This is a sample configuration of a multiple site-to-site IPsec VPN that uses an IPsec aggregate interface to set up redundancy and traffic load-balancing. The VPN tunnel interfaces must have
net-device disabled in order to be members of the IPsec aggregate.
Each FortiGate has two WAN interfaces connected to different ISPs. OSPF runs over the IPsec aggregate in this configuration.
The supported load balancing algorithms are: L3, L4, round-robin (default), weighted round-robin, and redundant. The first four options allow traffic to be load-balanced, while the last option (redundant) uses the first tunnel that is up for all traffic.
Dynamic routing can run on the aggregate interface, and it can be a member interface in SD-WAN (not shown in this configuration).
There are five steps to configure the FortiGate: