1 You can also manually find your router's internal IP address by openning a Windows command prompt and then using the command line tool ipconfig. 2  The following steps will walk you through this process.e will cover a couple of easy methods here. 1  You can use our free Router Detector software to find your router's internal IP address. 2  You can also manually find your router's internal IP address by openning a Windows command prompt and then using the command line tool ipconfig.