Well if your device supports UPnP & doesn't show a brick wall then that's fine. But if you find it is inconsistent, then it means that BT's UPnP implementation is not as good as it should be. Different brands & models have different abilities at UPnP since there's more than one definition of it. And if that is the case then best to port forward. For public ip, see http://www.whatismyip.com/ & for internal ip ...
"If you are behind a firewall or router you will have to take one more step to find your private IP address:

Start, run, type command then hit enter
type ipconfig /all
look for the line that says IP address

if windows click run -> cmd. Type -> ipconfig /all"