Many fast packet switches for the broadband integrated services digital network (BISDN) in the literature are based on banyan networks. Although banyan networks possess nice properties such as a simple control and a low hardware cost, they are unique-path networks. Since there is a unique path from an input to an output in a banyan network, a single component failure may disrupt services of some nodes connected to such a network. Moreover, banyan networks are also blocking networks; packets can be lost within the networks. To reduce the packet loss, buffered banyan networks can be used.In an earlier work' we have proposed the addition of backward links to otherwise unidirectional banyan networks to create B-banyans (and B-delta networks). Backward links not only function as implicit buffers for blocked packets, but also provide multiple paths for each input-output connection. However, the multiple paths in B-banyans may not be disjoint.In this paper, we enhance B-banyans and B-delta networks in such a way that the resulting networks can provide disjoint multiple paths for each input-output pair. The existence of disjoint multiple paths has a significant effect on the network fault-tolerance. The new networks, called FB-banyans and FBdelta networks, are k fault-tolerant, where k is the number of backward links per switch and is less than the switch size. They are also robust to more than k faults, depending on the locations of faults. The maximal fault-tolerance is achieved when k is the switch size minus 1. The performance of the new networks is analysed and compared to that of other networks of interest. FB-banyans and FBdelta networks can be used as a switch fabric for fast packet switches to provide performance comparable to that of buffered banyan networks and good fault tolerance.