performs Time Domain Reflectometry on copper twisted-pair Ethernet cabling, not on fiber optic cables, which cannot be tested this way.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Copper SFP modules require Cat6a cabling to achieve a 100-meter reach.
Why it's wrong here
Copper SFP modules, such as GLC-T or SFP-GE-T, implement 1000BASE-T and are designed to operate over standard Category 5e, 6, or 6a cabling at distances up to 100 meters. Cat6a is only required for 10GBASE-T at 100m; 1 Gbps Ethernet over Cat5e uses all four pairs and does not need the higher bandwidth rating. Therefore, requiring Cat6a is incorrect; Cat5e is sufficient for 100-meter reach with these copper SFPs.
- ✗
Fiber SFP modules are typically identified by the 'GLC-T' or 'SFP-GE-T' product IDs.
Why it's wrong here
The product IDs GLC-T and SFP-GE-T are actually copper transceivers with RJ-45 connectors, used for 1000BASE-T over twisted-pair cabling. Fiber SFP modules have different naming conventions: for example, GLC-SX-MM is a multimode fiber SFP with LC connectors, and GLC-LH-SM is a single-mode fiber SFP for long-reach links. Confusing these identifiers is a common error, as the 'T' suffix indicates twisted pair, not fiber optics.
- ✓
The 'show interfaces transceiver' command displays optical power levels for both Tx and Rx on fiber SFPs.
Why this is correct
The command 'show interfaces transceiver' is valid on Cisco switches and provides detailed diagnostics for SFP modules that support Digital Optical Monitoring. It displays the transmit optical power and receive optical power in dBm, along with temperature, voltage, and bias current. For fiber SFPs, these readings are crucial for verifying that the link is within the optical budget and for detecting fiber degradation or dirty connectors before failures occur.
- ✗
The 'show cable-diagnostics tdr interface' command can measure the distance to a break in a fiber optic cable.
Why it's wrong here
TDR (Time Domain Reflectometry) is a copper-cabling diagnostic technique that sends a pulse down each pair and uses reflections to locate opens, shorts, or impedance mismatches; it is implemented in Cisco switches via 'show cable-diagnostics tdr interface' for copper ports only. Fiber optic cables use light, not electrical pulses, so a TDR cannot function on them; instead, an OTDR (Optical Time Domain Reflectometer) is required to locate breaks in fiber. Thus, this command is not applicable to fiber optic cables.
- ✓
A multimode fiber SFP with LC connectors is commonly used for short-reach connections up to 550 meters.
Why this is correct
A multimode fiber SFP with LC duplex connectors, such as the GLC-SX-MM, operates at 850nm and is commonly deployed for short-reach links within a data center or campus. The 1000BASE-SX standard specifies a maximum reach of 220m on OM1 fiber (62.5/125µm) and 550m on OM2 fiber (50/125µm), with higher grades allowing longer distances. Therefore, a multimode fiber SFP is indeed the typical choice for connections up to 550 meters.
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.
✓The 'show interfaces transceiver' command displays optical power levels for both Tx and Rx on fiber SFPs.Correct answer▾
Why this is correct
The command 'show interfaces transceiver' is valid on Cisco switches and provides detailed diagnostics for SFP modules that support Digital Optical Monitoring. It displays the transmit optical power and receive optical power in dBm, along with temperature, voltage, and bias current. For fiber SFPs, these readings are crucial for verifying that the link is within the optical budget and for detecting fiber degradation or dirty connectors before failures occur.
✗Copper SFP modules require Cat6a cabling to achieve a 100-meter reach.Wrong answer — click to see why▾
Why this is wrong here
The statement incorrectly mandates Cat6a cabling, whereas Cat5e and Cat6 also support the full 100-meter distance for 1000BASE-T.
✗Fiber SFP modules are typically identified by the 'GLC-T' or 'SFP-GE-T' product IDs.Wrong answer — click to see why▾
Why this is wrong here
This mixes up part number naming conventions; GLC-T and SFP-GE-T always indicate copper transceivers, not fiber.
✗The 'show cable-diagnostics tdr interface' command can measure the distance to a break in a fiber optic cable.Wrong answer — click to see why▾
Why this is wrong here
TDR relies on electrical signals and impedance changes; it cannot function on fiber optics.
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?”
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Key term
UTP
Unshielded Twisted Pair (UTP) is a copper cabling type with pairs of twisted wires and no shielding, used for Ethernet networks.
Key term
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An IDS is a security system that monitors network or system traffic for suspicious activity and alerts administrators to potential threats, but does not actively block them.
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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.