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Community Member

IOS version


Can someone either explain or let me know of a good document that I can learn more about the IOS versions.

What does it mean by 12.1(18)? If it was something like 12.1 and 12.2. then I would have understood it. But what I'm confused is what does it mean by (18) and sometimes you get some letters also in the version number.

My second doubt is, when I type "show version" command, I see something called,

BOOTLDR: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWA

RE (fc1)

what is this version that it says here? It says the version is 11.0<10c>. How do you read all the digits in this version please? For example what is that 10 that it says and what is that "c" that it says etc.

Thanking you in advance!


Re: IOS version

Hi Omal,

This link will give you everything what you want to know

HTH, if yes please rate the post.


Community Member

Re: IOS version

Hi Ankur

Thanks a lot for your quick reply.

The link you have given helps to identify each and everything that is there in the flash file name. But what I needed to clarify was, when you type, "show version" you get an output. And in that output, you get the version number as 12.11(8c)T. What does this mean?

Also I would appreciate it, if you know the explanation for this line, when I type "show version".

Many thanks!!!

Re: IOS version

Hi Omal,

Whatever version number you get in sh version that is the release of IOS which you are running in your router or switch.



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