Trying to connect a Sorenson VP200 to my network via Time Capsule (2nd Gen)

Question

I am attempting to set up a Sorenson VP-200 video phone on my network. I have cable internet with a Motorola SBG901 modem, with my Time Capsule (TC) connected via an Ethernet cable, extending the wireless network. The Video phone is connected to the TC via an Ethernet cable. I tried configuring the Motorola, but figured that I could try configuring the TC, since the VP-200 is plugged into it. I found a configuration for settings specifically for an Airport Extreme Base Station concerning the VP-200 from a few years ago. They are as follows: Airport Utility: Internet Connection -> NAT -> Enable default host at (checked) -> fill out: 162.168.1.253
The default host IP can be 10.0.1.XXX, 172.16.1.XXX or whatever IP address assigned to your VP. Generally XXX is selected from 253 thru 256. This will be your videophone IP address.
Then: Advanced -> Port Mapping -> click on "+" (add) button -> fill out:
Public UDP Port(s): 1720, 15328-15348
Public TCP Port(s): 1720, 15328-15348
Private IP address: 192.168.1.253 (or whatever IP address assigned to your VP - see above about enabling default host)
Private UDP Port(s): 1720, 15328-15348
Private TCP Port(s): 1720, 15328-15348"
My IP address on my VP-200 is 168.192.0.125. The IP address of my TC is 192.168.0.17.
After I followed those instructions, I get the following error:
The DHCP range you have entered conflicts with the WAN IP address of your Apple Wi-fi Base Station. Any help that anyone can give is greatly appreciated!

Answer 1

Sorry but this is likely to be the wrong way to do things.
The SBG901 cable modem is also a router.. a very very poor router but none the less a router.
Have you bridged it, ie turned off NAT??
Strongly recommend you do that. Unless your cable speed is relatively slow that model is cpu bound and likely to halve your connection speed. If you bridge it you probably then need to power it down, as well as the TC and rest of the network. Power up the modem.. wait a couple of minutes and then power up the TC.. make sure you actually now get the public ip on the WAN interface of the TC. Then you can proceed to port forwarding.
OR..
You can leave the cable modem as the main router and bridge the TC.. on the internet tab in the airport utility simply choose sharing internet connection, and select bridge in the pull down box.
Then all port forwarding will happen in the cable modem and you can proceed from there. It won't matter if the vp-200 is plugged into the TC, once bridged it will simply be a dumb WAP, switch and hard drive on the network.