Probably a totally dumb question, but... Trying to install 3CX version 9 (the last version I can get to install under XP Pro). The software talks to the SIP provider OK, but when I try to add an extension, the only IP address available in the drop-down box is that of the system itself, so I can't add any extensions. I can ping any address on the network and the system shows up on the network correctly. What am I doing wrong?