This book covers the design of multilayer switches starting from the basic concepts, and continues with the basic architectures. It then delves into router and switch systems. It is written to appeal to a broad audience from students to experienced researchers and engineers. The book describes the evolution and design of networking devices, helping those interested in knowing the bigger picture understand how these devices are made, their various advances, and how these devices will continue to play a major role in interworking for the foreseeable future. All discussions are done taking into consideration applicable examples, cases, and illustrations.