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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LAN is a local network where every connected computer can communicate with each other openly using ethernet. To route traffic between different networks you would typically use a router that is connected to both LANs and can copy the IP package inside the ethernet package from one to the other based on the destination IP address. By default all ports of a switch is part of the same LAN.
You would typically have multiple LANs for security reasons or when there is too much traffic on one LAN. Because of the broadcast nature of a LAN you will typically have problems when you connect more then 100 devices to the same LAN.
A virtual LAN is a feature in some switches where it can act as multiple switches at once. Each port is only a member of one vLAN and you can have multiple vLAN on one switch. This way you can for example have one vLAN for your printers and one vLAN for your workstations on the same switch. This means workstations and printers can not communicate directly with each other through the switch.
When connecting switches with vLANs together it can become hard if each vLAN needs a seperate cable. So instead we “tag” each ethernet package with the vLAN id when sending the package out on a single port acting as a trunk. That allows the receiving switch to put the package in the correct vLAN. Normal ports would still not have this tag on it and only send and receive traffic on a single vLAN. This allows you to stretch several vLANs through multiple switches located in different location. For example if you have both workstations, wifi and printers throughout the building in different floors, or even in different buildings on the campus.
But you can also use the vLAN tags between switches and computers, typically servers and routers. One trunk cable will then split into multiple vLAN network interfaces in the software. This is how a router with a single downlink cable can be connected to all the vLANs and route traffic between these.
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