Overview
802.1Q-in-802.1Q (QinQ) adds an 802.1Q tag to 802.1Q tagged customer traffic. It enables a service provider to extend Layer 2 connections across an Ethernet network between customer sites.
QinQ provides the following benefits:
Enables a service provider to use a single SVLAN to convey multiple CVLANs for a customer.
Enables customers to plan CVLANs without conflicting with SVLANs.
Enables customers to keep their VLAN assignment schemes unchanged when the service provider changes its VLAN assignment scheme.
Allows customers to use overlapping CVLAN IDs. Devices in the service provider network make forwarding decisions based on SVLAN IDs instead of CVLAN IDs.