US Patent 9130870 Methods for determining network topologies

A network may include switches that have controller clients that are controlled from one or more controller servers. Clusters of the switches that have the controller clients may be isolated from other clusters by switches without the controller clients. The controller server may use graph searches to identify the clusters. The controller server may use information on the cluster topology of switches containing controller clients along with information in per-switch forwarding databases to generate per-cluster forwarding databases. The controller server may use the per-cluster forwarding databases in generating flow tables for the network switches that direct the switches to forward packets along desired paths through the network.