What is Cisco IOS software, and how does it work?

What is Cisco IOS (Cisco Internetwork Operating System)?

Cisco IOS (Internetwork Operating System) is a collection of proprietary operating systems (OS) that run on Cisco Systems hardware, including routers, switches and other network devices.

Developed in the 1980s by William Yeager, an engineer at Stanford University, the core function of Cisco IOS is to enable data communications between network nodes. Cisco IOS enables the management, operation and management of Cisco network devices.

Cisco IOS includes the following key features:

  • Interface configuration.
  • Network management and monitoring.
  • Quality of service (QoS).
  • Routing.
  • Security.
  • Transfer.

Cisco IOS offers many additional services that an administrator can use to improve the performance and security of network traffic. These services include authentication, encryption, firewall capabilities, policy enforcement, deep packet inspection, intelligent routing and proxy server capabilities. In Cisco’s Integrated Services Router, IOS can also support call processing and unified communications services.

In addition to the standard Cisco IOS, there are three main variants of the OS: IOS XE, IOS XR and NX-OS.

Cisco IOS is not to be confused with Apple iOS, the consumer OS for Apple’s mobile devices.

photo of the Cisco MDS 9000 Fiber Channel switch
The proprietary Cisco IOS (Internetwork Operating System) runs on Cisco Systems hardware, such as switches (pictured), routers and other network devices.

What is Cisco IOS based on?

As proprietary software, Cisco IOS is not based on other OSes, such as Linux. It is a monolithic OS with a custom kernel. However, recent incarnations, including IOS XE, are based on the Linux kernel. It provides modularity and other modern features not found in basic IOS, including memory protection, virtualization support, high availability (HA), scalability, automation capabilities, improved security features and enhancements. service software upgrade.

Cisco IOS software releases are categorized into what Cisco calls trains, throttles and rebuilds:

  • Trains. The trains have numbers and letters. The number is similar to a software version number, such as 8 or 12. The letter represents the type of release. For example, T (technology) train releases include the latest features and functionality but may be considered less robust. In contrast, the M (mainline) train releases are more focused on stability, including time-tested features and bug fixes, although that often comes at the expense of more up-to-date and new features.
  • Throttles. Throttles are represented as numbers in parentheses, such as (5) or (11). Cisco calls it “a minor version number” to indicate minor feature updates that do not require a full software version update.
  • Rebuilding. Reconstructions appear as numbers after the train. They are issued primarily for additional bug fixes.
kernel layout diagram
Newer editions of Cisco IOS, including IOS XE, are based on the Linux kernel.

What is Cisco IOS XE?

Cisco IOS XE is an IOS version that runs on top of the Linux kernel. It is supported by Cisco’s newer enterprise switching, routing and wireless devices. IOS XE can be found in many Cisco products, including its Catalyst 9000 switches, 1000 Series Aggregation Services Routers and Catalyst 9800 wireless controllers, among others.

Although IOS XE and IOS share much of the same code, IOS XE is a more modular, feature-rich version. IOS XE provides more advanced functionality and scalability. In particular, it separates the data plane and the control plane — providing greater agility — and allows programmability using open, standards-based interfaces. Other key features and benefits of IOS XE include improved user experience, unified management, modular architecture virtualization, HA and software redundancy.

What is Cisco IOS XR?

Cisco IOS XR runs on networking devices intended for service providers. It has a completely different codebase from IOS XE. Since its 6.x release, Cisco IOS XR has been based on Linux. Previously, it was based on QNX, a Unix-like OS.

IOS XR is designed for scalability and reduced complexity in large networks operated by carriers and internet service providers. The latest version of IOS XR focuses on a modular design with management application programming interface (API) integration and network automation. Other key features and benefits of Cisco IOS XR include HA, advanced multicast, extensive QoS and software package management.

What is NX-OS?

Cisco NX-OS is a network OS specifically for data center-oriented products, especially the Nexus series of switches. NX-OS provides modularity, resilience and scalability. NX-OS also offers enhanced features optimized for modern data centers that host hybrid clouds and other complex business environments. Key features and benefits of Cisco NX-OS include operational simplicity, architectural flexibility, system stability and end-to-end visibility.

What are Cisco IOS devices?

Cisco IOS devices are network hardware devices that run IOS. These devices include a variety of networking products, such as routers, switches, network security devices, wireless controllers and special hardware for wide area network aggregation.

photo Cisco UCS X-Series integrated computer system
Cisco UCS X-Series is a unified computing system for hybrid clouds.

What is Cisco IOS Firewall?

The Cisco IOS Firewall is a set of security features available in Cisco IOS. IOS Firewall provides integrated firewall functionality directly within Cisco routers, enabling simultaneous routing and firewall capabilities.

IOS Firewall includes the following features:

  • Application inspection and control.
  • Context-based access control.
  • Disk protection OS.
  • Intrusion detection system.
  • URL filtering.
  • Blocking Java.
  • Per-user authentication and authorization.
  • Stateful packet inspection.
  • Virtual private network integration.

What are Cisco IOS commands?

Cisco IOS commands are used to configure, manage and troubleshoot Cisco networking devices. Administrators can enter these commands through the Cisco IOS command-line interface (CLI). These commands can be categorized based on their uses, such as global configuration, interface configuration, routing, diagnostic and maintenance commands.

The specific commands and their syntax often vary depending on the IOS version, the device type and the installed feature set. IOS commands include different subsets of arguments and keywords to enable additional functionality.

What is the help command in Cisco IOS?

IOS’ CLI provides context-sensitive help accessible via a question mark (?) immediately. Whenever users type a question mark, it presents a list of available options and commands relevant to the current context. It is important to master Cisco IOS commands to engineer and manage Cisco devices.

Read how network automation software eases challenges for IT and why network modernization fuels automation and orchestration. Explore the seven characteristics of next-generation networking, and learn about the elements of a modern network security architecture. Explore 12 common network protocols and their functions, and discover four network resiliency factors.

Leave a comment