Cisco Network Operating Systems
Depending upon the platform, the purpose, and the required features, Cisco delivers networking devices with various types of network operating systems. This note summarizes each of them.
IOS
Cisco's Internetwork Operating System or IOS is the original operating system for Cisco networking devices, designed for older routers and switches. It uses a monolithic architecture, meaning all processes run as a single system, making it simple but less fault-tolerant. While lightweight and suitable for basic networking, it lacks modern features like programmability and advanced modularity. It is primarily found in legacy equipment, such as the Cisco 2800 and 3800 series routers.
IOS-XE
Cisco IOS-XE is a modern, modular operating system built on a Linux kernel with an IOS process running on top. It supports advanced programmability, automation frameworks (like NETCONF and RESTCONF), and enhanced security features. The modular design separates control and data planes, improving fault tolerance and stability. IOS-XE powers newer devices like the Catalyst 9000 switches and ASR 1000 routers, making it ideal for enterprises and SD-WAN deployments.
IOS-XR
Cisco IOS-XR is a carrier-grade operating system designed for service providers and high-performance routing. Its microkernel architecture isolates processes, allowing for in-service software upgrades (ISSU) and high fault tolerance. With support for advanced routing protocols like BGP, MPLS, and segment routing, IOS-XR is built for scalability and reliability in large-scale environments. It is commonly used on platforms like the ASR 9000 and NCS 5500 series routers.
NX-OS
Cisco NX-OS is a Linux-based operating system tailored for data center environments. It offers advanced Layer 2 and Layer 3 switching, support for data center fabrics (such as VXLAN and EVPN), and integration with Cisco ACI. With its modular design and focus on high availability, NX-OS is optimized for high-throughput, low-latency environments. It is deployed on Cisco Nexus switches, including the Nexus 9000 series, making it a cornerstone of modern data centers.
Comparison Table
| Feature | IOS | IOS-XE | IOS-XR | NX-OS |
|---|---|---|---|---|
| Primary Use | Legacy routers/switches | Enterprise routing/switching | Carrier-grade routing | Data center switching |
| Architecture | Monolithic | Modular Linux-based | Microkernel | Modular Linux-based |
| Scalability | Limited | Medium | Very high | High |
| High Availability | Minimal | Supported | Strong | Strong |
| Key Features | Basic networking | Automation, APIs | Carrier protocols | Data center fabrics |
| Example Devices | 2800, 3800 routers | Catalyst 9000 | ASR 9000, NCS | Nexus 9000 |
Links
https://networklessons.com/cisco/ccie-routing-switching-written/introduction-cisco-ios-xe
https://networklessons.com/cisco/ccna-routing-switching-icnd1-100-105/cisco-ios-boot-system-image
https://networklessons.com/cisco/evolving-technologies/device-programmability
https://networklessons.com/miscellaneous/how-to-build-a-network-home-lab