To get admission in M.Tech in NITs, you will have to crack Gate entrance and counseling will be done through CCMT only.

Also, the cut off varies year, branch, quota and category wise so you can check the cut off trend in below link -

https://engineering.careers360.com/articles/gate-cutoff-for-nit-calicut

You can also refer below article to know all about Gate and CCMT counseling -

https://engineering.careers360.com/articles/gate

https://engineering.careers360.com/articles/ccmt

Good Luck!!!