197• IEEE 802.1ad, IEEE Standard for Local and Metropolitan Area Networks-Virtual Bridged Local AreaNetworks-Amendment 4: Provider BridgesRestrictions and guidelinesWhen you configure QinQ, follow these restrictions and guidelines:• EVB and QinQ are mutually exclusive. Do not enable both features on a port.• Before you configure QinQ on a port, remove existing VLAN mapping configuration on it. After youenable QinQ on the port, you can configure all VLAN mapping types except two-to-two VLANmapping. If QinQ and a VLAN mapping conflict, the VLAN mapping takes effect.• The inner 802.1Q tag of QinQ frames is treated as part of payload. For correct transmission ofQinQ frames, H3C recommends that you set the MTU to a minimum of 1504 bytes for each port onthe forwarding path of QinQ frames. This value is the sum of the default Ethernet interface MTU(1500 bytes) and a VLAN tag's size (4 bytes).Enabling QinQEnable QinQ on customer-side ports of PEs. A QinQ-enabled port tags an incoming frame with its PVID.To enable QinQ:Step Command Remarks1. Enter system view. system-view N/A2. Enter Layer 2 Ethernetinterface view or Layer 2aggregate interface view.interface interface-typeinterface-number N/A3. Enable QinQ. qinq enable By default, QinQ is disabled.Configuring transparent transmission for VLANsYou can exclude traffic of a VLAN (for example, the management VLAN) from the QinQ tagging actionon a customer-side port. This VLAN is called a transparent VLAN.To ensure successful transmissions for a transparent VLAN, follow these configuration guidelines:• Set the link type of the port to trunk or hybrid, and assign the port to the transparent VLAN.• Do not configure any other VLAN manipulation actions for the transparent VLAN on the port.• Make sure all ports on the traffic path permit the transparent VLAN to pass through.To enable transparent transmission for a list of VLANs:Step Command Remarks1. Enter system view. system-view N/A2. Enter Layer 2 Ethernetinterface view or Layer 2aggregate interface view.interface interface-typeinterface-number N/A
