Ienaga served various posts including Kurodo (Chamberlain), Meryo (Bureau of Horses), Hyogoryo (Bureau of Military Storehouses), Suke (assistant director) of Musashi Province, Suke of Bizen Province, Bingo no kami (Governor of Bingo Province), Mimasaka no kami (Governor of Mimasaka Province) and Tajima no kami (Governor of Tajima Province).
蔵人・馬寮・兵庫寮、武蔵国介・備前国介・備後守・美作守など地方官を歴任し、但馬守に任ぜられる。