How to access an external local network?

Question

System administration

There is remote access to a PC in the local network. A router on this network is connected to another router on a different LAN via the WAN. Is it possible to access an external router and other devices on an external network? Preferably via the web interface. No physical access to devices

Answer 1

VPN you need

Answer 2

For Windows "route add where through_what"
unless, of course, there really is access.