Chapter 22 WAN Optimization, Web Cache, Explicit Proxy, and WCCP for FortiOS 5.0 : The FortiGate explicit web proxy : Proxy chaining (web proxy forwarding servers) : Adding a web proxy forwarding server
  
Adding a web proxy forwarding server
To add a forwarding server, select Create New in the Web Proxy Forwarding Servers section of the Explicit Proxy page by going to System > Network > Explicit Proxy.
Server Name
Enter the name of the forwarding server.
Proxy Address
Enter the IP address of the forwarding server.
Proxy Address Type
Select the type of IP address of the forwarding server. A forwarding server can have an FQDN or IP address.
Port
Enter the port number.
Server Down action
Select what action the FortiGate unit will take if the forwarding server is down.
Enable Health Monitor
Select to enable health check monitoring.
Health Check Monitor Site
Enter the URL address of the health check monitoring site.
Use the following CLI command to add a web proxy forwarding server named fwd-srv at address proxy.example.com and port 8080.
config web-proxy forward-server
edit fwd-srv
set addr-type fqdn
set fqdn proxy.example.com
set port 8080
end