VLAN means : we divide a Local Area Network logically into multiple smaller networks.
In LAN, workstations are connected through a hub or a repeater. These devices propagate incoming data throughout a network. If two people send data at the same time, then a collision occurs and all the transmitted data is lost. But, to prevent the collision from further travel to all workstations, a bridge or switch is used.
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The workstations, hubs, and repeaters together form a LAN segment : known as a collision domain since collisions remain within the segment.
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VLAN is based on a feature called TAGGING. There are two types of tagging – explicit and implicit. In explicit tagging, once a LAN bridge receives data from a VLAN, it tags it with an associated VLAN identifier. In the case of an implicit tagging, there is no explicit tagging of the VLAN identifier. Instead, some additional reference data determines the VLAN information.
Why use VLAN ?
Performance : A VLAN addresses both the issues as it only broadcasts the data to the workstations within the VLAN. Furthermore, it uses switches and bridges, which require less processing time than a router.
Virtual Workgroup : lets a network admin segregate the network traffic so that broadcasts intended for a specific set of workstations remain within that set. Fore xample, data belonging to department A remains within this department.
Security : provides extra security in comparison to a LAN. This is because the broadcast stays within the virtual network. Thus, it provides better privacy of the data belonging to a department that is part of a VLAN.