3Com Switch 7750 Configuration Guide Guide

154 CHAPTER 18: QINQ CONFIGURATION
Configuration procedure
1 Configure Switch A and Switch C.
As the configuration performed on Switch A and Switch C is the same,
configuration on Switch C is omitted.
# Configure Ethernet1/0/2 port as a trunk port. Add the port to VLAN 10.
<SwitchA> system-view
[SwitchA] vlan 10
[SwitchA-vlan10] quit
[SwitchA] interface Ethernet1/0/2
[SwitchA-Ethernet1/0/2] port link-type trunk
[SwitchA-Ethernet1/0/2] port trunk permit vlan 10
# Enable QinQ for Ethernet1/0/1 port. Add the port to VLAN 10.
[SwitchA-Ethernet1/0/2] quit
[SwitchA] interface Ethernet1/0/1
[SwitchA-Ethernet1/0/1] port access vlan 10
[SwitchA-Ethernet1/0/1] stp disable
[SwitchA-Ethernet1/0/1] undo ntdp enable
[SwitchA-Ethernet1/0/1] vlan-vpn enable
[SwitchA-Ethernet1/0/1] quit
2 Configure Switch B.
Configure Ethernet3/1/1 port and Ethernet3/1/2 port as trunk ports. Add the two
ports to VLAN 10.
<SwitchB> system-view
[SwitchB] vlan 10
[SwitchB-vlan10] quit
[SwitchB] interface Ethernet 3/1/1
[SwitchB-Ethernet3/1/1] port link-type trunk
[SwitchB-Ethernet3/1/1] port trunk permit vlan 10
[SwitchB-Ethernet3/1/1] quit
[SwitchB] interface Ethernet 3/1/2
[SwitchB-Ethernet3/1/2] port link-type trunk
[SwitchB-Ethernet3/1/2] port trunk permit vlan 10
n
The following describes how a packet is forwarded from Switch A to Switch C.
■ As QinQ is enabled on Ethernet1/0/1 port of Switch A, when a packet from the
user’s private network reaches Ethernet1/0/1 port of Switch A, it is tagged with
the default VLAN tag of the port (VLAN 10 tag) and is then forwarded to
Ethernet1/0/2 port.
■ When the packet reaches Ethernet3/1/2 port of Switch B, it is forwarded in
VLAN 10 and is passed to Ethernet3/1/1 port.
■ The packet is forwarded from Ethernet3/1/1 port of Switch B to the network on
the other side and reaches Ethernet1/0/2 port of Switch C. Switch C forwards
the packet in VLAN 10 to its Ethernet1/0/1 port. As Ethernet1/0/1 port is an
access port, the outer VLAN tag of the packet is stripped off and the packet
restores the original one.