A method to determine the maximum number of VPNs assignable to plurality of routers in a VPN network. The first step in the method can be specifying a tolerance which is a probability that consumed router memory will exceed available router memory for each router in a plurality of routers. The second step can be computing the consumed router memory on each router in a plurality of routers by summing a route memory, an interface memory, a VPN memory, and a constant memory. The third step can be computing a number [V] of VPNs assigned to the router to insure that, with the specified probability tolerance, the consumed router memory will not exceed the available router memory for each router in a plurality of routers.