The usual default IP address of most routers are either 192.168.1.1 or 192.168.0.1. But it can happen that you might have changed this for some experiment. If you are not sure what your router IP is, here's how you can find out-

Go to Start –> Run and run the following command.

cmd /k ipconfig

The value against "Default Gateway" is your router IP address.

If you get some error or the IP address you get doesn't work, just re-set to router to factory defaults and use the router default IP. If you don't know it, you can find out easily by searching for "<router model> default IP" in Google.