The common large-scale enterprise LAN is a gigabit LAN system with dense information points. The existing thousands of information points it connects provide a fast and convenient information exchange platform for all departments working in the whole enterprise. Moreover, through the connection between the private line and the Internet, an external window has been opened, and all departments can directly communicate with netizens and inquire about information. Through the open server, enterprises can directly publish information or send emails. The adoption of high-speed switching technology and the design of flexible network interconnection scheme provide users with a fast, convenient and flexible communication platform, but it also brings greater risks to the network security. Therefore, it is not only feasible but also necessary to implement a complete and operable security solution on the original network.

2. 1. 1 network overview

The enterprise LAN provides the exclusive bandwidth of 1000M on the backbone network through gigabit switches, and connects workstations and servers of various departments through secondary switches, and provides the exclusive bandwidth of1000 m for them. After connecting the router to the central exchange, all users can access the Internet directly.

2. 1.2 network structure

Generally, the local area network of large enterprises can be divided into three main areas according to the access area: Internet area, internal network and public server area. The internal network can be divided into many subnets according to departments, functions and security importance, including: financial subnet, leadership subnet, office subnet, marketing subnet, central server subnet and so on. In the design of security scheme, based on the importance of security and the objects to be protected, four virtual local area networks (VLAN) can be directly divided on the core switch, namely, the central server subnet, the financial subnet, the leadership subnet and other subnets. Different LANs belong to different broadcast domains. Because the financial subnet, the leader subnet and the central server subnet belong to important network segments, these network segments are divided into independent broadcast domains on the central switch, and other workstations are divided into the same network segment.

2.2 Network application

Enterprise LAN will generally provide the following main applications:

1. File sharing, office automation, WWW service and email service;

2. Unified storage of file data;

3. Secondary development on the database server for specific applications (such as financial system);

4. Provide Internet access;

5. Publish enterprise information and send e-mails through public servers;

2.3 the characteristics of the network structure

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