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Wednesday, December 8, 2010

Why is CUCM Phones rebooting themselves?

We have a customer that has been plagued with an annoying problem for a couple months now. We have had a TAC case open with Cisco and haven't been able to get anywhere with them. Here is the issue.

Periodically (at least once a day), a small group of phones registered to CUCM 7.0.2 reboot themselves with no administrator involvment. Now at first we thought it was a network problem (missing keepalives), but further investigation into the QoS configuration showed that there were no packet drops in the priority or call control queues and that MOS scores throughout the network were averaging 4.43 with a low score of 4.3. Second we considered the possibility of a firmware bug (8-5-2s) however the issue happens to different phones everyday and not necessarily the SAME phones. The issue moves around the network affecting different phones one day and other phones another day. The only thing that we have been able to identify is that the syslogs show transient connection errors and it seems to be around 9:00AM and 9:00PM when the phones lose connection. Any ideas that anyone might have are GREATLY appreciated. Thanks for taking the time to read and consider.


You should disable Power Inline on any port that doesn't require it. You can do this by applying the power inline never at the interface level.

You can also use Show power inline to find out which ports are using POE and which wattage. You will also want to ensure that you have the correct power going to each phone model

Q. What are the power requirements for the various models of the IP phone models?

· CP-7902G (6.3W)

· CP-7905G (6.3W)

· CP-7910-SW (6.3W)

· CP-7910G (6.3W)

· CP-7912G (6.3W)

· CP-7940G (6.3W)

· CP-7960G (6.3W)

· CP-7906G (5W) (Class 2)

· CP-7911G (5W) (Class 2)

· CP-7941G (6.3W) (Class 2)

· CP-7941G-GE (12.9W) (Class 3)

· CP-7961G (6.3W) (Class 2)

· CP-7961G-GE (12.9W) (Class 3)

· CP-7970G (10.25W) (Class 3)

· CP-7971-G-GE (15.4W) (Class 3)

· CP-7985G (12.55W) (Class 0, Not full brightness)

· IEEE 802.3af Device - Class 0 (15.4W)

· IEEE 802.3af Device - Class 1 (4W)

· IEEE 802.3af Device - Class 2 (7W)

· IEEE 802.3af Device - Class 3 (15.4W)

Also if you need to change the POE Wattage used by the phone you can do this below:

A powered device might use more power than set by the power inline consumption command, so you must carefully make adjustments to the power budget. An accurate power budget protects the switch from an overcurrent condition.


In this example, the power budget is manually adjusted to 4 W on a specific port. When a Class 3 phone was connected, it required more power than 4 W: #

Switch(config-if)# power inline consumption 4000 .Click here for doc and this link gives you further info on the product.

Citation - This blog post does not reflect original content from the author. Rather it summarizes content that are relevant to the topic from different sources in the web. The sources might include any online discussion boards, forums, websites and others.


  1. Hi,
    Were you able to find out the issue? Oddly enough, we are having almost the exact issue. I'm very curious to know and would greatly appreciate it.

  2. Hi Showiz,

    Can you post your question at and we will get you an answer?

    The service is free.

    Qsolved Team


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