TeamViewer does not provide this functionality directly. But you can know the IP address by faking a connection, then reading the TeamViewer logs:
- Open TeamViewer
Fill in the partner ID, and click Connect to partner
Back on the main window, click Extra >> Open log files... in order to access the TeamViewer logs
Open (with Notepad or whatever) the TeamViewer7_Logfile.log file (located by default in C:\Program Files\TeamViewer\Version7)
- In the file, search from the bottom for the first line where it is written
CTXX GWT.CmdUDPPing.PunchReceived, a=XXX.XXX.XXX.XXX, p=XXXXX
a=XXX.XXX.XXX.XXX => That's the IP address you're looking for!