1. Apparatus operable in a 2547 BGP VPN comprising: an originating provider edge device (originating PE) for generating a first knowledge digest encoding first configuration information associated with a current set of information advertised for a virtual routing and forwarding engine (advertised VRF); the originating PE also for generating a second knowledge digest encoding second configuration information associated with cumulative information advertised for the advertised VRF; the originating PE being capable of receiving a message from a user provider edge device (user PE), the message including a third knowledge digest encoding third configuration information related to the user VRF, the originating PE being capable of comparing the first knowledge digest to the third knowledge digest and producing a first indication if the third configuration information encoded in the third knowledge digest is not a subset of the first configuration information encoded in the first knowledge digest, and the originating PE being capable of comparing the second knowledge digest to the third knowledge digest if the first indication is produced, and producing a second indication if the third knowledge digest is not a subset of the second knowledge digest.