Palace took the lead in an entertaining match in the 20th minute, Andrew Johnson heading in from 12 yards from Tommy Black's excellent cross.
Ipswich, man for man, looked far more comfortable on the ball than Palace though in the first half they did not have a cutting edge to add to it.
That changed in the second half especially after the introduction of substitute Pablo Counago. Palace boss Trevor Francis subsequently had to re-organise his side to wrest some control back that they largely held in the first half.
Ipswich nearly drew first blood after ten minutes with Marcus Bent's shot well saved by Cedric Berthelin.
The Palace keeper produced an even better save to tip Matt Holland's header over from the resultant corner. Then came Johnson's goal.
Palace could have doubled their lead later when Johnson's cross was nearly turned into his own goal by an Ipswich defender.
Shaun Derry almost missed a chance when he met another Johnson cross but Marshall turned it away.
Palace were to rue those missed chances as Ipswich stepped up the pace in the second half.
Marcus Bent and his namesake Darren both served warning to Palace as both of them narrowly failed to equalise.
Marcus Bent made amends though when he powered a header into the top corner from Jim Magilton's corner.
Counago shot widely over when well placed shortly after.
Palace's best chance to win it came when Danny Butterfield fed Dougie Freedman whose clever chip found Johnson at the far post but his header hit the top of the bar.
Martijn Reuser's injury-time free kick caused panic in the Eagles defence and Richard Naylor's glancing header fell wide of the far post and should have hit the target.
Both managers felt their respective sides can make the play-offs with both saying: "We haven't given it up yet."