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), wherein the current set of information advertised for the advertised VRF includes at least one forwarding table entry associated with the 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 over a period of time, wherein the cumulative information advertised for the advertised VRF includes at least one additional forwarding table entry with respect to the current set of 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; and 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.