Switch VLANS

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Hello,

In my networking classes, we have always discussed reasons why you would want to TAG any switchports. We also discussed the difference between Access and Trunk ports. I'm sure this is extremely simple, but reviewing VLAN info on switch recently, the previous tech specifically went under VLAN 2 , let's say and defined which ports that were untagged.

In my head, you either applied the VLAN to specific ports or you didn't. I'm a little confused why you would create a VLAN, then specify which ports you wouldn't tag. I really feel like i'm missing something here.

"untagged ethe 1/1/2 to 1/1/5" as an example.
Can anyone elaborate?

Thanks,

@Benjamin-Frame,

The terminology is different on Cisco switches. When referring to "tagged" ports, Cisco calls those "trunk ports."

Tagged ports allow for multiple vlans to use that connection even if that connection is only a single link...let's say between switches. Without the tagging, Each VLAN on SW1 would need to have direct link to same VLAN on SW2. So if your SW1 had 10 VLANs and SW2 had the same 10 VLANs, they could only communicate between ports if there is a direct connection between those VLANs. In this case a minimum of 10 links across those 2 switches.

You do not need to tag ports are really only supposed service that one device within the same vlan (e.g., workstation or server in VLAN 110). But if you need that port to carry traffic for multiple vlans, then it must be tagged.