1.15.1 Configuration Information:
On PE1:
#
Vsi test static
Pwsignal ldp
Vsi-id 1
Peer 111.111.111.111
#
Interface GigabitEthernet2/0/16.1
Vlan-stacking vlan 16 stack-vlan 17 (V1R6, V2R1 command line changed to qinq stacking vid 16 pe-vid 17)
L2 binding vsi test
#
On PE2:
#
Vsi test static
Pwsignal ldp
Vsi-id 1
Peer 90.90.90.90
#
#
Interface GigabitEthernet4/0/16.1
Vlan-stacking vlan 19 stack-vlan 20 (V1R6, V2R1 command line changed to qinq stacking vid 19 pe-vid 20)
L2 binding vsi test
#
1.15.2 Packets Entering the Tunnel:
The VLAN encapsulated by the packet sent by CE1 is 16:

After receiving the packet, PE1 adds a VLAN to the original packet. The value is the stack vlan configured on the port, which is 17 and then encapsulates the MPLS label information and forwards it to PE2:

If the packet received by PE1 is a two-layer VLAN, the VLAN will be added. If the received packet does not have a VLAN or the VLAN ID is inconsistent, it will be discarded.
1.15.3 Packets Out of Tunnel:
After receiving the packet from PE1, PE2 strips the MPLS label information, and then removes the outer VLAN of the original packet and restores the original packet sent by CE1 to CE2.

1.15.4 Supplementary notes:
The implementation of each version is the same.
On PE1:
#
Vsi test static
Pwsignal ldp
Vsi-id 1
Peer 111.111.111.111
#
Interface GigabitEthernet2/0/16.1
Vlan-stacking vlan 16 stack-vlan 17 (V1R6, V2R1 command line changed to qinq stacking vid 16 pe-vid 17)
L2 binding vsi test
#
On PE2:
#
Vsi test static
Pwsignal ldp
Vsi-id 1
Peer 90.90.90.90
#
#
Interface GigabitEthernet4/0/16.1
Vlan-stacking vlan 19 stack-vlan 20 (V1R6, V2R1 command line changed to qinq stacking vid 19 pe-vid 20)
L2 binding vsi test
#
1.15.2 Packets Entering the Tunnel:
The VLAN encapsulated by the packet sent by CE1 is 16:

After receiving the packet, PE1 adds a VLAN to the original packet. The value is the stack vlan configured on the port, which is 17 and then encapsulates the MPLS label information and forwards it to PE2:

If the packet received by PE1 is a two-layer VLAN, the VLAN will be added. If the received packet does not have a VLAN or the VLAN ID is inconsistent, it will be discarded.
1.15.3 Packets Out of Tunnel:
After receiving the packet from PE1, PE2 strips the MPLS label information, and then removes the outer VLAN of the original packet and restores the original packet sent by CE1 to CE2.

1.15.4 Supplementary notes:
The implementation of each version is the same.
The summary of Handling of VLANs in Packets in Various Versions of L2VPN Configurations .http://forum.huawei.com/enterprise/en/forum.php?mod=viewthread&tid=453137