Troy Parrott scored twice for the host nation, while it was contrasting emotions for Portugal's number seven as Ronaldo received the first red card of his storied international career, in his 226th match.

AZ Alkmaar striker Parrott gave Ireland the lead after 17 minutes when a deep corner towards the far post was headed across goal by Liam Scales, and Parrott was on hand in the six-yard box to convert past Diogo Costa.

Chiedozie Ogbene struck the upright with a low, curling effort, but Parrott doubled the lead on the stroke of half-time as he managed to squeeze the ball in at the near post after taking down a hopeful long pass from Dara O'Shea.

Portugal's hopes of a turnaround were all but gone when Ronaldo was sent off after a pitchside VAR review, after the forward caught O'Shea with his elbow in a moment of frustration.

Goncalo Ramos forced a late save from Caoimhin Kelleher, but Heimir Hallgrimsson's side is three points behind Portugal in Group F and trails second-placed Hungary by only one ahead of their meeting on Monday (AEDT), which will bring the curtain down on its campaign.