Jonson Clarke-Harris and Jack Taylor goals wrapped up the a win to give Posh the win they needed, with the Rams losing 1-0 at Sheffield Wednesday.
It means Posh host the Owls in the first leg of the play-off semi on Friday.
Club photographer Joe Dent captured just some of the travelling fans.
Check out this gallery and see if you can spot a familiar face.
All these pictures can be bought by visiting www.theposhpics.com
You can get all the build up to the big match, here.
Club photographer Joe Dent captured just some of the travelling fans.