Hello there!
I have an interesting usecase. I have an OpenWRT router which acts as a Wireguard server. I have an external WG peer (client - 192.168.10.1) which is configured correctly: I can reach the OpenWRT router subnet (192.168.1.0/24). Here's the simplified of my network.
So I'd like this internal host to use the wg external peer as a gateway for internet access. So this internal host is 192.168.1.14/24, and, except inter traffic, I'd like it to use the 192.168.10.1/24 gateway for all internet traffic, and not use the default 192.168.1.254/24 internal gateway for that.
The reason behind this is that in my home (where the router resides), my ISP blocks tcp 25 (SMTP), but at my VPS (external peer) it is not. But if I want to utilize this port as a mail server on my local host, it should access the internet through my external WG peer where the SMTP port is unblocked.
One of my solutions for that was that I created another WG tunnel exclusively between my local (192.168.1.14) and external peer (via public ip). This way I did manage to success to route all internet traffic from local to external, thus SMTP traffic as well.
I hope I gave all the details. If you need further info, just hit me.
Thanks,
Daniel