A network switch fabric is provided for a clustering system to facilitate flexibility of network-related interconnection selection and system scalability. The network switch fabric includes replaceable network switch(s) and network interface(s) selectively configured on a base board. Multiple types of interconnection protocols with similar characteristics will be able to implement on a common infrastructure of network switch fabric. A pass through card operating as a network interface is also applicable on the network switch fabric to directly connect with an external network. The pass through card allows the network switch fabric supporting the clustering system to be scalable, thereby capable of supporting a large-scale cluster computing.