In QinQ, you need to configure the mode of the port as hybrid. A scheme like that :
Networking Requirements
As shown in Figure, A users and B users connect to the carrier network through Switch LSW0 and Switch LSW1 and communicate with each other through the carrier network.
It is required that packets of A user and B user terminals are tagged VLAN 2 and VLAN 3 when the packets are transmitted through the carrier network.
the configuration are below:
LSW2 & LSW3:
#
interface GigabitEthernet0/0/1
port link-type access
port default vlan 20
#
interface GigabitEthernet0/0/2
port link-type trunk
port trunk allow-pass vlan 20 30
#
interface GigabitEthernet0/0/3
port link-type access
port default vlan 30
#
LSW0 & LSW1:
#
interface GigabitEthernet0/0/1
port link-type trunk
port trunk allow-pass vlan 2 to 3
#
interface GigabitEthernet0/0/2
port link-type hybrid
qinq vlan-translation enable
port hybrid untagged vlan 2 to 3
port vlan-stacking vlan 20 stack-vlan 2
port vlan-stacking vlan 30 stack-vlan 3
#
So in this scheme, port G0/0/2 in LSW0 and LSW1 have to config as hybrid mode to untagged more than one vlan when the packets output from the port.