Implementation Of Vlan-Vpn; Configuring The Tpid For Vlan-Vpn Packets - H3C S3100 8C SI Operation Manual

Operation Manual – VLAN-VPN
H3C S3100 Series Ethernet Switches
The VLAN-VPN feature provides you with the following benefits:
Saves public network VLAN ID resource.
You can have VLAN IDs of your own, which is independent of public network
VLAN IDs.
Provides simple Layer 2 VPN solutions for small-sized MANs or intranets.

1.1.2 Implementation of VLAN-VPN

With the VLAN-VPN feature enabled, no matter whether or not a received packet
already carries a VLAN tag, the switch will tag the received packet with the default
VLAN tag of the receiving port and add the source MAC address to the MAC address
table of the default VLAN. When a packet reaches a VLAN-VPN-enabled port:
If the packet already carries a VLAN tag, the packet becomes a dual-tagged
packet.
Otherwise, the packet becomes a packet carrying the default VLAN tag of the port.

1.1.3 Configuring the TPID for VLAN-VPN Packets

Note:
The contents of this section are only applicable to the S3100-EI series among S3100
series switches.
A VLAN tag uses the tag protocol identifier (TPID) field to identify the protocol type of
the tag. The value of this field is 0x8100 for IEEE 802.1Q.
Figure 1-3
0
Figure 1-3 The structure of the VLAN tag in an Ethernet frame
An S3100 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.
By default, S3100 series switches adopt the IEEE 802.1Q TPID value 0x8100. Some
vendors, however, use other TPID values such as 0x9100. For compatibility with these
systems, the S3100 series switches allow you to change the TPID that a port uses
illustrates the structure of the IEEE 802.1Q VLAN tag in an Ethernet frame.
TPID
Chapter 1 VLAN-VPN Configuration
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Priority
CFI
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VLAN ID