Standalone FortiGates or FGCP clusters can be integrated into the load balancing configuration using the FortiGate Session Life Support Protocol (FGSP) in a network where traffic is load balanced by an upstream load balancer and scanned by downstream FortiGates. FGSP can perform session synchronization of IPv4 and IPv6 TCP, SCTP, UDP, ICMP, expectation, and NAT sessions to keep the session tables synchronized on all entities. If one of the FortiGates fails, the upstream load balancer should detect the failed member and stop distributing sessions to it. Session failover occurs and active sessions fail over to the peers that are still operating. Traffic continues to flow on the new peer without data loss because the sessions are synchronized.
The FortiGates in FGSP operate as peers that process traffic and synchronize sessions. An FGSP deployment can include two to 16 standalone FortiGates, or two to 16 FortiGate FGCP clusters of two members each. Adding more FortiGates increases the CPU and memory required to keep all of the FortiGates synchronized, and it increases network synchronization traffic. Exceeding the numbers of members is not recommended and may reduce overall performance. By default, FGSP synchronizes all IPv4 and IPv6 TCP sessions, and IPsec tunnels. You can optionally add filters to control which sessions are synchronized, such as synchronizing packets from specific source and destination addresses, source and destination interfaces, or services.
All FortiGates in the FGSP deployment must be the same model and be running the same firmware version. FGSP is