H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – QinQ-BPDU Tunneling
H3C S7500E Series Ethernet Switches Chapter 1 QinQ Configuration
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Chapter 1 QinQ Configuration
When configuring QinQ, go to these sections for information you are interested in:
z Introduction to QinQ
z Configuring Basic QinQ
z Configuring Selective QinQ
z Configuring the TPID of a VLAN Tag
z QinQ Configuration Example
1.1 Introduction to QinQ
1.1.1 Understanding 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 VLAN are required to isolate users, especially in metropolitan area
networks (MANs), and 4,094 VLANs are far from satisfying such requirements.
QinQ provided by the S7500E series 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 shows the structure of a double-tagged Ethernet frame. The QinQ feature
enables a switch 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