VLAN Advanced

On a large, flat, switched network with thousands of computers, performance suffers and security concerns increase.

Using VLANs to divide a growing network can help with manageability, performance and security.

The VLAN structure makes it easier for administrators to manage network resources. Users can be grouped logically with the resources(servers, printers, etc.) that they need. When a user's computer physically moves to a different location (for example, with a laptop computer), the VLAN management software can recognize the computer and automatically assign it to the VLAN to which it's supposed to belong.

VLANs reduce the need to have routers deployed on a network to contain broadcast traffic. VLANs are separated by switches that divide the network into multiple broadcast domains, to reduce the amount of traffic going to all devices and thus increase performance.

By confining the broadcast domains, end-stations on a VLAN can be isolated from listening to or receiving broadcasts not intended for them. Moreover, if a router is not connected between the VLANs, the end-stations of a VLAN cannot communicate with the end-stations of the other VLANs.


Reference:
http://thebestechblog.blogspot.com/2009/06/vlan.html
http://www.frokwon.net/essays/VLAN.htm
http://net21.ucdavis.edu/newvlan.htm
http://www.techrepublic.com/article/scaling-your-network-with-vlans/5779489