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Cisco IOS

Cisco IOS is the operating system that runs on Cisco networking devices such as switches, routers, and firewalls, and is managed through a command-line interface using tools like PuTTY over SSH.

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About this video

Cisco is one of the leading manufacturers of enterprise networking hardware, producing switches, routers, firewalls, and other infrastructure equipment. Many of these devices run Cisco IOS, a proprietary operating system designed specifically for configuring and managing Cisco hardware at scale. Understanding IOS is a foundational skill for anyone working in network administration or cybersecurity. Access to a Cisco device running IOS is typically established remotely over SSH, using a terminal emulator such as PuTTY on a Windows machine. Once connected, the administrator works entirely within a command-line environment, entering commands and receiving text-based output in return. The interface is mode-driven, meaning the available commands depend on the current mode, whether that is privileged EXEC mode, global configuration mode, or an interface-specific configuration context. Navigating between these modes requires specific commands, such as configure terminal to enter global configuration mode or interface followed by the interface identifier to configure a specific port. The question mark can be entered at any point to display a list of valid commands in the current context, making it a useful tool when exploring an unfamiliar device. The show version command, run from privileged EXEC mode, returns key details about the device including the version of IOS currently installed, providing a reliable starting point for any diagnostic or configuration session.

What you'll learn

What's covered

Cisco IOS Overview

Aligned to

CompTIA A+ Core 1
2.2 Compare and contrast common networking hardware.
CompTIA A+ Core 2
4.9 Given a scenario, use remote access technologies.
Cisco CCST IT
3.3 Examine basic end-device connectivity to the network

Key terms

Secure Shell
SSH
A cryptographic network protocol that provides secure remote login and command execution over an unsecured network.
Switch
A network device that connects devices within a LAN and forwards traffic based on MAC addresses.
Internetworking Operating System
IOS
Cisco's proprietary operating system running on most Cisco routers and switches, providing a command-line interface for device configuration, management, and monitoring. IOS is the foundation for Cisco's network equipment and has evolved into variants such as IOS XE, IOS XR, and NX-OS.
Privileged EXEC Mode
A Cisco IOS CLI mode that provides access to all device commands, including monitoring and configuration commands, indicated by the # prompt.
Global Configuration Mode
A Cisco IOS CLI mode entered via the configure terminal command that allows system-wide configuration changes to the device.

Topics

Cisco Ios Command Line Interface Networking Ssh Cisco Switches Network Administration

Transcript

Connecting to a Cisco Device

Cisco is a large company that manufactures networking equipment — things like switches and routers and firewalls — and they build out some of their own operating systems for those devices. We're going to explore one of those.

I'm on a Windows machine here, so if I click on Windows you can see that it's just a Windows machine, but I've got this program running called PuTTY, and I've remoted in, I've SSH'd into a Cisco device. Now I have a console into that Cisco device, and I can start typing commands into this and then start getting responses back. This is very typical of how we interact with a lot of Cisco equipment.

Navigating with Commands

In here I can hit a question mark and it's going to show me a list of commands that I can do on this device — and this device is a switch, by the way. If I want to navigate through this, I have to use commands to do it. With configure terminal, or conf t for short, I can get into the global configuration mode. Or if I want to get into an interface, I've got to type in the interface that I want to get into, and then I'm in the interface and I can do configuration of that interface.

I'm going to go back to the privileged exec mode here and type in show version, where we actually see some detail around the version of this. We can see right from the get-go this is a Cisco IOS software, so this is the operating system for the Cisco device, and then it tells me things like the version that this is. So this is another operating system that we can find on many Cisco devices.

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