Dot1q trunk vlan translation

Unanswered Question
Mar 10th, 2009


If you are connecting 2 networks together via an ethernet switched dot1q trunk is there anyway to translate the vlans over it. i.e. your network is using vlans 10 and 20 but the network you are connecting to are using vlans 100 and 200. Any advice appreciated.

Kind Regards


I have this problem too.
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adamclarkuk_2 Tue, 03/10/2009 - 04:10


No this cannot be done using a standard trunk, although you could do this with a access port. You will need an access port for each VLAN and have one side of the access port in vlan 10 and the other in 100 and for the other, one side in vlan 20 and he other in 200.

kjbarrass Tue, 03/10/2009 - 04:13


thank you for the quick reply, I had a funny feeling that would be the case. The network we will be connecting to is using MPLS so the VLANS are localy significant on there side so I just need to convince them to make the VLANs match us as we are the customer :)



adamclarkuk_2 Tue, 03/10/2009 - 04:16

Can they not offer a QinQ solution for you, or possibly a EoMPLS solution, ie a layer 2 VPN.

kjbarrass Tue, 03/10/2009 - 04:23

my impression with QinQ is that its for tunneling vlans over your infrastructure not to translate VLANs but I dont know anything about QinQ so I may be way off :)

adamclarkuk_2 Tue, 03/10/2009 - 04:32

If I'm right, I'm guessing you have VLAN 10 and 20 across multiple sites and your provider wants you to use their VLAN numbering.

If so, then using QinQ, you can double tag the frame, the innner TAG being yours and the outer TAG begin there TAG. At the other end, the outer TAG is removed and the inner TAG is checked and processed by your kit.

kjbarrass Tue, 03/10/2009 - 04:36


we have a core switched network with say vlans 10 and 20 which have SVIs for them for routing. Normaly our sites connect direct to us on access ports over extended ethernet c.c.ts. on a few sites we are using a provider who will connect the sites direct into there MPLS network im guessing on access ports and then present all the vlans to us on a dot1q trunk. Im not sure if I can use QinQ and only the connection from us to the provider is trunked the sites connect into the provider on acces ports.




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