LANs are increasingly being divided
into workgroups connected via common backbones to form virtual LAN (VLAN)
topologies.
VLANs logically
segment the physical LAN infrastructure into different subnets
(broadcast domains for Ethernet) so that broadcast frames are switched
only between ports within the same VLAN. 
Initial implementations offered a
port-mapping capability that established a broadcast domain between a
default group of devices. Current network requirements demand VLAN
functionality, which will cover the entire network. This approach to
VLANs allows you to group geographically separate users in
network-wide virtual topologies. 
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