The win enabled India to avenge their 2-3 loss against the same opponents in the last round robin match yesterday.
For India Varun Kumar (5th, 32nd minutes) scored a brace, while Shilanand Lakra (28th) and Gurjant Singh (37th) found the bet once each.
Ireland's lone goal came from the sticks of Julian Dale in the 48th minute.
India began strongly and earned back-to-back penalty corners in the fifth minute. Though the first attempt was saved, Varun sounded the board from the second chance to hand his side he lead.
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India continued in the same vein and won another penalty corner in the 32nd minute and Varun scored with a fierce dragflick past Carr to help India tale a comfortable 3-0 lead.
India's next goal came off Gurjant's sticks in the 37th minute. It was brilliant play by Talwinder Singh, who received a good pass from Simranjeet Singh who laid it to Gurjant and the young striker from Punjab made no mistake in slotting the ball home.
India earned another penalty corner in the 50th minute and another one towards the dying minutes of the match, but they failed to make use of both the opportunities.