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,

The correct answer is A. Remove UNII-2 and Extended UNII-2 channels from the 5 Ghz channel list C. Disable DFS channels to prevent interference writ) Doppler radar. Explanation Near an airport, radar systems (including weather/Doppler radar) operate on DFS (Dynamic Frequency Selection) channels, which fall within the UNII-2 and Extended UNII-2 sub-bands of the 5 GHz spectrum (5.25–5.725 GHz). When an access point detects radar on these chann

Submitted by skyler.x· Mar 6, 2026Infrastructure

Question

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.)

Options

ARemove UNII-2 and Extended UNII-2 channels from the 5 Ghz channel list
BRestore the OCA default settings because this automatically avoids channel interference
CDisable DFS channels to prevent interference writ) Doppler radar
DEnable DFS channels because they are immune to radar interference
EConfigure channels on the UNII-2 and the Extended UNII-2 sub-bands of the 5 Ghz band only

How the community answered

(53 responses)

A
85% (45)
B
2% (1)
D
4% (2)
E
9% (5)

Explanation

Near an airport, radar systems (including weather/Doppler radar) operate on DFS (Dynamic Frequency Selection) channels, which fall within the UNII-2 and Extended UNII-2 sub-bands of the 5 GHz spectrum (5.25–5.725 GHz). When an access point detects radar on these channels, it is legally required to vacate them immediately - triggering the frequent channel changes users are experiencing. Removing UNII-2/Extended UNII-2 channels from the allowed channel list (A) and disabling DFS channels (C) are essentially two ways of describing the same corrective action - preventing the WLC from ever selecting those radar-affected channels.

Why the distractors are wrong:

B is incorrect because restoring OCA (Off-Channel Assistance) defaults does not inherently avoid radar-triggered channel changes - it still allows DFS channels to be used.
D is the opposite of truth; DFS channels are not immune to radar - they are specifically the ones most susceptible to radar interference and forced channel changes.
E is wrong because using only UNII-2 and Extended UNII-2 channels would make the problem worse, as those are exactly the DFS-affected sub-bands.

Memory Tip: Think "Airport = Avoid DFS" - near radar-heavy environments like airports, stick to UNII-1 (5.15–5.25 GHz) and UNII-3 (5.725–5.850 GHz) channels, which are DFS-free.

Topics

#Wireless LAN#DFS#5 GHz#Troubleshooting

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