802.1Q-in-802.1Q (QinQ) is a technology that addresses the shortage of public VLAN ID resources. This technology applies to a number of services in metropolitan area network (MAN) implementation.
The 802.1Q-in-802.1Q (QinQ) technology improves the utilization of VLANs by adding another 802.1Q tag to tagged packets. This technology enables services from private VLANs to be transparently transmitted over the public network. Packets transmitted on the backbone network carry two 802.1Q tags: a public VLAN tag and a private VLAN tag.
A QinQ-enabled device is capable of virtual local area network (VLAN) stacking, which expands VLAN space and reduces the consumption of VLAN ID resources.
This section describes how to configure QinQ-based virtual local area network (VLAN) tag swapping. This configuration enables a device to swap the inner tag with the outer tag in a double-tagged packet. QinQ-based VLAN tag swapping applies only on double-tagged packets.
IP services include proxy Address Resolution Protocol (ARP), Virtual Router Redundancy Protocol (VRRP), and Dynamic Host Configuration Protocol (DHCP) services. You can deploy IP services on QinQ/dot1q VLAN tag termination sub-interfaces so that users in different VLANs can communicate. This ensures non-stop and reliable connections between the users and the network.
Virtual private network (VPN) services are classified into L2VPN services and L3VPN services. You can configure VLAN tag termination sub-interfaces on the PEs to connect VPNs to enable the interworking between the CEs and users.
With the wide use of multicast services on the Internet, you need to deploy sub-interfaces for QinQ/dot1q VLAN tag termination to process the user packets carrying a single tag or double tags for multicast services. In this manner, the UPE can maintain information about the outbound interface of multicast packets according to the established multicast forwarding table to ensure the normal communications between hosts and the multicast source.
After tags are terminated on the PEs, packets are sent to the carrier IP or MPLS network. To ensure inclusion of all the required Quality of Service (QoS) information in the packets, the 802.1p values in outer and inner tags must be mapped to the DSCP fields or the EXP fields.
To enable a physical interface to provide multiple users with access to an L2VPN, configure a QinQ stacking sub-interface and bind it to a VSI or L2VC.
When VLAN users access an IP core network through a BRAS, the IP core network cannot identify users' VLAN tags. In this situation, configure a user-VLAN sub-interface on the BRAS to remove the VLAN tags carried in the user VLAN packets.
This section describes the QinQ application details, including networking requirements, configuration roadmap, and data preparation, and provides related configuration files.