3Com Switch 7750 Configuration Guide

160 CHAPTER 19: QINQ CONFIGURATION
■ Saves public network VLAN ID resource.
■ You can have VLAN IDs of your own, which is independent of public network
VLAN IDs.
■ Provides simple Layer 2 VPN solutions for small-sized MANs or intranets.
Implementation of QinQ QinQ can be implemented by enabling the QinQ function on ports.
With the QinQ function enabled for a port, the switch will tag a received packet
with the default VLAN tag of the receiving port no matter whether or not the
packet already carries a VLAN tag, and the switch will learn the source MAC
address of the packet into the MAC address table of the default VLAN. If the
packet already carries a VLAN tag, the packet becomes a dual-tagged packet.
Otherwise, the packet becomes a packet carrying the default VLAN tag of the
port.
Inner-to-Outer Tag
Priority Mapping
As shown in Figure 45, IEEE 802.1Q defines the structure of tagged packets in
Ethernet frames:
Figure 45 The structure of tagged packets of Ethernet frames
The user priority field is the 802.1p priority of the tag. This 3-bit field is in the
range of 0 to 7. Through configuring inner-to-outer tag priority mapping for a
QinQ-enabled port, you can assign different priority for the outer tag of a packet
according to its inner tag priority.
Refer to “Setting Port Priority” on page 666 for the detailed configurations about
priority mapping.
QinQ Configuration
Configuration
Prerequisites
Make sure that Voice VLAN is not enabled for the port where QinQ is to be
enabled. The QinQ feature is mutually exclusive with the Voice VLAN feature.
n
BPDU tunnel is a specific application of the QinQ feature. The BPDU tunnel feature
uses the vlan-vpn tunnel command to transmit the customers’ MSTP packets
transparently through the service provider’s network. Refer to “BPDU Tunnel
Configuration” on page 272.
Configuration Procedure
User Priority CFI
DA SA VLAN Tag Etype DATA FCS
TPID VLAN ID
6bytes 6bytes 4bytes
2bytes 3bits 1bit 12bits
4bytes2bytes 46̚1500bytes
Table 98 Configure QinQ
Operation Command Description
Enter system view system-view -