Ethernet Switches & Routers

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Posts: 1
Registered: ‎03-31-2014

Double-tagged Frames in a Single VPLS

[ Edited ]

I have been studying the Brocade documentation around implementing MPLS networks.  Specifically, I have been looking at various configuraitons for VPLS instances on MLX platforms.  I find it interesting that there are configurations allowed that would merge the broadcast domains for VLAN's.  I guess I can see a few reasons why you would want to do this, but most seem to indicate that this would not be a good idea. 

 

In any case, I have an application where I would like to place frames with inner and outer VLAN tags into a single VPLS and have them exit the instance on the other side with the same tags, or just the inner tags.  Where this gets more complicated, is that I have three or four different inner tagged frames with the same outer tag.  I believe I found an example of this in the Brocade documentation, but perhaps it is not what it seems to be:

 

Brocade(config-mpls)# vpls test 10
Brocade(config-mpls-vpls-test)# vlan 100 inner-vlan 200
Brocade(config-mpls-vpls-test-vlan-100-inner-vlan-200)# tagged ethernet 2/1
Brocade(config-mpls-vpls-test-vlan-100-inner-vlan-200)# exit
Brocade(config-mpls-vpls-test)# vlan 100 inner-vlan 300
Brocade(config-mpls-vpls-test-vlan-100-inner-vlan-300)# tagged ethernet 2/1

 In the above example, a single VPLS instance is created with a dual-tagged endpoint.  Are the broadcast domains for VLAN 200 and 300 merged or do they remain separate?  The default vc-mode for the VPLS says that raw mode strips the tags when the frame pass through, but does this mean that all tags are removed, inner and outer, or just the outer tag?  Does tagged mode (vc-mode tagged) or pass through mode change this behavior?  Also, I was told that changing the vc-mode was a global setting, and that it would change all VPLS instances, but I can find no documentation that supports this.  Perhaps they were talking about the vc-type setting ???

 

Thank you for any information regarding this concept.  I am trying to further my knowledge regarding this and your replies will help.

 

Thank you.

Frequent Contributor
Posts: 144
Registered: ‎11-07-2013

Re: Double-tagged Frames in a Single VPLS

Hi Cygnus_X1,

  " does this mean that all tags are removed, inner and outer, or just the outer tag?" - the default raw-mode will replace the origional TAG with the new inner TAG you set and add the outer TAG - So in raw mode we lose any set QoS, if you want to keep the origional TAG and QoS value then use Tagged mode.

 

"Does tagged mode (vc-mode tagged) or pass through mode change this behavior? " yes, see above.

 

"Also, I was told that changing the vc-mode was a global setting, and that it would change all VPLS instances, but I can find no documentation that supports this." - No, you can configure this per instance of VPLS.

 

As for the VLAN flooding as far as I know this would only be the case if going to the SAME destiination MAC address.

 

Hope this helps you.

 

Thanks

Michael.

Thanks
Michael

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