3Com S7906E - Switch, Руководство по настройке

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Figure 1-2 Scenario for one-to-two/two-to-two VLAN mapping
The VPN A user in Site 1 belongs to VLAN 10. When the packet tagged with VLAN 10 arrives at the
edge of the SP 1 network, PE 1 tags the packet with VLAN 100, the VLAN ID assigned to the VPN A
user in SP 1. The packet thus becomes double-tagged and this single-tag to double-tag translation
process is called one-to-two VLAN mapping. One-to-two VLAN mapping enables VPN users to plan
their own CVLAN IDs independent of SP network VLAN IDs, thus saving the VLAN resources of SPs.
When the double-tagged packet enters the SP 2 network, PE 3 replaces the outer VLAN tag (VLAN 100)
with VLAN 200, the VLAN ID assigned by SP 2 to the VPN A user. For the packet to reach the VPN A
user in Site 2, which belongs to VLAN 30, PE 3 replaces the inner tag (VLAN 10) of the packet with
VLAN 30. This double-tag to double-tag replacement is called two-to-two VLAN mapping.
You can use QinQ to achieve the same effect of one-to-two VLAN mapping. For more information about
QinQ, refer to QinQ Configuration in the Access Volume .