I obtained some IOS images to play around with using GSN3. Some of them are as follows:


I understand that there are different firmware versions for different feature sets, but the difference between these two does not appear to be clearly apparent. Can someone describe the difference between these two images, as well as explain in detail the Cisco versioning methodology (as it pertains to different feature sets, not different build types/numbers)?

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    The first google result for "difference between cisco IOS versions" is a Cisco Tech Note that covers your question pretty thoroughly. – Brett Lykins Dec 26 '13 at 21:12
  • That's not quite what I was looking for, but thanks. Regardless, those tech docs can be a bit hard to parse. It would be more useful to have an answer explaining it in plain English. – Bigbio2002 Dec 26 '13 at 21:22

Use the Cisco Feature Navigator to compare the features of the two images.

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I found some information here, which details the IOS Mainline 12.3 release.

It appears that c2600-i-mz.123-26.bin is part of the "Classic Feature Set" family of images. Beginning with the 12.3 Mainline release, the various feature set combinations were rejiggered into a simpler, more streamlined set of images called the "Cross-platform Feature Sets", of which c2600-ipbase-mz.123-26.bin is part of. IOS 12.3 is available in either the Classic or Cross-platform version; however, the Classic images are being phased out, and Cisco recommends that images be upgraded to the newer Cross-platform versions. Beginning with the 12.3T train, images are only available in the Cross-platform version.

Aside from the changing of the naming scheme, these two images correspond with each other and are otherwise functionally identical, as far as I can discern. Other Classic images may not necessarily have exact corresponding images, as the feature sets differ.

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