Upgrade ISR4451/4351 from 16.6.4 to 17.12.4b

[Tomson]

Hei all,

I was trying to find any information about this upgrade path through release notes, but it is lacking any information about steps in the upgrade.

I was also getting through some forum topics already posted and went through few.

It would be good to upgrade the ROMMON while upgrading the image. (although since 17.X. it should be upgraded automatically)

Also I found this -> https://community.cisco.com/t5/routing/isr4321-upgrade-from-16-3-8-to-17-6-x/td-p/5109102 
Which say, it is impossible to go straight to the 17.12.x so the step between should be 17.9.x

So I planned my approach like this
Upgrade to 17.9.x and upgrade ROMMON with that and after that I would go to 17.12.4b

Is there anyone who did this rather 'large step' 

Thank you all for info.  

[Leo Laohoo]

Upgrading, from 16.X.X, to 17.12.X is a major upgrade and direct upgrade cannot be done. 

There is a hidden documentation, buried in the ISR 1000 17.12.X Releases Notes (Cisco ISR1000 ROMmon Compatibility Matrix), which confirms: 

To upgrade to Cisco IOS XE Dublin 17.12.x, follow these steps:

1. If you are on a device that is running software version between Cisco IOS XE 16.x to Cisco IOS XE 17.4.x, upgrade to any IOS XE image between Cisco IOS XE 17.5.x to Cisco IOS XE 17.10.x.

2. After performing step a, upgrade to Cisco IOS XE 17.12.x.

3. For devices that are running on software version Cisco IOS XE 17.5.x or later, you can upgrade to Cisco IOS XE 17.12.x directly.

---

Upgrade first to 17.6.X or 17.9.X and then upgrade to 17.12.X.  

Don't believe me?  Raise a TAC Case or ignore my warning.  

[Tomson]

Yea ofc. I am not saying I don't beleive you, I even refer to the forum post which you've answered. So my question was if the path I've choset to go to 17.9.x while upgrading rommon and afterwards to 17.12.x is ok. Thanks for the info! and for the link!