I am using Genymotion Emulator with Nexus s and 4.2.2.
Previously i used regular AVD that we can create using Eclipse provided by ANDROID SDK.
In regular AVD we can enable/disable data packet access to internet by using
Settings->Wireless&Networks->Data Enabled
Or by pressing F8 key but i am unable to found it in Genymotion emulator.
Where i can find it?
You cannot do that on Genymotion.
If you want to test what your application will do without internet access, you can unplug your ethernet cable or switch off your Wi-Fi. It's not the same but could still help to test your app.