Cluster systems gain more and more importance as a platform for parallel computing. In this area the power of the system is strongly coupled with the performance of the network, which has to provide high bandwidth and low latency. Besides these performance aspects fault-tolerance within the network is very important. This paper shows how to build a flexible and faulttolerant router, the main building part of a network. In addition the overhead for the execution of fault-tolerant routing algorithms is examined.