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.
The workstations, hubs, and repeaters together form a LAN segment : known as a collision domain since collisions remain within the segment.
VLAN’s allow a network manager to logically segment a LAN into different broadcast domains : workstations do not have to be physically located together. Users on different floors of the same building, or even in different buildings, can now belong to the same LAN.
Why use a VLAN ?
If a user broadcasts a message in his/her LAN, it’ll be received by every other user on the LAN. These broadcasts stay within a LAN with the use of a router so that they do not travel beyond the LAN.
How does VLAN work ?
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.