Its Confusing me.

sina2011

Hey guys,
Had a quick question I currently come from a Cisco background and I'm trying to understand HP switching with the words like tagging and untagging can anyone give me a example of the difference I couldn't find any good examples on the internet that made sense to me.
Cheers,

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Comments

ande0255

From my understanding it is the same thing as Cisco L2 switching, though it's been months since I've worked on a frame tagging issue. Frames are tagged when traversing trunks between switches for delivery to their destinations, whereas untagged frames are delivered to 'host' ports on the local switch.

So if you send a frame destined to vlan 4, and the local switch only knows of vlan 1 and 3, it will forward that frame on with a vlan tag of 4. This is where VTP domains and VLAN pruning comes into play, as a dynamic frame switching protocol, and a traffic filter for unnecessary traffic.

sina2011

Thanks for your reply.

So i did a bit of extra googling and im confident that i get it now.

Untagged:a port in the native vlan

Tagged:A port belonging to a specific vlan e.g VLAN20 and then obviously the 802.1q header gets added to the packet when its been sent.

Correct?

pevangel

Tagging means adding the VLAN information to the frame. Untagging is removing it.

Tagged frame = VLAN information included
Untagged frame = no VLAN information included

ande0255 wrote: »

So if you send a frame destined to vlan 4, and the local switch only knows of vlan 1 and 3, it will forward that frame on with a vlan tag of 4. This is where VTP domains and VLAN pruning comes into play, as a dynamic frame switching protocol, and a traffic filter for unnecessary traffic.

That's a common misconception but the switch will not forward that traffic. If VLAN 4 is not configured on the switch and the switch receives a frame tagged with VLAN 4, then it will drop that frame.

sina2011

Thanks for your reply.

I understand what you are saying however what I'am saying is that correct as well?

pevangel

Not exactly. Tagged and untagged describes the traffic, not the port. I have heard people say tagged port and untagged port. What they mean by tagged port is a port that accepts tagged traffic (trunk port). Then an untagged port is a port that accepts untagged traffic (access port).

sina2011

ok sooo translating tagged port and untagged port to cisco terms what would that be?

pevangel

Tagged and untagged are general networking terms. It is even commonly used in Cisco documentation.

Can you explain what you think tagged and untagged means? I want to see where I'm falling short and see if I can describe it better. Keep in mind that tagged and untagged describes the traffic NOT ports.