Feature set codes IOS file images?

You need to think like a marketeer to be able to search for this ;-))

Look for IOS "packaging" - using IOS naming convention would be too mundane ...

The following is NOT exactly what you are looking for, but is related, and may help now or in the future:

Images | Types of Images Understanding Images | Image Naming Conventions (pretty much what you had already)

They seem to fall back to the following position:

In order to find out which Cisco IOS Software supports all of the features you plan to use, it is best to use the Cisco Software Advisor (registered customers only) , which allows you to search by feature(s) or by release, and it even allows you to compare two releases. Write down the different software versions that meet your requirements and that are compatible with your hardware.

For additional information on features and hardware support for any particular IOS release, refer to Cisco IOS Software. From this page, select the required IOS version under The Latest Cisco IOS Software Releases section. Next, click the Bulletins link and refer to the Cisco IOS Release Features and Hardware Support document.

Best Regards, News Reader

There is some stuff in the release notes of each IOS rev. There have been some tables published, but they rapidly go out of date.

A big problem is that the feature set for one line of routers may or maynot include features at the same level on a different line.

Some are fairly constant like i = IP, s = Plus feature, k = crypto. But once you get to ios3k3 vs. ios1k9, then you get really shakey as to what is really in what.

The easiest by far to compare is in the Feature Navigator (cisco.com/go/fn) where you can diff features between any image on any platform. That is far more useful than learning arcane codes that haven't been in use since 12.3 was current like 3-4 years ago. The FN is your pal.

Thanks guys for your responses. This was all helpful. The link the the feature navigator was particularly helpful. Thanks, John