Host side method of using a controller assignment list

Some embodiments provide a novel method for distributing control-channel communication load between multiple controllers in a network control system. In some embodiments, the controllers manage physical forwarding elements that forward data between several computing devices (also called hosts or host computers), some or all of which execute one or more virtual machines (VMs). The method of some embodiments distributes a controller assignment list to the host computers. The host computers use this list to identify the controllers with which they need to interact to perform some of the forwarding operations of their associated logical forwarding elements. In some embodiments, agents executing on the host computers (1) review the controller assignment list to identify the appropriate controllers, and (2) establish control channel communications with these controllers to obtain the needed data for effectuating the forwarding operations of their associated physical forwarding elements. These agents in some embodiments are responsible for out-of-band control channel communication with the controllers.