Configuration：<?xml:namespace prefix = "o" ns = "urn:schemas-microsoft-com:office:office" />
the VSI configuration of PE1：

#

vsi teststatic

 pwsignal ldp

  vsi-id 1

  peer 111.111.111.111

#

interfaceVlanif16

 l2 binding vsi test

#

the VSI configuration of PE2：
#

vsi teststatic

 pwsignal ldp

  vsi-id 1

  peer 90.90.90.90

 #

interfaceVlanif18

 l2 binding vsi test

#
 
 
 
 
 

  Message into the tunnel:

Send a VLAN 16 packet from CE1:

   

figure 1

Because the VSI is a VLAN encapsulation mode, when a tunnel is entered, the VLAN in the original packet is forwarded to the peer PE2. The packet received on the peer PE2 is as follows:

 

figure 2

As you can see from the packet capture above, when the packet enters the tunnel, the original packet is still intact, and a layer of source/destination MAC, PW-side VLAN, and two-layer label are encapsulated.

If the packet sent by CE1 carries two layers of tag, it will not modify the VLAN information in the packet, but directly encapsulates the MPLS information.

1.1.3 packets out of the tunnel:

After PE2 receives an MPLS packet, PE2 must decapsulate the packet and bind the VLAN 16 cost offset in the original packet to the VLAN corresponding to the VLANIF of the VSI. The other contents are the same as the original packet:

 

Figure 3

If the packet sent by CE1 carries a double-tag, PE2 modifies the outer VLAN information of the original packet to the VLAN corresponding to the VLANIF of the local VSI. The other contents are the same as those of the original packet.

1.1.4 Supplementary explanation:

For applications where VSI is bound to VLANIF, no matter how the corresponding physical port is added to the VLAN, the packets on the CE side must all have the same VLAN. Otherwise, the packets cannot be forwarded by VPLS and will be discarded. And each version has this requirement.  

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