Showing results for 
Search instead for 
Did you mean: 
Ng Tian Sheng

Firmware Upgrade on CUCM version 9.X

Hi All,


I will carry out the CUCM firmware upgrade for my customer. There are 4 CUCM servers running in their environment (1 Publisher, 3 Subscribers). Out of these 3 Subscribers, there is one acts as TFTP Server. My customer has concern on the downtime while upgrading the firmware. As far as I know, we can actually upgrade the firmware into these 4 servers before switching them to the newer version. 


What I want to know is when the time I switch the Publisher from current version to the newer version while other 3 Subscribers still in current version, will the phone service goes down? Because they feedback to me saying that if Publisher is rebooting (switch to new version), by right phone service should not down since they still have 3 Subscribers on the line.


Besides, I also recommend customer to backup (DRS) the existing configuration in SFTP Server just in case if the firmware upgrade fails, we can still rebuild the server (back to old version) and restore the configuration. What I want to know is whether we need to perform the backup on all the 4 servers or just Publisher will do?


Need your advice.



Ajith Nayak

Hello !!

You mentioned as firmware upgrade.

Will it be phone firmware upgrade

Or you will be switcing over to new version on your current CUCM  like 9.1.1 to 9.1.2? or 9.X to 10.X?

And yes you will have to take DRS backup of publisher that would be sufficent.


Install the upgrade file for 9.x on Publisher , do not reboot.

Install the upgrade file for 9.x on Subscriber , do not reboot.

Now  Switch version on Publisher Switch version on Subscriber.

Make sure you always open a proactive TAC whil doing this major upgrade as its a production environment.




Hi Ajith,


Thanks for your reply. I am going to upgrade the CUCM from version to version


What I want to know is that during the time I switch the Publisher to the newer version (I believe the Publisher will not available) will the phone service goes down? Or the phone service is still available as Subscribers still up and running?




To my understanding you are doing a patch upgrade.

It depeds on were your phones are registerd currenlty is it pub or on sub.

When you do a upgrade from OS admin by mapping the image using softwares like freeftpd the upgrade runs in the back end. you have to perform this for all the servers. (Pub and your all Sub's)

During switch version yes there will be a server reboot however if you are doing one by one the phone will get registerd to avaiable subscriber if you have designed your cluster with ccm group and mentioned the server details for failover scenarios the phones will get register to respective avaiable servers.

You will require "utils system switch-version". It will lead to a reboot and the system will boot up with new version. Let the Publisher be fully up and running with new version before doing it on subscribers.

But you will have to do switch version to all the servers.

And after completeion you will have to check DB replication status.

Always there is a rollback option avaiable if incase you suspect any issue by switching to existing version.






Make sure that when upgrading your CUCM to a minor release that if there is new phone firmware, you either prepare for an upgrade since the next time the phones reboot they would get the firmware or change it back to what they are on currently.  Otherwise you will get certain users asking why their phones are upgrading in the middle of the day should you lose power or they restart the phone for one reason or another.


Just FYI. You can't upgrade the Subscribers unless the Publisher is running on the new version.



HTH Regards, Yosh

hi,please explain it will be helpful for all of us..


Recognize Your Peers
Content for Community-Ad