A Virtual Local Area Network (VLAN) is a group of devices on one or more LANs that are configured to communicate as if they were attached to the same wire, when in fact they are located on several different LAN segments. VLANs define broadcast domains in a Layer 2 network. The default VLAN typically uses VLAN identifier 1. Remote management of the switch requires that the administrative functions be associated with one or more of the configured VLANs.
VLANs work by applying tags to network frames and handling these tags in networking systems. Early network designers often segmented physical LANs to reduce the size of the Ethernet collision domain thus improving performance. Since VLANs share bandwidth, a VLAN trunk can use link aggregation, quality-of-service prioritization, or both to route data efficiently.
Because VLANs are based on logical instead of physical connections, they are extremely flexible. VLANs can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed. You can define one or many virtual bridges within a switch. VLANs allow network administrators to group hosts even if the hosts are not directly connected to the same network switch. A VLAN can also serve to restrict access to network resources without regard to the physical topology of the network.