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

I've been working with a startup for sometime. Now I have an offer from a competing company (in India) 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. 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 reasonable?) They have not specified anywhere what businesses are competing businesses of the company. Should I assume they mean any company that has a similar business? 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 - whether its within India or within the city/district or anywhere.