FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.

This article explains how to add a static route for predefined internet services  (ISDB) available in FortiGate.

From GUI:

- Go to Network -> Static Routes,
- Select 'Create New'.
- Select the Destination as 'Internet Service'.
- Select the Internet service from the drop down list.
- Add the gateway IP address.
- Select the Internet Interface.
- Select 'OK' to save the changes.

From CLI.
# Config router static
    edit <ID>
        set gateway <Gateway of Internet interface>
        set device <internet interface>
        set internet-service <Internet Service ID #>
# diag firewall internet-service list   <----- This command would provide the list of available Internet services.
ISDB static route will not create entry directly in routing-table.
ISDB is acting as policy route. So to verify ISDB route:

This means, that for ISDB routes are applying same rules as for policy-routes.
Mainly, that in order for policy-route to work, it is necessary to have valid route in the routing-table for the outgoing interface.
Otherwise, the traffic will not follow policy route.