VLANs

A Virtual LAN (VLAN) is a group of devices on one or more LANs that are configured so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, it is very flexible for user/host management, bandwidth allocation and resource optimization. Most home or small office networks will not find it necessary to use this method of network management. But a business with, say, a networked point of sale system, a public network (like a wi-fi hotspot), and an internal office network will want to keep these systems separate for security reasons, but yet still have them all on the same physical network for ease of management. Here's how it works.

Virtual LANs fall into the following categories:-

1. Port-Based VLAN: each physical switch port is configured with an access list specifying membership in a set of VLANs.

2. MAC-based VLAN: a switch is configured with an access list mapping individual MAC addresses to VLAN membership.

3. Protocol-based VLAN: a switch is configured with a list of mapping layer 3 protocol types to VLAN membership ¡§C thereby filtering IP traffic from nearby end-stations using a particular protocol such as IPX.

4. ATM VLAN  using LAN Emulation (LANE) protocol to map Ethernet packets into ATM cells and deliver them to their destination by converting an Ethernet MAC address into an ATM address.