Edison,

Thanks. What is the purpose of the different IOS's?

Different feature sets and what the router will support .

Richard,

It can be quite confusing to determine the proper IOS to download. Often, customers call TAC just for that reason.

Different Tracks are created depending on customer needs. The mainline track offers the most stable IOS of all tracks but it does not provide the latest and greatest technologies that Cisco has to offer. When you introduce latest and greatest, you often find that things don't work as expected. Usually that's the 'T' track.

I'm not saying the T track shouldn't be used but if you have all the needed services out of the mainline track, you should stick with mainline for better uptime and router reliability.

Those other tracks listed in your initial posts are the odd tracks. There are often created when a group within Cisco is coming up with a technology that isn't part of the T track nor the mainline track. I would only use those odd tracks if you need the services they are offering.

I recommend visiting the Cisco Feature Navigator and compare tracks to learn their differences: http://www.cisco.com/web/go/fn

The 'Compare Images' link is very useful for this task

HTH

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Edison.

Edison ... thanks again. Questions beget more questions. Can you load the same IOS on a 2650XM and a 2651XM? Is this the same for all routers ... like 2620XM and 2621XM?

Some router models share the same IOS file while others have specific IOS files for their model.

To be sure, when downloading - select the hardware in question and the images will be presented to you for that specific hardware.

If you have an image already downloaded and want to know what hardware does it support, go to the link I posted in my previous message for hardware support for that image.

In short, the answer is 'it depends'.

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Edison.