How to use a different WAN interface on different internal networks within OPNsense.
At the back of my house, there's a granny flat with a family with two high schoolers. Recently, the NBN has come to my area and we now have to share the same Internet connection. I use Mullvad as my VPN provider and VPNs are easily blocked by a lot of video streaming services like Netflix, Amazon Prime Video and Optus Sports. The high schoolers use Netflix a lot and I wasn't going to sacrifice my VPN for them. Instead, I had to find a way to have a network that did not use VPN. A network that sends its traffic over WAN instead of VPN.
I've visualised the goal with this diagram:
In this guide I will have two networks:
Granny: The Granny flat's network
My internal networks: My networks.
I have firewall rules for the that says for all traffic not using Internal networks, that they should be sent over the WAN Gateway.
My networks have a similar rule but with using the VPN Gateway.
I have two separate NAT rules to dictate how network traffic should leave the router.
Any traffic from Granny that isn't going to Granny should go over the WAN Gateway.
I simple check is to go to https://www.ipchicken.com/ which gives me WAN IP address instead of the VPN IP address