- A
The modem is defective.
Why wrong: A defective modem would typically not sync at all or would drop sync, not sync at a lower speed consistently.
- B
The distance from the central office is too great.
DSL speeds decrease with distance; 12,000 feet is near the limit for many DSL services, causing reduced sync rates.
- C
The router's firmware needs updating.
Why wrong: Firmware updates affect features and security, not the physical sync speed determined by line quality and distance.
- D
The ISP is throttling the connection.
Why wrong: Throttling would reduce throughput after sync, but the sync rate itself is a physical layer characteristic.
Question 705 of 1,020
DSL Slow Speed Due to Distance
This 220-1201 practice question tests your understanding of internet connection types. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A technician is troubleshooting a DSL connection that syncs at only 1.5 Mbps when the plan is 10 Mbps. The line is 12,000 feet from the central office. 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.
Quick Answer
The correct answer is that the distance from the central office is too great. DSL speed is fundamentally limited by signal attenuation over copper telephone lines, and at 12,000 feet, the signal degrades so severely that the maximum sync rate drops far below the advertised 10 Mbps plan. This direct relationship between DSL slow speed and distance from the central office is a core concept tested on the CompTIA A+ Core 1 220-1201 exam, often appearing in troubleshooting scenarios where a technician must differentiate between line noise, filter issues, and physical distance. A common trap is assuming the modem or ISP is at fault, but the key clue here is the specific distance—12,000 feet is well beyond the optimal range for high-speed DSL tiers. For a quick memory tip, remember the "12,000-foot rule": once you hit that distance, expect DSL speeds to drop to around 1.5 Mbps, no matter the plan.
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 distance from the central office is too great.
DSL speeds degrade significantly with distance due to signal attenuation and noise. At 12,000 feet from the central office, ADSL2+ typically cannot sustain 10 Mbps; 1.5 Mbps is consistent with the maximum achievable rate at that distance. The sync rate is determined by line conditions, not the plan speed, making distance the primary limiting factor.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 modem is defective.
Why it's wrong here
A defective modem would typically not sync at all or would drop sync, not sync at a lower speed consistently.
- ✓
The distance from the central office is too great.
Why this is correct
DSL speeds decrease with distance; 12,000 feet is near the limit for many DSL services, causing reduced sync rates.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The router's firmware needs updating.
Why it's wrong here
Firmware updates affect features and security, not the physical sync speed determined by line quality and distance.
- ✗
The ISP is throttling the connection.
Why it's wrong here
Throttling would reduce throughput after sync, but the sync rate itself is a physical layer characteristic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that DSL speeds are always limited by the service plan rather than physical-layer constraints, leading candidates to overlook distance as the primary factor when sync rates are far below the plan speed.
Detailed technical explanation
How to think about this question
ADSL2+ (ITU G.992.5) uses DMT modulation across up to 256 subcarriers, and at 12,000 feet, high-frequency carriers are attenuated below usable SNR, reducing the aggregate bitrate. The sync rate is set during the training phase via G.994.1 handshaking, where the modem and DSLAM negotiate the highest stable rate given loop attenuation and noise margin. Real-world tools like `adslctl` or modem stats show attainable rate vs. sync rate, confirming distance as the bottleneck.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Internet Connection Types — study guide chapter
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Internet Connection Types — This question tests Internet Connection Types — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The distance from the central office is too great. — DSL speeds degrade significantly with distance due to signal attenuation and noise. At 12,000 feet from the central office, ADSL2+ typically cannot sustain 10 Mbps; 1.5 Mbps is consistent with the maximum achievable rate at that distance. The sync rate is determined by line conditions, not the plan speed, making distance the primary limiting factor.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This 220-1201 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 220-1201 exam.
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