IP Phone 7912 G Latency Issue !

Unanswered Question
Jan 26th, 2010

currenlty we have around 400 7912 IP phones in production rest is 7911 and mid series. now an issue arises few days before and that is user is facing voice jittering ang droping problem also from IPT to IPT and from PSTN. normal as well in confrence call. R&D was done with all switching enviroment and the result was

when you ping 7912 phone IP you got 65ms delay but when u ping 7911 ip latency is 1ms, also when you ping to the pc behind 7912 its also 1ms .... dont know why ... this will cause problem in voice breakage and confrence. kindly share if any one also have got that issue

I have this problem too.
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muhammadzubair Tue, 01/26/2010 - 22:40

cisco TAC had given new firmware for 7912G which is 8.0.4  .... but issue is still same .... is this is the default behaviour or something else

muhammadzubair Wed, 01/27/2010 - 07:51

Dear ....

basically we are using different voice vlans .... and if there is some broadcast storm than it should also reflect with 7911 .... but same time it give 1 ms while 7912 65ms .... Cisco TAC engineer said that its by default behaviour .... but i am unable to digest that .... how is it possible that no one notice before that .......  let suppose if i have remote site and i am connecting on WAN which has 20 ms delay than thing wht happened .....  totally unacceptable

Paolo Bevilacqua Wed, 01/27/2010 - 08:10

Using different VLAn doe not mean that you can't possibly have a network problem.

I never heard of the 7912 specifically having problems so something else is going on, hope you can find what is is.

However to measure network perf do not use ping, just press "?" key twice while on a call.

Nothe if packets are lost, it is never phone's fault.

muhammadzubair Wed, 01/27/2010 - 10:46

basically we have five floor with 4 access switches on each floor .... when you connect 7911 in place of 7912 its <1ms but only with 7912 its 67ms ... on each floor .... if u ping from acces or core switch to the 7912 ip you got 65ms ... but if u ping to switch ip its <1ms ... also when pinging with > 600 datagram size ..... unable to ping ..... time out totally .... but with 7911 till 1100 its normal ......

can you please elaborate abot "?"

stuv Wed, 05/12/2010 - 02:46


Did anybody find the solution to this? If I ping the 7940 on my PC, response time = 2ms.  I ping the response time on the PC connected to the 7912, response time 2ms. I ping the IP phone, 80ms?

How is this possible?


muhammadzubair Wed, 05/12/2010 - 03:06

I had open a TAC case on that ... cisco answer that " its default behaviour of that phone" so no issue of that but i am unable to digest that coz on wireless network i had faced issues.

kindly share your experiences what you had faced

Paolo Bevilacqua Wed, 05/12/2010 - 04:02

Ping times do not indicate anything. Evidently the 7912 is slow in responding, and that's it.

j.huizinga Thu, 05/13/2010 - 06:00

As far as I know the 7912 has always been slow in ping responses. Even when everything voice wise is OK.

Check with wireshark


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