What is a VLAN?

VLAN, which stands for Virtual Local Area Network, is a logical Local Area Network (LAN) which goes beyond the single traditional LAN to and comprises a group of LAN segments that have specific settings. These settings enable communication between different hosts in the same way they would communicate had they been in the same LAN setting, irrespective of their physical location. But instead of the configuration being done through the physical relocation devices, in the case of VLANs it is done through software. Thus a VLAN is first and foremost a software concept, and as such, identifiers and configuration must be prepared just as required if the network is going to perform as intended. VLAN members or groups are identified through flame coloring, where packets are given a VLAN ID at the source so that they can be processed as appropriate as they travel through the network. Ultimately, the VLAN ID helps switching and making of the appropriate decisions as required in the VLAN configurations.

Why use VLANs?

VLANs avoid some of the problems encountered while using the traditional LANs of requiring additional bandwidth. This is because the packets are required to pass through multiple levels of network connections as the network is usually fragmented. Secondly the traditional LAN’s have tended to focus too much on the physical location on the equipment and personnel. And this has its drawbacks. When it comes to VLAN’s, someone in New York can access and make a computer printout using a printer in London! Further, a properly designed VLAN can ensure that only devices on the network can send o0r receive packets intended as a source or destination.

Types of VLAN’s.

There are several types of VLAN’s as defined. These include; Port Based VLANs, MAC Based VLANs, Protocol Based VLANs and IP Subnet Based VLANs.

Port Based VLANs.

Here, all the Internet traffic that arrives at a certain port of a switch is linked to a particular VLAN. In this way, several VLAN’s can be connected through a single switch and run concurrently without any hitches. This would work optimally in a static environment, where member of different VLAN’s remain the same over a prolonged period of time and seldom change.

MAC Based VLANs.

In this case, the incoming traffic is inspected for the source and destination MAC addresses and the respective VLAN’s are determined. By working like that, the VLAN connects to all computers to all the ports and a switch will then associate the respective computers with the appropriate VLAN as configured.

Protocol Based VLANs.

As the name suggests, the VLAN is protocol that is used to transmit data, and the each protocol is assigned on a different port. This method allows for the logical segmentation of a network.

IP Subnet Based VLANs.

All the traffic in this type of VLAN is split, depending on the Internet Protocol (IP) subnet of each source or destination. In this type of VLAN, users can physically move the computers from one place to another and still retain the same VLAN settings intact.

Additional Reading on VLAN’s