Operation Manual – QinQ-BPDU TunnelingH3C S7500E Series Ethernet Switches Chapter 1 QinQ Configuration1-2Advantages of QinQ:z Addresses the shortage of public VLAN ID resourcez Enables customers to plan their own VLAN IDs, with running into conflicts withpublic network VLAN IDs.z Provides an easy-to-do Layer 2 VPN solution for small-sized MANs or intranets.Note:The QinQ feature requires configurations only on the service provider network, and noton the customer network.1.1.2 Implementations of QinQThere are two types of QinQ implementations: basic QinQ and selective QinQ.1) Basic QinQBasic QinQ is a port-based feature, which is implemented through VLAN VPN.With the VLAN VPN feature enabled on a port, when a frame arrives on the port, theswitch will tag it with the port’s default VLAN tag, regardless of whether the frame istagged or untagged. If the received frame is already tagged, this frame becomes adouble-tagged frame; if it is an untagged frame, it is tagged with the port’s default VLANtag.2) Selective QinQSelective QinQ is an implementation more flexible than basic QinQ. In addition to all thefunctions of basic QinQ, selective QinQ can tag frames with different outer VLAN tagsbased on their inner VLAN IDs.The S7500E series implements selective QinQ by using customer VLAN IDs as matchcriteria to classify frames and then tagging the frames that match a certain VLAN IDwith the outer VLAN tag defined in the associated traffic behavior.1.1.3 Modification of the TPID Value in VLAN TagsA VLAN tag uses the tag protocol identifier (TPID) field to identify the protocol type ofthe tag. The value of this field, as defined in IEEE 802.1Q, is 0x8100.Figure 1-2 shows the 802.1Q-defined tag structure of an Ethernet frame.
