les explications sur le site sont claires :

"Why auto-interactive routing is not autorouting

An autorouter requires a lot of setup to work correctly. Since it is going to do all of the routing for you, you must train it to route the way you want it to. In order to train the autorouter, you need to load it with design rules and routing strategies. Although design rules, like net classes and topology constraints, can be imported from the layout software, they may still need to be fine-tuned for peak performance in the autorouter. However, the real challenge is in setting up the different auto-routing strategies. These strategies determine how a trace is to be routed and how many attempts should be made before giving up on it. They will also include wrong way routing distances and how many routing cleanup attempts that you want the autorouter to make. Setting up autorouting strategies is difficult and takes experience to understand how the autorouter will work in different circumstances.



On the other hand, the auto-interactive router gives you the ability to direct the path of the routing without the cumbersome strategy setup steps. Since the auto-interactive router is only going to route the nets that you have selected—instead of the entire design—it doesn’t need the strategies that an autorouter does. Once you select the net or group of nets to be routed, you can engage the auto-interactive router. Here, you have the option to either allow the router to choose its own route path or to follow a path that you manually draw for it as a template. Drawing the template for the route path yourself allows you to direct where the routing will take place while the auto-interactive router does the actual heavy lifting of putting the traces in."