A method of implementing a logical switching element. The method generates data for programming a set of two or more physical forwarding elements to implement the logical switching element. The method uses a first controller to distribute at least a first portion of the generated data to a first plurality of physical forwarding elements in the set of physical forwarding elements. The first controller serves as the master controller for the first plurality of physical forwarding elements. The method uses a second controller to distribute at least a second portion of the generated data to a second plurality of physical forwarding elements in the set of physical forwarding elements. The second controller serves as the master controller for the second plurality of physical forwarding elements.