I try to set up port forwarding for webcam DVR via Comcast Modem SMCD3G-CCR. I have Linksys WRT-120N router conntected to the modem. I would like to know how to set up the modem and Linksys to watch the webcam outside the network. I tried to connect webcam dvr to modem directly bypassing the router, but fail to connect via internet. Can someone let me know to do it? Please....
The SMC is NOT a modem, it's a gateway. You have Comcast Business service? The best way to handle this is connect the webcam to directly to the SMC so you don't have a double NAT, and port forwarding only needs to be handled by the SMC (which is your link to the outside world). Simply go into the SMC's settings and forward the appropriate port to the new IP address assigned to the webcam (it should different than it was behind the Linksys router).
If you try and attach the webcam to the Linksys, you have to port forward through the SMC to the Linksys's WAN interface, then in the Linksys port forward again to the webcam's IP because you have a double NAT setup. While I don't recommend double NAT setups, they can be made to work, but chains of port forwards to get by each NAT function can be fragile and some servers might not function properly, so always put the servers needing port forwarding directly behind the first NAT device, in this case the SMC gateway.
If that doesn't work, you will need to lake out hte exact webcam being used, the exact port forwards you ahve setup, the IP address of the webcam, etc.
That's the first thing to do, verify you can access the DVR locally to see if it is indeed responding on the proper port. You might want to investigate upgrading the firmware, there appear to be some available. Assuming that all works...
Now connect it to the SMC. Confgure the SMC port forwarding to the DVR's IP address and you should be good to go. Another option is to place the DVR's IP in the SMC's DMZ.
If you want to keep it connected to the Linksys, you need the port forwarding setup in the SMC to the Linksys, and in hte Linksys to the actual DVR IP address.