QTECH
Software Configuration Manual
5-74
5.4.6
Examples for GVRP configuration
! Enable GVRP on Ethernet port 2
QTECH(config-if-ethernet-0/0/2)#gvrp
! Disable GVRP on Ethernet port 2
QTECH(config-if-ethernet-0/0/2)#no gvrp
5.5 Brief introduction of QinQ
QinQ is used for the commnunication between discrete client vlan whose service model is the
interconnection of one or more switches supported QinQ by service provider interfaces which are in service provider
vlan. The interface linking client vlan is called customer interface. Packet with client vlan tag will add a tag head with
the vlan id being service provider vlan when passing through the customer interface. The tag head will be stripped
when passing through service provider vlan.
5.5.1
Introduction to QinQ
In the VLAN tag field defined in IEEE 802.1Q, only 12 bits are used for VLAN IDs, so a device can support
a maximum of 4, 094 VLANs. In actual applications, however, a large number of VLAN are required to isolate users,
especially in metropolitan area networks (MANs), and 4, 094 VLANs are far from satisfying such requirements.
The port QinQ feature provided by the device enables the encapsulation of double VLAN tags within an
Ethernet frame, with the inner VLAN tag being the customer network VLAN tag while the outer one being the
VLAN tag assigned by the service provider to the customer. In the backbone network of the service provider (the
public network), frames are forwarded based on the outer VLAN tag only, while the customer network VLAN tag is
shielded during data transmission.
Figure 1 shows the structure of 802.1Q-tagged and double-tagged Ethernet frames. The QinQ feature
enables a device to support up to 4, 094 x 4, 094 VLANs to satisfy the requirement for the amount of VLANs in the
MAN.
Figure 1
802.1Q-tagged frame structure vs. double-tagged Ethernet frame structure
Advantages of QinQ :
·
Addresses the shortage of public VLAN ID resource
·
Enables customers to plan their own VLAN IDs, with running into conflicts with public network VLAN IDs.
