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; 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.