FortiAp 221C 5ghz radio 99% with 0 clients

[sanderl]

1 out of 3 221C APs has radio 2 with 3 ssids on 5 ghz. No client are connected (they cant because ssids are not seen there). The channel utilisation is99% ans client count 0. NOTHING helps... what can be wrong?

[tanr]

Have you tried it, at least temporarily, with non-DFS channels, like 36, 40, 44, 48?

[sanderl]

Hi tanr, have tried to configure APs for 5G on only on 36, 40, 44, 48. And yes so far the AP (that said 99% channel util with no clients connected before) shows met the SSID and my mobile device connects to it... I will monitor this the next few days.

but with regards to this DFS... I have now selected on two APs to only use 36, 40, 44 and 48. A 3rd AP however has no issues in allowing clients on 116...

What is this thing with DFS exactly for? I read about is in: https://en.wikipedia.org/wiki/List_of_WLAN_channels

I read http://wifinigel.blogspot.com/2018/05/the-5ghz-problem-for-wi-fi-networks-dfs.html

But I still cannot get my head around DFS being a culprit of my issues so far (due to the fact another AP which is away about 15 meters line of sight) does not have this issue (and the 2nd one also not... if I configure there other channels that non-DFS...

Any tips/suggestions/hints?

[tanr]

Sounds like you’re narrowing it down. If nearby APs that are also on only DFS channels don’t show the same behavior then it sounds like a DFS false positive, which could be caused by multiple things. The second link you referenced has a section on false positives. Assuming it’s a false positive, if moving it around (especially in the same place as that AP 15m away, with that AP turned off) still shows that it’s detecting DFS, then it might be a bad antenna or sensor in the unit. If that’s the case then contact TAC to get it replaced. If moving it solves the problem, then it’s more likely environmental and you’ll need to track down what’s giving the false positive.

[Dave_Hall]

Enable the admin access for the AP then log into the GUI - go to the Wireless Information tab and see if Radio 2: AP is active/enabled and what SSIDs are assigned there.