Chapter 1 What’s New for FortiOS 5.2.1 : Top Features : Using a Virtual WAN Link for Redundant Internet Connections
  
Using a Virtual WAN Link for Redundant Internet Connections
A virtual WAN link consists of two or more interfaces that are connected to multiple ISPs. The FortiGate unit sees the virtual WAN link as a single interface so the FortiGate’s security policy configuration no longer has be redundant to support dual Internet links. In addition, the virtual WAN link includes load balancing and new link health checking and settings.
For more information, see “Using a Virtual WAN Link for Redundant Internet Connections”.