What is Virtual LAN (VLAN)?

VLAN is a logical grouping of network devices with different physical LANs.

What Are VLANs Helpful With?

The early Ethernet is a data network communication technology based on CSMA/CD (Carrier Sense Multiple Access/Collision Detection) sharing communication medium. When the number of hosts is large, it will lead to serious conflicts, broadcast flooding, performance degradation and even network unavailability. Although LAN interconnection through two-layer devices can solve the problem of serious conflicts, it still can’t isolate broadcast frames and improve network quality.

In this case, VLAN technology appears. This technology can divide a LAN into multiple logical VLANs, and each VLAN is a broadcast domain. The communication between hosts in a VLAN is the same as that in a LAN, but the VLANs cannot directly communicate with each other, so the broadcast frames are limited to one VLAN.

Therefore, VLAN has the following advantages:

1. Restrict broadcast domain: the broadcast domain is limited to one VLAN, which saves bandwidth and improves network processing capacity.
2. Enhance the security of LAN: Framesin different VLANs are isolated from each other during transmission, that is, users in one VLAN cannot communicate directly with users in other VLANs.
3. Improve the robustness of the network: the fault is limited to one VLAN, and the fault in this VLAN will not affect the normal work of other VLANs.
4. Flexible construction of virtual workgroups: VLAN can be used to divide different users into different workgroups, and users in the same workgroup don’t have to be limited to a fixed physical scope, so network construction and maintenance are more convenient and flexible.

VLAN vs Subnet

By further dividing the network part of the IP address into several subnets, the problems of the low utilization rate of IP address space and inflexible two-level IP addresses can be solved.

Similar to VLAN, the subnet can isolate communication between hosts. Hosts belonging to different VLANs cannot communicate directly with each other, nor can hosts belonging to different subnets communicate directly with each other. But there is no necessary correspondence between them.