The Design And Implementation Of The Hybrid Firewall Based On NAT In The City Defense Control System

The city area alarming and monitoring network system is an important technical platform of the police department to prevent, control and beat all kinds of violence and crime. It is depended on the public network. How to ensure the interior network's security that to provide convenient and quick police service is important. Based on it, the author participates in a project group to design and implement a hybrid firewall based on NAT and to carry through a test in the city defense and control system.This paper's research and realization can be concluded as follows:Investigate the function, capability, network frame and realization flow and analyze the security of the city defense and control system.Investigate the classification, function and design strategy and analyze the excellence and disadvantage of the traditional firewall technology.Investigate the principle of work, pattern and realization function and analyze the security of the NAT technology.Analyze the function of the dynamic package filter module, transparent proxy module and based on Web disposition and management module, discuss detailedly the design and implementation of the NAT module.A test of the hybrid firewall based on NAT in the northwest city defense and control system.The author present one thought to use the NAT in the firewall technology and to construct a hybrid firewall. The actual test result indicated: the Bluedon hybrid firewall can possess dual control function of network accessing and address translating.This production adopts the port address dynamic translation, not only saved IP resources, but also enhanced the firewall's whole safe defense capability, has higher technical value and broad application value.