204
Figure 69
Application scenario of two-to-two VLAN mapping
Site 1 and Site 2 are in VLAN 2 and VLAN 3, respectively. The VLAN assigned for VPN A is VLAN 10
in the SP 1 network and VLAN 20 in the SP 2 network.
If Site 1 sends a packet to Site 2, the packet is processed on the way to its destination using the following
workflow:
1.
When the packet tagged with VLAN 2 arrives at the edge of network SP 1, PE 1 tags the packet
with outer VLAN 10 through basic QinQ or selective QinQ.
2.
When the double-tagged packet enters the SP 2 network, PE 3 replaces the outer VLAN tag (VLAN
10) with VLAN 20. Because the packet is destined for Site 2 in VLAN 3, PE 3 also replaces the
inner tag (VLAN 2) of the packet with VLAN 3. This process is two-to-two VLAN mapping.
3.
When PE 4 receives the packet with the new VLAN tag pair, it removes the outer VLAN tag and
forwards the packet to VLAN 3.
For more information about basic QinQ and selection QinQ configurations, see "
."
Concepts and terms
shows a simplified network to help explain the concepts and terms that you might encounter
when you work with VLAN mapping.
Figure 70
Basic concepts of VLAN mapping
•
Uplink traffic
—Traffic transmitted from the customer network to the service provider network.
PE 1
VPN A
Site 1
SP 1
CE a1
VPN A
Site 2
SP 2
CE a2
Data
VLAN 2
Data
VLAN 10
VLAN 2
Data
VLAN 20
VLAN 3
Data
VLAN 3
Traffic
PE 2
PE 3
PE 4
QinQ or selective
QinQ
Two-to-two VLAN
mapping
QinQ or selective
QinQ
