VLAN protocols enable an administrator to partition a LAN into multiple virtual LANs. Each VLAN is assigned a number that identifies it uniquely within the LAN.
Multiple VLANs share the switches and links in an underlying physical LAN. However, each VLAN logically behaves like a separate LAN. All of a VLAN's frame traffic (including its broadcasts and multicasts) is confined to the VLAN. This translates to improved performance because the total amount of traffic on the physical LAN can be reduced.
VLANs are constructed around a core set of switches that support the needed functions and protocols. These are called VLAN-aware switches, or more simply VLAN switches.
VLAN switches are Layer 2 switches—that is, bridges. ...