CUCM 7 to CUCM 10.5 roll back plan validation

[gene]

I am performing a jump upgrade. IP addresses remain the same. All new servers are pre-loaded and ready to go. I have already upgraded all the device firmware to the proper versions so when the old servers are unplugged and the new ones are plugged in firmware will not change.

My concern is a fall back plan. If for some reason I decide I want to plug in the old 7.X servers and let the phones register back to them I  am concerned about the ITL files. Would it be a good idea to go ahead set "Prepare Cluster for Rollback to pre-8.0"  to True on the 10.5 cluster? My logic is when the phones come over from 7 they will never get an ITL file and therefore can easily be rolled back if necessary. After all runs for a day or so and looks good I would set it back to false.

Does this sound like a good plan? Are there any negatives to doing this?

Thanks!

[Jaime Valencia · Accepted solution]

That's correct, if you register phones to CUCM 8.x+ they will get ITL files and it will be hard to move them around, setting that parameter would be the easiest way so there's no ITL before you move them, and then can move them back without problems.

[gene]

Thanks,

One other question. How can you tell the setting is actually taking effect? I have set it to true and restarted the proper services as well and rebooted the servers in the cluster; however my IP communicator still seems to work with extension mobility. There is a warning that said extension mobility should not work with the setting to true. 

Is there any way to be certain my phones will not download the CTL or ITL files?

Thanks!