The defender is currently out of favour at Crystal Palace.
The defender is out of favour at Selhurst Park, with defensive duo Scott Dann and Damien Delaney currently the first choice central pairing this season.
As a result, Mariappa has made just one Premier League appearance so far this season, and is free to leave the club in the January transfer window.
That has alerted Championship duo Fulham and Reading, who are both interested in a move for the defender according to the Mirror report.
Reading are keen to re-sign their former star, who made 29 appearances for them in the Championship during the 2012-2013 season before they sold him to Palace that year.
Fulham meanwhile, are more interested in a loan deal until the end of the season, with a view to taking him permanently in the summer.
Slavisa Jokanovic’s side could certainly do with adding some defensive steel to their team, with them currently having the second worst defensive record in the Championship.
They have conceded 47 goals in 27 games so far and could do with improving that record in the second half of the campaign if they are to avoid a relegation battle, with them currently just four points away from the bottom three.