Basic QinQ

Basic QinQ, also called QinQ tunneling, is performed based on interfaces. After basic QinQ is configured on an interface, packets received by the interface are tagged with the default VLAN ID of the interface. After being processed by basic QinQ on an interface, single-tagged packets change into double-tagged packets, and untagged packets change into single-tagged packets with the default VLAN tag of the interface.

Basic QinQ can be configured to expand VLAN space when multiple VLANs are required.

As shown in Figure 1, Department 1 has two offices (both connected to PE1), and Department 2 has three offices (one connected to PE1 and two connected to PE2). Each department is free to plan its own VLANs.

Figure 1 Networking diagram for basic QinQ

Table 1 provides the outer VLAN plan for Department 1 and Department 2.

**Table 1** VLAN plan for Department 1 and Department 2
Department	VLAN ID Range	Outer VLAN ID
Department 1	2 to 500	10
Department 2	500 to 4094	20

Basic QinQ is configured on PE1 and PE2 in the following way to implement communication within each department and isolate the two departments:

PE1 adds outer VLAN 10 to packets received on Port1 and Port2, and outer VLAN 20 to packets received on Port3.
PE2 adds outer VLAN 20 to packets received on Port1 and Port2.
Port4 on PE1 and Port3 on PE2 allow packets of VLAN 20 to pass.