I want to do some tests on a old version of CUCM, my Active Version is 220.127.116.1100-6, that version has been working for a while now (7 or 8 monts) and have a lot of configuration, the Inactive Version is 18.104.22.16800-28. If I perform a switch version to 9.1 and then return to 11.5, I'll lost the configuration of the 11.5? The double switch is possible?
You could cause problems with database replication. I would not take the risk in a production environment. Take a backup of the server and then revert in a lab environment. Or install the previous version in a lab. Switching versions to previous is meant for rolling back an upgrade which would require reverting all servers in the cluster to the previous version and resetting DB replication.
There are lot of risks associated with this scenario as your environment is running on 11.5 version for more than 7 or 8 months. If you revert back to 9.1 version, you will have to revert all CUCM servers in the cluster and you may face following issues:
If you revert back from 9.1 to 11.5 then you may again face following issues:
You will have to consider many things before doing such activity. The best option would be to copy CUCM virtual machine and restore it on lab VM environment and do the testing. See the best practices for copying virtual machine:
I concur with Brandon, doing it after running in production for months is asking for trouble. If you really need to get back to the old version and I assume the old config I would attempt to copy/clone the virtual machine of the production CUCM Pub onto a lab host, bring it up there in isolation and do what you need to do. Also, if you don't mind us asking what are you looking for on the 9.1 in particular perhaps there are other options to get your answer?
Thank you for your help,
I want to go back to an older version because I have a bunch of 8941 phones that are trying to upgrade to 9.4(2)SR2 but first, they need to downgrade to 9.3(4) in order to work. The problem is that CUCM 11.5 does not support the "cmterm-8941_8945-sip.9-3-4-17.cop", it says "error encountered: the selected file is not valid. please ensure that the cop/iso file is intended for this release" I read before right here that CUCM 11.5 does not support this files, that's why I'm trying to downgrade. I tried to install a new CUCM in a lab enviroment with an .ova and a bootable iso of CUCM 8.6, but that didn't work. I will try to copy the VM as you mentioned before, I will apreciate any other suggestions or comments.
All you need to do is download the .zip file and upload the files manually
Those are the same files the .cop file would have installed, I'd suggest you review the TFTP and phone logs to find out if it's actually trying to download the FW or not.
What I do if I have sulky phones that don't want to load their firmware is to create a test VLAN with DHCP pointing to my desktop PC as the TFTP server. Then you can make sure the correct load files are offered, and if it comes to it you can Wireshark to see what the phone's doing. It might be worth trying that for one of your problem phones, then make the appropriate changes in CUCM to get the others to behave.