Ethernet wan fallback to wifi wan to phone hotspot

Installing and Using OpenWrt
1

Hi all,

We had fibre (fiber!) internet installed last year (500Mb/500Mb) and it's been extremely reliable so far. Previously our copper internet connection was average and I had a 4g router as a backup internet connection with automatic failover in OpenWRT

I've decided to cease the 4g service as I just don't use it.

In an emergency my phone Sim has unlimited data and I can set it up as a hotspot. I can do a manual change over if required.

Is there anyway for me to Wifi connect from my OpenWRT router to my phone hotspot and use that connection as the home internet connection? Note- my main router is a Linksys E8450 and I currently do not use the Wifi on the router for anything- I have a seperate mesh wifi in the house.

I understand mobile networks in the UK use CGNat- will that cause a problem?

Thanks

2

On the E8450 go to wireless > scan > join (the phones hotspot).
Put the connection in the wan firewall zone.
Done.

Make sure phone's and router's LAN subnets aren't the same.