Introduction to VLANs
Use VLANs to increase traffic flow and reduce latency. With VLANs, you can organize your network by traffic patterns rather than by physical location.
In a conventional network topology, such as that shown in the following figure, devices communicate across LAN segments in different broadcast domains by using routers. Although routers add latency by delaying transmission of data while they are using more of the data packet to determine destinations, they are preferable to building a single broadcast domain. A single domain can easily be flooded with traffic.
By organizing the network into VLANs by using Ethernet switches, distinct broadcast domains can be maintained without the latency that is introduced by multiple routers. As the following figure shows, a single router can provide the interfaces for all VLANs that appeared as separate LAN segments in the previous figure.
The following figure shows how VLANs can be organized logically, according to traffic flow, rather than being restricted by physical location. If workstations 1-3 communicate mainly with the small server, VLANs can be used to organize only these devices in a single broadcast domain that keeps broadcast traffic within the group. This setup reduces traffic both inside the domain and outside, on the rest of the network.
