Hello Dheeraj

If you qualify paper 2 of JEE mains and are eligible for JEE Advance,you can go for Barch.If you want to do Barch from NITs ,you don't need to give advance and paper 2 itself will do but if you want to do it from IIT,then first you have to qualify JEE advance and after that you have to give one more exam specially for Barch.Qualifying both,you will be eligible for Barch from IIT.Hope this helps.

Good Luck