IPsec aggregate for redundancy and traffic load-balancing

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).

Configuring the HQ1 FortiGate in the GUI

There are five steps to configure the FortiGate:

  1. Create the IPsec tunnels.
  2. Create the IPsec aggregate.
  3. Configure the firewall policies.
  4. Configure the aggregate VPN interface IPs.