从L2TP协定入手，介绍了L2TP协议的基本技术和拨号访问服务器及L2TP网络服务器，详细阐述了在此基础上建立的认证模块、日志模块和LAC模块，并对用L2TP创建VPN进行了探索，在多种UNIX环境下建立了原型，积累了建立VPN的经验，为其他VPN的建立打下了基础。关 键 词 虚拟专用网; 第二层隧道协议; 隧道; L2TP集中器; L2TP网络服务器Abstract Virtual private network is the key technology of next generation Internet, L2TP is a dialup virtual private network specification which was defined by IETF. Its design and implementation are very significant. From the L2TP, basic technology and two kinds of servers of L2TP(LAC server and L2TP net server) are introduced and L2TP function models(authentication model、log model and LAC model) on this are expatiated. Based on this, a L2TP scheme was suggested and developed on a few UNIX latforms.Key words virtual private network; L2TP; tunneling; LAC; LNS