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We propose to introduce redundant interconnects for manufacturing yield and reliability improvement. By introducing redundant interconnects, the potential for open faults is reduced, at the cost of increased potential for short faults. Overall, manufacturing yield and fault tolerance can be improved. We focus on a postprocessing, tree-augmentation approach, which can be easily integrated in current physical design flows. Our contributions are as follows. 1) We formulate the problem as a variant of the classical two-edge-connectivity augmentation problem in which we take into account such practical issues as wirelength increase budget, routing obstacles, and the use of Steiner points. 2) We show that an optimum solution can always be found on the Hanan grid defined by the terminals and the corners of the feasible routing region. 3) We give a compact integer program formulation which is solved in practical runtime by the commercial optimization package CPLEX for nets with up to 100 terminals. 4) We give a well-scaling greedy algorithm which has a practical runtime up to 1000 terminals, and comes on the average within 1%-2% of the optimum computed by CPLEX. 5). We give a comprehensive experimental study comparing the solution quality and runtime of our methods with the best methods reported in the literature.