Hi people! I hope you are fine.
This problem was concerning me a long time ago. The infraestructure to establish the VPN connection is the following: Ipad2, dsl connection, IPSEC between ipad and Fortigate 60c. The only way i have to avoid disconnection when the ipad sleep was set "Automatic Block: Never". I try with Cisco anyconnect but i cant because my VPN does not use cert., only user, group and PSK. Jailbreak... Nah... the solution was Update the ipad to the version 5.1 (9B176).
After the upgrade, i set the VPN again and set the auto lock to 2 minutes. Then, when i go Unlock with the button the vpn still connected (or reconnected, do not investigate a lot)!!!
I hope this comment can help more than one!
Regards, Diego (Uruguay)