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IP Phone restart and reset issue

Hi Hariharan,

Cisco Unified IP Phone 7900 series introduced a Geometric TCP mechanism to permit IP Phones to measure the round-trip delay between the IP Phone and Unified CM, then adapt the keepalive timeout value. This provided a very accurate failover mechanism when the network delay is consistent. However, if the network delay is inconsistent, this mechanism may cause the IP Phones to inaccurately attempt failover. Cisco Unified IP Phone firmware 8.4(2) introduces the ability for the Network Administrator to disable this behavior, if necessary, through the Detect Unified CM Connection Failure parameter defined on the IP Phone device configuration. The default value is Normal; this Geometric TCP mechanism can be disabled if the parameter is set to Delayed. That is documented in

Cisco Unified IP Phone Release Notes for Firmware Release 8.4(2) 7971G-GE, 7970G, 7961G-GE, 7961G, 7941G-GE, 7941G, 7931G, 7911G, and 7906G (SCCP and SIP)

Hope this helps


IP Phone restart and reset issue

Dear All

I am also facing same problem for Cisco 7941G and 7962 phones.

Problem remians unresolved, even with latest firmware.

Phone reset and re-register automatically with error,  last=reset-restart    last=TCP timeout

Is there any solution for this problem???? This probelm happens for the phone across WAN as well as LAN.

We continously piniging CUCM for couple of days, there not even single timeout...!

But Phone sometime un-register and register back its own....!



aku Beginner

IP Phone restart and reset issue

Hi all,

As you ca suspect, we have a similar issue, and can't find the cause for it.

rajesh.kumar, did you resolve your issue?

Hope to get some feedback,




IP Phone restart and reset issue

We are experinceing this issue only with remote users using VPn. Phones will restart atleast once in day. Checked the logs TCP time out and reboots take 5 to 10 minutes. Put the users into solarwinds no issues detected with connectivity.

Cisco Employee

IP Phone restart and reset issue

The only possible method for finding the root cause in this situation is :

!) Set up parallel packet captures for the primary callmanager ( to which the phone is registered ) and the IP phone itself and let it run until the issue is reported. You will need a dedicated pc with wireshark running to do so.

2) Analyze the captures from about 5 minutes before the issue is reported, looking for any packets that left the phone and did not make it to the callmanager or a delay in the same and the same thing in reverse direction.




Probably not an issue with v7

Probably not an issue with v7.1.5, but I just had a TAC case with identical issue on our v8.6.2.20000-2 >> 8.6(2a) where RTMT showed an alert for number of reg'd phones exceeded, even though we have a 7,500 endpoint OVA deployment on each node and the alerted node had less than 1,000 end points registered in a cluster with 4 CUCM subscriber nodes.   If you're running v8.6.2 this may be your issue as well on phones continously resetting themselves.

Conditions state ""client is connecting over an unstable network which causes the client to continuously attempt registrations to the backup subscriber," but that's not the case in our environment.  It is stable but TAC still deemed this as our problem.

Bug CSCts39201-

     Subscriber incorrectly indicates NumRegisteredDevices is exceeded:


     Unified CM Subscriber does not allow phones to register and generates a NumRegisteredDevices exceeded alarm even though there are only a few or no devices registered.


     None. Once this condition occurs, the Cisco CallManager service must be restarted on the affected subscriber.

Affected: >> 8.6(2a)

Fixed in:



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