A student with diploma can also take admission into IIT by following the same procedure as other students do but for diploma students it is not that easy to get into IIT because you won't be studying all the subjects as other as 12th students there for you will face difficulty in the entrance exam and unlike other colleges are lateral entry is offered there is no such rule in IIT and you need to first clear JEE main and then JEE advanced then only you will get into IIT that too when you get a very good rank