This is an example of a typical medium-sized network configuration using IS-IS routing.

Imagine a company with four FortiGate devices connected to one another. A FortiGate at one end of the network connects to two routers, each with its own local subnet; one of these routers uses OSPF and the other uses RIP.

Your task is to configure the four FortiGates to route traffic and process network updates using IS-IS, such that the farthest FortiGate (see ‘FGT4’ in Network layout and assumptions) receives route updates for the two routers at the opposite end of the network. Furthermore, FGT4 has been given a loopback subnet that must be identified by the router running RIP.

Since the internal networks use OSPF and RIP, those protocols will need to be redistributed through the IS-IS network. To keep the example simple, there will be no authentication of router traffic.

With IS-IS properly configured in this example, if a router fails or temporarily goes offline, the route change will propagate throughout the system.

This section includes the following topics: