Config: TMG is up at 10.0.3.1 with three network adapters, one of them is connected to Internet. Local Windows 8.1 PC at 10.0.3.xx attempts to connect to a managed switch (internal) at http://10.0.3.yy via browser. PC has 10.0.3.1 as gateway, the switch might not have this setting altogether. The switch is NOT published on TMG. The PC receives an error 12206: Proxy chain loop page into the browser, originating from 10.0.3.1. TMG's logs indicate a corresponding event id 14141 with about the same content.
How come traffic ever goes through the TMG, if the browser is configured to not use the proxy? And how to make the PC ignore TMG's presence and directly connect to the switch via HTTP?
telnet 10.0.3.yy 80 with
GET / HTTP/1.0 sent by hand also results in 12206 page retrieved from TMG, so this issue should be on an underlying network layer.