What is VLAN? And What is the purpose of using VLAN ?

What is VLANs? (Virtual Local Area Network)

Those who are learning networking first time they first misunderstood the VLAN concept and non-technical background students not able to understand it very well, so this article will describe the concept of VLAN in easy manner.

Let's understand the concept of VLAN using a small example!

Imagine you live in a big apartment building with lots of units, and there are many other people living there too. Each apartment has its own set of rooms and, usually, the people in one apartment don't want other people from different apartments coming into their rooms. They are private and have their own area.

Now, think of a VLAN (Virtual Local Area Network) like creating separate areas in this apartment building. It's as if you can use a magic paint to draw invisible lines that divide the building into sections, and each section has its own set of rooms.

With VLANs in a computer network:

• You can have different groups of computers, kind of like different apartments, and they don't see or interfere with each other. It's like people from one apartment can't just wander into another apartment's space.
• Each VLAN is like its own little network, even though all these networks might physically exist on the same wires or Wi-Fi in the apartment building (or office).
• You can set rules to control what each VLAN can or can't do. Just like some apartment sections might have certain rules about who can come in and what they can do there.

So, VLANs help organize and separate different groups of computers or devices on a larger network, given them their own "apartment" with privacy and rules, even though they all share building (or network infrastructure). This is handy for things like security, managing traffic, and making sure devices are on the right virtual floor, so to speak.

What is the purpose of using VLAN?

Now, from the explanation of VLAN it's clarified that there are two purposes of using VLAN:

• With help of VLAN, we can divide single switch into smaller mini switches. In simple words, VLANs help to divide physical switch into multiple virtual switches.
• Second purpose of using VLAN is to extend the virtual switches across different physical switches.

The first purpose of using VLAN is to divide the physical switch into multiple virtual switches. As an example, look at the below image of switch.

Think of every circle on the switch in the image above as a separate mini switch (or virtual switch). These switches are made up of a group of switch ports that function independently of one another, just as they would if there were three separate physical switches.

Every switch port on a virtual switch, or VLAN, has a unique number allocated to it. If this were the case, the blue circle would be allocated to VLAN#10, the green circle to VLAN#20, the red circle to VLAN#30, and the last violet circle to VLAN#40.

Traffic will never be permitted to cross a VLAN boundary by a switch. Without first going via a router, traffic from the VLAN#10 switch cannot just appear on the VLAN#20.

The second purpose of using VLAN is to expand the smaller virtual switches among several physical switches by using VLAN. Now consider the same image at above, through this purpose of VLAN we can extend the few virtual switches into multiple physical switches.

You can extend VLANs #10 and #40 onto a second physical switch in order to use this VLAN capability. This makes it possible for all of VLAN #10's VLAN ports as well as the extended portion of VLAN #10 to exist in the same VLAN even though they are connected to various physical switches that may be situated in various locations.

These connected switch ports will become a member of only a single VLAN. This is known as Access port. Only one VLAN is a member of an access port. 

Merits and Demerits of using VLAN.

Merits:

• VLANs make it possible to divide a network logically.
• VLANs help to separate the broadcast domains, so without broadcasting the whole network, devices in the same VLAN can communicate directly with one another.
• VLANs simplify network configuration and management.
• By isolating networks, VLANS improve network security.
• VLANs offer flexibility in how network resources are arranged.

Demerits:

• VLAN setup and configuration can be difficult, incorrect setup could result in problems with connectivity.
• Traffic must pass via a router in order for devices in different VLANs to communicate, which could increase network latency and congestion.
• VLANs are vulnerable to broadcast storms.
• Implementing VLANs may need network devices to have suitable hardware and software.

Overall, in this article, you have learned about VLANs, what VLANs are, what the purpose of using VLANs is, and, at last, what the merits and demerits of using VLANs are. I hope you guys have understood the concept of VLANs. If anyone has doubts, they can ask questions.