Restrictions and guidelines
When you configure QinQ, follow these restrictions and guidelines:
EVB and QinQ are mutually exclusive. Do not enable both features on a port.
Before you can configure QinQ on a port, you must remove any VLAN mappings on the port. After you enable QinQ on the port, you can configure any VLAN mapping types except two-to-two VLAN mapping. 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 the payload. As a best practice to ensure correct transmission of QinQ frames, set the MTU to a minimum of 1504 bytes for each port on the forwarding path. This value is the sum of the default Ethernet interface MTU (1500 bytes) and the length (4 bytes) of a VLAN tag.