What is Cisco IOS Software?

Cisco IOS (Internetwork Operating System) is a family of network operating systems used on a wide range of Cisco Systems hardware. It's the software that powers the vast majority of Cisco's routers and switches. It provides a command-line interface (CLI) for configuration and management, and implements key networking functions like routing protocols (e.g., OSPF, BGP), switching, security features (e.g., firewalls, VPNs), and quality of service (QoS).