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Difficulty: MediumTroubleshooting Physical Cabling and Connectors

A network technician is troubleshooting an intermittent connectivity issue on a 90-meter Category 6 unshielded twisted-pair (UTP) cable run between an intermediate distribution frame (IDF) switch and a desktop workstation. A basic continuity cable tester indicates that all eight conductors are mapped pin-to-pin correctly according to T568B standards. However, the switch port reports frequent cyclic redundancy check (CRC) errors and link flapping. Which diagnostic tool should the technician use to identify the exact distance to the physical fault or impedance mismatch along the cable run?

  1. Time-Domain Reflectometer (TDR)Answer
  2. B
    Tone generator and inductive probe
  3. C
    Optical power meter
  4. D
    Loopback plug

Answer

A Time-Domain Reflectometer (TDR) should be used to locate the exact position of the cable defect along the copper run.
A Time-Domain Reflectometer (TDR) transmits electrical signal pulses along metallic conductors and measures the reflections caused by physical irregularities. By timing these reflections, a TDR precisely pinpoints the location of impedance mismatches, cable damage, opens, or shorts along copper UTP runs.

Step-by-Step Solution

1
Analyze the symptoms and initial test results
Basic pin-to-pin continuity is verified, ruling out simple miswires, but CRC errors and link instability point to physical signal degradation or an impedance defect along the cable path.
Simple continuity testers only check DC wire mapping and fail to detect high-frequency signal faults such as impedance anomalies, subtle cable damage, or distance-based breaks.
2
Select the appropriate physical layer testing tool for copper media analysis
Choose a Time-Domain Reflectometer (TDR).
A TDR injects signals down copper media and measures reflection delays to calculate the precise distance to any impedance disruption, open, or short.

Key Concept

Selecting appropriate physical cabling diagnostic tools for copper media fault isolation
Estimated Time:1m 15s
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Topics

Troubleshooting Physical Cabling and Connectors

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