The client-side and server-side FortiGate units are called WAN optimization peers (see Figure 327) because all of the FortiGate units in a WAN optimization network have the same peer relationship with each other. The client and server roles just relate to how a session is started. Any FortiGate unit configured for WAN optimization can be a client-side and a server-side FortiGate unit at the same time, depending on the direction of the traffic. Client-side FortiGate units initiate WAN optimization sessions and server-side FortiGate units respond to the session requests. Any FortiGate unit can simultaneously be a client-side FortiGate unit for some sessions and a server-side FortiGate unit for others.

To identify all of the WAN optimization peers that a FortiGate unit can perform WAN optimization with, you add host IDs and IP addresses of all of the peers to the FortiGate unit configuration. The peer IP address is actually the IP address of the peer unit interface that communicates with the FortiGate unit.