Cisco IOS software is the embedded software architecture in all Cisco IOS devices and is also the operating system of Catalyst switches. Its functions include carrying the chosen network protocols, connectivity, security, scalability, and reliability.
A switch or IOS device can be configured from a local terminal connected to the console port or from a remote terminal connected via a modem connection to the auxiliary port.
The CLI is used by network administrators to monitor and configure various Cisco IOS devices. CLI also offers a help facility to aid network administrators with the verification and configuration commands.