Due to some renovation work being done on our building, we need to move everything out for a couple months until the construction is complete. The temporary building has internet but no static IP or inbound open ports (it's just a basic business service) so instead of ordering new service and updating all of our domains, we plan to keep an OPNsense system in place and and setup a site-to-site VPN (we have a small protected space we can keep during construction).
It's my understanding that a site-to-site VPN requires different subnets on either end, so what would be the easiest way to setup this up with minimal network reconfiguration? Create the site-to-site and duplicate the WAN rules? We've never done a site-to-site, I'm sure it's easier when you're creating it from scratch, but not sure exactly how to do this for a fully active network with minimal changes.
Any suggestions would be appreciated!