IPSec VPN with iOS 9.3 requires Diffie Hellman group 14
With iOS 9.3 Apple changed the default connection profile for IPSec VPN. It now requires Diffie-Hellman group 14 to be in the phase 1 proposal. Other DH groups are allowed but 14 is required for iOS devices to connect.
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.