Understanding Cisco IOS Releases

[davidhuynh5]

I've been reading about Cisco IOS releases from this site: http://www.cisco.com/warp/public/620/1.html

and it's so confusing! It there a simple way to understand what all the T, S, etc. means?

[platinum_jem · Accepted solution]

You can also refer to this for more info

http://www.cisco.com/en/US/products/sw/iosswrel/ps1818/products_tech_note09186a0080101cda.shtml

In general, the various IOS releases

T = Testing and training releases

ED = Early deployment

GD = General deployment

Normally T releases are the versions that were released for ad hoc bug fixes

ED are initial stages of deployment but still subjected to bugs.

GD are the most stable versions and can run for a long time before the next maintenance reboot.

[Edison Ortiz · Accepted solution]

Regular IOS routers would use the 12.4M (Mainline) or 12.4T (Technology). You will find the T train to contain the newest features but it may also contain the most bugs. We often recommend Mainline over T train if you are interested on stability in your network without the need of new features.

Other tracks would be platform specific, for instance;

12.2SX = Catalyst 6500

12.2SE = Catalyst 3xxx switches

12.2SR = Cisco 7600 Routers

12.2SB = Cisco 7200 and 7300 Routers.

There are a lot of tracks out there and I can understand your confusion but if you stick to the main ones, you should be ok.

Any track in particular you are looking for?

__

Edison.

[pompeychimes · Accepted solution]

It used to be even harder!

Check out Stretch's cheat sheet over on packetlife...

http://www.packetlife.net/static/cheatsheets/cisco-ios-versions.pdf

[pompeychimes]

I forgot to mention that they have books dedicated to the subject. This ones a real page turner...

http://www.informit.com/store/product.aspx?isbn=9781578701797

[iyde]

Well, that book is from the year 2000. Cisco has made changes a lot of times since then on the naming and numbering of IOS....

Stay with Edison's post; it's the most helpful.

HTH