Virtual Local Area Network (VLAN)

What happens if we need a virtual connection between two stations belonging to two differ ent physical LANs? A virtual local area network (VLAN) is defined as a local area network configured by software, not by physical wiring. Virtual LANs (VLANs) have recently developed into an integral feature of switched LAN solutions from every major LAN equipment vendor. One of the reasons for the attention placed on VLAN functionality now is the rapid deployment of LAN switching that began in 1994/1995. The shift toward LAN switching as a replacement for local/departmental routers—and now even shared media devices (hubs)— will only accelerate in the future. With the rapid decrease in Ethernet and Token Ring switch prices on a per-port basis, many more ambitious organizations are moving quickly toward networks featuring private port (single user/port) LAN switching architectures. VLANs represent an alternative solution to routers for broadcast containment, since VLANs allow switches to also contain broadcast traffic. With the implementation of switches in conjunction with VLANs, each network segment can contain as few as one user (approaching private port LAN switching), while broadcast domains can be as large as 1,000 users or perhaps even more. This paper present, in details, exactly what a VLAN is and how VLAN memberships are used in a switched network. Membership in a VLAN can be based on port members, MAC addresses, IP addresses, IP multicast addresses and/or a combination of these features. VLANs are cost and time effective, can reduce network traffic, and provide an extra measure of security.