Why implement VLAN?

        Creating virtual LANs allows system and network administrators to control traffic patterns, react quickly

 to relocations and keep up with constant changes in the network due to moving requirements and node

relocation just by changing the VLAN member list in the router configuration.

        A valid reason for VLAN implementation is a reduction in the time spent and cost of handling user moves

and changes. This is fairly significant in IP networks because normally when a user moves to a different subnet,

 IP addresses must be manually updated in the workstation. In VLAN, membership is not fixed to a workstation’s

location in the network, allowing moved workstations to recover their original IP addresses and subnet membership.

        Another reason is the reduction of routing for broadcast containment. The philosophy “switch when you can,

route when you must” has become popular among networking and in VLAN it is carried through quite well. LAN

switches supporting VLAN can be used to control broadcast traffic, reducing the need for routing. Broadcast traffic

 is blocked from ports with no end-stations belonging to that VLAN, therefore it creates the same type of broadcast

firewall that a router provides. Only packets that are intended for addresses outside the VLAN need to advance to

a router for forwarding.