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Community Member

Sporadic No Ring back and No Audio

Hi, I have an odd issue in our office. Just confirmed today but, myself and staff have noticed that sporadically when I try to call a number via PSTN we will not hear any ringback or any audio once the call is connected. I tested this a couple of times to my cell phone. The call is made and I do not hear any call back, and my cell phone rings, I answer my cell phone but, neither I can hear my office phone nor can I hear anything on my cell phone.

This is sporadic, it will happen once and a few hours later after several successful calls it will happen again. We are also experiencing a similar issue when we transfer calls thourgh the PSTN. If I try to transfer a call to a cell phone the call seems to transfer but, the transferee never gets to the destination just seems to stay on hold. We have also noticed several times calls coming in our main DID and we hear nothing. It looks like this has been happening for several days however, its so sporadic its just now coming out.

I've read a couple of doc's about enabling IP routing, Binding the H.323 Signaling to a Specific IP Address, and other standard configuration issues however, this is not a new install we have had this router and config for about three years and nothing has changed at least within the last year.

I kinda think that maybe its a DSP issue but, I'm curious on other peopels thoughts. Here are the specs.

Cisco 2821 H323 Gateway with PRI running IOS c2800nm-ipvoicek9-mz.124-24.T2.bin.
Cisco Unified Communications Manager System version:

Any thoughts?


Everyone's tags (4)
Cisco Employee

Re: Sporadic No Ring back and No Audio


It could be a DSP issue. To get a better understanding of the environment, can  you post the following?

show version

show voice dsp detail

show voice dsp group all

show diag

show call active voice brief

show call history voice brief

show run

show controller t1/e1 (if applicable)

What is the typical call volume through the gateway?  Has the gateway been reloaded since the issue was first reported? If not, can you get the following as well.

show log


Community Member

Re: Sporadic No Ring back and No Audio

Hi Felipe, thanks for the info.....I found out a couple of days ago what had happened. A co-worker that was creating some dspfarm groups I guess for testing codec. Heres the output:

sccp ccm group 1
bind interface GigabitEthernet0/0.3
associate ccm 1 priority 1
associate profile 102 register VoIP-RTR-TCode
dspfarm profile 102 transcode 
codec g711ulaw
codec g711alaw
codec g729ar8
codec g729abr8
maximum sessions 3
associate application SCCP

Since we have removed the above commands everything is back to normal.

Thanks for the advice and the helpful commands!



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