Hello everyone, I’d like to understand how do VLAN tags work. I am a kid starting my IT journey in my first job and I found out about VLAN tags but I have no idea what they do. What is the difference between tagged and untagged? Looking forward to your replies 😊
EDIT: Thank you guys so much for all your replies. I’ve read all of them and now I get it ❤️
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If you’re asking this I assume you already know what a VLAN actually is but I’ll quickly try and put it in simple terms – A VLAN is a virtual-LAN (Local Area Network). It’s used as a way of segregating one physical network in to multiple logically-isolated networks.
A classic example is on a network switch. On a default configuration where all ports are on the default VLAN, all the devices connected to the switch can see each other and communicate. If you then assign one of the switch ports to a different VLAN than the default, that port will no longer be able to communicate with the other devices on the switch as it’s now essentially in a different network. This can be useful for various security or admin reasons.
A lot of the time you don’t want your VLANs just to be limited to one switch though. You might want VLANs that span across your whole network. That’s where VLAN tagging comes in. Using VLAN tagging you can essentially stamp the VLAN number on to a network packet before it is sent out of the switch. This means that when it arrives at its destination the receiving device knows which VLAN the packet belongs to.
The upside of tagging is it means you can jumble up all the data being sent from every VLAN on a switch and send it all together through one port, known as a “trunk” port and when it gets to its destination, the device can read the VLAN tag and easily know where the packet needs to be sent.
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