ROMMON images for Cisco IOS XE release 17.1.x through 17.5.x are aligned with release 16.12(2r).
After upgrading to the 16.7(5r) ROMMON release, based on the IOS XE 16.x image, the ROMMON release can be auto-upgraded to a later ROMMON release.
The ROMMON release 16.9(1r) is the first release that supports the Cisco BIOS Protection.
After a device is upgraded to the 16.9(1r) ROMMON release, the ROMMON release cannot be downgraded to a release earlier than 16.9(1r).
All future ROMMON releases can be downgraded to the 16.9(1r) release.
Also, if a platform has a 16.9(1r) or later release installed, an IOS XE 16.9.1 or later release, or a SD-WAN 16.11.1 or later release must be used for the upgrade.
