This specifies the ifIndex of the Ethernet port associated with this VC for point-to-point Ethernet service, or the ifIndex of the virtual interface of the VPLS instance if the service is VPLS, and two rows can point to the same ifIndex only under certain multi-COS conditions. This is the access-side binding -- which physical port or VPLS virtual interface actually feeds this pseudowire -- and the MIB's note about shared ifIndex values specifically anticipates multi-COS deployments where several VCs, each carrying a different traffic class, legitimately share one port. For example, three VC rows all pointing at the same physical port's ifIndex, each carrying a different priority mapping via cpwVcEnetMplsPriMapping, would represent a legitimate multi-COS design rather than a misconfiguration.