I have been getting alerts in SolarWinds when the registered phones drop below 5% of the total. All of our devices are set to register to the same "main" subscriber, but I notice different devices trying to register with other servers in the cluster. When I check them in CUCM, they always show up registered to the correct subscriber. This leads me to think these devices are briefly losing connectivity and then trying to register to each of the other servers in the clusters before settling back on the correct subscriber. Is there something in RTMT that I can pull to see why this is happening? A couple of devices here and there will just show up as unregistered on another server.
Install the RTMT on your computer, at RTMT > go to Syslog viewer > Select the Node where the phone is registered > click on the Application Logs or Get console logs of ip phone to check what happened.
In logs “ReasonForOutOfService” value will show you the exact reason why the phone is loosing the connection with CUCM or check “EndPointUnregistered” keyword in logs.
Check your network connectivity with CUCM
See if the IP Phone is not loosing the IP Address for some reason
Make a packet capture on the server to see at packet level whats is going on
https://supportforums.cisco.com/document/44376/packet-capture-cucm-appliance-model (This is old but gold)
I have seen mostly the devices show unregistered of reason code 10, 18 or 23. These indicate TCP timeout or the device closes the TCP connection due to seeing higher preference in CUCM group. This happens sometimes even when it is already registered to the highest preferred node. I am seeing strange things in SYSLOG also like a device with a /0 and another entry showing the /23 subnet which it should be. This is getting uglier the deeper I look. Now I start to wonder if I should look for something in DHCP.
The phones are all in same location for the most part. This is a fairly simple environment with about 150 devices. Only a handlful are in another smaller site. These devices showing up unregistered are not related to the smaller site, though. As for DHCP, I am really not in control of that here. I thought it was strange that the SYSLOG would show devices with a /0 subnet. The majority of the /0 devices are CSF clients that bounce between wireless and wired LAN when they dock/undock laptop. There is at least one device I have seen in the SYSLOG that is a 7841 hard phone that showed a /23 and a /0 entry which made me curious.
The majority of the /0 devices are CSF clients that bounce between wireless and wired LAN when they dock/undock laptop. (This could be normal since them are disconnecting from the wireless to wired)
But if this is disconnections are occuring the IP Phones you have a network problem.