The Reds stretched their unbeaten run at the City Ground to 17 matches as they turned up the heat to net three times in the second half, to ensure they will finish in the top six and challenge for a place in the Premier League.
West Brom's triumph at Doncaster finally put automatic promotion beyond Billy Davies' side, as the Baggies secured their place in the top-flight.
But the Reds will go into the play-offs in confident mood, following another thumping victory on home turf, earned through goals from Luke Chambers, Guy Moussi and Robert Earnshaw.
Forest almost took a second minute lead after the dangerous Nathan Tyson had burst down the right flank before feeding Chris Cohen on the edge of the box, where the midfielder bent a testing shot towards the far post that Brian Murphy did well to palm around the post.
Daryl Murphy forced a save from Forest keeper Lee Camp following a quick break from the visitors.
But the Ipswich players also twice came close to scoring at the other end, as defender Damien Delaney forced a scrambled save from his own keeper with a misdirected headed clearance that was headed for the top corner and as Shane O'Connor prodded another clearance narrowly wide of the visitors' goal.
A David Norris volley had to be cleared off the Forest line as Ipswich forced a spell of pressure of their own.
A defensive misunderstanding between Kelvin Wilson and Camp almost allowed Connor Wickham to sneak in on goal, with the keeper having to produce a strong tackle to deny the young striker after the defender had attempted to allow the ball to run through to him.
Moussi might have scored for Forest had he not lost his footing after a bending corner found him in acres of space at the far post.
The lively Wickham flashed an effort narrowly wide of the post at the other end. But, as half-time approached, Tyson came close for Forest with a carbon copy strike.
It took only two minutes of the second half for the home side to take the lead - even if the goal came in fortunate circumstances, as Earnshaw struck a powerful shot across goal from the edge of the box, which hit Luke Chambers, seemingly on the backside, sending it bouncing inside the near post.
Ten minutes later Forest made it 2-0 as Chris Gunter strode into space down the left before picking out Moussi at the near post, where the Frenchman converted at the second attempt after Murphy had initially blocked.
Forest's third goal was a result of another burst down the left as Tyson's ball in from the left saw a Blackstock shot charged down - only for the ball to fall perfectly for Earnshaw to drive a crisp effort through the keeper's legs.