DFS on the R7800

I have SE set as country for wifi on the Netgear R7800, however if I try to use channel 100 or 116 I get " hostapd: could not get valid channel" Shouldn't it start scanning for radars? It just seem to give up.

My neighbor is using channel 60 which's also kind a "DFS" channel too afaik

I tried changing the country to HT then I could use channel 100 but none of the Linux laptops would connect to it, they were set to SE country code for wifi. Some other devices did connect tho'.

# iw reg get
country SE: DFS-ETSI
        (2400 - 2483 @ 40), (N/A, 20), (N/A)
        (5150 - 5250 @ 80), (N/A, 23), (N/A), NO-OUTDOOR, AUTO-BW
        (5250 - 5350 @ 80), (N/A, 20), (0 ms), NO-OUTDOOR, DFS, AUTO-BW
        (5470 - 5725 @ 160), (N/A, 26), (0 ms), DFS
        (5725 - 5875 @ 80), (N/A, 13), (N/A)
        (57000 - 66000 @ 2160), (N/A, 40), (N/A)

I've seen similar behavior on my TP-Link Archer C2600. Saw the radar alert in syslog (caused by scanning for other 5GHz networks, go figure), saw the message for the channel change and the error you describe. After that, no client can connect anymore.

I've set it to a non-dfs channel for now. It's a new regression for me on 21.02. Never experienced this on 19.07.

Mhm... maybe I need more logging somewhere, I don't even see the dfs scan in the log.

Okay, so using driver default setting for country makes it say "hardware does not support the selected channels" or something like that.
Setting country to Haiti (HT) makes channel 100 work fine and all devices seem to be able to connect now.
Setting country to Sweden makes it say "could not get valid channel"...

It's very odd.

My reg data is identical to yours, but my error happened a bit differently. I could get the interface up and running with channel 100, but the interface died as soon as it was supposed to change to a non-DFS channel due to radar. And I got the "could not get valid channel" message, with no client able to connect.

If you scroll down to the table for 5GHz, it should be channel 100@20MHz width, 102@40MHz and 106@80MHz for Europe. I think OpenWRT/Firmware automatically sets the appropriate channel in the background depending on the channel width. I wonder, does every channel selection in luci between 100-116 throw out the same error? Based on what I could find from Google, Haiti should also consider the frequency range of channel 100 as DFS.

Maybe the firmware switching from DFS to non-DFS triggers the issue? I don't know how I'd manually trigger a radar detect event to test it out. The "Channel Analysis" page isn't triggering it by mistake again.

I fail to see the width limitation for europe.
I read on a swedish page that for band U-NII-2, (100 – 140). it's eleven 20 MHz channels, five 40 MHZ channels, and two 80 MHz channels.

However they don't list the channels.

If you select channel 100 the actual frequency center will change depending on if you have 20/40/80/160 selected as the width. That's what the table I linked shows at least. Don't see why it would complain about not being able to find a valid channel.

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