Spurs rally to reach FA Cup semis
Bobby Zamora gave Fulham an early lead against his former club in the quarter-final replay as Fulham, still going strong in the Europa League, looked to continue their hot streak.
However, a goal with his first touch by second-half substitute David Bentley levelled the tie.
Another substitute, Roman Pavlyuchenko, continued his great scoring run with the second and Eidur Gudjohnsen completed the job.
The victory took eight-times winners Spurs into the last four for the first time since they lost to Arsenal in 2001 as they seek to win the trophy for the first time in 19 years.
It also meant an emotional April 11 Wembley reunion with Portsmouth for Redknapp, who won the Cup there with the troubled south-coast club in 2008.
"It will be a funny old day, a strange day really," Redknapp told reporters.
"They have got great support. It will be a great atmosphere. Everybody would love to see Portsmouth go back and get to a Cup final. They have been through the mill this year."
Holders Chelsea play Aston Villa in the other semi on April 10.