This is a lookup-table entry that maps a non-TE (LDP or manually signaled) MPLS pseudowire binding back to its corresponding row index in the primary cpwVcTable, letting a management station find the base VC entry when it only has the non-TE-specific identifying information at hand. It matters on routers running a mix of TE-protected and plain LDP-signaled pseudowires, where distinguishing which table to query first affects how you diagnose a given VC's outer-tunnel behavior. Without this mapping, correlating a non-TE-specific alarm back to the actual pseudowire's name and counters in cpwVcTable would require an indirect search.