Chapter 3. A crash course on Cisco’s Internetwork Operating System
If you’re used to using a graphical user interface (GUI) for system administration, administering a Cisco network will take some getting used to. Although Cisco has made a modest effort at point-and-click configuration utilities, the command-line interface (CLI) has always been available. It’s powerful, efficient, and mostly unambiguous. When you type configuration commands into a switch or router, you’re generally going to have a pretty good idea about what that command will do. Unlike a GUI, which hides a lot of things behind colorful buttons and user-friendly messages, the CLI is black and white.
If you’re not used to using the command line on other platforms like Windows or Linux, don’t worry. In many ways, the IOS CLI is easier because it provides inline help, which I’ll show you how to access in a moment.
The vast majority of Cisco routers and switches run the Cisco Internetwork Operating System (IOS). IOS controls every aspect of a device’s operation, including who can log into it, what traffic is allowed or blocked, whether an interface is enabled or disabled, and so on.