This read-only object reports the VPI value to which this DLCI is mapped internally, paired with casfFAMapInternalAtmInterface and casfFAMapInternalAtmVci. Combined with the interface, this VPI completes the internal ATM address a given frame-relay DLCI's frames are translated onto, so it's the number to cross-reference against a VC endpoint's own state on that VPI/VCI pair when a DLCI's frames seem to vanish after interworking translation. A DLCI mapped internally to VPI 0 that should instead be riding VPI 1 due to a provisioning slip would deliver its translated cells onto the wrong internal virtual path, effectively disconnecting it from where it needs to go.