We have a cluster composed of one publisher and two subscribers running CUCM 8.5. We are experiencing a problem with SIP phones only, 9971 and 89xx. The SIP Phones restarts once a day at different times. We have also skinny phones and we are not experiencing any problems with them. We tried connecting an SCCP phone to the same port and the issues disappears. The problem only happens for the SIP phones. Moreover, the SIP phones restart at different times not all of them at once. Even if the caller is on the phone the phone restarts. We are seeing the below messages on CUCM:
CUCM closed TCP connection
Any ides please?
For something like that the best thing to look at would be a packet capture. This can be seen when CUCM stops receiving keepalives from the phone. I'd check to see if there are any TCP (default is TCP but UDP can be used too) retransmissions in the capture from both CUCM and the phone when the problem happens.
Thanks a lot Joe for the feedback. This is a customer of mine and I already requested a packet capture. However, the weird part is that if we put SCCP phone this doesn't happen...
What's between the CUCM and phone? I've seen some network devices treat SIP messages differently, much differently than SCCP. Since the messaging flow will be quite different between SIP and SCCP a packet capture is your best bet from both ends.
I checked and there is nothing between the CUCM cluster and voice VLAN, just inter-vlan routing. I will ask for packet capture to check why this happening.