This disclosure provides systems, methods and apparatus for providing a network verification system (NVS) to analyze and detect anomalies and errors within a network. The NVS requests forwarding tables from each of the switches within the network being analyzed, and generates directed forwarding graphs for each subnet within the network. Certain graph properties of the directed forwarding graphs are analyzed to detect anomalies or errors in the subnets represented by the directed forwarding graphs. In some implementations, the NVS can execute the generation of the directed forwarding graphs in parallel. In some implementations, the NVS can be implemented on a MapReduce system.