Some embodiments provide a system that includes a set of network controllers for receiving definitions of first and second logical switching elements. The system includes several managed switching elements. The set of network controllers configure the several managed switching elements to implement the defined first and second logical switching elements. The system includes several network hosts that are each (1) communicatively coupled to one of the several managed switching elements and (2) associated with one of the first and second logical switching elements. Network data communicated between network hosts associated with the first logical switching element are isolated from network data communicated between network hosts associated with the second logical switching element.