1. A method comprising: parsing, by a network appliance configuration converter, network security policies of an input configuration file of a first network appliance to intermediate representations, wherein the network security policies of the input configuration file are expressed in a first language and the intermediate representations are general data structures for describing the network security policies; optimizing, by the network appliance configuration converter, the network security policies contained in the intermediate representations; and converting, by the network appliance configuration converter, the intermediate representations to security policies of an output configuration file expressed in a second language.