The Belfastmen, who lifted the Heineken Cup in 1999, inflicted Munster's first home quarter-final defeat and will now face Scottish outfit, Edinburgh, in an all Pro12 semi-final at the Aviva Stadium in Dublin.
Ferris overcame an ankle injury to make the starting line-up and he praised his side's heroic defensive effort in which they made a staggering 159 tackles.
"We have a good squad here and that is what it takes to break this Munster team down," he said.
"We got off to a terrific start, with Ruan Pienaar kicking well, but our defence was the difference. It was just a great team effort, especially when the Munster boys came at us with their crowd behind them.
"We knew it was going to be a long afternoon for us but the defence was key and we kept on getting on top of them. I don't think they had a linebreak all day and I thought we were outstanding in that area.
"We talked at the start of the season of taking another step as a side, and we feel we have the team to go places. We wanted to make a statement in European rugby and we had to come here and get a win to do that.
"It's a tough place to come down here but I said in the build up I firmly believed we could come down here and win. We have done that now.
"Edinburgh showed against Toulouse that they are a good side. They are playing some good rugby and we know that is going to be a tough game for us, but one we are really looking forward to."