QinQ – 802.1Q–in-802.1Q
“Q-in-Q” also known as “dot1q tunneling” or “VLAN stacking” or “double VLAN” is a technique used in Metro-Ethernet networks to encapsulated 802.1Q tagged packets by adding an additional 802.1Q tag hence the name “QinQ“.
QinQ enables packets with double VLAN tags to traverse the backbone network (service provider network) of a carrier, so as to expand VLAN space and implement refined user management. By using a different VLAN tag (Service VLAN or S-VLAN) for each customer we can separate the traffic from different customers and also transparently transfer it throughout the service provider network.
