I have a question related to the attached scratch.
It's my intention to transport all VLANs (which are part of a dot1q-trunk) from the lefthand side to the righthand side and vice versa. The outer VLAN has only local relevance between the switch access port and the VLAN subinterface on the router. It is not necessary to transport the full QinQ traffic (including the outer VLAN) via the L2TPv3 tunnel. Customer VLANs must remain from end to end.
I'm not sure if the outer VLAN ID 200 (from the left) will be encapsulated in the L2TPv3 tunnel. In this case, on the other end of the tunnel, the same VLAN ID would be necessary. But in general, I would prefer "encapsulation dot1q 200 second-dot1q any".
This would lead to QinQ via L2TPv3 and only a few devices support this feature.
