H3C Technologies H3C S10500 Series Switches - Manual (Page 186)

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Figure 58 VLAN tag structure of an Ethernet frame
The device determines whether a received frame carries an SVLAN or CVLAN tag by checking the TPID
value. For example, if a frame carries an SVLAN tag with TPID value 0x9100 and a CVLAN tag with TPID
value 0x8100 and the configured TPID value of the SVLAN tag is 0x9100 and that of the CVLAN tag is
0x8200, the device considers that the frame carries only the SVLAN tag but not the CVLAN tag.
Devices of different vendors may set the TPID of the outer VLAN tag of QinQ frames to different values.
For compatibility with these devices, modify the TPID value so that the QinQ frames, when sent to the
public network, carry the TPID value identical to the value of a particular vendor, allowing
interoperability with the devices of that vendor.
The TPID in an Ethernet frame has the same position as the protocol type field in a frame without a VLAN
tag. To avoid problems in packet forwarding and handling in the network, do not set the TPID value to
any of the reserved values.
Table 21 Reserved protocol type values
Protocol type Value
ARP 0x0806
PUP 0x0200
RARP 0x8035
IP 0x0800
IPv6 0x86DD
PPPoE 0x8863/0x8864
MPLS 0x8847/0x8848
IPX/SPX 0x8137
IS-IS 0x8000
LACP 0x8809
802.1X 0x888E
Cluster 0x88A7
Reserved 0xFFFD/0xFFFE/0xFFFF
Protocols and standards
IEEE 802.1Q: IEEE standard for local and metropolitan area networks: Virtual Bridged Local Area
Networks