can someone explain to me, how to configure QinQ on 6509 with Sup720, WS-X6748 with IOS 12.2(18)SXE6a.
I'm not shure, but I think there is something missing in the cisco-docs.
I found that I have to set the "switchport mode" to dot1q-tunnel, but how does the switch know where the "tunnel" starts and where it ends?
switchport mode do1tq-tunnel
switchport access-vlan 10
On the ingress and egress interfaces on the switches.
Make sure to allow vlan 10 on the 802.1q trunks.
The external Vlans will not be known to your switches. Your switches only care about Vlan 10.
A configuration example is provided in the Cat6500 QinQ configuration.
I don't have the hardware to do a customer duplication example, per your config.