Cisco OS software types

[Vencola]

Hello there,

I know that IOS is differ than IOS XE software. as I know IOS XE is an evolution of cisco IOS, so the switch should either has IOS or IOS XE, when I type show version on the following switch, I found both IOS and IOS EX >> so which one is correct, what is the exact software type of this switch.

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Switch-D#show version
Cisco IOS Software [Denali], Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version 16.3.7, RELEASE SOFTWARE (fc4)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2018 by Cisco Systems, Inc.
Compiled Fri 03-Aug-18 23:49 by mcpre

Cisco IOS-XE software, Copyright (c) 2005-2018 by cisco Systems, Inc.
All rights reserved. Certain components of Cisco IOS-XE software are
licensed under the GNU General Public License ("GPL") Version 2.0. The
software code licensed under GPL Version 2.0 is free software that comes
with ABSOLUTELY NO WARRANTY. You can redistribute and/or modify such
GPL code under the terms of GPL Version 2.0. For more details, see the
documentation or "License Notice" file accompanying the IOS-XE software,
or the applicable URL provided on the flyer accompanying the IOS-XE
software.

ROM: IOS-XE ROMMON
BOOTLDR: CAT3K_CAA Boot Loader (CAT3K_CAA-HBOOT-M) Version 3.58, RELEASE SOFTWARE (P)

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one more question regarding software types 

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Switch#show version
Cisco IOS Software, C3750 Software (C3750-ADVIPSERVICESK9-M), Version 12.2(25)SE
E2, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2006 by Cisco Systems, Inc.

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is C3750 Software consider a type of cisco IOS software? Just need to make sure

[Leo Laohoo]

Except the 1000-series switch and the 900-series router, everything after 3650/3850 and ASR 1k are IOS-XE. 

900-series router and 1000-series switch are running "classic" IOS.  Anything older than these two are "classic" IOS.

[Reza Sharifi]

Hi,

so which one is correct, what is the exact.

When you see both IOS and IOS-XE, usually, IOS-XE is the correct software. Native IOS is usually run on older devices like 3750, 3650, 2960, 5500, 6500, 6700, etc... However, most newer devices like 3800, 3600, 9200, 9300, etc... support IOS-XE only. Overall, there are still some devices that run native IOS but that is eventually being phased out.

is C3750 Software consider a type of cisco IOS software? Just need to make sure

No, the c3750 series switches run native IOS.

HTH

[Joseph W. Doherty]

is C3750 Software consider a type of cisco IOS software? Just need to make sure

No, the c3750 series switches run native IOS.

@Reza Sharifi Do you really mean to so no, or did your mean to differentiate native IOS vs. IOS using an XE variant?

[Joseph W. Doherty]

"I know that IOS is differ than IOS XE software. as I know IOS XE is an evolution of cisco IOS, so the switch should either has IOS or IOS XE . . ."

Evolution, yes and no.  As I understand it, XE is a combination of a "shell", or perhaps an OS, that runs a modified version of classical IOS under it.  Sort of like running Windows under Linux.  This also explains why there are two version numbers because you basically have two OSs involved.  (One reason for XE, again as I understand it, it allows Cisco to add other major functions to XE that work in conjunction with the IOS running under XE, also taking advantage of multiple processors, which I believe classical IOS, whether native, [or in the past?] the IOS image running under XE's control.)

XR, though, and once again as I understand it, is a "rewrite" of IOS into a new more modular format.  I.e. somewhat like taking Windows features and adding them to Linux.

"is C3750 Software consider a type of cisco IOS software? Just need to make sure"

Well consider:

Switch#show version
Cisco IOS Software, C3750 Software (C3750-ADVIPSERVICESK9-M), Version 12.2(25)SE
E2, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2006 by Cisco Systems, Inc.

Earlier switches had/ran Cat(alyst)OS, L2, while routers had IOS, L3.

CatOS pretty much only supported L2, while some earlier switches, like the Catalyst 5xxx (?) and/or 6xxx (?) series, might run CatOS for L2, and if they had a routing module on it, optional on the 5xxx, run IOS for L3.  I remember when they first provided a "native" IOS that supported such switch's L2 and L3 using one software image.

Both CatOS and IOS were OSs, just CatOS, being L2 focused, was not Internet focused, as IOS was so focused because of it supporting L3 routing features.

PS:

BTW, on the Catalyst 5xxx, that switch, by itself, might only support L2, but it could interface with an external Cisco router providing multi-layer switching on the Cat.  Basically, the switch would pass a new flow's first packet to the router, the router would then "inform" the switch where the packet went next, and then the switch would "switch" all the remaining flow's packets, at the switch, at switch processing speeds.

When you had both CatOS and IOS on the same L3 switch, you would actually configure them separately even though they were on the same device.