He can keep it. Just degrade the original, obviously crap router to a modem. If it lacks this functionality then create a transfer net between it and your server. Connect your internal networks to your box, run your own dhcpd if you need. Get in control of your network. Have you box do the routing, masquerading, translations.
If you need the WiFi of your router, this gets harder, but can still be made to work by defining a 2nd network on the link between isp-router and user controlled router. If not supported by router then via manual IP config of clients.this does usually not work in modem setups but with the transfer network only. Port forwarding on ISP router needs to be possible in all scenarios with transfer net.
Sounds like a fun project and possibly a deeper dive into selfhosting territory:)
He can keep it. Just degrade the original, obviously crap router to a modem. If it lacks this functionality then create a transfer net between it and your server. Connect your internal networks to your box, run your own dhcpd if you need. Get in control of your network. Have you box do the routing, masquerading, translations.
If you need the WiFi of your router, this gets harder, but can still be made to work by defining a 2nd network on the link between isp-router and user controlled router. If not supported by router then via manual IP config of clients.this does usually not work in modem setups but with the transfer network only. Port forwarding on ISP router needs to be possible in all scenarios with transfer net.
Sounds like a fun project and possibly a deeper dive into selfhosting territory:)