hi vijayakumar,

The JEE Main eligibility for admission to the NITs has changed from the year 2017.while on the surface the criteria specified seems to be pretty simple and clear ,the reality begs to differ. the JEE Mains eligibility had two main changes. first thing was the removal of the normalization that was used to arrive at the JEE Mains score. the second one is the new eligibility clause for b.tech admissions at the NIT's , IIT's and the CFTI's ; that is ' Admission to NIT's , IIT's and the CFTI's  participating through central seat allocation board will be based on All India Rank subject to the condition that the candidate should have secured atleast 75% marks in the 12th class examination or be in the top 20 percentile in the 12th class examination conducted by the respective boards . for SC/ST  candidates the qualifying marks would be 65% in the 12th class examination.

hope the information was helpful

all the best:)