There's a simple method to root LG Optimus Net P690 (Android 2.3.4):
It's complete rooting guide to root LG Optimus Net with 'UnlockRoot'.
1. Download and install 'Unlock Root' on your PC from here: Unlock Root of Android
2. Download LG Android Drivers from here: http://www.junefabrics.com/bin2/LGDriver.exe
Reastart your PC after installing drivers.
3: On your phone, Check 'USB Debugging'. Path: Menu > Settings > Applications >
Development > Tick 'USB Debugging'.
4. Again on phone, Unmount your SD Card. Go to: Menu > Settings > Storage > Tap on
'Unmount SD Card'. It'll give you a warning. Just press OK.
5. Connect your phone with PC. Phone will ask you to 'Turn on USB Storage'. DO NOT TURN IT
You should see this message on phone's notification bar: 'USB Debugging connected'.
6. On your PC, open UnlockRoot.exe ( A shortcut should be created on your desktop )
or Path: X:\Program Files\Unlockroot
7. Press root button! After process completes, it'll ask you to install 'Superuser.apk' and
'Bettery Sever.apk'. Just press OK. Then you'll be asked to reboot your phone. Press
OK. After reboot completes, go to menu and you'll find Superuser app there.
Congratulations! You've rooted your LG Optimus Net P690!
This worked on mine and will work on yours also.