H3C S7500E Series Operation Manual page 142

Operation Manual – QinQ-BPDU Tunneling
H3C S7500E Series Ethernet Switches
Figure 1-2 VLAN Tag structure of an Ethernet frame
An S7500E switch determines whether a received frame is VLAN tagged by comparing
its own TPID with the TPID field in the received frame. If they match, the frame is
considered as a VLAN tagged frame. If not, the switch tags the frame with the default
VLAN tag of the receiving port.
The systems of different vendors may set the TPID in the outer VLAN tag of QinQ
frames to different values. For compatibility with these systems, the S7500E series
switches allow you to modify the TPID values in the VLAN tags in QinQ frames,
including:
The TPID value in customer network VLAN tags. The switch uses it to determine
whether a frame received from the customer network is VLAN tagged. If the frame
is considered as VLAN untagged, the switch tags the frame with the default VLAN
tag of the receiving port. This default VLAN tag uses the TPID that you have
configured.
The TPID value in service provider network VLAN tags. The switch uses it to
determine whether a frame received from the service provider network is VLAN
tagged. In addition, the switch uses the configured TPID in the outer VLAN tag for
customer network frames for compatibility with third-party devices.
The TPID in an Ethernet frame has the same position with the protocol type field in a
frame without a VLAN tag. To avoid problems in packet forwarding and handling in the
network, you cannot set the TPID value to any of the values in the table below.
Table 1-1 Reserved protocol type values
ARP
PUP
RARP
IP
IPv6
PPPoE
MPLS
IPX/SPX
Protocol type
1-3
Chapter 1 QinQ Configuration
Value
0x0806
0x0200
0x8035
0x0800
0x86DD
0x8863/0x8864
0x8847/0x8848
0x8137