1. Connect the computer to the LAN port of the router, and change the IP address from the router to another network segment address, as long as it is not the same network segment as the main router
Will do. For example, most router addresses are 192.168.1.1. We only need to change from one router address to 192.168.0.1.
2. Turn off the DHCP function of the router in the Settings;
3. Finally connect the network line from the main router to the LAN port from the router (either one will do), and be careful not to use WAN port.