Unless I’m misunderstanding something, this is just how networking works. All of your local traffic is going to go through that router at some level. The router is making all the decisions for… routing. It has to be a part of the network.
If it’s truly an untrusted device, you need physical separation. Subnets are just informational for routing purposes. The trivial setup is “tandem routers”: ISP – ISP_router – Your_router – (( your home network )). The downside is the double NATing is going to cause weird problems unless you go to a lot of trouble of port forwarding (and don’t forward all ports to your “favorite” machine).
Advanced “I have a Cisco certification” setups for separation involve VLANs and many distinct, specialist devices: a pure router/firewall (no switch/hub, no wifi), a managed switch, and a mesh of managed wifi access points. Some home routers automate this to give you a “guest network” or maybe even an “IOT network”.
Unless I’m misunderstanding something, this is just how networking works. All of your local traffic is going to go through that router at some level. The router is making all the decisions for… routing. It has to be a part of the network.
If it’s truly an untrusted device, you need physical separation. Subnets are just informational for routing purposes. The trivial setup is “tandem routers”: ISP – ISP_router – Your_router – (( your home network )). The downside is the double NATing is going to cause weird problems unless you go to a lot of trouble of port forwarding (and don’t forward all ports to your “favorite” machine).
Advanced “I have a Cisco certification” setups for separation involve VLANs and many distinct, specialist devices: a pure router/firewall (no switch/hub, no wifi), a managed switch, and a mesh of managed wifi access points. Some home routers automate this to give you a “guest network” or maybe even an “IOT network”.