When internet connection is lost RPi doesn't switch to another network with it

Question

RPi 3B+ PRETTY_NAME="Raspbian GNU/Linux 11 (bullseye)"
At /etc/wpa_supplicant/wpa_supplicant.conf I have some network definitions like:

network={
        ssid="SID 1"
        psk="###"
        key_mgmt=WPA-PSK
        priority=1
}

network={
        ssid="SID 0"
        psk="###"
        key_mgmt=WPA-PSK
        priority=0
}

network={
        ssid="SID 2"
        psk="###"
        key_mgmt=WPA-PSK
        priority=2

Turning on the RPi it uses "SID 2" because its priority=2.
When "SID 2" loses internet I want connection switch to other network with internet.
It doesn't happen automatically. It still keeps connected to SID 2 without internet connection. How to perform that?

Answer 1

wpa_supplicant knows nothing about internet.

It will only select the highest priority or strongest WiFi signal.

You will have to write some code to detect internet loss and to switch networks.