Ulster A were made to work hard for their victory over Leinster A at Ravenhill.
The home side scored the only try of the game but it was a strong defensive display in the second half that paved the way to a second consecutive victory following a win over Connacht.
Out half Kieran Hallett gave Ulster an early lead with a long range penalty.
Winger Paul Kenzie went over for the sole try on 14 minutes.
The Belfast Harlequin took a pass from centre Darren Cave and sprinted over in the corner but Hallett was unable to convert.
Leinster out half Ian Keatley reduced Ulster's lead at the break to 8-3 when he slotted over a long range penalty.
Keatley was on target with his second penalty on 50 minutes after winger Fionn Carr cut through a static Ulster defence.
Hallett landed his second penalty from just inside the Leinster half to extend the home side's lead after the visitors failed to release the ball on the ground.
Ulster should have added another try but centre Seamus Mallon was unable to put winger Chris Cochrane away.
Leinster finished the game stronger but couldn't create a winning score.
They kicked a penalty to touch but Ulster were able to stop the resulting rolling maul while scrum half Paul O'Donohoe nearly broke free.
Leinster last chance ended when they lost the ball forward from another attacking drive and conceded a penalty which allowed Ulster to clear their lines and hold out for victory.