FortiOS Handbook: High Availability

FortiGate high availability (HA) provides a solution for two key requirements of critical enterprise networking components: enhanced reliability and increased performance. FortiGate HA is implemented by configuring two or more FortiGate units to operate as an HA cluster. To the network, the HA cluster appears to function as a single FortiGate unit, processing network traffic and providing normal security services such as firewalling,Unified Threat Management (UTM), and VPN services. This document describes how FortiOS HA works and how to configure it.