A simple post about simple things in CUCM

     I figured I needed to make another post today.  It's been awhile and I like to keep things fresh when I have the time.  I have been knee deep in service tickets for a customer lately and have been trying to keep track of those one offs that people rarely encounter, but when they do, can never find an answer.  I figured today I would post some simple things about CUCM if you didn't already know.  For anyone that actually reads my blog, this stuff is very basic so if you are a CCNP Voice or a CCIE then you can probably read on because you are bored.  Nothing to follow will be of use to you if you are already at that level.

CUCM Phone Registration Unknown vs Unregistered:

     This one time and time again has come to me by junior voice initiates.  They find a phone that isn't working and assume that something is terribly wrong because it went unregistered.  The problem is, phones can go unregistered for a myriad of reasons from switch failures, network failures, the phone itself dumping, someone blocking traffic on the network, etc.  The key here is to check RTMT and see why the phone unregistered.  It generally gives you a cause code when you look at the syslogs of CUCM. 

     On the matter of Unregistered and Unknown, keep in mind that Unknown generally indicates that the phone has never been on the network...since the last restart of CUCM if it ever has been restarted.  What this means is that if you never restarted CUCM (assuming this is a fresh install since everyone reboots at some point) and the phone is Unknown you might want to check the phone and make sure it has power, the correct VLAN on the wall drop, and is programmed with the correct MAC address.

     When a phone is Unregistered, this indicates that the phone was on CUCM and registered at some point between before you logged in and since the last reboot.  Something has happened between then and now.  This could be something like a user unplugging the phone, the switchport being shutdown, etc.  Check to see if you can ping the IP address, if the phone still responds to ICMP but is failing to register, I would perform a reboot of the phone followed by a factory reset if that doesn't solve the problem. 

     As you can see, the two status messages of the phones indicate what steps to take in order to solve the problem.  My write-up is by no means an exhaustive list of things you can do.  You could always setup a packet capture with wireshark and see what is going on as well.  Maybe the phone is requesting a file upon boot that for some reason, it is not getting.