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New Member

Q in Q and ?MPLS

Hello NetPros, i'am posting this issue here because you are familiar with metro networks. I'll explain what I am tryin to do.

I have a siemens DSLAM that connects to my 6504-E Sup32 switch. I have configured dot1q-tunnel on the ingress interface where the dslam resides and aggregate the pppoe session at a 10008 PRE2 router. Everything works fine but we are trying to implement MPLS and need to avoid to add the double tag to some vlans according to a numbering plan already defined.

I want it to work like this if I receive fram with vlan 44 tag i have to double tag it with another vlan id (q-in-q) but if another frames arrives with a different vlan id I don't want it to be double taged, just leave the fram as is and terminate it in a vlan interfaces acting as the gateway of the CPE.

I need some coexistance of qinq and simple vlans.

As long as I know the siemens dslam supports 802.1q and q-in-q also.

Any help would be very helpfull. Thanks in advance.

Santiago Enciso CCNA/CCDA/WLANSE


Re: Q in Q and ?MPLS

Did you try that scenario and does the sup32 stops forwarding mpls traffic

New Member

Re: Q in Q and ?MPLS

Yes I have tryed many scenarios and didnt work. I think it is because the dot1q-tunnel command tags all the traffic with out distinction and if the ip traffic that comes from a customer with a tag of vlan 33 for exemple is double tagged It doesnt match the corresponding interface vlan 33 with the default gateway of the customers CPE. I dont know if it clarifies the situation but this is what is happening. Can send more diagrams of the current network.

New Member

Re: Q in Q and ?MPLS

Hi guys,

I don't have much experience about MPLS but as for q-in-q is concern native vlan from customer switch will not be taged but you have to explicitly tag it at your ingress switch to make it distinguesable to you backbone but if you don't tag it untagged packet will be going to your native vlan and it will be lost in your backbone.

So for ur requirment it could be possible to have a SVI with vlan id of ur customer switch and route it. generally it is used to give internet access to customer site.

please rate if it is correct and help.


New Member

Re: Q in Q and ?MPLS

just look at this document too if it can help you to short out your problem.

please rate if it helps.

Kamlesh SHarma

New Member

Re: Q in Q and ?MPLS

Thanks for your help Kamlesh but my problem is at the ingress port un my service provider switch where the customer X resides. I want the ability to tag some frames and other not selectively. If you know anything about it please let me know.


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