Choose a specific WiFi AP or Frequency

Question

My router (Google WiFi) have 2 access points with the same ssid: a 2.4GHz and a 5GHz. It seems that multicasting between these networks is unstable, so I want my raspberry (buster) to force a connection to the 2.4GHz network.

I've tried to add bssid and bssid_blacklist to the config, but it did not work. After a while, the connection changes to 5GHz

# /etc/wpa_supplicant/wpa_supplicant.conf
network={
        ssid="name"
        psk="*****"
        bssid=70:3A:CB:84:01:B4
        bssid_blacklist=70:3A:CB:84:01:B0
}

Is there a way to achieve this?

Update: None of the options seem to work. Here is a discussion on the official forum

Update 2: freq_list seems to solve the problem, although many on the internet say it won't work. Here is my new config:

network={
        bssid=70:3A:CB:84:01:B4
        freq_list=2412 2417 2422 2427 2432 2437 2442 2447 2452 2457 2462
        ssid="..."
        psk="*****"
        bssid_blacklist=70:3A:CB:84:01:B0
}

My raspberry has been running on Buster Raspbian at 2.4GHz for a week now

Answer 1

Making that choice on the Raspberry Pi seems to be a problem. I would have thought that bssid or bssid_blacklist would have worked for you, at least. Being able to choose which access point to connect to based on BSSID is rather important...

I've tried to limit a Pi 3B+ to 2.4 GHz frequencies using the freq_list parameter in wpa_supplicant.conf, but with no success. This seems to be a common problem. Something seems to be broken in the Raspberry Pi's wpa_supplicant.

An ugly work-around would be to choose a restrictive Wi-Fi country code that does not allow the 5 GHz frequency your router is using. Mainland China or Israel seem like good choices. By setting my Pi 3B+ to "Israel", which does not allow the 5 GHz frequency used by my router, it then connected using 2.4 GHz.

You COULD look at rebuilding the Central Regulatory Domain Agent (I think this is where the country Wi-Fi frequencies live, but I do not know for sure) to create your own custom "country" that only allows 2.4 GHz. Hopefully this work-around is good enough, though. :-)

EDIT: The link to the Raspberry Pi forum discussion of this problem was incorrect.

Answer 2

Change the APs SSID on the 2,4GHz and 5GHz so they do have separate names.

The other solution is to specify the parameter freq_list in the file /etc/wpa_supplicant/wpa_supplicant.conf:

ctrl_interface=/var/run/wpa_supplicant

network={
    ssid="Your_AP"
    psk="Your_Passphrase"
    freq_list=2412 2437 2462
}

Ref.: https://askubuntu.com/questions/1058622/how-to-force-to-linux-to-connect-only-5ghz-channel