iOS 4 Devices Won’t Connect To SonicWALL L2TP VPN
If you have any users in your organization using Apple devices, the L2TP VPN on SonicWALL devices is a necessity. With the introduction of iOS 4, both the iPhone and the iPad no longer support 3DES encryption and have switched to AES-128 encryption. This is a fairly simple change in the SonicWALL to make, edit the properties of the WAN GroupVPN, set the encryption settings for both Phase 1 and Phase 2 to AES-128 and voila, your iDevices will connect.
The resulting issue is that all Macs will no longer connect, as they still attempt to connect using 3DES.