Chennai airport Taxi

I read the stories of walking up 1/2 kM to get Uber/Ola in the new building at the Chennai airport. Where can I get the local airport taxi? Is the counter to buy the airport taxi tickets inside or outside the airport? I am flying from Mumbai early morning and need to reach Nanganallur, I believe it is just 3 Kms from the airport. Are the airport Taxi guys reliable and not like auto drivers who haggle over prices ? Thank you.