Riyad Mahrez's double and goals from Jamie Vardy and Marc Albrighton sealed a comfortable 4-2 win for the Foxes in Ranieri's first game in charge.
The Foxes were 3-0 up inside the first 25 minutes as they clinically brushed aside their woeful visitors.
Leicester picked up from where they left off after winning seven of their last nine games to stay in the Barclays Premier League.
It marked Ranieri's first game in the top flight since leaving Chelsea in 2004 but the Italian, who replaced Nigel Pearson in July, will not dwell on it
He said: "I've already forgotten what happened today, I am looking for a new team, a new squad and I am thinking 'Saturday - West Ham'.
"I asked the players, 'you finished very well last season' and I wanted to see them restart at the same level, the performance was very good.
"The first half was outstanding, the second half was normal.
"It's OK, we made mistakes but when you win you are more confident and I say 'hey, you made mistakes, this, this and this' and I think they are more receptive when they win.
"I said to them before 'here is a band, a strong band, a rock band and when you score the song comes on' and it was fantastic."
Second-half goals from Jermain Defoe and Steven Fletcher saved the Black Cats from embarrassment but they were beaten by half time with Leicester rampant.
They improved after the break but boss Dick Advocaat admitted he feared for his side.
He said: "It's not only the result which scares me a little bit, but the way we played, especially in the first half.
"We still know what we have to do, we still have to change some things.
"The first cross was a goal, the second cross was 2-0 and for the third goal the left-back was sleeping.
"So then it was 3-0 and they were sharper and better.
"But hopefully we'll learn from this
And hopefully next week we can do better than today.
"You cannot only buy players for £1million, £2million or £3million
That was the mistake because we have a president who's doing everything he can to help us to help the team.
"Today has nothing to do with the investment we made, the players were not in the right shape."
Source : PA
Source: PA