CWNP Exam CWAP-404 Topic 4 Question 36 Discussion

Actual exam question for CWNP's CWAP-404 exam

Question #: 36
Topic #: 4

You have installed a new 802.1 lac WLAN configured with 80 MHz channels. Users in one area are complaining about poor performance. This area is currently served by a single AP. You take a spectrum analysis capture in the poor performing are

a. While examining the waterfall plot you notice the airtime utilization is higher on the first 20 MHz of the 80 MHz channel when compared to the rest of the channel. What do you conclude?

AThe AP is misconfigured and needs to be reconfigured to 80 MHz operation

BNon-Wi-Fi interference is preventing the APs 80 MHz operation

CThe first 20 MHz is the AP's primary channel and higher airtime utilization on the primary channel is normal when an AP is configured for 80 MHz operation

DRRM is enabled and has dynamically picked a 20 MHz channel

Show Suggested Answer

Suggested Answer: B

The most likely cause of higher airtime utilization on the first 20 MHz of the 80 MHz channel is non-Wi-Fi interference. Non-Wi-Fi interference can prevent an AP from using its full channel width, as it will degrade the signal quality and increase the noise floor on some parts of the channel. This will force the AP to fall back to a narrower channel width, such as 20 MHz or 40 MHz, to maintain communication with its clients. The waterfall plot can help identify non-Wi-Fi interference by showing spikes or bursts of RF energy on specific frequencies or sub-channels. The other options are not correct, as they do not explain why only the first 20 MHz of the channel has higher airtime utilization.Reference:[Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 74-75

by Malinda at Jul 07, 2025, 12:54 PM

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