A lot of people confuse the above 3 items. I’ll explain exactly what each of the 3 above items do, how you can see them, and how the routers use them to provide a L3VPN service. Let’s take the following topology for this post: Here we have 2 L3VPN customers running over our MPLS core. R5 is advertising 5.5.5.5/32. R8 is also advertising 5.5.5.5/32 Route Distinguisher The route distinguisher’s sole job is to keep a route unique while the PE routers advertise NLRI (Network Layer Reachability Information) to each other. If R5 and R8 both advertise 5.5.5.5/32 to R3, how will R3 advertise both of those routes to R4 while keeping them unique.