I am connecting the DVR to the P1 modem DV230 and its Firmware v1.3.7-g1.2.6-p1.

If the DVR is direct connect to the modem LAN port, it is successfully connected after the port forwarding thing is done. But, if the modem is connect to a switch / hub, then, the DVR connects to one of the LAN ports at the switch, the connection to DVR is unsuccessful. But internet sharing among the PCs is ok by connecting to the switch.

What when wrong? Thanks.