You can use the Ethernet NICs (10GE defined in BMS specifications) not used by the system to configure a user-defined VLAN. The QinQ technology is used to isolate networks and provide additional physical planes and bandwidths. You can allocate VLAN subnets to isolate traffic in various scenarios including SAP HANA and VMware. User-defined VLAN NICs are in pairs. You can configure NIC bonding to achieve high availability. User-defined VLANs in different AZs cannot communicate.
QinQ is a layer 2 tunnel protocol based on IEEE 802.1Q encapsulation. It adds a public VLAN tag to a frame with a private VLAN tag to allow the frame with double VLAN tags to be transmitted over the service provider's backbone network based on the public VLAN tag. This provides a layer 2 VPN tunnel for customers.