The benefits of using VLANs include security improvement, cost reduction, higher performance, broadcast storm mitigation and simplified network management.
The security of the network can be improved by reducing both internal and external threats with VLANs. Internally, by assigning different groups of users to different VLANs, users can only access the network applying to their own responsibilities and sensitive data will be protected from unauthorized people. External threats are also reduced. When an attacker can gain access to one VLAN from outside, the other VLANs still cannot be accessed since they are separated from each other.
VLANs are covered in depth in the CCNA course.
The cost of separating the networks of multiple departments of a company can be reduced by configuring VLANs. Especially for a small-sized company, each department may have only a few computers connected to the switch. In this case, all the computers in the company can be connected to a single switch while each department can have its own VLAN. Otherwise, the company may need to purchase a switch for every department and it will be too costly.
VLANs can increase the number of broadcast domains and help manage broadcast traffic such as ARP, DHCP and routing protocols. Broadcast traffic will not be passed to other VLANs so that the network traffic is reduced and the apparent bandwidth for users is increased. Moreover, the CPU utilization of the switch is also reduced as less traffic is processed.
When a Layer 2 switch is configured with multiple VLANs, the size of the broadcast domain is reduced. Since broadcast traffic is only passed to devices within the same VLAN, the number of devices participating in the broadcast storm is reduced, and devices in other VLANs will not be affected. In conclusion, the broadcast storm can be mitigated by VLANs.
Another benefit of VLANs is that it simplifies management. By logically grouping users into the same virtual networks, it is easier to set up and control policies at a group level. When users physically move workstations, they can remain on the same network with different equipment. Conversely, when users change teams but not workstations, they can easily be given access to the new VLANs of the new teams. In addition, if the company expands with more employees, and a new switch is added to the network, the IT staff can simply configure the new switch with the same VLAN settings by using VLAN Trunk Protocol. It is unnecessary to change the ports of the existing switches.