What is the final criterion for route selection in FortiGate?

The final criterion for route selection in FortiGate is most specific route. This concept refers to the routing decision process where the system evaluates available routes and selects the route that has the most detailed prefix match for the destination address.

When multiple routes are available for the same destination, FortiGate first considers the prefix length; a longer prefix indicates a more specific route. This means that if one route encompasses a broader range of IP addresses and another route is defined for a smaller, more specific range, the more specific route will take precedence.

For example, if there is a route defined for 192.168.1.0/24 and another route for 192.168.0.0/16, the 192.168.1.0/24 route would be chosen when forwarding packets to any destination that falls within that specific range (192.168.1.0 through 192.168.1.255).

In summary, the FortiGate's routing decision-making process prioritizes the specificity of routes to ensure that packets are directed to the most accurate destination available within the routing table.