Lansdowne, who won three titles between 2013 and 2018, sit third in the standings, just two points behind second-placed Cork Constitution.
It was a close run thing when Lansdowne and Clontarf met in early December on the back pitch at the Aviva Stadium.
Both sides secured a try-scoring bonus point in a high-scoring match that ended 31-27 and saw Andy Wood's pacesetters take the spoils - watch the highlights here.
So, it is all nicely set up for a cracking rematch between the top flight heavyweights at Castle Avenue today. Our coverage starts at 2.15pm, 15 minutes ahead of kick-off.