BGP prefix limit based on route target to limit VPN prefixes

Typically L3VPN deployments limit routes at the customer edge peer level with the prefix-limit configuration for a BGP peer family. This control is shifted to a central location such as the route reflector or a ASBR so that routes originating at all sites in a VPN are taken into account. BGP maintains and enforces the prefix limit as specified by the route target communities originating at various VPN sites to limit the number of prefixes a BGP peer can advertise or receive to conserve resources.