H3C Technologies H3C S12500 Series Switches - Manual (Page 204)

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Configuring VLAN termination
The switch does not support QinQ termination when it is operating in standard mode. For more
information about the commands of system operating modes, see Fundamentals Command Reference.
Overview
VLAN termination assigns a received VLAN-tagged packet to the corresponding interface according to
its VLAN tag, and then the interface removes its VLAN tags, and forwards it through Layer 3 or processes
it in another way. Before sending a packet, the port adds VLAN tags to the packet according to the
VLAN termination configuration on the port.
VLAN termination types
VLAN termination includes the following types:
• Dot1q termination—Terminates packets which carry one or more layers of VLAN tags and whose
outermost VLAN tag matches the number of the receiving VLAN interface. Packets sent out of the
VLAN interface are tagged with the ID of that VLAN. By default, Dot1q termination is enabled on
all VLAN interfaces.
• QinQ termination—Terminates packets which carry two or more layers of VLAN tags and whose
outermost VLAN tag matches the number of the receiving VLAN interface. Packets sent out of a
QinQ termination interface are double-tagged.
Application scenarios
Inter-VLAN communication
Hosts in different VLANs cannot directly communicate with each other. You can use Layer 3 routing to
allow all VLANs to communicate. To allow the specified VLANs to communicate, configure VLAN
termination on VLAN interfaces.
As shown in
Figure 68 , Host A belongs to VLAN 2, Host B belongs to VLAN 3, and Host C belongs to
VLAN 4. Create VLAN-interface 2 and VLAN-interface 3 on the device, and specify Host A's gateway
IP address as 1.1.1.1/24 and Host B's gateway IP address as 1.1.2.1/24. With the configuration, Host A
and Host B can communicate at Layer 3 through VLAN interfaces. When VLAN-interface 2 receives a
packet from Host A, the interface removes the VLAN tag 2 of the packet and forwards the packet to
VLAN-interface 3. VLAN-interface 3 then tags the packet with VLAN 3 and forwards it to Host B. The
packet sent from Host B to Host A is processed in the same way.
Because VLAN-interface 4 is not created on the device, the device cannot terminate packets from Host C.
As a result, Host C cannot communicate with Host A or Host B.