To use VPN resiliency/redundancy, configure a list of FortiGate IP/FQDN servers, instead of just one:
This is a balanced but incomplete XML configuration fragment. All closing tags are included, but some important elements to complete the IPsec VPN configuration are omitted.
This XML tag sets the IPsec VPN connection as ping-response-based. The VPN connects to the FortiGate that responds the fastest.
By default, RedundantSortMethod =0, and the IPsec VPN connection is priority-based. Priority-based configuration attempts to connect to FortiGates by starting with the first FortiGate on the configured list.