iptables is the most recent entry in a series of Linux firewall services. Because iptables is a security product in widespread use, software faults are a serious concern and firewall testing is an important activity. Firewall testing is hard because there are many parameters, resulting in a huge number of possible parameter combinations. We present a methodology for iptables regression testing based on test templates: parameterized test cases. Templates have been developed for the main iptables rules along with algorithms for generating combinations of template parameters. A GUI has also been developed, integrating the templates and the tuple generation algorithms.