This read-write TruthValue, false by default, enables or disables 802.1 QinQ double-tagging functionality on a specific interface, indexed by ifIndex. An admin sets this to true on interfaces that need to add an outer service-provider VLAN tag on top of customer traffic, which is the fundamental switch that turns QinQ on for that port. For example, an admin provisioning a customer-facing uplink for a Layer 2 VPN service would set this object to true to begin QinQ tagging traffic on that interface.