intermittent sip trunk outbound dtmf digit drop

Unanswered Question
Jun 22nd, 2009

SIP trunk to ISP with CUBE (H323 to SIP)Inbound/outbound call is fine. Inbound DTMF works. Outbound DTMF work intermittently with random digit drop. (happens to approx 1 out of 3 calls) "debug voip rtp session named-event" shows router sending the correct digit out to telco everytime. What could be causing this?

HW: 3845

IOS: 12.4(20)T1

UC: 6.01

dial-peer to UC: dtmf-relay h245-alphanumeric

dial-peer to telco: dtmf-relay rtp-nte digit-drop

MTP: use IOS MTP on the same router

I have this problem too.
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Nicholas Matthews Mon, 06/22/2009 - 19:25

Hi Joanne,

Try adding:

voice service voip

dtmf-interworking rtp-nte

There are some interop issues with the way some other IP solutions look at RTP-NTE RFC 2833 packets. This command frequently solves that type of problem. Plus, there's no real downside as nearly everyone that accepts the default method will also accept this method.


mariannehw Fri, 04/02/2010 - 09:47

I was having DTMF issues just when calling particular numbers, while all the rest would work just fine.  Symptoms were that the auto-attendant on the called side would continue "talking" even when key presses were made, so it appears that nothing went through, not even intermittently.  Adding this to my config fixed the issue to both the numbers I knew to be a problem.  Thank you!

I know this is an old thread, but I wanted to put in my $.02. I was having a similar issue to a few specific numbers. In my case it was CUCM->SIP->CUBE->Static NAT on an ASA Firewall->Internet->TSP. Not the optimal solution but it's what my customer ordered. In any case, I added the command listed above but it did not resolve the issue. I ended up, creating a new SIP profile in CUCM and increased the DTMF volume. This appears to have resolved the issue. Hope this helps for anybody running into this issue going forward.



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