Security camera DVR and the internet: problem with TP-Link WAN router

[setishock]

Let me start out with the parts list:

SVAT Defender 4
TP-Link TL-R480T+ dual wan router
Ambit U10C018 cable modem (ISP provided/ Suddenlink)
12Mbps down, 1.8Mbps up

The internal settings on the DVR server have been set up according to the instructions in the owners manual. In the router I have set up on the virtual server page to have port 2000 forwarded to the DVR's internal IP address.
We can see it on the local network but not outside it. I have some friends out of state that have been trying to hit it with no sucess.
Since the TP-Link doesn't have a port forwarding page I did switch to another router that does for experimenting. It's a D-Link EBR-2310. But due to overheating issues with it leading to faulty performance, I had to switch back to the TP-Link. They could get in to the DVR server using the D-Link but not using the TP-Link.
The owner of the hotel is pressing me to get this working but I'm at a loss as to what I'm doing wrong.

By the way I found this forum on Google. And I notice you're a fellow vBulletin user.

The only thing I can suggest is to request help from tplink.com.

[setishock]

I though of that but my Chinese isn't so good. But I did run across an idea here that I ran by my ISP. Here's the Readers Digest version.

A member here had tossed out the idea of using a switch behind the modem, with the modem, router and cameras on the switch.
I ran it by a tech lady at my ISP and she said it does in fact work that way. She issued me the second out of a 5 pack of static IP's we have. She said to program in the IP along with the gateway and DNS info in to the DVR.
I reprogrammed the DVR info, made the wiring changes, and rebooted the entire network.

It works.
There's a little bit of a lag in the router side of the network when some one is looking at the cameras but it's really quite minor. People like us would see it but I don't think users would notice.

I used a TP-Link unmanaged desk top 5 port switch. For the cost of a switch and a little time, the issue has been resolved.