Understand Cisco's new IOS Packaging

David Davis explains Cisco's move from a legacy naming system for IOS versions to a new packaging system that simplifies your software selection decisions.

Even if you haven't bought a new router lately, or made a recent upgrade, you should be aware that Cisco has begun repackaging all IOS versions with its new naming conventions, starting with IOS version 12.3. (If you don't know what version of the IOS you have, see my article on the show version command). In this article, I will explain Cisco's "Legacy Naming," and then summarize the updated IOS Packaging system, which reduces the possible version names from 40+ to only eight. Armed with this background knowledge, you'll be better equipped to make your next upgrade or purchasing decision.

Legacy Naming

For IOS versions prior to IOS 12.3, Cisco used a confusing combination of letters and numbers to indicate which version of the IOS you had. There weren't just a few versions either; taking into account all of the possible combinations you could create, there were probably more versions of the IOS than of drinks at your local coffee bar (you know which one I am talking about). According to Cisco, there were a possible 44 versions available for most of the device series.

Cisco now refers to this older convention as "Legacy Naming." Since many of you are still using an IOS version older than 12.3 on your routers, here's a little background on how the Legacy Naming worked.

As an example, if I perform a show version command on my 2611 router, I see the following line in the output:

System image file is "flash:c2600-ik9o3s3-mz.122-15.T9.bin"

This is the actual name of the IOS file that my router is running, which indicates the following:

  • The c2600 tells me this is for the 2600 series of routers.
  • The i in ik9o3s3 tells me that this is the IP routing version of the IOS.
  • The k9 tells me that this is the 3DES encryption version of the IOS.
  • The o3 tells me that this is the Firewall/IDS version of the IOS.
  • The s3 tells me that this is the "Basic limited routing / limited memory" version of the IOS for the 2600 and 3600 series routers.
  • The mz tells me that this version of the IOS runs from RAM and is compressed.
  • The 122-15.T9 tells me that this is IOS version 12.2, patch level 15, and "training" version 9.

As you can see from this breakdown of the IOS name on my router, the old way was pretty confusing. These aren't the only letters and numbers used. Cisco's document, "Portable Product Sheet – IOS Naming," offers explanations on all of the old IOS naming conventions, along with the new packaging system.

New IOS Packaging

To make software selections easier, Cisco has adopted a new method of naming IOS versions, called "IOS Packaging." Cisco says that this will allow them to reduce the amount of IOS versions available for each device from 44 to only eight.

Here are the new versions of the IOS Cisco offers:

  • IP Base
  • IP Voice
  • Enterprise Base
  • Advanced Security
  • SP Services
  • Advanced IP Services
  • Enterprise Services
  • Advanced Enterprise Services

Each of these versions, of course, groups a large number of features inside the package. For example, the Advanced Security package contains the Cisco IOS Firewall, IPSEC, 3DES, VPN, and SSH. So, I should be able to use that version to replace the IOS on the 2611 router that I used as an example above (assuming I have enough RAM and Flash). In other words, I would be moving from this IOS version:


To this IOS version:


As you can see, the designation is less confusing and there are fewer options. If you still need guidance on which version of the IOS you need and what the hardware requirements are for that version, take a look at the Cisco Feature Navigator II and the IOS Upgrade Planner (requires Cisco Web site registration).

When I look at the show version output of a new 3845 router on my network, I see the following:

System image file is "flash:c3845-ipbase-mz.123-11.T7.bin"

This router is running the 12.3 IOS and is using the new package naming. This router has the IP Base IOS, which is the most entry level Cisco IOS available. However, it still has most of the standard IP routing features you are used to. Some of these packages roll up into larger packages with more and more features (and cost, of course). Figure A shows an illustration of the packages from the Cisco Web site.

Figure A


All of the details of Cisco's legacy naming and new IOS packaging information can be found at the Cisco IOS Packaging Web site. In addition, I just read that Cisco has expanded this new IOS packaging to switches as well as routers.

The new IOS Packaging is something that will affect all Cisco users the next time you buy a new router or go to upgrade your existing router. By being more informed about it now, you can make the right decisions later.

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David Davis has worked in the IT industry for 12 years and holds several certifications, including CCIE, MCSE+I, CISSP, CCNA, CCDA, and CCNP. He currently manages a group of systems/network administrators for a privately owned retail company and performs networking/systems consulting on a part-time basis.

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