Help! Driven mad by my Nest Thermostat.

I have a Vigor 2860n and an ADSL2+ BT connection (WAN1) and a Radio Broadband connection (WAN2, ethernet). I have a Nest Thermostat for my central heating that requires a Wi-Fi connection to the internet to function.

The best way to describe the issue I'm having is to indicate what does and doesn't work with my setup as follows:

1. Nest Thermostat works perfectly with WAN2 only enabled and connected
2. Nest Thermostat has no internet connectivity with only WAN1 enabled and connected
3. Nest Thermostat has no internet connectivity with both WAN1 & WAN2 enabled and connected
4. When I swap out my Vigor for my BT Homehub for my BT connection (WAN1 above) Nest Thermostat works perfectly

I have tried the most recent few firmwares and several factory default resets. I have used the onboard Wi-Fi to connected to the Nest and have also used my Develo powerline Wi-Fi modules adapters connected directly to the router as an alternative with the same result. I have checked policy routes, ports and firewall settings but to no avail.

I am certainly no network/hardware expert. I know my way around the configuration GUI and would be eternally grateful for any assistance anyone may be able to offer me with this issue.

Thanks!

have you done the simply step? to change the wifi channel at the 2860 (Wireless LAN >> General Setup)

Thanks for your reply. Yes I have tried various channels using the wifi onboard and separately as an alternative another wireless access point plugged into my Draytek with the onboard wifi switched off. Both yield the same result.

I should have made it clear in my first post that I am able to successfully connect to the WLAN however I have no connectivity. It is not that I am not able to join the wireless network.

Thanks for your reply.

did you set up any routing rules at any time and forgot to remove them?

Back up your config, do a complete factory resert and set up from scratch with
the minimum/simplest config and see if it works then, or with later firmware...

Thanks for the reply.

I have done several factory resets and set up from scratch and tried the latest few firmwares with very basic configuration all without luck. I have three 2860n routers (for different sites) and have tried them all with the same result so am fairly sure it is a software/configuration issue rather than a hardware one.

Any further suggestions very gratefully received!

It is strange then..you might have to raise a support ticket and lend them your
thermostat to test if you can't do the packet capture yourself.