2-3Figure 2-2 Learn MAC addresses of selective QinQ packetsVLAN3MAC-AVLAN4MAC-APVID=2PrivateNetworkPublicNetworkPrivateNetworkPublicNetworkPVID=2VLAN4MAC-AReceives the data that theprivate network sends to theservice provider’s networkReceives the data that theservice provider’s networksends to the private networkAs shown in Figure 2-2, the default VLAN of the port used to receive packets is VLAN 2. The port isconfigured to receive packets of VLAN 3, tag the received packets with the outer tag of VLAN 4, and addthe source MAC addresses (MAC-A) of the packets to the MAC address table of its default VLAN (VLAN2).When a response packet is returned to the device from VLAN 4 of the service provider network, thedevice searches the outbound port for MAC-A in the MAC address table of VLAN 4. However, becausethe corresponding entry is not added to the MAC address table of VLAN 4, this packet is considered tobe a unicast packet with unknown destination MAC address. As a result, this packet will be broadcast toall the ports in VLAN 4, which wastes the network resources and incurs potential security risks.The S5600 series Ethernet switches provide the inter-VLAN MAC address replicating feature, whichcan replicate the entries in the MAC address table of the default VLAN to that of the VLANcorresponding to the outer tag. With the inter-VLAN MAC address replicating feature enabled, when adevice receives a packet from the service provider network, this device will find the path for the packetby searching the MAC address table of the VLAN corresponding to the outer tag and unicast the packet.Thus, packet broadcast is reduced in selective QinQ applications.Likewise, the entries in the MAC address table of the outer VLAN can also be replicated to that of thedefault VLAN on a port, through which the outbound port to the service provider network can bedetermined through the MAC address table of the default VLAN and user packets destined for theservice provider can be unicast.Selective QinQ ConfigurationSelective QinQ Configuration Task ListComplete the following tasks to configure selective QinQ:Task RemarksEnabling the Selective QinQ Feature for a Port RequiredEnabling the Inter-VLAN MAC Address Replicating Feature OptionalIf IRF Fabric has been enabled on a device, you cannot enable the VLAN-VPN feature and the selectiveQinQ feature on any port of the device.
