Can't connect PSTN callers from Unity Auto Attendant

Unanswered Question

Hello all,

Hope everyone is well !! I've got an issue in India. I just brough up a new site in India and I am having a problem with PSTN callers trying to connect to an extension by enter a 4-digit extension number from Unity auto attendant. What is happening is when callers dial our main number the call get routed to Unity aa and no mater what extension they enter it always route the call to the operator extension. But if I dial auto attendant internally then everything works fine. I have a feeling DTMF tones are not being sent when dial from PSTN.

Has anyone run into this issue in India ?

Here is the call flow: PSTN caller -> 3825 router with vic2-4FXO -> Unity AA -> IP Phone

and one thing I noticed is all analog lines in India are centrex lines. This might have something to do with the issue.

Thank you all in advance !!!


I have this problem too.
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Jaime Valencia Mon, 03/23/2009 - 17:42

it does sound like DTMFs are not being relayed.

open the port status monitor on unity and place a call to confirm you see DTMFs. you can place one internally so you can see how it works and the one from PSTN that probably won't have the DTMF events.

depending on the protocol make sure you have configured the relay for DTMFs. H323? MGCP?



if this helps, please rate

Nicholas Matthews Mon, 03/23/2009 - 20:23

Hi Danny,

Please note that if your gateway is on 12.4(15)T code, and you're not on the latest 12.4(15)T8, you're probably hitting this bug: CSCso87127.

You'll get duplicate DTMF and it will really do a number on your IVRs.

12.4(20)T and later should be fine.

Otherwise, if you're using H323, it may be a dial peer issue. Make sure your outgoing dial peer has 'dtmf-relay h245-alpha' configured.



Hello Nick ! I am running IOS version 12.4(22)T and I do have dtmf-relay h245-alpha configured.

any other ideas ?

And one thing I noticed is that the greeting continues to play as I enter the extension, where as if I dial the aa internally the greeting stops as I enter the first digit.

Thanks Nick !!! I appreciate your inputs !!


Hello Nick,

I found that 12.4(6)T11 is not affected by this bug and it is the version that I am running now and all seems to be working fine but the issue with this version is that it does not support the WAAS module that I have in this router, the minimun IOS version requirement to support WAAS is 12.4(15)T. So I am stuck right now, I fix one thing but break another. Do you what version that has both the bug fix and the support for the WAAS module ?

Thanks ! appreciate your help !!!


Nicholas Matthews Mon, 03/30/2009 - 11:34

Hi Danny,

12.4(15)T8 100% has the fix for this bug. You may be hitting something else - very hard to tell by speculation at this point.

You can try 20T or later (20,22,24T), and see if you get a different result.




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