Dot1q tunnel question

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May 27th, 2008
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hi guys,

just a qucik question.

i am planning to configure Dot1q tunnel in my network. becoz i need to hide some vlans. my concern is , when we configure Dot1q tunnel . what happens to the cos marking on the original dot1q packet ? are they coppied to the newly imposed tunnel tag ?


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Amit Singh Tue, 05/27/2008 - 21:45
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  • Cisco Employee,

Hi Amit,

No the COS making is not imposed anutomatically to the new tunnel tag. You have to manaully define it on the port.

All packets entering through a tunnel port on an edge switch are treated as untagged packets, whether they are untagged or already tagged with IEEE 802.1Q headers.All the packets will be tagged with a Metro tag VLAn ID. This metro Tag has a priority field which carries the COS value asssinged on the port. If no value is configured it will bydefault take it a COS 0.

Here is the command that you need put on the interface :

l2protocol-tunnel cos value


-amit singh

amitbatra Tue, 05/27/2008 - 23:06
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Hi Amit,

thanks for your quick reply. i was under same impression. i just wanted to confirm that.

The problem is that we have multiple COS valused used in the network. and we have differentiated treatment for different COS vlaues.

now i need to find adifferent way to accomodate my COS requirements.

If i use this command all traffic will be marked with newly configured COS value in the metro tag.

Thanks for ur help.


amit batra.


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