Learn the interesting explanation of the differences of the Cisco Operating Systems, including IOS, IOS-XE, IOS-XR, NX-OS and CatOS. http://nhprice.com/difference-cisco-operating-systems.html

1. DIFFERENCES OF
THE CISCO OPERATING SYSTEMS
IOS | IOS-XE | IOS-XR | NX-OS | CatOS

2. FOREWORD
• Using Cows to Explain the Differences of the Cisco Operating Systems
• (the cows are CPUs or independent processes on the same CPU.)

3. IOS
YOU HAVE ONE COW. IT CHEWS GRASS.
Concept: Cisco IOS (originally Internetwork Operating System) is a family
of software used on most Cisco Systems routers and current Cisco
network switches.
Feature: IOS is a package of routing, switching, internetworking and
telecommunications functions integrated into a multitasking operating
system. Although the IOS code base includes a cooperative multitasking
kernel, most IOS features have been ported to other kernels such as
QNX and Linux for use in Cisco products or simulators such as Cisco
VIRL.
Note: Not all Cisco products run IOS. Notable exceptions include ASA
security products, which run a Linux-derived operating system, and
carrier routers which run IOS-XR.

4. IOS-XE
YOU HAVE TWO COWS. ONE CHEWS GRASS AND
OTHER TELLS IT WHAT TO CHEW.
Concept: IOS XE is a train of Cisco Systems' widely
deployed Internetworking Operating System (IOS),
introduced with the ASR 1000 series.
Feature: It is built on Linux and provides a distributed
software architecture that moves many operating
system responsibilities out of the IOS process and has
a copy of IOS running as a separate process. Since it
runs a copy of IOS, all CLI commands are the same
between Cisco IOS and IOS XE, in contrast to IOS XR
which has a completely different code base and its
developers implemented quite a different CLI
command set.

5. IOS VS. IOS XE
• 1. Cisco IOS is a monolithic operating system running directly on the
hardware while IOS XE is a combination of a linux kernel and a (monolithic)
application (IOSd) that runs on top of this kernel.
• 2. IOS XR is based on QNX (since version 5.0 it's also based on linux) where
the IOSd application has been separated into many different applications.
While IOS XE (IOSd) and IOS share a lot of the same code, IOS XR is a
completely different code base.
• 3. Since IOS XE has IOSd running as an application on top of linux, it
becomes possible to also run different applications on the hardware, a
good example of this is running Wireshark on a switch. Another example is
the Cisco IOS XE Open Service Containers.

6. IOS-XR
YOU HAVE 27 COWS. YOU HAVE NO IDEA WHAT THEY DO BUT WHEN THEY
OVER A NEW COW INSTANTLY REAPPEARS. SOMEHOW THEY COST MORE
YOUR HOUSE.
Concept: IOS XR is a train of Cisco Systems' widely deployed Internetworking Operating System (IOS), used on their high-end
Network Converging System(NCS), carrier-grade routers such as the CRS series, 12000 series, and ASR9000 series.
Features: IOS XR aims to provide the following advantages over the earlier IOS trains:
1. Improved high availability (largely through support for hardware redundancy and fault containment methods such as
protected memory spaces for individual processes and process restartability)
2. Better scalability for large hardware configurations (through a distributed software infrastructure and a two-stage forwarding
architecture)
3. A package based software distribution model (allowing optional features such as multicast routing and MPLS to be installed
and removed while the router is in service)
4. The ability to install package upgrades and patches (potentially while the router remains in service)
5. A web-based GUI for system management (making use of a generic, XML management interface)

7. IOS VS. IOS XR
Example BGP configuration for both IOS and IOS XR. More examples can be found in the Cisco
document Converting Cisco IOS Configurations to Cisco IOS XR Configurations.

8. NX-OS
YOU HAVE A PENGUIN WITH A COW ATTACHED.
IT YELLS INSTRUCTIONS AT A ROBOT MEGA -COW. THE ROBOT
CHEWS GRASS REALLY FAST.
• Concept: NX-OS is a network operating system for the Nexus-series
Ethernet switches and MDS-series Fibre Channel storage area network
switches made by Cisco Systems. It evolved from the Cisco operating
system SAN-OS, originally developed for its MDS switches.
• It is based on MontaVista Software embedded Linux and is inter-
operable with other Cisco operating systems. The command-line
interface of NX-OS is similar to that of Cisco IOS.

9. SWITCHES RUNNING NX-OS:
• Nexus B22
• Nexus 9000 series
• Nexus 7700 series
• Nexus 7000 series
• Nexus 6000 series
• Nexus 5000 series
• Nexus 4000 (for IBM BladeCenter)
• Nexus 2000 series
• Nexus 3000
• Nexus 1000V
• MDS 9700 FC Directors
• MDS 9500 FC Directors
• MDS 9250i FC Switch
• MDS 9222i FC Switch
• MDS 9100 FC Switches

10. IOS VS. NX-OS
• 1. NX-OS does not support the login command to switch users.
• 2. NX-OS does not distinguish between standard or extended access lists,
all lists are named and "extended" in functionality.
• 3. NX-OS did not support scp server prior to 5.1(1) release.
• 4. In NX-OS, there is no "write" command to save the configuration like on
IOS (one uses the "copy" command, instead). Instead, command aliases
can be created to provide the "write" command.
• 5. When accessing NX-OS, users authenticate directly to their assigned
privilege level.
• 6. SSH server is enabled while Telnet server is disabled by default in NX-OS.

11. CATOS
YOU HAVE A VERY OLD COW IN A HUGE METAL BOX THAT ONLY SPEAKS
SPANISH.
GRASS GIVES IT DIARRHEA WHICH IT THEN SPEWS OUT ITS 275
AT HIGH SPEED.
Concept: CatOS (Catalyst Operating
System) is the discontinued operating
system for many of the Catalyst brand of
legacy network switches. CatOS ran on
switches such as 1200, 2948G, 4000, 4500,
5000, 5500, 6000, 6500 series. It was
originally called XDI by the switching
company Crescendo Communications, Inc.
Cisco renamed it to CatOS when they
acquired Crescendo in late 1993.
CatOS can still run on some of Cisco's
modular switches, "hybrid" mode. In
hybrid mode, the NMP (switch processor)
runs CatOS and the route processor runs
Cisco IOS.

12. SOURCE
• https://en.wikipedia.org/wiki/Cisco_IOS
• https://en.wikipedia.org/wiki/Cisco_IOS_XE
• https://en.wikipedia.org/wiki/Cisco_IOS_XR
• https://en.wikipedia.org/wiki/Cisco_NX-OS
• https://en.wikipedia.org/wiki/Cisco_Catalyst#CatOS
• https://www.reddit.com/r/Cisco/comments/2o619f/would_someone_pl
ease_explain_succinctly_what_the/cmk1tma/

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