VLAN is a virtual local area network that groups separate network nodes and computers as if they are sharing the same physical connection. VLAN also enables communication between computers that are a part of separate segments of a local area network as long as users configure them to utilize the virtual network.
One of the advantages of VLAN is that it allows users to divide the network as necessary without modifying the existing network infrastructure or running new cables. A network administrator uses a network switch that supports the VLAN functionality to specify which network ports gain access to the virtual network. He then groups the ports and forms a VLAN, making it impossible for computers outside the virtual network to access the information that users share within that network.
Although separate VLANs are isolated from each other, a network administrator uses a router that supports VLAN tagging to route the information internally between individual VLAN interfaces. Alternatively, he uses a network switch capable of inter-VLAN routing to share the information between networks without having it leave the switch. To determine which piece of data is intended for specific virtual networks, a network switch examines the data and automatically assigns a VLAN tag to it based on the port configuration settings.