I've seen many posts covering how to set up two LANs off of one modem that involve cascading the routers. I came back from vacation to see someone had hooked up a second router to the modem (the modem has 4 LAN ports) for our office neighbors to have their own network. i.e. we want both networks to be private from the other.
The modem is in bridge mode and when I check the WAN IP on our router it's public facing, so it would appear everything is and has been OK since the second router was added. Is there something I'm missing? The only item I'm not confident in is port forwarding for a VPN hosted on our server. As long as their router isn't also trying to forward the same ports, it should work?