Configuring Q-in-Q tagging behavior for the native VLAN

When Q-in-Q tunneling is configured and an untagged packet is received on a C-VLAN interface, you can configure these switches to add either one or two tags before sending the packet out of the S-VLAN interface. To send two tags, set the configuration statement input-native-vlan-push to "enable" and ensure that the input-vlan-map configuration is set to "push".