Tagged vs. Untagged (34028 Views)
Reply
Advisor
Robert Peirce
Posts: 28
Registered: ‎05-09-2007
Message 1 of 6 (34,028 Views)
Accepted Solution

Tagged vs. Untagged

Can anyone explain the true purpose of tagged vs. untagged members of a VLAN? A real world example would be very helpful. I have read the documentation, but it is not really clear.

Any help with this will be greatly appreciated.
Please use plain text.
Trusted Contributor
Joel Belizario
Posts: 197
Registered: ‎09-19-2006
Message 2 of 6 (34,028 Views)

Re: Tagged vs. Untagged

The terminology of tagging is confusing if you don't have some understanding of how the protocol works. Have a look and see whether this clears up anything for you:

http://en.wikipedia.org/wiki/IEEE_802.1Q

But anyways, an untagged port in a VLAN is a physical member of that VLAN, ie. when you plug your host into that port it is physically connected to that VLAN (also known as an "access port" in Cisco terminology).

A tagged port will normally carry traffic for multiple VLANs from the switch to other network devices such as an upstream router or an edge switch (In Cisco terminology this is called trunking, HP have no specific term for it).

Hope this clears any confusion for you!
Please use plain text.
Trusted Contributor
Jonathan Axford
Posts: 226
Registered: ‎11-08-2004
Message 3 of 6 (34,028 Views)

Re: Tagged vs. Untagged

Hi Robert,

In the simplest form, I used to remember a 'Tagged' port as an inter-switch link and an 'Untagged' port as a host port.

Basically, its all about the VLAN information that gets 'tagged'into the Ethernet frame.

When you configure a port as 'Tagged' you are telling the switch to place an 802.1q tag in the frame that can identify the VLAN that the frame came from.


That way, the switch that receives the frame knows which VLAN to send the Frame to.

So if you have 2 switches, each with ports 1-10 in VLAN 10 and ports 11-22 in VLAN 20.

You want PC's to be in VLAN 10 and Servers to be in VLAN 20, so you would :

VLAN10 untag ports 1-10 on each switch
VLAN20 untag ports 11-22 on each switch

This sets your hosts up. You want to use interface 24 to connect the switches.

VLAN10 tag port 24
VLAN20 tag port 24

So, the Interswitch links are TAGGED and the hosts are UNTAGGED...

Where there is a will there is a way...
Please use plain text.
Advisor
Robert Peirce
Posts: 28
Registered: ‎05-09-2007
Message 4 of 6 (34,028 Views)

Re: Tagged vs. Untagged

Thank you for taking the time to respond.

I just want to be clear.

Are you saying that a physical ethernet cable is needs to be connected from port 20 to port 10 on the same switch to enable communication between VLAN 10 and VLAN 20? If so, I am assuming a physical cable would only be needed if IP Routing was not enabled on the switch?

Thank you for your help.
Please use plain text.
Advisor
Robert Peirce
Posts: 28
Registered: ‎05-09-2007
Message 5 of 6 (34,028 Views)

Re: Tagged vs. Untagged

Disregard the last question. I read the last response again and now I am clear.

Thanks to all who responded.
Please use plain text.
Honored Contributor
Patrick Terlisten
Posts: 1,781
Registered: ‎07-12-2005
Message 6 of 6 (34,028 Views)

Re: Tagged vs. Untagged

Hello,

if you want that a port only belongs to one VLAN, set the port to UNTAGGED. If you want a port in more then one VLAN, you need to set it to TAGGED. If a host should belong to more than one VLAN, the port must be TAGGED (for example an VMware ESX Server with guests that belongs to different VLANs). If you want to uplink a switch to another, you need to set the uplink port to TAGGED, for each VLAN which should be acccessable over the uplink.

Kind regards,
Patrick
Regards,
Patrick
Please use plain text.
The opinions expressed above are the personal opinions of the authors, not of HP. By using this site, you accept the Terms of Use and Rules of Participation