Rather than use an IP address, you should ask your friend for their 10 digit phone number for their video phone.
The IP address is actually stored in the Neustar iTRS database by your friend's videophone provider, and Viable looks that up to place the call to your friend's phone.
Using IP addresses for VP dialing simply doesn't work with many videophones today, including Purple P3 and nTouch, as they use a gateway IP address instead of giving each videophone its own IP address to call.
So, again, ask your friend for their 10 digit phone number. This is really the best thing to have to call them.