220-1101 Question 80
Single answerChannel selectionA technician is troubleshooting slow and unstable Wi-Fi in a small office. Users report frequent disconnects and poor performance on the 2.4 GHz network, especially in the afternoon when neighboring businesses are active. A wireless scan shows several nearby access points already using channels 1 and 6 with strong signal strength. The office router is currently set to channel 4 on 2.4 GHz. Which action should the technician take FIRST to reduce interference and improve reliability?
- A
Change the router to channel 11 on the 2.4 GHz band
- B
Change the router to channel 3 on the 2.4 GHz band
- C
Increase the channel width to 40 MHz on the 2.4 GHz band
- D
Move the 2.4 GHz network to channel 9 because it is farther from channel 1
Show answer and explanation
Correct answer: A
Explanation
The best first action is to move the 2.4 GHz network to channel 11. In 2.4 GHz Wi-Fi, overlapping channels are a major source of interference and degraded performance. Best practice is to use non-overlapping channels, typically 1, 6, and 11 in regions where channel 11 is allowed. Because neighboring access points already occupy channels 1 and 6, channel 11 is the most appropriate choice. Leaving the router on channel 4 is problematic because channel 4 overlaps with both channel 1 and channel 6. CompTIA A+ Core 1 expects technicians to recognize practical wireless troubleshooting steps such as selecting a non-overlapping channel, especially on congested 2.4 GHz networks. This aligns with common WLAN design guidance from wireless vendors and IEEE 802.11 deployment best practices for minimizing adjacent-channel interference.
- A. Correct.
Correct. On 2.4 GHz, the commonly recommended non-overlapping channels in many regulatory domains are 1, 6, and 11. Since nearby networks are already heavily using channels 1 and 6, moving this router from channel 4 to channel 11 reduces adjacent-channel overlap and co-channel contention. Channel 4 overlaps with both 1 and 6, which commonly causes poor performance and instability.
- B. Incorrect.
Incorrect. Channel 3 is still an overlapping 2.4 GHz channel and would continue to interfere with nearby networks on channels 1 and 6. A common misconception is that simply moving to any different channel helps, but in 2.4 GHz, overlapping channels can make performance worse than staying on a properly selected non-overlapping channel.
- C. Incorrect.
Incorrect. Expanding 2.4 GHz to 40 MHz usually increases interference because it consumes more spectrum in a band that is already crowded. In small office and apartment environments, 20 MHz is generally the better practice for 2.4 GHz to minimize overlap and improve compatibility.
- D. Incorrect.
Incorrect. Channel 9 still overlaps significantly with channel 6 and partially with channel 11. Although it may seem numerically separated from channel 1, 2.4 GHz channel planning is based on frequency overlap, not just channel number distance. Choosing channel 9 would not be the best first step.