Traffic Engineering with MPLS

Forwarding Traffic Down Tunnels with Autoroute

Autoroute is fairly detailed. Its behavior is intuitive, but you might have to stare at it for a while to understand why you need it. This section explains not only how it works, but also why you need it.

If you bring up most types of interfaces in Cisco IOS Software (a physical interface, subinterface, or GRE tunnel), you need to enable your Interior Gateway Protocol (IGP) on that interface in order to form routing protocol adjacency, learn routes, and build a routing table involving that interface. If you don't do this, you won't be able to dynamically figure out what traffic to send down that interface. Of course, you can point static routes down an interface without running your IGP on that interface, ...