A method implemented in a network element functioning as one of a plurality of controllers for one of a plurality of areas of a split architecture network, the controller to provide a control plane for the area of the split architecture network where the controller is remote from a plurality of switches providing a data plane for the area of split architecture network, the controller to facilitate optimized routing across the plurality of areas of the split architecture network by providing limited intra-area link cost data to other controllers of other areas of the split architecture network and to traditional routers of a network including the split architecture network, the limited intra-area link cost data providing costs of each possible shortest path traversal of the area of the controller without providing all internal link cost data, the method comprising the steps of: learning a topology of the area of the controller in the split architecture network including each border switch in the area of the controller, wherein each border switch in the area of the controller has at least one external port linking the area of the controller to another area of the split architecture network or to one of the traditional routers in the network; computing a shortest path between each border switch pair in the area of the controller; storing a cost of each shortest path between each border switch pair in a routing table of the controller; identifying each neighbor controller in the split architecture network or neighbor traditional router in the network using a hello protocol, wherein each neighbor controller controls switches in another area of the split architecture network accessible through at least one external port of the area of the controller; exchanging a link state database with each neighbor controller and neighbor traditional router, the link state database including the cost of each shortest path between each border switch pair; calculating a shortest path tree for the network with the controller as a root of the tree; and updating forwarding tables in switches of the area of the controller to implement forwarding according to the shortest path tree. learning a topology of the area of the controller in the split architecture network including each border switch in the area of the controller, wherein each border switch in the area of the controller has at least one external port linking the area of the controller to another area of the split architecture network or to one of the traditional routers in the network; computing a shortest path between each border switch pair in the area of the controller; storing a cost of each shortest path between each border switch pair in a routing table of the controller; identifying each neighbor controller in the split architecture network or neighbor traditional router in the network using a hello protocol, wherein each neighbor controller controls switches in another area of the split architecture network accessible through at least one external port of the area of the controller; exchanging a link state database with each neighbor controller and neighbor traditional router, the link state database including the cost of each shortest path between each border switch pair; calculating a shortest path tree for the network with the controller as a root of the tree; and updating forwarding tables in switches of the area of the controller to implement forwarding according to the shortest path tree.