Some embodiments of the invention provide a method of upgrading a firewall module executing on a host computer to process traffic sent to and from machines executing on the host computer. While a first version of the firewall module executes on the host computer to process the traffic to and from the machines, the method loads a second version of the firewall module alongside the first version of the firewall module. For each of multiple ports associated with machines executing on the host computer for which the firewall module processes traffic sent to and from the port, the method saves a runtime state of the first version that relates to the port, transfers association of a firewall filter associated with the port from the first version to the second version, and restores the saved runtime state for the port to the second version.