iPhone and Android has a built-in VPN client but originally they need Cisco, Juniper or other expensive hardware-based VPNs for remote-access. SoftEther VPN has a same function to Cisco, and supports iPhone and Android easily.
Principles
SoftEther VPN has a clone function for Cisco VPN routers. SoftEther VPN can accept VPN connections from iPhone and Android. The principles of constructing the remote access VPN for smart-phones is exactly same to the Remote Access for PCs. As an additional steps you have to enable the L2TP/IPsec function on SoftEther VPN Server. Only that, your SoftEther VPN Server can now listening new VPN connections from iPhone and Android.
Step 1. Install SoftEther VPN Server
Step 2. Enable L2TP/IPsec VPN Function on VPN Server
Enabling L2TP/IPsec VPN Function is just one click. It is very easy. Compare this step with Cisco's complicated command-line based configurations.