The Bluebirds will head into the Wembley showpiece against Liverpool on the back of a reverse to a resurgent Town side, who recorded a fourth successive league victory for the first time since 2004 under Joe Royle.
It could have been so different following a controversial ninth-minute incident in which Ipswich goalkeeper Arran Lee-Barrett was lucky to avoid red for bringing down Joe Mason outside the area.
Lee Martin soon took full advantage of the let-off to send the Suffolk club into the lead against the run of play with a well-taken finish.
In-form marksman Michael Chopra doubled the lead minutes after the interval with his fifth goal in four games and his second this season against the club he left last summer.
Martin then grabbed his second and Town's third to ensure a miserable 40th birthday on Sunday for Bluebirds boss Malky Mackay, although the Scot's mood could be a much happier one next Sunday should his side cause an upset in the capital.
Chopra shook off a slight calf strain to start, with Paul Jewell naming an unchanged 16 from the side who triumphed 1-0 at crisis club Portsmouth in midweek.
Cardiff, meanwhile, brought Mason and Filip Kiss into the XI who saw off Peterborough 3-1 on Tuesday, securing the Welsh club's first win in four games since booking their place at Wembley.
The first real talking point of the encounter came after nine minutes. Town keeper Lee-Barrett hauled down Mason outside the penalty area but, after lengthy deliberation by referee Simon Hooper, escaped with merely a booking.
Cardiff had certainly started the better of the two sides, enjoying five corners inside the opening 17 minutes.
But they were made to pay the price for failing to convert their dominance into goals as Town took an undeserved lead, Daryl Murphy's pass from the byline finding Martin, who stroked the ball into the bottom corner.
The Town midfielder wasted a great chance for a second just over a minute later, before Lee-Barrett escaped again at the other end as he cleared Peter Whittingham strike off his goal-line at the second attempt.
Ipswich became more involved following their breakthrough but it remained Cardiff who marginally enjoyed the better of proceedings.
There was a five-minute delay to the second half but the majority of the 17,032 present were soon celebrating an Ipswich second.
Carlos Edwards' superb cross from the right found its way to Chopra and the striker did the rest from close range.
Town started the second half much the brighter, Aaron Cresswell stinging the gloves of David Marshall.
But Cardiff gradually restored their first-half dominance and Ben Turner headed a good chance wide which could have sparked a comeback from the visitors.
Yet that was soon put to bed as Martin made it 3-0, again against the run of play, with his fifth of the season from close range.