TPID

The Tag Protocol Identifier (TPID) specifies the protocol type of a VLAN tag. The TPID value defined in IEEE 802.1Q is 0x8100.

Figure 6-3 shows the Ethernet packet format defined in IEEE 802.1Q. An IEEE 802.1Q tag lies between the Source Address field and the Length/Type field. A device determines whether packets carry the specified VLAN tag according to the TPID. When an interface receives a packet, the device compares the configured TPID with that in the packet. If they are the same, the packet carries the VLAN tag. If they are different, the packet does not carry the VLAN tag.

Figure 6-3 802.1Q encapsulation

To implement interoperation between QinQ-capable devices of different vendors, devices of different vendors use 0x8100 as the inner TPID value but may use different outer TPID values. You can set the TPID value in outgoing QinQ packets sent from Huawei devices to the TPID value used by non-Huawei devices so that the Huawei and non-Huawei devices can communicate.