Operation Manual – QinQH3C S7500 Series Ethernet Switches Chapter 1 QinQ Configuration1-1Chapter 1 QinQ Configuration1.1 QinQ Overview1.1.1 Introduction to QinQThe QinQ function enables packets to be transmitted across the operators’ backbonenetworks with VLAN tags of private networks encapsulated in those of public networks.In public networks, packets of this type are transmitted by their outer VLAN tags (that is,the VLAN tags of public networks). And those of private networks which areencapsulated in the VLAN tags of public networks are shielded.Figure 1-1 illustrates the structure of a single-tagged packet.Destination MAC address0 31DataSource MAC address15VLAN TagFigure 1-1 Structure of a single-tagged packetFigure 1-2 illustrates the structure of a double-tagged packet.Destination MAC address0 31DataSource MAC address15Inner VLAN TagOuter VLAN TagFigure 1-2 Structure of a double-tagged packetCompared with MPLS-based Layer 2 VPN, QinQ has the following features:z It provides simpler Layer 2 VPN tunnels.z QinQ can be implemented through static configurations only, without the supportof signaling protocols.The QinQ function provides you with the following benefits:z Saves public network VLAN ID resources.
