Can I move my wireless router without giving direct internet access to my other devices?

Question

My internet is hooked up in the basement. I currently have a wifi router plugged in down there. It is then connected to a powerline adapter. I have three other locations throughout the house that have powerline adapters with various devices plugged in either directly or with ethernet switches (PC, rokus, theater receivers, etc.). My wifi is pretty weak on the second floor.

I would like to move my router to my main floor. But, if I plug my ISP's device directly into a powerline adapter, wouldn't I be providing direct internet access to all the devices that use other powerline adapters? And isn't that a bad idea because I would lose the firewall capabilities of my router protecting these devices? If so, is there some way to ensure these devices connect to the internet through the router, and not directly through whatever network I have created through the powerline adapters?

I have a couple of old routers I can use if necessary. I can also buy some new bit of equipment if required. My main goal is to have secure wired internet for devices that can use it, and good wifi coverage for the rest. Thanks.

Answer 1

It depends on what exactly your ISP's device is. Assuming it's only a modem, or you can't find out, a simple way is to connect a spare router to the ISP's device in the basement, and also connect it to the powerline LAN. This spare router can provide a firewall etc., assuming it has that feature. Plug your wifi router into powerline LAN on the second floor, configure it to just forward the LAN to wifi.

Diagram:

DSL --- ISP modem --- Old Router with Firewall
                           |
----+---------------+------+----------+-------- powerline
    |               |                 |
Equipment       Wifi Router       More Equipment
                    :    
                    : 
                Wifi Equipment