DTMF strangeness on MGCP gateway

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Jun 30th, 2009
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I'm encountering a peculiar issue regarding DTMF. DTMF tones are not always being recognized by our call center, this problem seems to coincide with out recent IOS upgrade on our MGCP gateway. Most calls from outside of our organization, when calling our call center from within, are able to send DTMF with no problems. However, other phones are not. There doesn't seem to be a connection between the problem calls; the phones having trouble are both cell and land lines, within the same exchange and from without, etc. Also, DTMF is being sent out of band in the MGCP syntax.

My question is; is there a setting to adjust DTMF settings on the gateway? I suspect that the DTMF is not being recognized because it may not be loud enough or the tone sent may be too brief.

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Kenneth Mohammed Tue, 06/30/2009 - 15:16
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What IOS and what type of router? We once upgraded a 3845 to 12.4(18)b advanced IP services feature set, and experienced the same issues you report with DTMF. When we rolled back to the previous IOS, the issue disappeared.

Hope that helped, if so please rate.

shikamarunara Tue, 06/30/2009 - 15:20
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Hi Kenneth,

Thanks for replying. The version we are using is c2800nm-advipservicesk9-mz.124-22.T.bin. This is on the 2811.

Kenneth Mohammed Tue, 06/30/2009 - 15:45
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I am looking at some bugs, what exactly does the dtmf statement say in your mgcp config?

shikamarunara Tue, 06/30/2009 - 20:35
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The dtmf syntax is to specify that it should be out of band;

mgcp dtmf-relay voip codec all mode out-of-band


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