Short answer is Yes! Ignou takes an entrance exam commonly known as OPENMAT which is conducted by the National Test Agency (NTA). If you wish to pursue MBA from IGNOU, it is mandatory to qualify the openmat exam for being eligible to enroll. The exam is conducted twice every year.
Difficulty level: The Openmat exam is an aptitude test, which is not very tough to clear. It comprises subjects like English, reasoning, mathematics/quant & general awareness.
Process: Candidates need to fill an application form online for appearing in the openmat entrance exam. After qualifying the exam your scorecard is valid for a year & you can take admission accordingly in any semester if you fulfill other eligibility criteria of the university as well. Detailed information of the university like fees, admission procedure, eligibility, accreditation can be easily found at this link.
However, there are various other universities you can choose from if you are not desirous to take an entrance exam. This link will help you in doing that task.