Book excerpt: To become a Cisco Certified Network Associate (CCNA), you must learn the hundreds of IOS commands used by Cisco routers and switches. This handy reference from Cisco networking authority Todd Lammle is just what you need to master those commands. From a thorough introduction to Cisco's basic operating system to making the transition to IPv6, Todd Lammle walks you through hundreds of commands with short, to-the-point explanations and plenty of figures and real-world examples.