For data links that have an Up/Down state, such as L2TP or FB105 tunnels, or PPP links, the ability to actually send traffic to the route target will depend on the state of the link. For such links, you can specify route(s) to automatically create each time the link comes up - when the link goes down these routes are removed automatically. Refer to Chapter 13 for details on how to achieve this via the routes attribute on the tunnel definition objects.

This can be useful where a link such as PPPoE is defined with a given localpref value, and a separate route is defined with a lower localpref value (i.e. less preferred), and therefore acts as a fallback route if the PPPoE link drops.