Need to set up the router

I am not sure where you are, but you need to set up the router with right information. I had AT&T cable modem before when they first came out. I had to set up my router with all the information such as gateway, IP address, etc. When you connect your PC to the cable modem without router, do you have to set up anything in your PC or just leave everything default? Basically you have to give all the setup in your PC to the router or it will not connect.