GST ON TRANSPORTATION

Dear sir/ Madam. I want to know that when I registered in Bihar State and goods purchase from Delhi and bought in Bihar by transport who has registered in Delhi. in this case what should I paid- IGST under reverse or CGST and SGST what is the nature of transaction- Interstate or Intrastate. I use the tally software in which when I enter the GST of transporter then it auto take IGST under reverse charge. Please clarify my doubt. thanks in advance.