Thank you for your reply, whenever I use the VPN my PC connects to the 2.4GHz access point I use for my thermostat and security cameras instead of going directly through the modem so it slows down my connection dramatically. Not sure why, it is driving me crazy, so my thought was connect the T3200 to the LAN2 on the ONT and have it completely separate from the rest. Is there a way to activate the 2nd port on the ONT?
On residential connections, only one port is active on the ONT. If the access point for your thermostat has a different network name / SSID than your other network, have you tried forgetting that network on your PC so it would no longer connect to it? That would have been my first step to take.
If you're completely set on connecting two devices to the ONT, the only way is to put a gigabit switch between the ONT and the router / T3200.