Catalyst IOS - Naming conventions

Unanswered Question
May 12th, 2008

Hi all,

I'm trying to select the appropriate image for my Cat.3560s, and am confused as to the differences between the following versions:




Can anyone help explain this? I've also wondered the same thing regarding SE and SX on the 6500. Can't seem to find any docs that explain this.

I have this problem too.
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padramas Mon, 05/12/2008 - 19:28

Hello Brian,

An IOS image can be chosen from a combination of version( 12.2(XX) and feature set ( IP base/Adv IP services/ etc..)

Following links will provide more info

How to Choose a Cisco IOS Software Release

Cisco IOS Packaging

Guide to Cisco IOS Release Naming

Cisco IOS Software Roadmap



Baz Stefan Thu, 01/16/2014 - 08:15

Hello! I realise that since you last asked this question, you probably found it's answers. Just in case..

here's what I found out by skimming the "Cisco IOS and NX-OS Software Reference Guide" White Paper


12.2(3)SE is different from 12.2(4)SE through what's called the "Maintenance Identifier": generally, having

a higher Maintenance Identifier means additional software fixes.

The Cisco IOS Software 12.2S release family is comprised of the following Trains: 12.2S, 12.2SB, 12.2SE,

12.2SG, 12.2SR and 12.2SX. Different trains generally means different available IOS features.

To exemplify the differences, I took a couple of the trains' descriptions from the Cisco White Paper:

12.2SE  -  Provides Cisco IOS Software  functionality and hardware support for mid-range and low-end Ethernet  LAN switching for enterprise access and distribution networks, and  mid-range and low-end Metro Ethernet for service provider edge networks  that include the Cisco Catalyst 2960 Series, Cisco Catalyst 3550 Series,  and Cisco Catalyst 3750 Series Switches.


12.2SX  -  Provides Cisco IOS Software  functionality and hardware support for high-end Ethernet LAN switching  for enterprise access, distribution, core, and data center networks.

What one can gather from this is that 12.2SE will more likely be available for lower-end switches (CAT2900

range) while 12.2SX would be installed on higher-end switches (CAT 6000).

The difference then between 12.2(3)SE, 12.2(3)SEE and 12.2(3)SED is given by the third uppercase

letter called the "New Technology Introduction Identifier", where each new individual release includes new

features and/or hardware support.

Finally, the "Rebuild Identifier", the last number that can be used in a release name, such as 12.2(4)SXC15

or 12.2(4)SXC16 typically includes fixes to a limited number of caveats deemed by the IOS developers as a

sufficiently significant reason for releasing a newer version.

Each new fix and software feature implemented in a release is then inherited by the next software iteration.




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