Help with downgrade IOS-XE on Cisco ASR 1009-X

[Eugene Batenev]

Hi guys, can you please tell me how to downgrade IOS-XE on Cisco ASR 1009-X?
I need a step by step guide because I lack knowledge.

[marce1000]

   - This is not without risk , explain the need and make sure that you really need a downgrade (which is counter intuitive) ; the reason it being dangerous because you may get into ROMMON version conflict. If pursuing then safe the running config to an external repository to too (besides saving to startup-config). In principle you can download a lower image and set it as boot variable which the system will then run afterwards , but it is not advised , 

 M.

[Eugene Batenev]

why we decided to roll back:

We were decreed ASX 1009-X hardware with a pre-installed license. Then IOS upgraded to version 16.10 and we need to convert the existing license into a smart license. After the IOS upgrade we cannot see our license and our vendor told us that we have to roll back to IOS 16.8 to see the license again. I am not very good at Cisco so I have no idea what to do in this situation and we only have 1.5 days left.

[pieterh]

why do you only have 1,5 days left ?
license (also evaluation license) are valid for longer periods
first register your device at Cisco.com or your local sattelite
then convert the pre-installed license with "license smart conversion start" 
NB! it takes some time to complete.
when using a satellite it takes two synchronization periods to complete

output from "show license summary" and  "show license status" may help determining errors in smart licensing

[Eugene Batenev]

As far as i understand we have 26 day to convert our license to a smart license right?
Please correct me if I'm wrong. Im sorry for a such stupid questions, I work only 3 day in a company and no one can help me

[pieterh]

you are correct, the evaluation period is 90 days
apparently you've already used some of the evaluation period and now is 26 days remaining

after evaluation period has ended, you have no right to use the license (unless purchased)
(here the HA license I guess, post output of "show license summary" to be sure)

but your router will not stop functioning, only logging about missing license will come in shorter intervals
If you do own such a license there is still time to activate it

as said before you first need complete the smart licensing function and the registration of your device to a smart-licensing server
(directly at Cisco or through a local sattelite)
after registration you can convert the built-in license to smart-licensing

Cisco Software Licensing | Software License Management - Cisco

[Joseph W. Doherty]

Just curious, do you have any references to ROMMON version conflicts and/or other advisories to not downgrade?

Reason I ask, in my experience, I don't recall bumping into either.

BTW, it's possible I've just been lucky.

In my experience, the biggest problem has been an upgrade automatically changing config which will not be understood when you downgrade.  (It's often worthwhile to retain copies of config pre-upgrade.  Very handy if you need to backout/revert IOS version.)

Regarding ROMMON upgrades, generally newer versions usually appear backward compatible with earlier versions.

Release notes should (hopefully) note downgrade issues.  If you have active maintenance, contact TAC, and ask them.

[M02@rt37]

Hello @Eugene Batenev,

Performing software downgrades on network devices carries a certain level of risk, and it's important to ensure that you have a backup of your configuration first and compare the features [https://cfnng.cisco.com/compare]. As marce1000 said check the matrix compatibility IOS-XR/ROMMON (ASR1000) 

https://www.cisco.com/c/en/us/td/docs/routers/asr1000/rommon/asr1000-rommon-upg-guide.html

[Joseph W. Doherty]

Ah, the release notes M02@rt37 references does note a downgrade restriction and/or special ROMMON related actions!