The person, who spoke on condition of anonymity Monday because the league hasn't announced the suspension, says Johnson violated the league's performance-enhancing drug policy. Johnson played all but one snap last season after being the fourth overall selection in the draft.
It's not known if Johnson will appeal the suspension. He's allowed to play in preseason games.
Johnson was part of an offensive line unit that started every game last season, helped the Eagles set several offensive team records and win the NFC East. Allen Barbre or Dennis Kelly could replace him the first month of the season. Kelly started seven games at right tackle in 2012.
The Philadelphia Daily News first reported the suspension.