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CLI-based Configuration Guide - Ethernet Switching

AR650, AR1600, and AR6100 V300R003

This document describes how to configure the components for LAN services, including link aggregation groups, VLANs, voice VLANs, MAC address tables, transparent bridging, as well as GVRP, STP/RSTP, and MSTP protocols.
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QinQ Fundamentals

QinQ Fundamentals

QinQ expands VLAN space by adding an additional 802.1Q VLAN tag to an 802.1Q-tagged packet. Devices forward packets over the public network according to outer VLAN tags of the packets, and learn MAC addresses from the outer VLAN tags. The private VLAN tags in the packets are forwarded as payload of the packets.

QinQ Packet Encapsulation Format

A QinQ packet has a fixed format, in which an 802.1Q tag is added outside the existing 802.1Q tag of the packet. A QinQ packet has 4 more bytes than an 802.1Q packet.

Figure 7-1  802.1Q encapsulation

QinQ Encapsulation

QinQ encapsulation changes a single-tagged packet into a double-tagged packet.

QinQ encapsulation falls into basic QinQ and selective QinQ depending on the data encapsulated. Basic QinQ refers to interface-based QinQ, and selective QinQ includes VLAN ID-based QinQ and 802.1p priority-based QinQ.

  • Interface-based QinQ encapsulation

    This encapsulation mode is also called QinQ tunneling. It encapsulates packets arriving at the same interface with the same outer VLAN tag, and therefore cannot distinguish users and services at the same time.

  • VLAN ID-based QinQ encapsulation

    This encapsulation mode determines whether to add outer VLAN tags and which outer VLAN tags to add based on data flows.

    Traffic can be classified based on VLAN ID ranges if a customer uses different VLAN IDs for different services. For example, PC users access the Internet through VLANs 101 to 200, IPTV users through VLANs 201 to 300, and VoIP users through VLANs 301 to 400. When receiving service data, the underlayer provider edge (UPE) adds outer tag 100 to packets from PCs, outer tag 300 to packets from IPTV users, and outer tag 500 to packets from VoIP users.

  • 802.1p priority-based QinQ encapsulation

    This encapsulation mode determines whether to add outer VLAN tag and which outer VLAN tags to add based on priorities of data flows.

    For example, when different services of a user have different priorities, these services can be transmitted over different data channels based on priorities.

QinQ Implementation

QinQ can be implemented in either of the following ways:

  1. Basic QinQ
    Basic QinQ is implemented based on interfaces. After basic QinQ is configured on an interface, the device adds the default VLAN tag of this interface to all packets regardless of whether the packets carry VLAN tags.
    • If a single-tagged packet is received, the packet becomes a double-tagged packet.
    • If an untagged packet is received, the packet is tagged with the default VLAN ID of the local interface.
  2. Selective QinQ
    Selective QinQ is implemented based on interfaces and VLAN IDs. That is, an interface can forward packets based on a single VLAN tag or double VLAN tags. In addition, the device processes packets received on an interface as follows based on their VLAN IDs:
    • Adds different outer VLAN tags to packets carrying different inner VLAN IDs.
    • Marks outer 802.1p fields and adds different outer VLAN tags to packets according to the 802.1p fields in inner VLAN tags.

    In addition to separating carrier and customer networks, selective QinQ provides extensive service features and allows flexible networking.

QinQ/Dot1q VLAN Tag Termination Sub-interface

Termination removes the single or double tags from packets before the packets are sent.

Different termination modes are used in different situations when QinQ technology is applied to an MPLS/IP core network.

QinQ VLAN tag termination sub-interfaces provide different functions in different scenarios.

Updated: 2019-04-12

Document ID: EDOC1100041791

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