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christian.pinedo
Beginner

Transport of Q-in-Q traffic

Hello,

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,

Christian

4 REPLIES 4
lgijssel
Engager

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

http://en.wikipedia.org/wiki/IEEE_802.1Q

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 .

regards,

Leo

Could I change the ethertype?

No.

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.