After 4+ years of trying every "safe", natural ant remedy known to man -- including cinnamon which stained the white tile back splash in my kitchen -- I found Terro ANT Killer at Walmart to be the ONLY thing that prevented them from even entering the house because it kills the whole colony.
It comes in a special orange bag that has holes in the bottom which allow the granules to be sprinkled around the base of the house outside. Try to use them on a day when you expect a bit of rain within 48 hours or so. I have outside cats and worried about them, but there doesn't seem to ever have been a problem.
Jan in VA