It is not the end if one could not crack the CAT entrance exam and get admission to a coveted IIM. In fact, some of the IIMs do not match with established institutes like TISS, XLRI, FMS, and IIFFT. So there are other opportunities for you to enter the management institutions. The easier way is the entrance test conducted by the institution on its own. Institutions like XLRI accept GMAT and have their own group of admission tests. Most of the others do accept the scores of common entrance exam that include MAT, ATMA, and GMAT.
In the case of a particular state, most of the states conduct State-level entrance exams for institutions within the state including the affiliated universities of relevant states. The best thing to remember is that MBA may be the dream but, not an end. CAT is just a means to reach your dream. Besides CAT, there are other MBA entrance exams you can get through to reach the destination.