Use any online tool (like base64encode.net to encode your Shared Secret into Base64 format) Just open config file in any text editor and add the fields: <key>PPP</key> <dict> ... your current l2tp config... </dict> <key>IPSec</key> <dict> <key>AuthenticationMethod</key> <string>SharedSecret</string> <key>PromptForVPNPIN</key> <false/> <key>OnDemandEnabled</key> <integer>0</integer> <key>SharedSecret</key> <data> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! PAST YOUR ENCODED SHARED SECRET HERE !!!!!!!!!!!!!!!!!!!! </data> </dict> Save, send to your device.