What are VLANS ?
VLAN’s allow a network manager to logically segment a LAN into different broadcast domains. Since this is a logical segmentation and not a physical one, 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. VLANs are created mainly for administrative purposes to ensure that network traffic is seen only by members of a specific group, rather than by all members of the LAN. This way confidentiality is maintained and additionally nodes are protected from unnecessary traffic. For example, in an enterprise, each department (like Engineering, HR, Accounts etc.) may be maintained as a separate VLAN. Similarly, in a campus or a university network, each department (e.g. maths, physics, computer science etc.) would typically be part of a separate VLAN.
