1. A database storing information indicating relationships between: a first virtual private network and a first provider edge router (PE); the first PE and a second PE; the first PE and a first customer edge router (CE); a first PE-PE interface of the first PE and a first PE-PE interface of the second PE; a first PE-CE interface of the first PE and a first CE-PE interface of the first CE; a first virtual routing address and the first PE-CE interface; and the first virtual routing address and the first virtual private network; wherein a first logic identifies the first virtual private network from the relationship between the first PE-CE interface and the first virtual routing address and the relationship between the first virtual routing address and the first virtual private network.