Difference between 12.x and 15.x versions of IOS Firmware??

[simonwynn]

Some routers use 15.x version and some models have the option of 12.x and 15.x versions - likely a dumb question, but what is the main difference here?

Simon

[Bradford Chatterjee]

As I recall from a session at Cisco Live last year called "IOS Strategy and Evolution," one of the main differences is that in IOS 15 Cisco is trying to standardize the code base across all platforms. For example, the code that makes OSPF work on 7200s and 2800s is probably very different in IOS 12.x, but should be the same or as close as possible in IOS 15.x. IOS 15 is also supposed to have fewer disparate code trains than 12. I'm sure there are a lot of other differences that I'm forgetting.

I checked and the session that I attended at Cisco Live is available on Cisco Live Virtual, and should be free for everyone to watch. It's BRKARC-2007: IOS Strategy and Evolution. It's a good overview of this topic.

[paolo bevilacqua]

Old routers model run cannot new software.

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

15.x

12.x -

===

3.x

- but seriously, marketing probably didn't want to jump to version 13.x, and 15 probably "polls" better than version 14.

Consider that version 15.x is the mainline version of 12.4T, so it might also be tagged as version 12.5.  Here too, I suspect, marketing may thought a new version would be better than another point release.

Technically, there are many enhancements, and if you have access to the feature navigator tool, you can compare versions.  Whether the enhancements truly merit a new version can be subjective and often can have as much to due to marketing as technical merit.

[stephen.stack]

I read, not long after IOS 15.x was released that 13 was skipped as it is generally belived to be an unlucky number. But, 14 was also skipped because of the huge market that is China, 14 is an unlucky number there also. Hence 15 was the next number to go with...

Regards

Stephen