Fred Durst Busts Out Some Nookie ... Karaoke Style!!!

Fred Durst partied like it was 1999 Monday night -- reprising the classic Limp Bizkit song "Nookie" at an L.A. bar ... and it was all caught on tape!

Sources tell TMZ, Durst hit up open karaoke night at Rock & Reilly's with Nick Swardson and Cedric Yarbrough from "Reno 911" -- and the trio performed a bunch of other songs ... like Gnarls Barkley's "Crazy."

Overall, the beatboxed version of "Nookie" ain't too bad -- in fact, we now feel slightly less embarrassed about listening to Limp Bizkit in high school.