Chapter 11 IPsec VPN for FortiOS 5.0 : Dynamic DNS configuration
  
Dynamic DNS configuration
This section describes how to configure a site-to-site VPN, in which one FortiGate unit has a static IP address and the other FortiGate unit has a domain name and a dynamic IP address.
The following topics are included in this section:
Dynamic DNS over VPN concepts
Dynamic DNS topology
General configuration steps
Configure the dynamically-addressed VPN peer
Configure the fixed-address VPN peer
Testing