It's highly modular, highly available, and does have some command line differences between it and IOS and IOS-XE.Ĭisco NX-OS is the latest iteration of what used to be SAN-OS, which ran on the MDS series of fabric channel switches. There's also a different version number, which has a 1:1 correlation to the IOS-XE release version, which is the IOSd version number (i.e., each IOS-XE release number has a corresponding IOSd version number), and is the classic IOS version scheme like 15.2(4)S6.Ĭisco IOS-XR is an operating system designed to run on carrier-grade equipment like CRS routers and ASR9ks. The first is the IOS-XE release number, which is in the usually in a format like 3.7.3S. One important note is that you'll often see two version numbers for IOS-XE. Because an actual copy of IOS is the front end, there's very, very little difference between the IOS-XE command line and classic IOS. A lot of the stuff is still handled by code inside the IOSd process, others are in different Linux processes. This is what you'll sometimes hear referred to as "IOSd".
It's essentially a Linux-based platform with a copy of Cisco IOS running as a separate process, or daemon, acting essentially as the front-end and control process.
You'll find this version of software on most "older" Cisco routing and switching products.Ĭisco IOS-XE is the "new and improved" version of Cisco IOS and is found on most new platforms.
It's a monolithic kernel with limited modularity and multitasking features. Cisco IOS is the "original" Cisco operating system.