Madrid arrive in the Bavarian capital holding a 1-0 lead thanks to Karim Benzema's 19th-minute goal in last Wednesday's first leg in Madrid and are looking to avenge their defeat at the same stage to Bayern two years ago.
History is on the Germans' side.
Bayern have never lost to Real in Munich, with eight victories and one draw, to lead the overall series with 11 victories to Madrid's eight from 21 encounters.
The second-leg is finely poised.
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Ballon d'Or winner Cristiano Ronaldo proved he is fit for the Munich clash after a hamstring injury by scoring twice to leave him on 47 goals for the season.
Real coach Carlo Ancelotti rested stars Benzema, who picked up a knee knock in the first leg, and Gareth Bale, who was recovering from flu, at Osasuna.
The Italian has insisted both men should be fit to start at the Allianz Arena.
"Everyone should be calm because we are going to prepare properly.
"The objective is to score, not to defend, and that is the manner in which we will continue to work."
Ancelotti has never lost to a German team in six encounters from his time as AC Milan manager, but the key to Tuesday's game will be who scores first.
Real will be chasing the first goal in Munich which would leave Bayern needing to score at least three times to progress to their fourth Champions League final in five years.