R3303-HP HSR6800 Routers Layer 2 - LAN Switching Configuration Guide

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Figure 51 Single-tagged Ethernet frame header and double-tagged Ethernet frame header
NOTE:
For correct transmission of tagged frames, set the MTU of each interface on the service provider networ
k
to at least 1504 bytes, which is the sum of the default interface MTU (1500 bytes) and the size of a VLAN
tag (4 bytes).
The devices in the service provider network forward a tagged frame according to its SVLAN tag only,
and they transmit the CVLAN tag as part of the frame's payload.
Figure 52 Typical QinQ application scenario
As shown in Figure 52, customer network A has CVLANs 1 through 10, and customer network B has
CVLANs 1 through 20. The service provider assigns SVLAN 3 for customer network A, and assigns
SVLAN 4 for customer network B.
When a tagged Ethernet frame from customer network A arrives at a PE1, the PE tags the frame with
SVLAN 3. When a tagged Ethernet frame from customer network B arrives at a PE1, the PE tags the frame
with SVLAN 4.
The double-tagged Ethernet frame is then transmitted over the service provider network and arrives at the
other PE. The PE removes the SVLAN tag of the frame before sending it to the target CE.
CE 1
Customer
network A
PE 1
Public network
PE 2
CE 2
VLANs 1 to 10
VLANs 1 to 20
CE 3
VLANs 1 to 20
VLANs 1 to 10
CE 4
Customer
network A
Customer
network B
Customer
network B
IP network
VLAN 4
VLAN 4VLAN 3
VLAN 3