CP-7841 will not register after self-updating firmware

[quinn-allen]

Hello Community,
I am working with CUCM ver 14.0.1.13900-155 and working CP-7841s are running sip78xx-14-2-1-0001-14. We have found that 7841s that have been off our network for awhile will often not register. They correctly find the server and update their firmware, when we wipe ITL and other certs via factory reset it correctly gathers the cert that working phones have. The phone will stay at registration in progress status indefinitely and there is no log of it registering in CUCM. That said, when we strike the settings button the registered screen comes up briefly with the correct DN and info that was configured to the device, seemingly indicating the device has registered since otherwise it would not have that correct information. Our lead VOIP engineer for our site has not found something that works for these cases.

I have observed this occurring across numerous initial versions of FW, including and not limited to sip78xx-12-8-1-0001-45, sip78xx-12-5-1SR2-2, and sip78xx.11-7-1-17. I have not yet isolated a specific connecting factor between each case, but have had this experience with 30-40 phones so far.

Any leads?

Thanks,
Very Confused Network Admin

[Leo Laohoo]

Roll back the firmware of the phone and see if it works or not.

[quinn-allen · Accepted solution]

We did rolling back firmware and it was not a solution. In the end we found the cause and were able to get it fixed.
Expired manufacturer installed cert. Caught us off guard because the vast majority of our phones were already using LSCs and no longer had a manufacturer cert. It appears that a number of years ago we were leaving the MIC on there but upgraded to using LSC, leaving only phones not online at that time with MICs.
Initially we had been trying updating the cert but it was consistently failing. We found that a dialpad factory reset just after setting CUCM to install/update the cert for that device was necessary for it to resolve.

Field notice regarding this issue:

https://www.cisco.com/c/en/us/support/docs/field-notices/704/fn70496.html