Configure the VLAN Mapping Table to map the C-VLAN of traffic ingressing the Ethernet (LAN) port of the SM to a S-VLAN before being forwarded to the air interface on the UL. In the DL direction, the SM will automatically un-map the S-VLAN to the C-VLAN before forwarding the tagged packets to the Ethernet (LAN) interface of the SM.
C-VLAN is supposed to refer to Customer's tags, and S-VLAN to Service's tags.
C-VLAN supposed to be configured lower SM, and S-VLAN above the AP.
VLAN Mapping works in both directions.
Example: