What is the validity of Non-compete clauses in India?

I have been working with a startup for sometime. Now I have an offer from a competing company which I'm inclined to accept. I've had a chat with the founder of my current startup, and he is saying I won't be able to join the company as I had signed a non-compete, and if I do, legal action will be taken against me. According to this non-compete, I won't be able to be employed with or be engaged in any business that is directly competing with the business of the company for a period of 24 months (Is this time period reasonable?). They have not specified anywhere what businesses are competing businesses of the companies, should I assume they mean any company that has a similar business? Also, I read that in non-compete clauses, the distance within which you aren’t allowed to be engaged in a competing business is supposed to be mentioned. This is not there in the clause of my current employer. They haven’t specified the limits anywhere in the clause within which I’m not allowed to be engaged a competing business - whether its within India or within the city/district or anywhere in the world. The clause is of 3 lines, saying - I won’t be allowed to be employed, or engaged in any business that is directly competing in material aspects with the businesses of the company for a period of 24 months.