本论文主要阐述了中型企业的局域网建设问题，本着办公自动化和资源共享的原则将企业的一百台计算机组织成为一个小型的办公局域网。本方案主要采用星形与树型相结合的混合型拓扑结构对网络进行构建，将本企业的一百台计算机分为五组，每组二十台，采用多台交换机将五组计算机连接起来组成内部局域网。并使用拨号上网的方式进行网络连接。-This paper described the construction of medium-sized local area network problem, based on office automation and resource sharing principles will enterprise organizations to become more computer a small office LAN. The program mainly uses a combination of star and tree topology of the mixed type of network build, will be the enterprise computer 100 is divided into five groups of twenty units, using multiple switches to connect the computer into five groups the composition of the internal LAN. And use dial-up approach to network connections.