QinQ over tagged provider link (MTU=1504)-would this work?

[cristip]

Hi all

I am trying to understand if this is possible. Any help would be much appreciated.

I am planning to use a pair of Catalyst 3750 for QinQ over a L2 link (lan extension)

We neeed to have control over what vlans we propagate over this link and we want to avoid incuring costs for every aditional vlan we might need to add to the trunk that would connect to the QinQ provider switches

Our workaround for this would be to ask the provider to give us an end to end vlan that supports MTU-1504B (QinQ frame size) and connect our switches to this. Would this work ? Do you see any problems with this ?

thaks

Cristi

[Giuseppe Larosa]

Hello Cristi,

with the correct MTU  the setup will work giving you the desired flexibility in term of internal Vlans carried over the link.

In a case like this I would look at OSI layer 2 MTU that is 1526 = 1500 + 18 + 2*4  bytes

including all the overhead and the 4 byte FCS this is what has to pass over the provider link.

It shouldn't be a problem for the provider to give you this MTU

Hope to help

Giuseppe