Chapter 1 What’s New for FortiOS 5.2.1 : IPsec VPN : Internet Key Exchange (IKE) : Assigning Client IP Addresses Using the DHCP Proxy
  
Assigning Client IP Addresses Using the DHCP Proxy
IKE can now use the system DHCP proxy to assign client IP addresses.
To use this feature, the DHCP proxy must be enabled and a IP set. Up to 8 addresses can be selected for either IPv4 or IPv6. After the DHCP proxy has been configured, the assign-up-from command is used to select assign IP address via DHCP.
Syntax
1. Enabling the DHCP proxy and setting an IP range.
config system settings
set dhcp-proxy enable
set dhcp-server-ip <IP_address>
set dhcp6-server-ip <IP_address>
end
2. Setting the IPsec phase one to assign IP addresses using the DHCP proxy.
config vpn ipsec phase1
edit <id>
set assign-ip-from dhcp
end
end
 
IP assignment can also come from a locally defined range or via the user group.