What Is A VLAN?

Date First Published: 14th June 2022

Topic: Computer Networking

Subtopic: Network Setups

Article Type: Computer Terms & Definitions

Difficulty Level: 7/10

Learn more about what a VLAN is in this article.

Short for a virtual local area network, a VLAN is a customisable network that is created from multiple LANs. It allows groups of devices that are available in multiple networks to be joined into a single logical network. A virtual LAN can be maintained in a similar way to a physical LAN.

In a VLAN, the nodes are logically connected regardless of their physical location. This is because a VLAN is capable of separating the nodes into virtual networks. Data must be mapped to a specific network since traffic from several VLANs may travel over the same physical network.

Mapping Data

In order to map data, a VLAN protocol is used, such as IEEE 802.1Q, Cisco ISL, or 3Com VLT. The IEEE 802.1Q is used by most modern VLANs and works by adding an extra header (tag) into each Ethernet frame. The header identifies where the sending device in a VLAN belongs, preventing data from being routed to a destination outside of the VLAN.

Use Of VLANs

VLANs may be used to separate the network broadcast traffic between different departments in a company. The use of VLANs on a router or switch that has VLAN capabilities isolates traffic between different departments.

For example, a VLAN could be used to separate the finance, marketing, and human resource departments within a company. The departments will not be able to see any traffic created by the other departments. They will only see their own network traffic even though all of the computers from the different departments share the same cabling and router/network switch. This type of configuration reduces the chances of unauthorised access to sensitive information and provides additional security within a LAN.

There are so many different reasons for creating VLANs, but the main reason is for traffic management as a LAN. This is because as a LAN grows and more nodes are added, it will cause the frequency of the broadcasts to increase and the network will get overloaded with data. The creation of VLANs, which divide the network up into broadcast domains reduces the broadcast traffic and the load on the network.

How Are VLANs Created?

A VLAN can be configured by a software administration tool that allows the virtual network to be customised. The software administration tool can be used to assign specific hardware ports on the router or switch to a specific VLAN. For example, if a VLAN was created for a department of a company, all the computers that belong to that department would be plugged into those ports. Another set of ports can be assigned on the switch or router for more VLANs, separating traffic between different departments.

History

W. David Sincoskie joined Bellcore and began addressing the problem of expanding Ethernet networks after successful voice-over Ethernet experiments from 1981 to 1984. Ethernet was quicker than other alternatives at the time, with a speed of 10 Mbit/s. Ethernet was a broadcast network, and there was no easy method to combine different Ethernet networks together. The overall bandwidth of an Ethernet network was limited to 10 Mbit/s, and the maximum distance between nodes was limited to a few hundred feet.

Sincoskie created VLANs to help solve this problem by adding a tag to each Ethernet frame. These tags can be compared to colours, such as red, green, or blue. Each switch might be set to handle frames of a certain colour and discard the rest in this method. Three spanning trees, one for each colour, might be used to connect the networks together. The overall bandwidth could be increased by sending a variety of various frame colours. This was referred to as a multitree bridge by Sincoskie.

He and Chase Cotton developed and improved the algorithms required to make the system work. This colour is now known as the IEEE 802.1Q header, or the VLAN tag, in Ethernet frames. VLANs are commonly used in current Ethernet networks, but not in the way that was originally intended.

VLANs were first used to separate different broadcast domains across one physical medium. In 1998, Ethernet VLANs were defined in the first edition of the IEEE 802.1Q-1998 standard. IEEE 802.1ad was an extension of this standard that enabled nested VLAN tags for use by provider bridging. In IEEE 802.1ah-2008, this mechanism was improved.

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