shifting to a new cucm and dhcp shift

[baselzind]

im going to shift from an old cucm to a new cucm , the thing is if i change option 150 in the dhcp pool will the phones register to the new cucm right away? or do i need to do "clear binding"?

[Anthony Holloway]

You will need to reboot the phones. So, make the DHCP change first, then in the old/original CUCM go to Enterprise Parameters and click Reset to reset all phones in the cluster. The phones will request DHCP and get the updated option 150. There is one huge caveat here though: ITL. Have you already considered how you will handle this security aspect of phone registration in a CUCM 8.5+ cluster?

[baselzind]

Sorry what do you mean by itl? Is it the cucm trust list?

[Anthony Holloway]

Yep! That's right. A Phone, on a CUCM 8.5+ cluster, will only register to that cluster, unless you do something extra. Have you already done this something extra? Since you didn't know what an ITL was, but you did know about CUCM trust lists, it's not clear to me that you addressed this in your plan.

[baselzind]

So please how can i solve the trust list if i want to shift the phones to new servers ip? The new cucm is 12.5

[Sandro Nardi]

You need to remove the trust between the phone and the cluster.
There are a lot of official guide about migration between cluster version 8.5+ and how to handle the trust
I recently planned a migration like that using Phone view from Unified FX to clear ITL/CTL/Trust list on the phone: https://www.unifiedfx.com/
After all the test we did this was the easiest and more reliable solution.

[baselzind]

there is an option under enterprise parameters called "Prepare Cluster for Rollback to Pre-8.0" , it supposedly remove trust list for all phones , but have anyone tried it? do i just enable it and restart all phones and the trust list would be removed?