For point to point, this is the cross-connected VCL's ifIndex of this VCL. For point to multi-point connection, this will be the root VCL's ifIndex for a leaf VCL entry in the multicast chain, or it's the 1st leaf VCL for a root VCL entry. If it's zero, it means it's not cross-connected yet. Atomically set ciscoAtmVclConnState, ciscoAtmVclCrossIfindex, ciscoAtmVclCrossVpi and ciscoAtmVclCrossVci will create or delete a cross connection to crossed half leg of this ciscoAtmVclCrossIfindex, ciscoAtmVclCrossVpi and ciscoAtmVclCrossVci for p2p PVC, or add or drop a multicast connection to/from the root of this ciscoAtmVclCrossIfindex, ciscoAtmVclCrossVpi and ciscoAtmVclCrossVci on the multicast chain for p2mp PVC.