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The Graveyard - Products No Longer Supported => Hubs and Switches => DGS-1248T => Topic started by: yonglu on January 23, 2013, 06:39:49 PM

Title: Need ULTIMATE clarification of tagged and untagged ports
Post by: yonglu on January 23, 2013, 06:39:49 PM

All,

I like to make myself totally/absolutely clear about a Dlink switch's tagged and untagged ports behavior upon receiving different tagged and untagged packets. The exhaustive list is like below:

On a tagged port:

1. What happens if it receives an untagged frame? Drop it immediately?
2. What if it receives a tagged frame with the VLAN ID that this port belongs to? Take it and forward it with the VLAN ID tag I think?
3. What if it receives a tagged frame with a VLAN ID that this port does NOT belong to? Drop it immediately?

For an untagged port:

4. What happens if it receives an untagged frame? Take it and forward it?
5. What if it receives a tagged frame with the VLAN ID this port lelongs to? Take it and forward it?
6. What if it receives a tagged frame with a VLAN ID tthis port does NOT belong to? Drop it?

Also can a port be tagged port for multiple VLANs? I think so and this implements the "trunk port" in Cisco term, corrct?
can a port be untagged port for multple VLANs? Acutally the answer should be yes because I already have a switch with such config, but how does the switch decide the VLAN for an incoming untagged packet?

Thanks a lot!

Title: Re: Need ULTIMATE clarification of tagged and untagged ports
Post by: FurryNutz on January 24, 2013, 06:34:22 AM

Which DLink switch are you referring too?

Title: Re: Need ULTIMATE clarification of tagged and untagged ports
Post by: yonglu on January 24, 2013, 05:43:25 PM

DGS-3120-24TC

Title: Re: Need ULTIMATE clarification of tagged and untagged ports
Post by: dovydas on January 25, 2013, 06:52:50 AM

I am struggling to configure vlans using D-Link and Linux LACP bonded vlan interfaces ("bond0.2"). Coming from Cisco world to D-Link terminology is a huge confusion for me.

I would like to ask exactly the same questions that user Yonglu has asked. And I have DGS-3120-24TC - exactly the same switch as Yonglu.

Title: Re: Need ULTIMATE clarification of tagged and untagged ports
Post by: FurryNutz on January 25, 2013, 07:03:52 AM

I highly recommend phone contacting DLink support for these models and inquired about the information and terminology that you need regarding this units.

Title: Re: Need ULTIMATE clarification of tagged and untagged ports
Post by: Planck on February 21, 2013, 01:47:24 AM

Tagged/untagged is a function for forwarding a package. If a tag-aware switch receives a tagges packed, it will forward it with the tag. The only place it untagges it, is if you have a full untagged VLAN.
Here is what i normally do:
Vlan 1: Untagged all the way, an used for discovery and management
All other VLAN's: Tagged until end destination

If you do it like that, then you never hav these issue.

Remember if you use PVID, then all traffic on that port vil be tagged from that port and onwards!


Best regards

Mikkel Planck
www.structureit.dk