After a first half full of chances for the home side it was Mason Spence who opened the scoring just before the break, capitalising on a loose ball in the box to score from close range.
The second half was slightly more balanced and Irish had a scare with just over ten minutes to go, conceding an equaliser against the run of play that threw their passage into the next round into serious doubt.
Their response however was strong and two goals in quick succession, the first a Ty Ward penalty and the second a trademark long range effort from Ryan Smith, secured the victory and qualification for the Preliminary Round of the competition.
It had been a slow start to the game as both sides struggle to assert their dominance on the ball.
The opening fifteen minutes was full of attempted long balls from Irish and Dunstable that amounted to little, until Irish eventually managed to get the ball on the deck and fashion the first chance of the game.
Breaking down the left was Andre Olukanmi, who played it back into Ty Ward’s path for the midfielder to deliver a cross. The delivery was deep towards George Shrieves at the back post and then fell to Mason Spence, who couldn’t convert from just a few yards.
MK Irish grew in confidence after the first chance and started to turn up the pressure on opponents Dunstable.
Spence went close again just a couple of minutes later, seeing a header from close range at the back post saved.
Shrieves then went through on goal after Ward’s pass set him free down the right, racing through and aiming his strike across the Dunstable keeper. His shot was saved but only touched out to Ryan Smith on the edge of the box, but his shot on the rebound was wide.
The game had started to take a worryingly similar shape to the Real Bedford fixture in midweek as Irish were now dominating but struggling to take their chances, looking almost hesitant in front of goal.
Ryan Smith had another chance moments later, finding space on the left-hand side and collecting a through ball from Shrieves who was breaking down the middle however his shot was saved.
And then right on the stroke of half-time came the moment the home fans were waiting for.
In the scrappiest of styles, MK Irish finally took the lead through Spence, scoring his first competitive goal back in green and white.
The ball was worked down the right and found its way into the box before dropping to numerous Irish players, all seeing their shots blocked, it then fell to Shrieves with his back to goal who turned and scuffed a shot towards goal that was turned in by Spence to make it 1-0
The start of the second half brought a much scrappier feel to the game, with numerous fouls from Dunstable earning the referee’s attention as a couple of players went into the book.
Ty Ward almost doubled the scoring with what could have been one of the goals of the season just before the hour mark.
Picking up the ball on the left, just outside the area, the skipper turned one man and started making his way into the box. He went past a second, third and then beat a fourth before seeing his low shot saved.
With their FA Cup hopes on the line, Dunstable Town started pressing forward with twenty minutes left and Irish had seemed to fall back slightly, trying to protect the slender lead.
A succession of balls into the Irish penalty area followed and when one was met with a shot at Kyeremateng, the keeper spilled it and it fell kindly for a Dunstable attacker to score from close range.
Irish now had ten minutes left to find a way back into the game and looked to have the perfect chance as Shrieves was played through on goal.
The wide man had the pace to race past the defender and as he closed in to take a shot he was brought down, and the ref rightly pointed straight to the penalty spot.
Stepping up under pressure was Ty Ward – and he dispatched calmly into the bottom left corner to make it 2-1.
Dunstable Town had seemed to have already given their all to find the first equaliser and posed little threat in the search for a second, with Irish looking confident again after taking the lead.
With full time approaching and qualification in sight, the result was put out of any doubt after Ryan Smith collected the ball around 30 yards out and struck a powerful left footed drive past the goalkeeper to make it 3-1.
With the draw already made for the next round of the competition, the result means that Irish will now face the winner of FC Clacton v Real Bedford, with that fixture due to be rescheduled after a postponement today.