GNS3 is freely available and open source software that allows users to explore router configurations, design and test their own networks, and study for certification tests, all without spending a dime.

Before virtualization, the only way to learn about networking hands-on was to build expensive labs with physical hardware or pay outrageous training fees. No more.

No Starch Press' The Book of GNS3 (http://tinyurl.com/p9ehv6r), shows readers the many ways the software can be used—all without plugging in a single network cable. It's 272 pages and costs US$39.95. Readers of the book learn how to:

° Build networks of unlimited size and scope using Cisco and non-Cisco technology;

° Add Juniper routers to their projects with VirtualBox and QEMU;

° Connect GNS3's devices to physical hardware.

Author Jason C. Neumann is an active member of the GNS3 project, supplying code, moderating forums, and beta testing the GNS3 software. He's a network engineer with more than 20 years of IT networking experience, who holds multiple certifications from Cisco, Juniper, Microsoft, Novell, and VMware.