Hi, everyone! Today I’m going to introduce you VLAN Stacking Sub-interface Accesses VSI and Ethernet Encapsulation.
1.16.1 Configuration Information:
On PE1;#
Vsi test static
Pwsignal ldp
Vsi-id 1
Peer 111.111.111.111
Encapsulation ethernet
#
Interface GigabitEthernet2/0/16.1
Qinq stacking vid 16 pe-vid 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
Encapsulation ethernet
#
Interface GigabitEthernet4/0/16.1
Qinq stacking vid 19 pe-vid 20 (V1R6, V2R1 command line changed to qinq stacking vid 19 pe-vid 20)
L2 binding vsi test
#
1.16.2 Packets Entering the Tunnel:
The VLAN encapsulated by the packet sent by CE1 is 16:

After receiving the packet, PE1 does not add a layer of VLANs based on the original packet. Instead, it directly encapsulates the MPLS label and other information, and then forwards it to PE2:

If the packets received by PE1 do not carry a VLAN or have a VLAN, but the VLAN ID is inconsistent with the configuration on the interface, the packets are discarded. If the packets received by PE1 are in the same VLAN, the configuration of the outer VLAN is the same as that of the single-layer VLAN.
1.16.3 Packets Out of Tunnel:
After receiving the packet, PE2 strips the MPLS label and other information to the original packet sent by CE1 and forwards it to CE2:

1.16.4 Supplementary notes:
The V1R2 version does not support the binding of the VSI to the VLAN stacking sub-interface. The V1R3 version supports the V1R3 version.
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
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