Cisco Support Community
Community Member

IP Phone does not register automatically after total network outage

Hi Guys,

When every time there is a network outage/Power outage around 20% of the Cisco IP Phones does not get register automatically. Is there any thing can be done to fix this issue ?



Hi,Where are these IP phones


Where are these IP phones located w.r.t the callmanager server?

What is done to make these phones register back to callmanager?

Which phone models / firmware versions are affected?

What is the cucm version?

Most importantly, if your system is suffering an unclean shutdown due to a power outage you should be aware of the following

You can run recovery disk to start with, it may also need a rebuild.





Community Member

Hi  Manish,yes. the Phone are

Hi  Manish,

yes. the Phone are located at the same site where the call manager is located. CUCM 9.1.2 with Cisco 7821 and 8941 phones.

The issue happen due the L3 core switch down/ or power outage for network. There is no issue with CUCM around 80 % of the phones get register automatically. but about 20% of the phone do not register automatically even if we leave for couple of days. The current work around is to reset the phone in order to get it register.


Hi,In that case i would start


In that case i would start by checking for any switchport errors or ios related bugs for the switch. Additionally, if the issue can be replicated, then try capturing a sniffer from one of the switchports to which the affected phone is connected. This will provide details of the exact step in the registration process where the phone gets stuck , like if its failing to get dhcp info or tftp file or something else. I am aware of this kind of behavior on ATA's as there is a known bug for this, but not for the phone models specified by you. You may need to engage TAC if it requires extensive digging in.



Community Member

Hi,I have the same problem.


I have the same problem. CUCM 8.6.1. Was this issue ever solved?



Community Member

We had the issue for Cisco

We had the issue for Cisco 7800 series phones. There was a bug on this model phone. We got this fixed with ES6.

CreatePlease to create content