Virtual LANs (VLANs) give an administrator the ability to break up a switched Layer 2 network into multiple broadcast domains. The advantage of this approach is that it can be done using switches that cost less than traditional routers. However, each broadcast domain is typically considered to be a separate subnet. To go between subnets, a Layer 3 component, such as a router, is still required.
VLANs can be based on the port identifier of a switch, on an end station's MAC address or Layer 3 address, or on directory or application information. They also can be implemented in many different ways, depending on the media topology (Ethernet, FDDI, or ATM) that's deployed.
Advantages of VLANs
One of the main reasons that network administrators ...