The OLT supports QinQ and VLAN stacking attributes.

QinQ Overview :

QinQ (IEEE 802.1ad) is a double-tagging mechanism that adds an outer VLAN tag to an already tagged packet.

It is commonly used in carrier networks to extend VLAN capacity and support hierarchical VLAN architectures.

VLAN Types :

Sub VLAN : Part of a Super VLAN configuration, used for IP address conservation. Does not support QinQ.

Common VLAN : Supports only single-tag VLANs. Does not support QinQ.

Super VLAN : Aggregates multiple Sub VLANs for IP address sharing. Does not support QinQ.

Smart VLAN : Specifically designed to support advanced features like QinQ and VLAN stacking.

Why D?

Smart VLAN is the only VLAN type that supports QinQ and VLAN stacking, making it the correct choice.

Thus, the correct answer is D .

References:

HCIA Huawei ACCESS Official Documentation , Chapter: VLAN Design.

IEEE 802.1ad QinQ Standards .