The switched fabrics are going to play an impor- tant role in the future internetworking. At present the major architecture for internetworking is router- based. The bridges are also important players in in- ternetworking but considering the variety of proto- cols and lack of intelligence in bridges, the routers are the major players. The problem with the existing router based internetworking architecture is limita- tions on the speed. The new applications, specially the multimedia and real-time ones demand more and more bandwidth and speed. The virtual switch-based networks are the solution and the latency in switch fabrics is much less than the latency of fast routers. The simple form of such switch fabrics is switched LAN. Switched LANS are basically layer 2 bridging. But the new generation of virtual networks is mostly based on ATM. ATM-based switched virtual LANS have different formats. ATM LAN emulation, ATM virtual routers, and ATM edge routers are different approaches that try to combine the routing and switching. ATM LAN emulation started with simply bridging LANS and now has started to support multi- protocol routing too. Edge routers and virtual routers are based on the switching, routing, and virtual sub- nets. Relational network combines the multilayer re- lational switches with traditional routers and in this case the relational switches don't do the routing. Each of these different approaches to switched virtual networks has its own cons and pros. Lots of standards have to be defined in this field. The ATM-based switched virtual networks are used in all levels of in- ternetworking, from small workgroups up to large WANS.