This article explains How to Configure Repeater Mode on Xiaomi MI 3C Wireless router. Its management IP is 192.168.31.1 or miwifi.com.
Reset MI router to Factory defaults
We could see RESET button on the rear of Xiaomi MI 3C Wireless router, with the router powered on, press and hold the RESET button (more than 10 seconds). Then release the button and wait the router to reboot to its factory default settings.
Log in Xiaomi MI 3C Wireless router
Open a web-browser (such as Microsoft Internet Explorer, Google Chrome, Mozilla Firefox or Apple Safari). Enter the ip address of Xiaomi MI 3C wireless router: 192.168.31.1 or http://miwifi.com.
Because you have set the router as the factory default, you don't need to enter a password. Click "Agree" button.
Configure Repeater Mode On Xiaomi MI 3C Wireless router
There are two modes you can choose: Mode (Set up Wi-Fi network) and Amplifier mode (extend existing Wi-Fi).
We select " Amplifier mode ". Choose an existing wireless network to repeat or enter the SSID and password. Then click " Next ".
Set new network name and password, select "Mixed (WPA/WPA2-personal)" Encryption, then click " Next ".
Set admin password
If you check the box of "Same as Wi-Fi password", the input box of password will be filled with Wi-Fi password, but it's not safe. You'd better use another password. Then click " Set up successfully ".
You can also download the app to make other settings.
Notice : If the superior router isn't a Mi Wi-Fi, the IP address may changed by the upper router. Install Miwifi app to manage your device in that case.
The IP address of Xiaomi MI 3C Wireless router has been changed to 192.168.100.110.