I do not know if I have understood it well.
In step 3: Exclude given server subnet from authentication in UI / Squid / Exclusions / by Authentication. This allows connections from the server subnet to the proxy to be non-authenticated.
Do I add a test ip like this?
In step 4: Add the server subnet to the UI / Web Filter / Policies / Locked Policy/ Members by Subnet. Configure the locked policy as needed allowing connections to a handful of web sites and blocking all others.
It doesn't seem to work, can you help me?
Now, a Windows host with domain authentication and proxy settings is working fine. And a Linux machine with IP 10.4.0.212 without proxy settings is not working.