1. A packet forwarding system for use in a communications network providing internetworking services to a plurality of distinct and isolated user networks, comprising: at least one edge forwarder terminating a plurality of service interfaces and forwarding packets received on said service interfaces in accordance with forwarding information received from at least one route server, wherein at least two of the service interfaces from the plurality of service interfaces is uniquely associatable to one of the plurality of distinct and isolated user networks; said at least one route server is adapted to compute the forwarding information appropriate to the user networks based on at least routing information exchanged with other routing agents, the forwarding information including multiple forwarding rules being particular to the respective service interfaces of the corresponding user networks; and said at least one edge forwarder being adapted to forward each received packet according to an appropriate forwarding rule selected from the multiple forwarding rules based on the service interface from which the packets is received and a destination address in the received packet.