Vlan – Understanding VLAN tagging and untagging of ports

vlan

I have to go through and find out the configuration set up on the old Dell Force10 switches that we have. I was wanting to make sure that I fully understand what is going on with what I see. I have the configuration of the VLANs for the ports below:

VLAN Config IDF3

I am just trying to fully understand what this all means. I know that the U is for untagged and that T is for tagged.
The question that I have is what the meaning of untagged and tagged has on the ports. I thought that if the port is in use you would want to tag that port with the VLAN that you want it to be on. But I know that untagged is what is getting used because I know they are physically plugged.

So, I am just a little confused. If someone could please help me understand.

Thank you

Best Answer

The meaning of "tagged" and "untagged" is this:

If a VLAN is tagged on a port, it means that data from that VLAN is sent out the port in 802.1q format, which has a VID (a tag) that identifies what VLAN it's associated with. Also, data received with a VLAN tag is placed in the appropriate VLAN.

If the VLAN is untagged, it is sent in "standard" 802.3 Ethernet, with no VLAN information. Data received on the port in "standard" format is placed into this VLAN.

Note that a port can have only one untagged VLAN, but multiple tagged VLANs.

A VLAN can be untagged on one port, but tagged on another.

In the Cisco world, an untagged VLAN is called the "native VLAN."

Related Topic