VLAN stands for Virtual Local Area Network. It’s a way to divide a computer network into smaller, separate parts—even if all the devices are connected to the same equipment. In a big office building, HR has their computers, Finance has theirs,  and IT has theirs.  Everyone’s computers are plugged into the same set of network devices (like Wi-Fi or Ethernet cables). Without VLANs, every device could “see” every other device’s traffic, like everyone shouting in one giant room.  VLANs create private rooms,  with VLAN,  HR has their own digital room,  Finance has their own,  and so does IT.  Even though they’re all using the same physical wires and switches, VLANs keep them separated—like putting up soundproof walls.

We use VLANs for better security,  less traffic,  and easier management.  VLANs are more secure;  people in HR shouldn’t have automatic access to financial records. VLANs keep sensitive areas separate.  VLANs have less traffic;  if 100 people are all shouting in one room, it’s chaos. VLANs reduce the noise—each group only hears what’s meant for them. VLANs also make managing the network much easier;  if someone in Marketing moves to another floor, the IT team doesn’t need to rewire anything. They just put that person in the correct VLAN.

How VLANs Work

Each device on the network gets a VLAN ID, like a room number.  When a device sends information,  that info is tagged with the VLAN ID and the network checks the tag and delivers it only to the correct room. The tagging is called VLAN Tagging (802.1Q).  Imagine mailing letters; you write the room number on the envelope (VLAN tag) and the mail system (network switch) reads it and delivers it to the right room.  This is how the system marks traffic for each “room.”

VLANs require network switches and routers.  The network switches are like the mail sorters;  they direct traffic based on VLAN IDs.  The switches can carry multiple VLANs between devices similar to sending mail between buildings.  Routers are used when people in different rooms (VLANs) need to talk to each other—but with security checks.

Real-World Examples

A very common example of VLANs are guest networks that are provided by many modern wireless routers today. The guest wifi allows people to connect to your internet but doesn’t give them access to your files or your network.  They can’t see any of your printers or computers that you have on your network.  VLANs let guest devices use the internet without seeing the company’s internal network.  

Related Technologies

Trunk Ports

There are other terms that may be used with VLANs and one is called trunk ports.  A trunk port carries traffic for multiple VLANs down one cable. Like a delivery cart that drops off packages to different rooms. 

QinQ – Double Tagging

Used by internet service providers. Imagine one company has its own VLANs, and the provider needs to keep them organized while carrying many clients.  QinQ adds two tags: one for the customer, one for the provider,  it is like adding a second envelope with extra info for sorting.

VXLAN – VLAN Over the Internet

Big cloud networks (like Amazon AWS) use VXLAN to carry VLANs over long distances so your company’s VLAN can extend across cities or even countries.  VXLAN lets you put your “digital room” (VLAN) into an envelope and send it through the internet.

You can think of VLANs like a school.  Think of the classrooms as a VLAN,  teachers and students have different rules to follow and the building is shared by everyone but each classroom has its own curriculum.  You don’t need to be a wizard to understand VLANs. They’re just a way to organize and protect network traffic—just like dividing people into rooms or groups in real life.