@Didier_Jakarta Use this guide to configure 3G/4G backup feature.

@DavideD Ethernet ports on the modem router are bridged by default and those two devices should be able to communicate with each other.

@Gab123 Because C50 is not a gigabit router:

@Allispossible " My main router had its local IP 192.168.1.1 and the TP-Link device received IP 192.168.1.3. The TP-Link's device own network was 192.168.0.1. This worked completely fine until the...

@m_schulz This will depend on your particular environment and wireless clients - that's the reason this is not specified in the tech specs of the device. This story will be a good starting point.

@Nav97 Better consider an easymesh device - they have better compatibility and interoperability. A good candidates which fit your requirements: Archer AX55, AX53 (Wi-Fi 6) Archer C86, C64 (Wi-Fi 5)...