220-1101 Hardware and Network Troubleshooting Practice Question
A technician is troubleshooting a workstation that has intermittent network connectivity. The link light on the NIC is blinking, but the workstation frequently loses connection for several seconds at a time. The technician notices the patch cable runs along the ceiling near a fluorescent light fixture. The cable is an unshielded Cat5e cable. Which of the following is the MOST likely cause of the intermittent issue?
⚠ Common exam trap
The trap here is that candidates see a blinking link light and assume the physical layer is fine, overlooking that EMI can corrupt data without breaking the carrier signal, leading them to incorrectly blame the NIC or cable termination.
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
✓
Electromagnetic interference (EMI) from the fluorescent light is corrupting the signal on the unshielded cable.
The blinking link light indicates the NIC is detecting a carrier signal, but intermittent connectivity points to signal corruption. Unshielded twisted-pair (UTP) Cat5e cable lacks a metallic shield, making it susceptible to electromagnetic interference (EMI). Fluorescent light fixtures generate significant EMI, which can corrupt the differential signaling on the cable, causing packet loss and brief disconnections.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The cable is terminated incorrectly, causing intermittent shorts.
Why it's wrong here
Incorrect termination usually results in a permanent link failure or high error rates, not intermittent connectivity that comes and goes. An intermittent short from a bad termination typically appears as a link drop when the cable is moved or bent, not as a random connectivity issue near a light fixture. A cable tester would directly identify this, and it is not indicated as the root cause here.
- ✓
Electromagnetic interference (EMI) from the fluorescent light is corrupting the signal on the unshielded cable.
Why this is correct
Fluorescent lights emit EMI that can induce noise in unshielded copper cables. This noise can cause packet loss and intermittent disconnects. Replacing the cable with a shielded one or rerouting it away from the light would resolve the issue.
- ✗
The cable run exceeds the maximum length for Cat5e (100 meters).
Why it's wrong here
The 100-meter limit for Cat5e is the maximum total channel length including patch cables, and there is no evidence the cable run is that long. A run near a fluorescent light suggests an indoor, relatively short path. If the cable were too long, the symptom would be a link that never establishes or very high latency, not intermittent interference tied to a nearby light.
- ✗
The workstation's NIC is failing and needs to be replaced.
Why it's wrong here
While a failing NIC is a possibility, the symptom is directly correlated with the cable passing near a known EMI source. A NIC failure is not location-dependent and would likely persist regardless of cable routing. The correct troubleshooting step is to temporarily move the cable away from the light or use a shielded cable to confirm the interference hypothesis before replacing the NIC.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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