The technology “server virtualization” has been in gradual mature and been put in wider use. The kernel firewall based on the operating system “linux” is powerful. With the integration of netfilter firewall for linux and server virtualization of vmware server, it can work as the enterprise firewall as well as the server virtualization which provides all kinds of services. The server virtualization, together with free open-source software is applied in small and medium sized network for the benefit of low cost, effective management and direct maintenance.