220-1101 Hardware and Network Troubleshooting Practice Question
A user reports that their desktop computer intermittently loses network connectivity when the overhead fluorescent lights in the office are turned on. The link light on the network interface card (NIC) turns off during these events. The technician replaced the existing unshielded twisted pair (UTP) Cat5e cable with a shielded Cat6 cable, but the problem continues. Which of the following should the technician do NEXT to resolve the issue?
⚠ Common exam trap
Test-takers frequently assume replacing UTP with shielded cable will always solve EMI issues, but they overlook that physical proximity to the interference source can still cause problems, and that proper grounding of the shield is also critical.
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
✓
Move the Ethernet cable away from the fluorescent light fixtures
The problem is electromagnetic interference (EMI) from the fluorescent lights, which generates a strong magnetic field that induces noise in the Ethernet cable. Even with shielded Cat6 cable, the interference can still couple into the signal if the cable is routed too close to the light fixtures, especially if the shielding is not properly grounded. Moving the cable away from the fixtures physically separates the cable from the EMI source, which is the most direct and effective next step.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace the network switch
Why it's wrong here
The network switch is a shared device that typically serves multiple workstations; if it were the root cause, other systems would likely show similar intermittent connectivity at the same time. The issue is isolated to one workstation and correlates specifically with fluorescent lighting, which points to a localized electromagnetic interference source rather than a switch port or backplane defect. Replacing the switch would be an expensive, unjustified step without any evidence of switch malfunction, and it would not address the actual interference path.
- ✓
Move the Ethernet cable away from the fluorescent light fixtures
Why this is correct
Fluorescent light fixtures generate electromagnetic interference (EMI) from their ballasts, which can couple into nearby Ethernet cables and disrupt the differential signaling used by twisted-pair cabling. Even shielded cables can suffer if the interference is strong enough or the shield is not properly grounded, so rerouting the cable several feet away from the light fixtures physically separates the cable from the noise source. This directly solves the root cause, is low-cost, and requires no hardware replacement, making it the most appropriate first step.
- ✗
Replace the network interface card (NIC)
Why it's wrong here
A failing NIC typically presents persistent symptoms such as link drops, excessive CRC errors, or an inability to negotiate link speed, and these would occur regardless of whether the fluorescent lights are lit. The fact that connectivity is only lost when the lights turn on strongly suggests external electromagnetic interference rather than an internal hardware fault. Replacing the NIC before mitigating the environmental interference would likely leave the problem unchanged, wasting time and money while failing to address the true source.
- ✗
Check the grounding of the electrical system in the building
Why it's wrong here
Poor grounding can cause interference, but it is less targeted than physically separating the cable from the light source. The problem is clearly correlated with the lights turning on, making cable rerouting the best next step.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA 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 220-1101 exam.