Can't ping other computer in the same network, or open a port (use docsis 3.0 modem and a router)

[slimfit]

this is the map of my network connection
wall->docsis 3.0 modem-> wireless router-> pc
docsis 3.0 modem
Netgear wireless router

I don't know what happen but I can't open a port, or ping other computers in the same network (did set up ip address). If I use the modem alone, everything work fine.
Please teach me what to do to fix my problem.

 

[DistraughtSysop]

Does your router function properly otherwise? I mean, do you have internet access when connected through the router?