Telus Fibre + network switch

Hi all,

I am wondering about a couple of things:

1) If I want to use a network switch (unmanaged), do I place it after the router (and not between the ONT and router)? I'm assuming this is the case, but would like to confirm.

2) If I do place the switch after the router, is it of any use to run one ethernet cable to the switch and connect multiple devices to it while running other cables directly from the router to other devices?

For example, our ONT and router are in the basement. I have one computer hard-wired to the router in the basement and another hard-wired on the main floor. Could I put a switch between the router and the upstairs computer so that I could connect other devices on the main floor to the switch?

The reason I'm thinking of this kind of set up is that I'm hoping to avoid running more cable than I already have. Our home is older but the basement and main floor are finished & do not have the skills/time to run the cable through the walls.

Thanks