My environment has 329 registered devices with all of them set for registration first to a "main" subscriber and then the remaining subscribers and lastly the Publisher. I am seeing reports where the unregistered phone count will increase in a short burst, but when I check the devices they are showing registered to the main subscriber. I was thinking there may be a network problem causing some phones to drop registration with the main subscriber, but if that is happening it is very quick and very scattered about. Is there something I can look for in RTMT or any way to nail down why these devices would show up as unregistered in the other servers? I have read the device MUST have registered with the server at some point to show up as unregistered.
In RTMT, if you open the Syslog of the subscriber you must have a Device Unregistered event for each of the affected phones. In that event there is a Reason field, with a number that tells you why that particular phone unregistered.
Lookup the System Error messages guide for your particular CUCM version here:
And serch for the error message and you will find a table listing the possible reasons
I have done this and found a device usually shows:
ReasonForOutOfService=10 -- TCPtimedOut - The TCP connection to the Cisco Unified Communication Manager experienced a timeout error
--- OR ---
ReasonForOutOfService=18 -- TCPclosedConnectHighPriorityUcm - The device closed the TCP connection in order to reconnect to a higher priority Cisco Unified CM
The interesting part about reason code 18 is that I see this on the main subscriber in some cases. Since it is the highest priority in the CUCM group, I am not sure what would cause the device to go searching for a higher node.
How many TFTP nodes do you have? if all nodes working as TFTP then make sure firmware images, device packs & locale (language) files are installed on each node properly.
On the RTMT > Double click on the Trace and log central and look up for the event viewer - Application log and Event viewer-System log. you can troubleshoot the IP Phones which are getting unregistered.
If you need a detailed troubleshooting and suspecting on your network, you can use Wireshark and do the Packet Sniffig.