Longford Town 2 Limerick FC 1
Shane Barrett scored twice early in the second half to kill off cash-strapped Limerick's cup hopes at Flancare Park.
Barrett volleyed Town in front with a stunning goal on 48 minutes before driving home from the edge of the area for the second four minutes later.
Limerick battled away and gave Town some nervous moments late on after Paul Finucane headed home a Paul Heffernan free kick ten minutes from time.
But Alan Matthews' midlanders held on to book their place in the quarter-finals.