I have a semi-complex home network with a DSL Modem/Router, a Netgear Router, and a TPLink Router.
The TPLink Router has a permanent L2TP VPN connected to ExpressVPN. The devices behind this router get their internet through the VPN. (devices on the right in the attached diagram)
The Netgear router is for normal (non-VPN) internet.
Is it possible to configure all three routers in the diagram such that the devices behind the two routers can communicate one with another seamlessly (i.e. without port forwarding for every requirement)? I almost got there with a few static routes, but I had to turn off NAT to get them working, and then that killed the internet.
A working solution would allow devices to ping each other on the LAN, communicate on all TCP/UDP ports, have broadcast packets/requests routed across both networks, but still have "segregated internet" (e.g. devices on the right go through the VPN for internet).
Notes: (1) I can't turn the Netgear into a bridge/AP because it performs wireless mesh routing with satellite devices. The TP-Link can't be a bridge either, because I need its routing function to handle the L2TP VPN tunnel. (2) If the solution requires putting the TP-Link behind the Netgear, that's okay.