Cisco routers, switches and modems are one of the most well-known devices of its kind. This tutorial teaches you how to configure correctly the Cisco 2100 cable modem to a wireless or non-wireless router. Make sure the connection from your Cisco 2100 modem to your router is properly connected. The Cisco 2100 modem's RJ-45 port is connected to WAN port of your router.
The Cisco 2100 modem's default IP is 10.2.0.1. But this will not be used in your router settings but just as reference.
Router IP address
Usually the default IP of your router is one of these: 192.168.0.1, 192.168.1.1 or 192.168.2.1 or similar to that of the modem. If you are not sure please refer to your router's user's manual for the default IP, username and password (in case you didn't changed anything).
How to access router's web interface
You can access router's configuration by typing-in your router's IP address in the address bar of a web browser. Login using appropriate username and password.
Configuring your router
The only thing you need to configure is the LAN settings of your router. Change it to 10.2.1.1 so that it will not get conflict with the Cisco 2100 cable modem. Also changed the subnet mask to 255.255.255.0.
Hope this guide can help you.