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CUCM 8.5 and random phantom ringing

We have a UC on UCS deployment of about 800 phones across 13 different sites with 95% using 7942 model Cisco IP Phones. We are having an issue with IP phones ringing for about 1/4 or 1/2 ring and then clearing. When we try to call that extension back nobody is there. Turns out that nobody actually placed the call to begin with. We are calling this a phantom ring and it has been plaguing our UC environment for many months now. We opened a case with TAC and after looking at logs they determined that the there are off-hook and on-hook events occuring within 500 ms of each other on the phone being called... Based on that observation TAC had us RMA every phone due to a "mechanical" bug with the phones. We did indeed replace every phone. Things have been calm for about a month until today. The issue is happening again. Today we were informed that a 7975 phone rang 1/4 time and then cleared. The phone shows this as a missed call and shows the caller id in the directory. This is an internal call and upon dialing that number back nobody is there.

Has anybody run into issues like this in the field? We are running out of ideas here.

This is our UC environment:

(2) UCS-C210-M2 servers running ESXi

CUCM System version: - 1 Pub and 1 Sub

7942 firmware SCCP42.9-2-1SR2S

7975 firmware SCCP75.9-2-1SR2S

please ,any ideas or direction would be helpful as we are trying to step back and look at this again from another angle.

thanks again!

Cisco Employee

CUCM 8.5 and random phantom ringing

i guess you need to open a new case for 7975 phones with TAC.

as there were issues with 7942 phone going off hook and on hook but never seen this issue with 7975 phones.

it could be a bug but first tac has to validate the finding!!


Vipul Jindal