Derry City easily overcame near neighbours Finn Harps, 4-0, to book their place in the FAI Ford Cup fourth round.
Ex-Harps man Stephen McLaughlin helped himself to a first-half brace. Early in the second half Rory Patterson and Barry Molloy also found the net.
The Donegal men never looked like causing an upset as Declan Devine's side took complete control of the tie after McLaughlin's double and in truth should have won by a bigger margin.
Harps created the first chance of the tie on ten minutes when Paul Simon Tracey's pass released Paul McVeigh, but after breaking the Derry offside trap, his shot from just inside the box was saved by Gerard Doherty.
Soon after Derry's Rory Patterson began to cause problems for the visitors but after showing great strength inside the box to hold off Arron O'Hagan, his right footed shot was saved by Ciaran Gallagher.
On 28 minutes Tracey was inches away from giving his side the lead when his 30-yard effort, which had Doherty beaten, fizzed just past the keeper's right hand post.
City opened the scoring two minutes later after a goalkeeping error by Gallagher.
Patrick McEleney's left-wing corner drew the Harps net-minder from his line, but the ball sailed over him and the alert Stephen
McLaughlin was on hand to turn the ball home into the unguarded net, for the left-winger's fourth goal in as many games.
Ten minutes later McLaughlin netted his second of the tie in outstanding fashion, when he flicked the ball up for himself on the edge of the box before unleashing an unstoppable volley past Gallagher.
It was just before the hour mark when the Candy Stripes netted twice within a minute.
Firstly, Owen Morrison's clever through ball released Patterson and he calmly lifted the ball over the stranded Gallagher and then on 59 minutes a fantastic pass by Ruaidhri Higgins found an unmarked Barry Molloy who he headed home.
Six minutes from time Derry went close to adding a fifth, but Higgins' curling shot, which had Gallagher beaten crashed against the bar.
Derry City: Doherty, Madden, McEleney, McBride, McCaffrey; Morrison, Higgins, Molloy, McLaughlin; McEleney Patterson. Subs: Farren for P McEleney (64); McCallion for S McEleney (71); McDaid for Patterson (75).
Finn Harps: Gallagher, McVeigh, Coll, Hutton, O'Hagan, McGowan, McBride, Tracey, Bonner, Harkin, Green. Subs: Merritt for Harkin (57); Duffy for Tracey (71).
Referee: Paul Tuite (Dublin).