A brilliant opener from Benzema, plus further strikes from Arbeloa and Ronaldo double gave Real Madrid a dominant win in Amsterdam.
Los Merengues took the lead thanks to Karim Benzema, before an Alvaro Arbeloa long-ranger and the customary Cristiano Ronaldo goal and penalty put the game to bed, but in all honesty it was never even a contest.
Ajax badly needed a win to stay in contention in Group G but it was the away side took the game to Ajax from the off with Mesut Ozil having the first effort at goal, but he took to long in getting his effort away and it was blocked.
Benzema had the next chance for Real Madrid but he was kept out by Maarten Stekelenberg, and only a few minutes later Madrid had a real shout for a penalty when Ronaldo was brought down in the box by Gregory van der Wiel but the referee waved play on, much to the annoyance of the Portuguese.
Ajax did get into the match a bit more after being put under pressure for the opening 20 minutes but they failed to penetrate the Real Madrid backline and as a result Mounir El Hamdaoui and Luis Suarez were growing frustrated.
However, as the half wore on and Ajax started to venture further away from their own goal, Jose Mourinho's charges picked them off on the counter with Pedro Leon working back well to win possession and start such attacks.
Then from a quickly taken free-kick Xabi Alonso played a magnificent ball over the top to Ozil, who backheeled into the path of Benzema which set the Frenchman up to smash the shot into the top corner from just inside the penalty area.
That goal had been coming and only ten minutes later it was two and if the first was a special goal the second was even better.
Ronaldo's free-kick was deflected back away from goal and Arbeloa smacked the ball from 30 yards out. It completely fooled Stekelenberg and whistled into the back of the net just before the break.
Straight after the restart Ronaldo was played through on goal by Benzema but his shot from just inside the penalty area was saved by Stekelenberg who managed to deflect the ball onto the crossbar after is squirmed underneath him.
As the half wore on Real were still dominated proceedings but Ajax did eventually get a shot on target when a free-kick was saved by Casillas but seconds later Madrid went further ahead when a pass from Urby Emmanuelson was intercepted by substitute Angel Di Maria who found Ronaldo on the left and his shot was buried into the far corner.
Emmanuelson's evening was to get worse then he took down Ozil on the edge of the penalty area and Ronaldo converted the spot kick with consummate ease.
Los Merengues even found time to get Xabi Alonso sent off as he received a second yellow card for time wasting. As stupid as that was Real Madrid went down to nine men when Sergio Ramos was given his second yellow for time wasting as well.
Luckily both dismissals were in the closing stages of the game, but Mourinho was fuming at the stupidity of his players.
The result means Real Madrid are now confirmed as Group G winners, while Ajax travel to Milan in two weeks knowing that the best they can hope for is Europa League football after Christmas.
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