As the rapid development of e-business, e-government affairs and the telecommuting and managemtn, the needs of private network grow.At the same time, in face of the increase of demand, the high capability, dependability, flexibility, security, economy and expansibility also requires high qualification. Here is a company which needs to set up an inner information management system for its employees and those who often go out to transfer and publicize their information. These moving employees use the computer to visit their company web server through Internet to realize the information communication. The aim of this paper is to establish a VPN for this company with security, reliability, high-power, mutual operation and low-expense.First of all, this paper studies on theories, types and advantages of VPN, describing its key technology which includes password technology, ID authentication technology, tunnel technology, secret-key management technology and Qos technology. The description of concept, function, system struction and running mode of IPSec are emphasized.According to the system characteristics and demands, this article describes the VPN scheme, the setting-up of the the software and hardware environment, the visit control in the application and design of VPN system. At the same time, to this situation, the sheme includes the design explainatin and realization of the relevant LDAP interface, interface design to RADIUS, the establishment of RADIUS server as well as the description of the system interface and function, the creation of dynamic passpord.In order to guaranntee the security of the system inpute, the system adopts the dynamic passpord mechanism in the process of logging in validation. Different from the traditional static password, dynamic password and the mobilephone short messages are combined to eliminate the unsafe and discommodious factors in static password and make the system more secure and practical. The software and hardware frames and the design realization of the function moduls are described detailedly.Through the above program design, the secure and reliable virtual private network is set up for that company, so that the moving employees could visit the company inner network safely and conveniently and the illegal network visit to that company is also prevented. 本文来自织梦