A Customized Reconfigurable Interconnection Network (CRIN) refers to a minimal switching network, yielding routing solutions for any element in a pre-given set of routing requirements. The CRIN design problem looks for the best performance and resource-flexibility trade-off between two extreme design contexts ASIC and FPGA. In this paper we give the modeling of this problem for both directed and undirected interconnections. A heuristic algorithm for automatic generation of CRIN is proposed along with its experimental justifications. This study was motivated from the design of reconfigurable systems-on-a-chip for multiple applications.