Chapter 1 Qinq Configuration; Introduction To Qinq; Understanding Qinq - H3C S5500-SI Series Operation Manual

Operation Manual – QinQ-BPDU TUNNEL
H3C S5500-SI Series Ethernet Switches

Chapter 1 QinQ Configuration

When configuring QinQ, go to these sections for information you are interested in:

Introduction to QinQ

Configuring Basic QinQ
Configuring Selective QinQ
Configuring the TPID Value to Be Carried in VLAN Tags
QinQ Configuration Example
1.1 Introduction to QinQ
In the VLAN tag field defined in IEEE 802.1Q, only 12 bits are used for VLAN IDs, so a
switch can support a maximum of 4,094 VLANs. In actual applications, however, a
large number of VLANs are required to isolate users, especially in metropolitan area
networks (MANs), and 4,094 VLANs are far from satisfying such requirements.

1.1.1 Understanding QinQ

The port QinQ feature is a flexible, easy-to-implement Layer 2 VPN technique, which
enables the access point to encapsulate an outer VLAN tag in Ethernet frames from
customer networks (private networks), so that the Ethernet frames will travel across the
service provider's backbone network (public network) with double VLAN tags. The
inner VLAN tag is the customer network VLAN tag while the outer one is the VLAN tag
assigned by the service provider to the customer. In the public network, frames are
forwarded based on the outer VLAN tag only, with the source MAC address learned as
a MAC address table entry for the VLAN indicated by the outer tag, while the customer
network VLAN tag is transmitted as part of the data in the frames.
Figure 1-1
The QinQ feature enables a device to support up to 4,094 x 4,094 VLANs to satisfy the
requirement for the amount of VLANs in the MAN.
Figure 1-1 Single-tagged frame structure vs. double-tagged Ethernet frame structure
shows the structure of 802.1Q-tagged and double-tagged Ethernet frames.
1-1
Chapter 1 QinQ Configuration