The answer is that the HDMI cable is not rated for 4K bandwidth. This is the most likely cause because a standard HDMI cable, often labeled as “High Speed” or older, lacks the data throughput required to drive a 4K monitor at its native resolution and refresh rate, resulting in a “No Signal” error even though the PC boots and the monitor powers on. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of display interface limitations and bandwidth requirements—a common trap is assuming the GPU or monitor is faulty when the cable is the bottleneck. Remember that for 4K at 60Hz, you need a “Premium High Speed” or “Ultra High Speed” HDMI cable; otherwise, the handshake fails. A quick memory tip: “4K needs more than just a cable—it needs the right speed label.”
220-1101 Display Devices Troubleshooting Practice Question
This 220-1201 practice question tests your understanding of display devices troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During a hardware install, you connect a new 4K monitor to a desktop PC using an HDMI cable. The display shows a 'No Signal' message. The PC boots normally and the monitor is powered on. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The HDMI cable is not rated for 4K bandwidth.
Many older graphics cards or motherboards have HDMI ports that only support up to 1080p or 1440p, not 4K at the required bandwidth. The 'No Signal' error often means the graphics output is incompatible with the monitor's resolution or refresh rate. Checking the GPU specifications and using a DisplayPort cable if available is the correct approach.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 monitor's refresh rate is set too high in the BIOS.
Why it's wrong here
BIOS settings don't control refresh rate for external monitors; this is a driver/GPU capability issue.
✓
The HDMI cable is not rated for 4K bandwidth.
Why this is correct
Standard HDMI cables may not support 4K; using a high-speed HDMI cable or a DisplayPort cable would resolve this.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The PC's power supply is insufficient for the new monitor.
Why it's wrong here
Monitors have their own power supply; the PC's PSU doesn't affect monitor signal detection.
✗
The monitor's input source is set to VGA instead of HDMI.
Why it's wrong here
While input source can cause 'No Signal', it's less likely than a cable bandwidth issue given the 4K context.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Display Devices Troubleshooting — This question tests Display Devices Troubleshooting — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The HDMI cable is not rated for 4K bandwidth. — Many older graphics cards or motherboards have HDMI ports that only support up to 1080p or 1440p, not 4K at the required bandwidth. The 'No Signal' error often means the graphics output is incompatible with the monitor's resolution or refresh rate. Checking the GPU specifications and using a DisplayPort cable if available is the correct approach.
What should I do if I get this 220-1201 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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