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