Why does the modem turn off when connecting a laptop via wifi?

Question

WiFi

Hello.
There is a modem in which the Internet is connected using DOCSIS 3.0 . The router is connected to the modem via Ethernet.
There is a stationary PC that is connected to the router via ethernet and 2 smartphones via WIFI.
As soon as I turn on the laptop and connect to the Internet (WIFI / Ethernet), the Internet in the modem disappears, the LEDs flash and the modem tries to reconnect. If I turn off the laptop or disconnect from the network, the Internet in the modem will appear in 3-5 minutes.
How is this possible and how to solve the problem?

Answer 1

Try to go backwards. First, connect the laptop directly to the modem. If there are no problems, connect through a router. Problems will appear, reset the router to default settings.
If it does not help, you need to check the modem settings and the connection diagram. Several options are possible.
First, on the modem on the LAN port, the number of simultaneously connected devices can be limited. It is required that the router hide everything behind NAT, i.e. the router must receive an IP address from the modem.
Secondly, NAT and DHCP are already working on your modem on the LAN port, so you can try disabling the DHCP server on the LAN ports of the router and connect the cable from the modem and laptop there. Then the devices will be on the same network.

Answer 2

I would also check if the IP address on the laptop's Wi-Fi card matches the router's address...
Set the Wi-Fi and laptop network card settings to DHCP. (Automatically)