How does an interface enabled with VLAN mapping process a packet without a C-VLAN tag

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If the VLAN ID of the packet is within the range of C-VLANs, the VLAN tag is replaced according to the configuration. If the VLAN ID of the packet is out of the range of C-VLAN IDs or the packet does not carry any tag, the packet is processed as follows:

If qinq vlan-translation miss-drop is used, the packet is discarded directly.

If the qinq vlan-translation miss-drop command is not used on the interface but the default VLAN ID is used, packets are tagged with the default VLAN ID before being forwarded.

NOTE:
When an interface configured with VLAN mapping received a packet with the C-VLAN ID out of the specified range, the interface transparently transmits the packet through the normal forwarding version if the interface is added to the VLAN of the packet.

Other related questions:
How does a QinQ-enabled interface process a received packet that carries the non-C-VLAN tag
If the VLAN ID of the packet is within the configured QinQ C-VLAN range, the VLAN tag is added to the packet according to the configuration. If the VLAN ID of the packet is not within the configured QinQ C-VLAN range or the packet does not carry any tag, the packet is processed as follows: If the qinq vlan-translation miss-drop command is used, the packet is directly discarded. If the qinq vlan-translation miss-drop command is not used on the interface but the default VLAN ID is used, packets are tagged with the default VLAN ID before being forwarded.

Why inner tags are removed when the VLAN-Mapping transparently transmits double-tagged packets after the VLAN-Stacking is configured
In S2752, S3752, S5752EI V100R003, and subsequent versions, after the VLAN-Stacking and VLAN-Mapping are configured on outbound ports, inner tags are removed when cross-chip double-tagged packets are transparently transmitted, interrupting services. During the configuration, set the two ports for forwarding to the same chip.

How to process Vlan 0 packet ?
The S and E Switch will process VLAN0 packets as follows�?if VLAN ID is 0,mean that there is no virtual network identifier in the frame, only carry priority. if the VLAN 0 packet can match traffic policy or ACL, this packet will be processed as Tagged packet, if can not match, the VLAN 0 packet will be processed as untagged packet, it will be added a default tag.

Which VLAN does the interface enabled with VLAN mapping or QinQ obtain through MAC address learning
The VLAN mapping or QinQ implementation is prior to the MAC address learning. Thus, after the VLAN mapping or QinQ implementation, the interface obtains the outer VLAN through MAC address learning.

Can a bridge transparently transmit packets carrying VLAN tags
A bridge on an AR router supports the transparently transmission of VLAN packets. However, a VLANIF interface does not support the transparently transmission of VLAN packets. It is not recommended that the transparent transmission of VLAN packets should be performed on sub-interfaces.

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