Cisco ISR4331 - Upgrade From 17.06.06a to 17.12.3a

[ChevronTheWolf]

Hello, everyone!

I'm operating a Cisco ISR 4331 Router loaded with IOS 17.06.06a and ROMMON 17.6.2.

To get to the latest and greatest, I'd like to upgrade to IOS 17.12.3a. However, I read in another topic concerning upgrade procedures that going straight to the latest IOS from 17.06 without utilizing an intermediary version like 17.09.05 could cause a boot crash loop.

I'd like to know if there is a recommended intermediate IOS or if there is a more specific procedure for upgrading this router safely.

[Leo Laohoo]

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@ChevronTheWolf wrote:
To get to the latest and greatest, I'd like to upgrade to IOS 17.12.3a.

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The 17.12.4 is the latest release of the 17.12.X train. 

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@ChevronTheWolf wrote:
However, I read in another topic concerning upgrade procedures that going straight to the latest IOS from 17.06 without utilizing an intermediary version like 17.09.05 could cause a boot crash loop.

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Most likely that info came from me.  Several months ago we tested an 1100 directly upgrading, from 17.3.X, to 17.12.3 and it went into a silent boot-crash-loop.  It took awhile but we finally found out about ROMMON version 17.7(1r) (aka 17.7.1r).  

To cut a long story short, direct upgrade from 17.6.X (and earlier) to 17.12.X (and later) needs to have an intermediate jump to 17.9.X because of ROMMON version 17.7(1r).  

This information is not documented (publicly) anywhere else.

Alternatively, contact Cisco TAC and get them to verify as I have reported this to TAC Duty Manager in Sydney (July 2024).