upgrading isr-4451 from 3.13.2.s to 16.10.2 help?

[baselzind]

can i upgrade directly from 3.13.3.2.s to 16.10.2? i cant seem to find upgrade guide between these two versions?

[Leo Laohoo]

Read the Release Notes very carefully because it is not possible to upgrade to 16.X.X unless the ROMMON has been upgraded first.  

Release Notes for Cisco 4000 Series ISRs, Cisco IOS XE Gibraltar 16.10.x

[baselzind]

can i upgrade the rommon to 16.7(4r) from my current 15.3? or there is also a upgrade path for rommon?

[Leo Laohoo · Accepted solution]

ROMMON can be upgraded direct.

[Leo Laohoo]

WARNING: Upgrade ROMMON to version 16.12(2r) or else you'll brick the router due to CSCvr18589.

As of 11 November 2019, the fix to this bug can only be found in ROMMON version 16.12(2r).  If there is the need/requirement to upgrade the ROMMON, then upgrade to 16.12(2r).