Reference Links: https://blog.csdn.net/alone_map/article/details/52217094
This paper records the use of Huawei eNSP simulator configured to implement QinQ, and simple analysis QinQ packet.
QinQ Description: QinQ technology (also known as Stacked VLAN or Double VLAN ) refers to the private network VLAN tag is encapsulated in the public network VLAN tag, the packet with two VLAN tags through the operator's backbone network, the public network the only outer VLAN tag communication, private network VLAN tag is shielded, so that not only a distinction between data streams, and because the private VLAN tag is transmitted transparently different user VLAN tags can be reused, only the outer VLAN tag in the only public network it can, in fact, expanded the available VLAN number of labels. QinQ criteria IEEE802.1ad ( IEEE802.1ad stands for : Virtual Bridged Local Area Networks Amendment 4: Provider Bridges ). - From "In the road network - exchange topic"
Simply put, that is, two dozen packets vlan tag, aims to increase the number of available vlan.
QinQ encapsulation format is as follows:
QinQ packet format is as follows:
Here is QinQ Huawei eNSP simulator test, the topology is as follows:
The specific configuration is as follows:
1、PC1和PC3属于vlan2，PC2和PC4属于vlan3，它们的IP地址分别为：PC1：192.168.0.10，PC2：192.168.0.20，PC3：192.168.0.30，PC4：192.168.0.40
2、LSW1和LSW2作为主干网络（ISP网络），从LSW1的GE 0/0/1和LSW2的GE 0/0/2端口进入的报文会被打上外层标签（vlan10）这两个端口的配置是一样的，以LSW1的GE 0/0/1端口的配置为例进行举例：
[Huawei-GigabitEthernet0/0/1]port link-type dot1q-tunnel
[Huawei-GigabitEthernet0/0/1]port default vlan 10
3、LSW1的GE 0/0/2和LSW2的GE 0/0/1端口用于ISP网络内部通信，配置为trunk模式，这两个端口的配置是一样的，以LSW1的GE 0/0/1端口的配置为例进行举例：
[Huawei-GigabitEthernet0/0/1]port link-type trunk
[Huawei-GigabitEthernet0/0/1]port trunk allow-pass all
4、LSW3和LSW4用于局域网通信和连接到ISP网络，其中LSW3的Ethernet 0/0/1和Ethernet 0/0/2端口模式为access，GE 0/0/3为trunk，配置如下：
[Huawei-GigabitEthernet0/0/1]port link-type access
[Huawei-GigabitEthernet0/0/1]port default vlan 3
[Huawei-GigabitEthernet0/0/2]port link-type access
[Huawei-GigabitEthernet0/0/2]port default vlan 3
[Huawei-GigabitEthernet0/0/3]port link-type trunk
[Huawei-GigabitEthernet0/0/3]port trunk allow-pass vlan all
LSW4的配置和LSW3的配置一样，就不写出来了。
实验现象：
PC1 ping PC3可以ping通。
PC2 ping PC4可以ping通。
PC3 ping PC1可以ping通。
PC4 ping PC2可以ping 通。
下面我们在LSW1上抓个报文来分析以下报文的格式。
