Adjusting The Tpid Values Of Vlan-Vpn Packets - H3C S3600 Series Operation Manual

Operation Manual – VLAN-VPN
H3C S3600 Series Ethernet Switches-Release 1510
packet. Otherwise, the packet becomes a packet carrying the default VLAN tag of the
port.

1.1.3 Adjusting the TPID Values of VLAN-VPN Packets

Tag protocol identifier (TPID) is a field of the VLAN tag. IEEE 802.1Q specifies the
value of TPID to be 0x8100.
Figure 1-3 illustrates the structure of the Tag packet of an Ethernet frame defined by
IEEE 802.1Q.
6 bytes 6 bytes
DA DA DA DA DA DA DA DA
Figure 1-3 The structure of the Tag packet of an Ethernet frame
S3600 series switches adopt the protocol default TPID value (0x8100). Other vendors
use other TPID values (such as 0x9100 or 0x9200) in the outer tags of VLAN-VPN
packets.
To be compatible with devices coming from other vendors, S3600 series switches can
adjust the TPID values of VLAN-VPN packets based on ports. You can configure the
TPID value of a port connecting to the public network side by yourself. When a packet is
forwarded through the port, the port replaces the TPID value in the outer VLAN tag of
this packet with the user-defined value. Thus, the VLAN-VPN packets sent to the public
network can be recognized by devices of other vendors.
As the position of the TPID field in an Ethernet packet is the same as that of the protocol
type field in a packet without VLAN Tag, to avoid confusion in the process of
receiving/forwarding a packet, the TPID value cannot be any of the protocol type value
listed in Table 1-1
Table 1-1 Commonly used protocol type values in Ethernet frames
ARP
IP
MPLS
IPX
6 bytes 6 bytes 4 bytes 4 bytes
SA SA SA SA SA SA SA SA
TPID TPID TPID TPID TPID TPID TPID TPID User Priority CFI User Priority CFI User Priority CFI User Priority CFI User Priority CFI User Priority CFI User Priority CFI User Priority CFI
2 bytes 2 bytes 2 bytes 2 bytes 2 bytes 2 bytes 2 bytes 2 bytes 3 bits 3 bits 3 bits 3 bits 3 bits 3 bits 3 bits 3 bits
Protocol type
Chapter 1 VLAN-VPN Configuration
46 to 1,500 bytes 46 to 1,500 bytes
Tag Tag Tag Tag Tag Tag Tag Tag Frame Load Frame Load Frame Load Frame Load Frame Load Frame Load Frame Load Frame Load
VLAN ID VLAN ID VLAN ID VLAN ID VLAN ID VLAN ID VLAN ID VLAN ID
1bit 1bit 1bit 1bit 1bit 1bit 1bit 1bit 12 bits 12 bits 12 bits 12 bits 12 bits 12 bits 12 bits 12 bits
0x0806
0x0800
0x8847/0x8848
0x8137
1-2
4 bytes 4 bytes
FCS FCS FCS FCS FCS FCS FCS FCS
Value