How to set up your FortiADC : Configuring the network settings : Adding a gateway : Policy routes
 
Policy routes
If you want source-based routing, or to route packets based upon both destination address and source address, you cannot achieve this by using static routes. You must configure policy routes.
 
Alternatively, for traffic that your FortiADC is load balancing, you can control the direction which FortiADC forwards packets by using:
static routes (“Adding a gateway”) and/or
application layer content-based routing (see “Routing based on the application layer”)
For information on how FortiADC chooses between the multiple packet forwarding methods that may apply, see “Sequence of packet routing evaluation”.
Most policy route settings are optional, so a matching route might not provide enough information to forward the packet. In that case, the FortiADC appliance may refer to the routing table in an attempt to match the information in the packet header with a route in the routing table. For example, if the destination address is the only match criteria in the policy route, the FortiADC appliance looks up the IP address of the next-hop router in its routing table. This situation could occur when interfaces are dynamic (such as DHCP or PPPoE) and you do not want or are unable to specify a static IP address of the next-hop router.
To add a policy route
1. Go to Router > Static > Policy Route.
2. Click Add.
3. In Source and Destination, type the SRC and/or DST addresses that a packet’s header must match in order to match this policy route. To match any value, either leave it blank or enter 0.0.0.0/32.
4. If known, in Gateway, type the IP address of the next-hop router.
5. Click Save.
See also
Configuring the physical network interfaces
Adding a gateway
Routing based on the application layer