Quidway S3500-EA Series Operation Manual - page 3
Operation Manual - QinQ-BPDU Tunnel
Quidway S3500-EA Series Ethernet Switches
Chapter 1 QinQ Configuration
Huawei Technologies Proprietary
1-2
Note:
The QinQ feature requires configurations only on the service provider network, and not
on the customer network.
1.1.2 Implementations of QinQ
There are two types of QinQ implementations: basic QinQ and selective QinQ.
1) Basic
QinQ
Basic QinQ is a port-based feature, which is implemented through VLAN VPN.
With the VLAN VPN feature enabled on a port, when a frame arrives at the port, the port
will tag it with the port’s default VLAN tag, regardless of whether the frame is tagged or
untagged. If the received frame is already tagged, this frame becomes a double-tagged
frame; if it is an untagged frame, it is tagged with the port’s default VLAN tag.
2) Selective
QinQ
Selective QinQ is more flexible and is implemented based on both VLAN tag and port.
In addition to all the functions of basic QinQ, selective QinQ can take different actions
based on the VLAN tags carried by received frames, including to tag received frames
with different outer VLAN tags based on the inner VLAN tags.
1.1.3 Adjustable TPID Value of QinQ Frames
A VLAN tag uses the tag protocol identifier (TPID) field to identify the protocol type of
the tag. The value of this field, as defined in IEEE 802.1Q, is 0x8100.
Figure 1-2
shows the structure of an Ethernet frame defined in IEEE802.1Q.
DA
SA
Tag
Frame Load
FCS
6 bytes 6 bytes 4 bytes 46 ~1500 bytes
4 bytes
TPID
User Priority CFI
VLAN ID
2 bytes 3 bits 1bit 12 bits
DA
SA
Tag
Frame Load
FCS
4 bytes
TPID
User Priority CFI
VLAN ID
2 bytes 3 bits 1bit 12 bits
DA
SA
Tag
Frame Load
FCS
6 bytes 6 bytes 4 bytes 46 ~1500 bytes
4 bytes
TPID
User Priority CFI
VLAN ID
2 bytes 3 bits 1bit 12 bits
DA
SA
Tag
Frame Load
FCS
4 bytes
TPID
User Priority CFI
VLAN ID
2 bytes 3 bits 1bit 12 bits
Figure 1-2
Tag structure of an Ethernet frame
On devices of different vendors, the TPID fields of the outer VLAN tags of QinQ frames
may have different default values. You can set TPID values for QinQ frames to enable
them to be recognized and processed by devices of other vendors. When a port
receives a frame, it tags the frame with an outer VLAN tag with the specified TPID value