windows - 1 modem connect with 2 device, can it in the same network?

My ISP provide me a moderm that has 4 input and I can plug lan cable in it

the modem model: http://huawei.com/en/products/fixed-access/fttx/ont/hg863/index.htm

So I have attempt like this before

--> moderm --> router --> notebook
                      --> pc

it works perfectly as expected, they are in the same network.

However, recently I need to move my pc away, so I connect like this:

---> moderm --> router---> notebook
            --> pc

Although both pc and notebook can connect to internet, it no longer in the same network, any workaround to this? Thanks

Answer

Disable DHCP on your router, change the router cable port from WAN port to LAN port