S-Tag (QinQ) over VOSS Fabric

  • 22 October 2020
  • 6 replies

Userlevel 5

Hi Community


I have a Extreme SPBM fabric deployed (4 x VSP7400's).

We have a connection from a ISP connecting to the fabric. The ISP is sending multiple S-Tag (QinQ) traffic to us. I want to match each of the S-Tag's (QinQ) to an I-sid and then send it across the fabric, to ports located somewhere. Below is a diagram of what I am trying to achieve:


On the left I have the single link from the ISP and I indicated the 2 different S-Tag arriving on the port.

Light blue us S-Tag10 and Yellow is S-Tag 20.

I want to send the traffic from S-TAG10 to one location and the traffic from S-TAG 20  to another location in the Fabric.


I configure the fabric ports to as a Flex-UNI ports. When I create the I-SID I only have the option to match on C-VID (802.1Q) and not S-VID (QinQ). However I still apply the configure as follows: 


First I create the I-SID:

Then assign the C-TAG to the I-SID and port

i-sid 100010 elan

  c-vid 10 port 1/1


On the other side of the fabric I do the same config:

i-sid 100010 elan

  c-vid 10 port 1/2

This does not work.

I can see Mac's being learned on ingress but nothing on the egress side.

With a wireshark trace I can see the incoming traffic hit the fabric with the S-tag of 10.

I can see the I-sid learning the traffic but on the egress side I see the traffic has no S-tag and the C-tag is now configured with 10. 

If I replicate the same config using only 802.1q C-Tag's it works fine.

Using the elan transparent I-sid and mapping a port to it allows all traffic to be passed as it arrives.

 and on the egress side the traffic exits as it arrive.

This works fine.


So the question:

Can we map a S-tag to and I-Sid and egress the traffic with the same S-tag?

This works when using elan transparent but the problem is that you can not split the different S-Tag's  to different locations, it is all ingress to all egress.



6 replies

Userlevel 6
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The Flex-UNI is to be used when you want to do VLAN NATting.

As you want to keep the same VLAN id throughout the Fabric, just use “vlan i-sid 10 100010”, assign the vlan to the port and provision the same on the other side.

Very simple and easy.



Userlevel 5

Hi Miguel


Thank you for your replay but this does not work.

The issue is with the double tag on the QinQ traffic.

When creating the Vlan on the fabric as per your example this creates the c-tag.

Incomming traffic from the QinQ link is matches but when traffic is sent back out from the fabric to the QinQ link, the vlan ID is placed in the C-tag and not in the S-Tag.






Userlevel 6
Badge +1


I overlooked your post, sorry…

I’m pretty sure you can’t perform QinQ with the VSP other than SPBM encapsulation.

The QinQ mechanism in the VOSS is embedded in the OS and used to encapsulate the C-VLAN on the SPBM backbone VLANs.

This requires dedicated CPU resources and on some platforms you must sacrify SPF+ ASICs to handle the additional effort.

To get a confirmation you could open a case at GTAC.

As workaround you could put a front-end switch from Extreme to handle the non-SPBM QinQ to extract the C-VLAN and bridge them with a VSP.

Here some articles from GTAC on QinQ:





Circling back to this one, the answer is yes, you can map an S-TAG to an I-SID and egress the traffic with the same S-TAG. And you can do this with Switched UNI. However to be able to do that, you would have to change the Ethertype to 0x8100 to ensure that we see those packets as Q-tagged and classify them properly. I think this was the point you were missing in your tests. I just wanted to clarify for everyone so that this thread is also not mis-leading for the audience.



Emre Kurtman

Userlevel 5

The attached doc covers QinQ testing over VSP Fabric Connect and also in conjunction with XOS VMAN with Fabric Attach.

Userlevel 5

Great Ludovico


Thank you for the details document.

Will test on our side and provide feedback.