This read-only integer is the index identifying a specific position, or slot, in the network element's chassis, numbered from 1 up to the value reported by nncExtPositionMaxPossible. Since it is the position table's INDEX, an admin uses it to select which physical slot's card and module status they are viewing when walking or querying nncExtPositionTable. For instance (illustrative), an nncExtPositionIndex of 3 would identify the third slot in the chassis, whose card and module details appear in the rest of that table row.