Why divide a virtual LAN, a virtual LAN is a .

Virtual LAN: A network segment that connects many organizations.

What is a VLAN].

vlan（virtual

localarea

network, or virtual local area network, is an emerging technology that realizes virtual workgroups by logically dividing devices in a local area network into network segments rather than physically. In 1999, the IEEE published a draft protocol standard to standardize VLAN implementations.

VLAN technology allows network administrators to logically divide a physical LAN into different broadcast domains (or virtual LANs, or VLANs), each of which contains a set of computer workstations with the same requirements and the same attributes as the physically formed LAN. However, since it is logically rather than physically, workstations in the same VLAN do not need to be placed in the same physical space, i.e., they do not necessarily belong to the same physical LAN segment. Even if two computers have the same network segment, but they do not have the same VLAN number, their respective broadcast streams will not be mutually exclusive, which helps to control traffic, reduce equipment investment, simplify network management, and improve network security.

VLAN is proposed to solve the broadcasting problem and security of Ethernet, it adds VLAN header on the basis of Ethernet frame, and uses VLAN

The ID divides users into smaller workgroups, restricts users from accessing each other at Layer 2, and each workgroup is a virtual LAN. The advantage of a virtual LAN is that it can limit the scope of broadcasting and can form a virtual workgroup to dynamically manage the network.

Since VLANs isolate broadcast storms and communication between different VLANs, routes are required to complete the communication between different VLANs.

Advantages of VLAN].

Restrict broadcast domains. The broadcast domain is limited to a single VLAN, which saves bandwidth and improves network processing capacity.

Enhance the security of your local area network. Packets in different VLANs are isolated from each other during transmission, that is, users in one VLAN cannot communicate directly with users in other VLANs.

Flexibility to build virtual workgroups. VLANs can be used to divide different users into different workgroups, and users in the same workgroup do not have to be limited to a fixed physical range, making network construction and maintenance more convenient and flexible.

Answer]: A virtual local area network (VLAN) is a set of devices and users on the directory, these devices and users are not limited by physical location, they can be organized according to factors such as functions, departments and applications, and communicate with each other as if they are in the same network segment, hence the name virtual LAN. VLAN is a relatively new technology that works at Layer 2 and Layer 3 of the OSI reference model, where a VLAN is a broadcast domain, and communication between VLANs is done through Layer 3 routers.

Compared with traditional LAN technology, VLAN technology is more flexible, and it has the following advantages: the management overhead of moving, adding, and modifying network devices is reduced; It is possible to control broadcasting activities; It can improve the security of the network.

For example, in a scientific research institution, a number of virtual LANs have been divided, but because of a certain scientific research task, technical personnel are temporarily transferred from each virtual LAN to form a research group, which requires the research group to communicate freely, and at the same time, the scientific research personnel must maintain information exchange with the original virtual LAN.

A virtual LAN can use the Internet with insecure communication to build a virtual LAN with secure communication. In terms of distance, if two remote organizations want to build a LAN but do not have a dedicated line connection, they can use virtual LAN technology to realize a secure communication line between the two institutions.