Intro to Cisco Operating Systems
In this lecture, you'll learn about the different operating systems that run on Cisco's different router and switch platforms. You don't actually need to know this for the CCNA exam, but it's beneficial to have an understanding of Cisco's wider portfolio. Cisco's different operating systems are very similar from a management and administrative point-of-view, so it's easy to transfer your skills between platforms.
I'll start off by giving you a bit of history. Many people think of Cisco as being a routing and switching company, but they actually were just a purely routing company when they started out. IOS was the original operating system that they used on their routers. It's the same operating system that's used today, although obviously it's gone through quite a few upgrades in the time since Cisco started back in 1984.
Cisco then bought the company 'Crescendo' in 1993. The Catalyst switch product line came about because of that acquisition. The original operating system on the Catalyst switches was CatOS, but that's been deprecated for a long time now.
Cisco firewalls evolved from another acquisition, that of 'Network Translation' back in 1995. Cisco got their PIX firewall from that acqusition, which used the Finesse operating system. The PIX firewall has since evolved into the ASA Adaptive Security Compliance.
Both the CatOS and Finesse operating systems were ported over to IOS over the following years. Cisco standardised on IOS for all of their network infrastructure devices.
There are also some other operating systems on some of the newer router and switch platforms. IOS runs on the majority of Cisco routers and switches, but some of the newer platforms have new operating systems.
The Cisco Nexus and MDS Data Centre switches run on NX-OS.
The high-end NCS and CRS service provider routers and also the ASR9K and XR12K routers run on IOS-XR.
The ASR1K service provider routers run on IOS-XE.
You may be thinking "all these different operating systems are going to make things more difficult for network engineers." But they don't really, because all of the different Cisco operating systems have incredibly similar Command Line syntax. If you know a command in IOS, it's probably going to be exactly the same command in all of the other operating systems as well.
If you're now wondering why Cisco have different operating systems for their routers and switches then, the main difference is under the hood. IOS has a monolithic kernel, meaning that if one process running on the router crashes it can crash the entire router. The other, newer operating systems have microkernels, with processes running in separate, protected memory address space. If one of the processes crashes, it should restart without affect the rest of the system.
These operating systems other than IOS are mainly on the higher-end routers and switches, with the standard routers and switches still running IOS. Now, don't think that IOS is an inferior or unreliable operating system. It's been purpose-built by Cisco, who are the biggest networking company in the world, to run on enterprise-grade routers and switches. It is very hardened and still very, very reliable.
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