GNS3 is open source software that uses emulated router and switch hardware on Windows, OS X, and Linux to create a real world environment of complex networks. GNS3 is an excellent tool for network engineers, administrators, and anyone studying for Cisco or Juniper certifications. It can also be used to experiment with new network features or to verify configurations for later deployment on real devices. The Book of GNS3 shows network engineers and system administrators how to harness this tool. The author gently guides readers through the use of GNS3 with tutorial-based explanations, and each chapter introduces new concepts that build on skills from previous ones. You'll learn to create and manage simple to complex networks, using only a single computer or balancing the load across multiple computers.