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I have a self built Linux router with a wifi card that I had setup a year ago or more as an AP. I worked for some 8 months without an issue, until a few months back (I have no date) it just stooped working.

It took me a while to look into it, but finally today I got it working on channel 44 on the 5GHz band. I chose that channel because it was the only one available according to hostapd:

nl80211: Mode IEEE 802.11a: 5180[NO_IR] 5200[NO_IR] 5220 5240[NO_IR] 5260[NO_IR][RADAR] 5280[NO_IR][RADAR] 5300[NO_IR][RADAR] 5320[NO_IR][RADAR] 5500[DISABLED][NO_IR][RADAR] 5520[DISABLED][NO_IR][RADAR]

Because I got greedy, I wanted to keep configuring it to try to get 40GHz in the channel 46, but when I tried to run it again, I got:

nl80211: Mode IEEE 802.11a: 5180[NO_IR] 5200[NO_IR] 5220[NO_IR] 5240[NO_IR] 5260[NO_IR][RADAR] 5280[NO_IR][RADAR] 5300[NO_IR][RADAR] 5320[NO_IR][RADAR] 5500[DISABLED][NO_IR][RADAR] 5520[DISABLED][NO_IR][RADAR]
Channel 44 (primary) not allowed for AP mode, flags: 0x2073 NO-IR

There was no package updates in between, they might have been some 5 to 10 minutes. The router was not rebooted, and has been connected to internet ever since I set it up initially a year ago. The country regulatory information is for france:

nl80211: Regulatory information - country=FR (DFS-ETSI)
nl80211: 2402-2482 @ 40 MHz 20 mBm
nl80211: 5170-5250 @ 80 MHz 20 mBm
nl80211: 5250-5330 @ 80 MHz 20 mBm (DFS)
nl80211: 5490-5710 @ 160 MHz 27 mBm (DFS)
nl80211: 57000-66000 @ 2160 MHz 40 mBm

What could have happened, and could I somehow revert this?

Marcos Dione
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  • Some cards (such as Intel ones from 2020 onwards) ignore the regulatory domain you specify and try to figure it out themselves in firmware based on signals around you. If you have a card that does this, it can be difficult to get it to work on the channel you want, especially if you don't have other APs nearby that the firmware can use to deduce your regulatory domain. – Malvineous Dec 23 '21 at 02:46

1 Answers1

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It probably picked up country from a neighboring access points. APs announce their country and then others can configure based on that country. I assume you are not in France so country=FR is not what you expected.

How you configure your regulatory domain depends on the operating system or Linux distribution you are using. You didn't specify that.

Mitar
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  • The OP is using hostapd which means the regulatory domain is specified via the `country_code` option in `hostapd.conf`. It's the same on all Linux distros using hostapd. – Malvineous Dec 23 '21 at 02:40
  • > I assume you are not in France so country=FR is not what you expected. No, that's fine, I_do_ live in France. – Marcos Dione Dec 24 '21 at 18:35