Cork Con took advantage of Shannon's slip up to move back to the summit in Division One.
Five penalties from the boot of Munster-capped out-half Jeremy Manning helped Con to this win at the RDS.
Manning sent up a neat kick after only 90 seconds' play for winger Cronan Healy to collect and score in the right corner.
In the seventh-minute, Lansdowne's former Ireland U-20 prop Ruaidhri Murphy charged over for a try from 30 metres out.
However, Con fought back to lead 11-7 at half-time and Manning's boot did the rest.
Winless in their last five Division One games, Lansdowne came into this fixture looking to make amends for some poor recent performances, but they got off to an awful start when the New Zealand-born Manning orchestrated Con’s first try.
Manning combined well throughout with his half-back partner Duncan Williams, who caused plenty of problems for Lansdowne around the fringes of rucks.
Lansdowne responded in style to that early concession when young prop Murphy took the ball on and managed to beat the cover defence to score a fine try, which Robbie Dolan converted for the lead.
Unfortunately, both Murphy and Con front rower Colm Murphy went off injured during the first half and those stoppages broke up the play, as did former Con captain Frank Cogan’s yellow card in the 20th minute.
Playing with 14 men did not see to phase Con - it seemed to unify them.
Penalties followed from Manning after 27 and 32 minutes – his second kick a beauty from close to the halfway line – as Brian Walsh’s men moved 11-7 clear.
The second half saw the heavier Con pack gradually get on top and with Lansdowne’s lineout coming unstuck, the Leesiders added to their lead.
Dolan did briefly make it 11-10, but successful kicks from Manning after 52, 59 and 71 minutes helped close out the game.
After being suffocated in their own half for much of that period, Lansdowne managed to gain some decent territory in the dying embers of this game and a Dolan penalty in the 79th minute notched a losing bonus point for the Dublin 4 outfit.
Scorers: Lansdowne: Try: Ruaidhri Murphy; Con: Robbie Dolan; Pens: Robbie Dolan 2
Cork Constitution: Try: Cronan Healy; Pens: Jeremy Manning 5
