The Red Devils booked their place in the last eight of the UEFA Champions League with two goals four minutes into either half.
Nemanja Vidic headed the holders into the lead before Cristiano Ronaldo sealed the win when he nodded in Wayne Rooney's delightful cross shortly after the break.
But United were not without their nervous moments as both Zlatan Ibrahimovic and Adriano hit the woodwork for the visitors.
"It was the type of match where we had to play a different type of football," Ferguson told Sky Sports 2.
Experience "Inter showed fantastic experience at times and showed that South American mentality and were very difficult to break down.
"The end result was very good. Good result, not a great performance."
The close nature of the tie did not surprise the Scot as his side were made to work for the win.
"When I first heard the draw I thought it was the hardest," he added.
"Your playing a magnificently experienced Inter Milan team, who are seven points clear in their league, and you know you never get an easy game against the Italians and that proved again tonight."