Summary of QinQ Configuration Tasks

This section describes the QinQ features supported by the NetEngine 8000 F in terms of the QinQ configuration.

The QinQ configuration is described as follows:

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. If selective QinQ is configured, the device can add different outer VLAN tags to packets and transmit the packets.
QinQ supports the following features that meet different configuration requirements:
- Configuring QinQ-based VLAN tag swapping: The device can swap the inner tag with the outer tag in a double-tagged packet.
- Configuring QinQ mapping: The device can map the user VLAN ID in a packet to a carrier VLAN ID.
- Configuring VLAN tag termination sub-interfaces to transmit IP services: Proxy Address Resolution Protocol (ARP), Dynamic Host Configuration Protocol (DHCP) (DHCP server/DHCP relay), and Virtual Router Redundancy Protocol (VRRP) can be configured on sub-interfaces for QinQ/dot1q VLAN tag termination.
- Configuring VLAN tag termination sub-interfaces to transmit virtual private network (VPN) services: The L2VPN (VPWS/VPLS) and L3VPN can be configured on sub-interfaces for QinQ/dot1q VLAN tag termination.
- Configuring QinQ VLAN tag termination sub-interfaces to support 802.1p mappings: The mappings include the 802.1p-to-DSCP mapping and 802.1p-to-MPLS-EXP mapping.
- Configuring L2VPN access on QinQ stacking sub-interfaces: With this configuration, QinQ stacking sub-interfaces can implement L2VPN (VPWS/VPLS).
QinQ stacking sub-interfaces can be used to solve the problem that one physical interface cannot provide L2VPN access for multiple users.

Access Services Provided by VLAN Tag Termination Sub-Interfaces

Sub-interfaces for QinQ/dot1q VLAN tag termination support IP services (for example, proxy ARP, DHCP, and VRRP), VPN services (for example, L2VPN and L3VPN), 802.1p-to-DSCP mapping, and 802.1p-to-MPLS-EXP mapping. Table 1 shows the application scenario of a VLAN tag termination sub-interface providing access services.

**Table 1** Application scenario of VLAN tag termination sub-interfaces providing access services
Sub-Interface Type	Service Type	Application Scenario
QinQ/Dot1q	Proxy ARP	If users on the same network segment belong to different VLANs, they cannot communicate at Layer 2. To implement communication between VLANs at Layer 3, proxy ARP can be enabled on VLAN tag termination sub-interfaces. For details about proxy ARP, see the chapter "ARP" in the NetEngine 8000 F Feature Description - IP Services.
	DHCP DHCP relay	If the DHCP client and DHCP server belong to different sub-nets, you need to deploy a DHCP relay agent to forward DHCP request packets from the client to the server so that the client can dynamically obtain IP addresses from the DHCP server. DHCP relay can be configured on the VLAN tag termination sub-interface to insert tag information into Option82. The tag information provides a reference for the DHCP server in IP address allocation. For details about DHCP, see the chapter "DHCP" in the NetEngine 8000 F Feature Description - IP Services.
	VRRP	When a VLAN tag termination sub-interface is used to access a VRRP-enabled, this sub-interface also needs to be enabled with VRRP to ensure reliable and stable communication. For details about VRRP, see the chapter "VRRP" in the NetEngine 8000 F Feature Description - Reliability.
	L2VPN Virtual private wire service (VPWS) Virtual private LAN service (VPLS)	When a VLAN tag termination sub-interface is used to access a L2VPN network, this sub-interface needs to be bound to a Virtual Switching Instance (VSI) or virtual private wire service (VPWS) to enable Layer 2 communication. For details about L2VPN, see the chapters "VPWS" and "VPLS" in the NetEngine 8000 F Feature Description - VPN.
	L3VPN	When a VLAN tag termination sub-interface is used to access an L3VPN network, this sub-interface needs to be bound to a VPN instance to enable Layer 3 communication. For details about L3VPN, see the chapter "BGP/MPLS IP VPN" in the NetEngine 8000 F Feature Description - VPN.
QinQ	802.1p, DiffServ Code Point (DSCP) remark	After a packet is terminated on a PE, the packet is sent to the carrier network. To ensure the completeness of the QoS information in the packet, the 802.1p values in the outer and inner tags need to be mapped to the DSCP remark field.
QinQ	802.1p, EXP (MPLS) remark	After a packet is terminated on a PE, the packet is sent to the carrier MPLS network. To ensure the completeness of the QoS information in the packet, the 802.1p values in the outer and inner tags need to be mapped to the MPLS EXP field.

Figure 1 shows how to configure sub-interfaces for QinQ/dot1q VLAN tag termination.

Figure 1 Flowchart of configuring sub-interfaces for QinQ/dot1q VLAN tag termination

Differences Between the VLAN Tag Termination Sub-Interface and Dot1q Sub-Interface

Table 2 shows the differences between the VLAN tag termination sub-interface and dot1q sub-interface.

**Table 2** Differences between interfaces
Interface Type	Supported VPN Service				Description	Difference
Interface Type	VPWS (CCC mode)	VPWS	VPLS	L3VPN	Description	Difference
Dot1q sub-interface	Supported	Supported	Supported	Supported	You can run the vlan-type dot1q command to configure an Ethernet sub-interface to be a dot1q sub-interface.	The dot1q sub-interface and dot1q VLAN tag termination sub-interface have the same function. The difference between them is that packets sent from the dot1q sub-interface are encapsulated with only one VLAN tag whereas packets sent from the dot1q VLAN tag termination sub-interface can be encapsulated with multiple VLAN tags. You can configure both dot1q VLAN tag termination sub-interfaces and QinQ VLAN tag termination sub-interfaces on a main interface. With this configuration, the main interface can terminate both single-tagged packets and double-tagged packets. You can configure a dot1q VLAN tag termination sub-interface or a dot1q sub-interface on a main interface to terminate single-tagged packets.
Dot1q VLAN tag termination sub-interface	Supported	Supported	Supported	Supported	You can run the dot1q termination vid command to configure a dot1q VLAN tag termination sub-interface to terminate single-tagged packets. NOTE: VPWS The VLAN tag to be terminated must be a specific value. VPLS The VLAN tag to be terminated can be either a specific value or a value range.
QinQ VLAN tag termination sub-interface	Supported	Supported	Supported	Supported	You can run the qinq termination pe-vid ce-vid command to configure a QinQ VLAN tag termination sub-interface to terminate double-tagged packets. NOTE: VPWS In asymmetrical mode, both VLAN tags to be terminated must be specific values. In symmetrical mode, the outer VLAN tag to be terminated must be a specific value, but the inner VLAN tag to be terminated can be either a specific value or value range. VPLS In asymmetrical mode, both VLAN tags to be terminated can be either specific values or value ranges. In symmetrical mode, the outer VLAN tag to be terminated must be a specific value, but the inner VLAN tag to be terminated can be either a specific value or value range. You can run the qinq termination l2 command to configure the asymmetrical or symmetrical mode.

Table 3 and Table 4 show how different types of interfaces process VLAN tags carried in packets to be transmitted across a VPLS network.

**Table 3** Packet processing on an inbound interface
Inbound Interface Type	Packet Processing for VPLS Network Access
Inbound Interface Type	Ethernet-Encapsulated Packets	VLAN-Encapsulated Packets
Dot1q sub-interface	Tags are stripped.	No action is performed.
Dot1q VLAN tag termination sub-interface	Tags are stripped.	No action is performed.
QinQ VLAN tag termination sub-interface	In symmetric mode, the outer tags are stripped. In asymmetric mode, both inner and outer tags are stripped.	In symmetric mode, no action is performed. In asymmetric mode, both inner and outer tags are stripped and then a different tag is added.
QinQ stacking sub-interface	The outer tag is added.	The outer tag is added.
QinQ mapping sub-interface	The outer tag is replaced.	The outer tag is replaced.

**Table 4** Packet processing on an outbound interface
Outbound Interface Type	Packet Processing for VPLS Network Access
Outbound Interface Type	Ethernet-Encapsulated Packets	VLAN-Encapsulated Packets
Dot1q sub-interface	A specific tag is added.	The tag is replaced.
Dot1q VLAN tag termination sub-interface	A specific tag is added.	The tag is replaced.
QinQ VLAN tag termination sub-interface	In symmetric mode, outer tags are added. In asymmetric mode, both inner and outer tags are added.	In symmetric mode, outer tags are replaced. In asymmetric mode, one tag is stripped and both inner and outer tags are added.
QinQ stacking sub-interface	The outer tag is stripped.	The outer tag is stripped.
QinQ mapping sub-interface	The outer tag is replaced.	The outer tag is replaced.

To configure VLAN encapsulation or Ethernet encapsulation, run the encapsulation (VSI view) command.

VLAN encapsulation

Each Ethernet frame transmitted between CEs and PEs carries a VLAN tag called a Provider-Tag (P-tag). The tag is a service delimiter required by a carrier for user differentiation.
Ethernet encapsulation

Ethernet frames transmitted between CEs and PEs do not necessarily carry VLAN tags. If an Ethernet frame carries a VLAN tag, the tag is an internal VLAN tag called a User-Tag (U-tag) in user packets. The U-tag is carried in a packet before the packet is sent to a CE. The U-tag is used by the CE to identify the packet, but PEs do not recognize U-tags.

By default, the encapsulation type is VLAN.