From down the Maurienne valley you start this climb in Modane at the Pont de Loutraz (1060m) and it is still not a +1000m climb from there, but it will likely be as you probably arrive here from further down the valley. It is a fairly steep climb up from Aussois where the three possible roads up here join up. If you want to pass by the nice forts below Aussois, you continue on the main Maurienne valley road to Villarodin and descends to the bridge below Avrieux (1094m a bit lower than the IGN map suggests) where the climb properly starts and it might be the hardest variant.

If you come down from Col de l’Iseran (2764m) or from the Col du Mont Cenis/Colle del Moncenisio (2083m, road height 2094m) you would do well to start the climb in Sollières (1271m) as I did myself in 2014. It is a little up and down on this road with some extra climbing, but you do after all start higher up. The road has apparently been paved since 2014 to the upper parking at the end and thus ends at 2037m rather than 2015m as before.