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Exam 350-401 topic 1 question 587 discussion

Actual exam question from Cisco's 350-401

Question #: 587
Topic #: 1

A customer has recently implemented a new wireless infrastructure using WLC-5520s at a site directly next to a large commercial airport. Users report that they intermittently lose Wi-Fi connectivity, and troubleshooting reveals it is due to frequent channel changes. Which two actions fix this issue? (Choose two.)

A. Enable DFS channels because they are immune to radar interference.
B. Restore the DCA default settings because this automatically avoids channel interference.
C. Remove UNII-2 and Extended UNII-2 channels from the 5 Ghz channel list.
D. Disable DFS channels to prevent interference with Doppler radar.
E. Configure channels on the UNII-2 and the Extended UNII-2 sub-bands of the 5 Ghz band only.

Show Suggested Answer

Suggested Answer: CD 🗳️

by kebkim at Sept. 21, 2022, 8:33 p.m.

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kebkim

Highly Voted 2 years, 10 months ago

DFS is Dynamic Frequency Selection, which is a function of using 5 GHz Wi-Fi frequencies that are generally reserved for radar. Because the 2.4Ghz band is free of radar, the DFS rules only apply to the 5.250 – 5.725 Ghz band. UNII-2 (5.250-5.350 GHz and 5.470-5.725 GHz) shared with radar systems. Therefore, APs operating on UNII-2 channels are required to use Dynamic Frequency Selection (DFS) to avoid interfering with radar signals.

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Badger_27

Highly Voted 2 years, 4 months ago

Really..really?

upvoted 6 times

Dv123456

2 years ago

I haven't see DFS in the official cert guide

upvoted 4 times

ihateciscoreally

1 year, 11 months ago

man you talking about DFS not being covered in OCG, but its not the problem xD problem is that they are asking about high level wireless, its not topic for ENCOR.

upvoted 5 times

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Megon

Most Recent 1 year ago

At this stage, i believe the software they use to generate the exam questions from question bank is somehow glitchy as it mixes up different tracks together. How on earth such high level of channel selection can be asked for ENCOR exam ? what is then left for wireless track if they assume this is ok ???

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sinaghozati

2 years, 5 months ago

C and D

upvoted 2 times

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x3rox

2 years, 6 months ago

From Source: If you want to use the UNI II band DFS channels, don't have your site near an airport! If you have newer.... https://blog.iptel.com.au/wifi-and-the-problem-with-radar#:~:text=If%20you%20want%20to%20use%20the%20UNI%20II%20band%20DFS%20channels%2C%20don%27t%20have%20your%20site%20near%20an%20airport!%20If%20you%20have%20newer

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bora4motion

2 years, 8 months ago

Selected Answer: CD

DFS channels are actually extended UNII-2 and 3. To me the answer is C and D. Disable DFS as that will stop taking the radios down to scan for a free channel and stop using UNI2.

upvoted 3 times

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winder

2 years, 8 months ago

my understanding of this is for answer A is "DFS channels because they are immune to radar interference" , they aren't immune. believe the question mentioned channel keeps changing is due to DFS, so the provided answer is right https://www.cisco.com/c/en/us/support/docs/wireless-mobility/80211/213882-radar-detection-in-dynamic-frequency-sel.html

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tckoon

2 years, 10 months ago

This mean answers are A & C ?

upvoted 2 times

Nassir76

2 years ago

apologies I accidently upvoted you response. I meant to say it could not be A because the question states that there is frequent channel change. We need to stop that by disabling DFS,

upvoted 4 times

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