- A
802.11b/g on 2.4 GHz
Why wrong: These standards use the crowded 2.4 GHz band and will suffer from the same interference from Bluetooth and cordless phones.
- B
802.11n on 2.4 GHz
Why wrong: Although 802.11n can use 5 GHz, the technician would need to ensure it is configured for 5 GHz; otherwise, it still faces 2.4 GHz interference.
- C
802.11ac on 5 GHz
802.11ac operates exclusively on 5 GHz, which is far less crowded and avoids the interference from 2.4 GHz devices.
- D
802.11ax on 2.4 GHz
Why wrong: Even though 802.11ax is advanced, using it on 2.4 GHz still subjects it to the same interference sources.
Question 260 of 1,020
Minimizing Wireless Interference from Bluetooth and Cordless Phones
This 220-1201 practice question tests your understanding of wireless networking technologies. 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.
A technician is setting up a wireless network for a small office that experiences heavy interference from neighboring businesses. The office uses many Bluetooth devices and cordless phones. Which 802.11 standard and frequency combination would minimize interference and provide the best performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Quick Answer
The answer is 802.11ac on the 5 GHz band. This combination minimizes interference because Bluetooth devices and cordless phones predominantly operate on the crowded 2.4 GHz spectrum, so shifting to 5 GHz avoids that congestion and provides cleaner, faster performance. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of frequency bands and their interference sources—a common trap is choosing 802.11n, which supports both bands but is slower than ac, or picking 2.4 GHz because it has better range, forgetting that range is useless if the signal is jammed. Remember the memory tip: “Blue and cordless use two-point-four, so go five for a clean drive.”
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
✓
802.11ac on 5 GHz
802.11ac operates exclusively on the 5 GHz frequency band, which is far less congested than 2.4 GHz. This avoids interference from Bluetooth devices and cordless phones (which predominantly use 2.4 GHz), providing cleaner channels and better performance in a dense interference environment.
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.
- ✗
802.11b/g on 2.4 GHz
Why it's wrong here
These standards use the crowded 2.4 GHz band and will suffer from the same interference from Bluetooth and cordless phones.
- ✗
802.11n on 2.4 GHz
Why it's wrong here
Although 802.11n can use 5 GHz, the technician would need to ensure it is configured for 5 GHz; otherwise, it still faces 2.4 GHz interference.
- ✓
802.11ac on 5 GHz
Why this is correct
802.11ac operates exclusively on 5 GHz, which is far less crowded and avoids the interference from 2.4 GHz devices.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
802.11ax on 2.4 GHz
Why it's wrong here
Even though 802.11ax is advanced, using it on 2.4 GHz still subjects it to the same interference sources.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that newer standards like 802.11ax automatically solve interference problems, but the trap is that the frequency band choice (2.4 GHz vs. 5 GHz) is the primary factor in avoiding interference from common office devices like Bluetooth and cordless phones.
Detailed technical explanation
How to think about this question
802.11ac uses only the 5 GHz UNII bands (5.15–5.825 GHz), which have many non-overlapping channels (e.g., 20, 40, 80, and 160 MHz widths) and are not shared with Bluetooth Classic or most DECT cordless phones. In contrast, 2.4 GHz has only three non-overlapping channels (1, 6, 11) and is saturated by Bluetooth frequency-hopping spread spectrum (FHSS) and cordless phones, causing packet retries and throughput collapse. Real-world testing shows that even with 802.11ax's interference mitigation, 2.4 GHz performance degrades significantly in such environments.
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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Wireless Networking Technologies — This question tests Wireless Networking Technologies — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 802.11ac on 5 GHz — 802.11ac operates exclusively on the 5 GHz frequency band, which is far less congested than 2.4 GHz. This avoids interference from Bluetooth devices and cordless phones (which predominantly use 2.4 GHz), providing cleaner channels and better performance in a dense interference environment.
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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
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