H3C Technologies H3C WX3000 Series Unified Switches - Manual (Page 573)

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1) As GigabitEthernet 1/0/11 of Switch A is a VLAN-VPN port, when a packet from the customer’s
network side reaches this port, it is tagged with the default VLAN tag of the port (VLAN 1040).
2) The device sets the TPID value for the outer VLAN tags of packets to user-defined value 0x9200
and then forwards these packets to the public network through the VLAN-VPN uplink port
GigabitEthernet 1/0/12.
3) The outer VLAN tag of the packet remains unchanged while the packet travels in the public network,
till it reaches GigabitEthernet 1/0/22 of Switch B.
4) After the packet reaches Switch B, it is forwarded to GigabitEthernet 1/0/21 of Switch B. As the port
belongs to VLAN 1040 and is an access port, the outer VLAN tag (the tag of VLAN 1040) of the
packet is removed before the packet is forwarded, which restores the packet to a packet tagged
with only the private VLAN tag and enables it to be forwarded to its destination networks.
5) It is the same case when a packet travels from Switch B to Switch A.