This chapter provides an overview of Cisco routers, all of which share the common Cisco Internetwork operating system (IOS). This common operating system allows for simplification and generalization of administration, affording administrators ease of use. The majority of routers also have two physical interfaces—a console port and an auxiliary port. Cisco routers can use Simple Network Management Protocol (SNMP) to interoperate with common network management systems such as CiscoWorks, HP OpenView, and SMARTS. A Cisco router has two basic levels of access—user mode and privileged mode. Commands generally fall into two types—configuration commands and shows commands. Administrators also have the capability of taking advantage of shortcuts in the Cisco IOS. Shortcuts enable an administrator to enter the beginning of a command and the system recognizes the rest. Enough information should be provided for the command entry to be unique. Another feature built into the IOS is the capability of auto-completing a command by pressing the Tab key. Enough information should also be provided to make the command unique. Cisco has several shortcut keystrokes built into the system to make entering commands quicker. A common management and configuration framework is the goal of any good network equipment provider, and Cisco systems have achieved this goal in a commendable fashion.