220-1101 Networking Practice Question
A technician is replacing a 10/100 Mbps network switch with a new Gigabit switch. After connecting all devices, the technician notices that the link LEDs on several ports are showing amber instead of green. The switch documentation states that green indicates a 1000 Mbps link, and amber indicates a 10/100 Mbps link. All connected devices support Gigabit Ethernet. Which of the following is the MOST likely cause of this issue?
⚠ Common exam trap
Watch out — candidates often assume a software or configuration issue (like duplex mismatch or a 'Gigabit mode' setting) when the real culprit is a physical-layer problem—specifically, cabling that fails to meet the stricter requirements for 1000BASE-T.
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 Ethernet cables between the switch and devices are faulty or of poor quality.
The amber link LED indicates that the switch is operating at 10/100 Mbps rather than the expected 1000 Mbps. Since all connected devices support Gigabit Ethernet, the most likely cause is that the Ethernet cables are faulty or of poor quality, as Gigabit Ethernet requires all four twisted pairs (8 wires) to be fully functional, whereas 10/100 Mbps only uses two pairs. A marginal or damaged cable can cause auto-negotiation to fall back to a lower speed.
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 devices are configured for half-duplex, causing auto-negotiation to fail.
Why it's wrong here
Auto-negotiation on Gigabit Ethernet requires both devices to support the same duplex settings for gigabit; a mismatch typically causes a link at 10/100 Mbps in half-duplex, but the most common cause for a speed fallback on gigabit-capable devices is a cabling issue, not duplex mismatch.
When this WOULD be correct
A technician replaces a switch and notices that some devices are not connecting or have excessive errors. The switch and devices support auto-negotiation, but the link is established at half-duplex. In this scenario, incorrect duplex settings (e.g., one side forced to full-duplex) would be the likely cause.
- ✗
The power supply of the switch is insufficient for all ports.
Why it's wrong here
Insufficient power would cause ports to not function at all, not to link at a lower speed. Power over Ethernet (PoE) might cause issues, but this switch is not specified as PoE, and a standard switch does not have power issues that cause speed downgrades.
When this WOULD be correct
A technician installs a new PoE switch and connects multiple IP cameras. After powering on, some cameras fail to operate and the switch logs show 'power budget exceeded'. In this scenario, the switch's power supply is insufficient for the PoE demands, causing ports to shut down or underpower devices.
- ✓
The Ethernet cables between the switch and devices are faulty or of poor quality.
Why this is correct
Correct. A faulty or low-quality cable is the most common reason for a Gigabit connection to fall back to 100 Mbps. The cable may have damage or exceed length specifications, forcing auto-negotiation to a lower speed.
- ✗
The switch is not properly configured for Gigabit mode.
Why it's wrong here
Gigabit Ethernet (1000BASE-T) is defined by IEEE 802.3ab and requires no user configuration for speed negotiation. Unmanaged switches have no management interface or configuration pages; they physically advertise 1 Gbps on every port and rely on auto-negotiation to select the highest mutually supported speed. If a link falls back to 100 Mbps, the switch itself is not misconfigured—it is almost always a physical-layer issue, such as faulty or poor-quality cabling, that forces the negotiation to a lower speed.
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 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓The Ethernet cables between the switch and devices are faulty or of poor quality.Correct answer▾
Why this is correct
Correct. A faulty or low-quality cable is the most common reason for a Gigabit connection to fall back to 100 Mbps. The cable may have damage or exceed length specifications, forcing auto-negotiation to a lower speed.
✗The devices are configured for half-duplex, causing auto-negotiation to fail.Wrong answer — click to see why▾
Why this is wrong here
Half-duplex configuration does not cause auto-negotiation to fail in a way that would result in a 10/100 Mbps link when both devices support Gigabit. Auto-negotiation handles duplex and speed separately; a duplex mismatch might cause poor performance but not a speed downgrade to 10/100.
★ When this WOULD be the correct answer
A technician replaces a switch and notices that some devices are not connecting or have excessive errors. The switch and devices support auto-negotiation, but the link is established at half-duplex. In this scenario, incorrect duplex settings (e.g., one side forced to full-duplex) would be the likely cause.
Why candidates choose this
Candidates may confuse duplex mismatch with speed negotiation issues, or assume that half-duplex forces a lower speed due to auto-negotiation failure.
✗The power supply of the switch is insufficient for all ports.Wrong answer — click to see why▾
Why this is wrong here
An insufficient power supply would typically cause ports to not function at all or cause intermittent connectivity, not specifically cause all ports to negotiate at 10/100 Mbps instead of 1000 Mbps. The switch's power supply is designed to support all ports at full speed.
★ When this WOULD be the correct answer
A technician installs a new PoE switch and connects multiple IP cameras. After powering on, some cameras fail to operate and the switch logs show 'power budget exceeded'. In this scenario, the switch's power supply is insufficient for the PoE demands, causing ports to shut down or underpower devices.
Why candidates choose this
Candidates may think that insufficient power could degrade performance or cause link speed downgrades, confusing power delivery with signal integrity issues.
Analysis generated from the official 220-1101blueprint 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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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.