A virtual local area network (VLAN) is defined in a switch that sets the boundary of a
broadcast domain for hosts to communicate with each other. A VLAN has the same attributes
as a physical local area network (LAN) and it can be extended between different switches
within or across different sites.
Today, VLANs are created in the switch to mimic the Ethernet segmentation services that are
traditionally provided by the routers in LAN configurations. Figure 1-1 gives a conceptual view
of a VLAN.