BGP AS-Path Prepending BGP is rich in features that you can have more control than on what IGP's offer however, you can only have control on how the traffic leaves your autonomous system and can't really control how other autonomous systems reach you. Other AS'es might have BGP policies that route the traffic in a way you don't intend it to go. You don't have control over those because, its their autonomous systems after all. However, there are work arounds which allow, an autonomous system affect the other autonomous systems, one of this is called BGP AS-path prepending. It is basically adding additional AS-paths by repeating your own AS number. Consider the diagram below. (Click image for a bigger view) By looking at the diagram, if you are familiar with BGP, the AS-path the networks from R4 will take towards R1 will be AS4, AS3 and then AS1. If all the attributes are set to the default values, most likely the AS-path attribute will determine which path to take. ...