Genesis 25:17,18

And these are the years of the life of Ishmael, an hundred and thirty and seven years: and he gave up the ghost and died; and was gathered unto his people. And they dwelt from Havilah unto Shur, that is before Egypt, as thou goest toward Assyria: and he died in the presence of all his brethren.

That is the south of Moab. From the river Euphrates on the east, to Egypt on the west.