Actually you should see it's value since your batch file does not turn echo off. However, this will work:
for /f "tokens=1-6 delims=:. " %%i in ('ipconfig ^| find /i "ip address"') do set ip=%%k.%%l.%%m.%%n
echo %ip%
When debugging batch files (scripts too!) echo is a very handy instruction to have around.
Hope this helps.
