Ipswich 1 Man City 4
A stunning away-day display ensured that one half of Manchester will be represented in the fifth round of the FA Cup.
It may have taken a slice of luck for Manchester City to succeed where United failed as referee Graham Poll's gaffe handed them the lead.
City, the First Division leaders, started brightly and it took a precisely-timed intervention by Hermann Hreidarsson to halt a free run on goal for Shaun Wright-Phillips, in pursuit of Eyal Berkovic's pass.
Ipswich's own fluent passing might have seen them take an eighth-minute lead as Jermaine Wright and Sixto Peralta worked an opening down the right and Marcus Bent flashed a drive narrowly over the top from the latter's centre.
Despite the dominance of Ipswich Poll's refereeing blunder handed Keegan's side the lead two minutes before the interval.
Benarbia's cross hit Jensen on the backside and cannoned out of play but Poll awarded a corner, incensing both captain Holland and John McGreal, who confronted the official.
Meeting Benarbia's flag-kick on the full some 20 yards from goal, Israeli midfielder Berkovic thundered his effort through the crowd and past the combined efforts of Marshall, who got a hand to the ball, and Reuser on the left-hand post.
Having gone in front just before the break, City could have doubled their advantage three minutes after the restart.
Benarbia sent Shaun Goater racing clear and when the First Division's top scorer was foiled by Marshall's rush from goal, Huckerby's goalbound shot was blocked by Bramble.
If Ipswich had been warned, they did not heed it and the Premiership were two goals behind 20 minutes into the second half.
Wright's loose ball went straight to Jensen and the Dane strode forward before finding Benarbia, who, in turn, fed Goater for the striker to beat Marshall and guide in his 25th goal of the season.
Substitute Alun Armstrong went close to pulling a goal back as he sidefooted over and Stewart struck the bar in a goalmouth melee.
Then, seven minutes from time Ipswich gave themselves hope as Bent, seizing on a lay-off from Stewart, curled a shot past Weaver from 25 yards via a slight deflection.
Moments later, Armstrong's header was turned away at full stretch by Weaver.
But another clever assist from Benarbia killed off any hope as Huckerby's drive was parried by Marshall and Goater rose to head home his second.
Chasing the game, Ipswich conceded a fourth at the death as Richard Dunne's punt forward allowed Huckerby to beat the offside trap, round Marshall and fire into an empty net. -PA