By defining VLANs on a LAN the following goals should be achieved:
- Data traffic of certain logical units should be shielded against other network users.
- Broadcast traffic should also be reduced to logical units, not bearing a burden on the entire LAN.
- Data traffic of certain logical units should be transmitted with a specific priority compared to other network users.
An example to clarify: A switch is connected to a hub within a LAN, which connects four stations from the marketing department to the network. One server and two stations of the accounting department are directly connected to the switch. The last section is the base station of a wireless network, where four WLAN clients reside from the sales department.
The stations from marketing and sales should be able to communicate with each other. Additionally, they should be able to access the server. The accounting department needs also access to the server, but should otherwise be shielded against the other stations.