VLANs Overview

Though VLANs is among us for a long time, still many of us don’t know how they work. This article’s going to provide you an overview of VLANs. Before taking a look at what and how they work, let’s have a quick view of pre VLANs. Earlier before we add VLANs, we would create separate networks like this.

The point here is we have two physically separated switches. The host connected to LAN 1 cannot communicate to the host over at LAN 2 because there’s no connection between these two switches they are physically separated. They’re physically on two different networks. Before VLANs, this is the way things work. Why do we want to have hosts in different networks? 

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For example :

VLANs implementation example
VLAN implementation example

How Do They work?

LAN 1 is our hotel’s finance department and LAN 2 is our guest network for any guest coming in. Its obvious we never want our guest’s network traffic or the guest network to be able to reach the host in our finance department right that wouldn’t be good for a company. In that case, we need to separate those networks and before VLANs, we had to do that physically. The host needs to be physically connected to separate networking hardware in this case switches. That’s good in order to separate the traffic from LAN 1 and LAN 2 we have to have them connected to separate switches. 

VLANs stands for Virtual Local Area Networks. It means that they provide us with logical separation or segmentation of our network. The traffic is actually separated in each one of those networks.

VLANs with switches
VLANs with switches

We can have any number of networks or VLANs all on the same networking hardware or networking switch.

In our example, we have 2 separate networks but if we use VLAN we have two separate networks but on the same hardware. We could have our single switch here and implement VLANs and then we could have our two separate LANs or separate networks attached to the same physical device, same networking hardware but we can still keep their traffic completely separate and implement our own security controls on those networks individually and separately. So, the traffic is still completely separated from VLAN 1 and VLAN 2 but it’s done logically inside the switch rather than physically.


Last point that needed to be stated the VLAN’s provide us with logical segmentation of networks. It gives us freedom and allows us to be unlimited in our physical locations of hosts. In VLAN’s it doesn’t matter where the host is, we can put them in any VLAN we want to, no matter the location. The LANs connected to VLAN would share the same VLAN database, will know about all the VLANs in the network. You’ll be able to just go into any switch and assign any host to any VLAN thus giving you a vast amount of flexibility. This is the purpose of VLANs, logically separating our networks using VLANs.

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