LinuxFirst, navigate to: Applications > System Tools > Terminal and type 'ipconfig'. You will see your router's IP listed beside 'inet addr'.
iPhone iOSIf using iOS9 or iOS8, navigate to Settings > WiFi and click the wireless network to which you are currently connected. Look in the DHCP section to find our your router's IP.
AndroidA third-party app called Wi-Fi Analyzer is the easiest method for Android devices. After installing the app, tap on the 'View' menu and choose 'AP list'. You'll see 'Connected to: [Network Name]'. If you tap on it, a window will display your network's information including your router's IP.
If you have questions or need any assistance troubleshooting, just visit:
Google Wifi Setup | Linksys Router Login