Afghanistan were steered to their target by a 139-run partnership between Shah, who made 76, and debutant Janat, who hit an unbeaten 65.
Chasing 147 to win, Afghanistan were 29 for one at stumps. Ihsanullah Janat, on 16, and Rahmat Shah, on 11, were batting at close of play
The Irish team lost captain William Porterfield in the closing hour of the game at 22-1 after Afghan batsmen had dominated the day
Bowlers put Afghanistan in control despite a defiant half-century from Ireland number 11 Tim Murtagh
Left-arm spinner Geroge Dockrell led a disciplined bowling attack to set up the win as Ireland kept down Afghanistan to 216 for six
Afghan, who hit four fours and three sixes in his 70-ball stay, put on a crucial seventh-wicket partnership of 50 with Nabi
Balbirnie hit eight sixes and eight fours to set up the morale-boosting win that levelled the five match one-day series 1-1, with two matches to play.
Afghanistan, led by Asghar Afghan, lead the five-match series 1-0 after winning their opening match.
Teenage spinner Mujeeb Ur Rahman also played a key role in setting up the win after returning impressive figures of 3-14 from his 10 overs.
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