VLAN summarized!

VLAN summarized!

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Virtual LANs are very common these days with most enterprises. In order to understand the concept of VLAN, it is important to know the basic concept of LAN. In a nutshell, all devices in the same broadcast domain constitute a LAN.

A VLAN is a broadcast domain created by a switch. Each broadcast domain connected to the interfaces of the switch is known as a separate VLAN. A VLAN should be configured when a LAN has lots of traffic or more than 200 devices. It is also required when groups of users need more security or when a group of users have the same type of work and need to be on the same broadcast domain.

If VLANs are not configured, a switch puts all interfaces in a single broadcast domain. Cisco switches put all interfaces in VLAN1 by default. By configuring VLANs, a switch creates multiple broadcast domains. Cisco switches configure multiple broadcast domains by putting some of the interfaces into one VLAN and the remaining interfaces into other VLANs. Instead of all ports on a switch forming a single broadcast domain, the switch separates them into many according to the configuration.

Broadcast Domain

A broadcast domain is a group of devices that receive broadcast frames generated by any device within the group. It is a logical network segment in which any device connected to the network can be directly transmitted to any other device on the domain without having to go through a routing device. The only condition is that they must share the same subnet address and be in the same VLAN.

Benefits of configuring VLANs

The benefits of configuring VLANs are as follows:

• It improves security, as broadcasts are limited.


• As broadcast domains are separated, there is efficient use of network bandwidth.


• It is helpful in creating more flexible designs for grouping users.


• It reduces the workload for the Spanning Tree Protocol (STP).

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