3com S7906E 설치 설명서

 

1-2 

The devices in the public network forward a frame only according to its outer VLAN tag and learn its 

source MAC address into the MAC address table of the outer VLAN. The inner VLAN tag of the frame is 

transmitted as the payload.  

Figure 1-1 Schematic diagram of the QinQ feature 

Network

Service provider network

Customer network A

VLANs 1 to 10  

Customer network A

VLANs 1 to 10

Customer network B

VLANs 1 to 20 

Customer network B

VLANs 1 to 20 

VLAN 3 

VLAN 3 

VLAN 4 

VLAN 4 

 

 

As shown in 

, customer network A has CVLANs 1 through 10, while customer network B has 

CVLANs 1 through 20. The SVLAN allocated by the service provider for customer network A is SVLAN 

3, and that for customer network B is SVLAN 4. When a tagged Ethernet frame of customer network A 

enters the service provider network, it is tagged with outer VLAN 3; when a tagged Ethernet frame of 

customer network B enters the service provider network, it is tagged with outer VLAN 4. In this way, 

there is no overlap of VLAN IDs among customers, and traffic from different customers can be identified 

separately.  

A QinQ frame is transmitted double-tagged over the service provider network. The inner VLAN tag is the 

CVLAN tag while the outer one is the SVLAN tag that the service provider has allocated to the customer. 

 shows the structure of single-tagged and double-tagged Ethernet frames.