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New Member

Transport of Q-in-Q traffic


I have a very basic question; can I transport Q-in-Q traffic through switches that only understand dot1q traffic and not Q-in-Q??

My intention is to use Cisco Small Bussiness switches, which don't understand Q-in-Q, for the transport network and Cisco SPS switches, which do support Q-in-Q, for the access network. Cisco SPS switches will encapsulate customer's VLANs, C-VLANs, into the unique VLAN assigned to the customer, S-VLAN. Cisco Small Business switches will deal only with S-VLANs.

However, Cisco Small Business switches will be able to transport S-VLAN? I have read that S-VLANs have ethertype 0x88a8 so if the transport switches don't understand that ethertype, will they be able to transport it?

Thanks in advance,


Everyone's tags (2)

Transport of Q-in-Q traffic

As long as it is pure layer 2, any switch should be able to transport frames, regardless of its ethertype.

However, trunking will probably not work while the type is not recognized as dot1q. This means you can only forward such packets within a single vlan i.e. you will be unable to separate traffic from multiple customers.

You may be able to use it for a single customer but for a bigger environment, it will not scale and you may end up mixing traffic from different customers .



New Member

Transport of Q-in-Q traffic

Could I change the ethertype?

Transport of Q-in-Q traffic


New Member

Transport of Q-in-Q traffic

In any case, I am not sure if i would have the issue with the ethertype.

The access switch that encapsulates dot1q traffic in q-in-q traffic (switchport mode dot1q-tunnel) will also provide a trunk of service provideer VLANs (switchport mode trunk) towards distribution switches. I'm not sure that those traffic would have the q-in-q ethertype or the clasicall dot1q trunk ethertype. In the second case we shouldn't have any problem.

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