RIP uses hop count as the metric for choosing the best route. A hop count of 1 represents a network that is connected directly to the FortiGate unit, while a hop count of 16 represents a network that cannot be reached. Each network that a packet travels through to reach its destination usually counts as one hop. When the FortiGate unit compares two routes to the same destination, it adds the route having the lowest hop count to the routing table. As you can see in “RIP packet structure”, the hop count is part of a RIP v2 packet.

Similarly, when RIP is enabled on an interface, the FortiGate unit sends RIP responses to neighboring routers on a regular basis. The updates provide information about the routes in the FortiGate unit’s routing table, subject to the rules that you specify for advertising those routes. You can specify how often the FortiGate unit sends updates, the period of time a route can be kept in the routing table without being updated, and for routes that are not updated regularly you can specify the period of time that the unit advertises a route as unreachable before it is removed from the routing table.

If hops are weighted higher than one, it becomes very easy to reach the upper limit. This higher weighting will effectively limit the size of your network depending on the numbers used. Merely changing from the default of 1.0 to 1.5 will lower the effective hop count from 15 to 10. This is acceptable for smaller networks, but can be a problem as your network expands over time.

In RIP, you can use the offset command to artificially increase the hop count of a route. Doing this will make this route less preferred, and in turn it will get less traffic. Offsetting routes is useful when you have network connections of different bandwidths, different levels of reliability, or different costs. In each of these situations you still want the redundancy of multiple route access, but you don’t want the bulk of your traffic using these less preferred routes. For an example of RIP offset, see “Access Lists”.