One of our users was in concall (he was taken in concall by other party). His call was dropped and the error was displayed as "CM down Features disabled". On Cisco site, they stated that this error comes while making calls. But we saw it immediately after dropping the call. On callmanager, only device unregistered error log has got generated for that IP Phone. What could be the cause? can anything be traceable on CCM server side? Below is link I found on Cisco
Was this phone the only one in the system that had the "CM down" message displayed? Are there any other device unregistrations at around the same time? From the logs, are there any other significant events taking place at around the same time? If other devices unregistered as well, then the cause might have been network or system related. If this one phone was the only one that had a problem, then we could probably focus on what is special or unique about it, such as version of phone load, switch port errors or switch port configuration.
Hope this helps.
Several IP Phones were unregistered at the same time and only "device unregistered" error log can be seen for these phone. Only one phone was showing CM down error.
All these phones are connected to same 4506 switch and are at remote place from the cluster. This remote place is connected via 45 mbps WAN link. There is no problem seen on any of the IP Phones local to this CCM cluster.
The CM down error shows up when the phone goes into SRST mode while there's an existing call on it. Otherwise they simply transition without much fanfare and if everything is configured correctly, users may never know of the problem.
So the cause of the problem was an event that caused the phones at that site to lose connectivity. The CM down error was just a symptom of the problem. The root cause, however, could have had several likely causes, such as the 45mbps link bouncing, a routing issue resulting momentary loss of connectivity to the site where the CCM cluster is located, a problem on the 4506 switch, etc. So you'd have to do additional investigation to determine the most likely cause.
Hope this helps.
I am experiencing the exact same issue, my thoughts are the same as this is the result of the phones losing connectivity to the ccm cluster across the wan.
I am currently troubleshooting the Lan/Wan side of things, I will keep you posted!
If it's a cluster the same symptoms happen if the communication between CUCM servers(SDL link) has problems.
Could be a duplex mismatch on a server port.
Look for the message "SDL link OOS" in the syslogs.