Objective 5.2Network Troubleshooting· 1 min read
Common Cabling and Physical Interface Issues
Common cabling and physical interface issues
What you will learn
- Recall common cable problem symptoms: attenuation, crosstalk, open and short circuits.
- Explain the TX/RX reversed problem.
- Recall the cable tester's role in diagnosing these problems.
- Choose the most likely cause of a given cable symptom in a simplified scenario.
Most cable problems are purely physical and have a direct test, not a guess: excessive length causes attenuation (signal weakening), unshielded cables running close together cause crosstalk, and a manufacturing defect or damage causes an open circuit or a short — all of which show up immediately on a cable tester.
Common symptoms and problems
| Attenuation | Gradual signal weakening as cable length exceeds the supported maximum. |
|---|---|
| Crosstalk | Signal interference from an adjacent wire pair within the same cable or a nearby unshielded cable. |
| Open / Short | An open circuit (a complete break in the wire) or a short (unintended contact between two wires) — both cut the connection entirely. |
| TX/RX Reversed | Transmit and receive wires swapped when terminating the cable, leaving the device with no actual link despite the cable looking fine. |
| Cable Tester | A tool that actually checks every wire pair and its order, directly revealing any of the above problems without guessing. |
What matters on the exam
- "The connection works but is weak or intermittent over a long distance" usually points to attenuation.
- "No connection at all despite the cable looking fine" points to an open, a short, or TX/RX reversed — a cable tester settles exactly which one.
Quick check
Answer in your head first, then reveal.
What causes gradual signal weakening with excessive cable length?Reveal the answer
Attenuation.
What tool immediately reveals any physical cable problem?Reveal the answer
A cable tester.
Why might a cable look fine despite there being no connection at all?Reveal the answer
Because the transmit and receive wires were swapped when the cable was terminated.
Sign in to track your progress on this topic.
Your next step
Read the lesson, then mark it complete
Sources
Used to verify the facts. The writing is original to Passuit.