Problem with Inward calls on MGCP gateway

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Apr 7th, 2008
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Hello , Iv a cm setup consisting of an ISDN PRI terminating on a 3825 configured as MGCP Gateway on Call manager 5.x setup. Calls are coming through(establishing) but there is no sound. Calls dont drop either until graceful disconnected by user. Configs are as attached. Ive not yet tried the outbound configs yet. Please help

Correct Answer by kthorngr about 9 years 3 months ago

The MGCP setup looks ok. You might have DSP issues. Not sure what hardware you have but this link might help:


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Overall Rating: 5 (1 ratings)
adowfille Mon, 04/07/2008 - 07:38
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Yes I got a response but is has not helped. Any other idea.


Jaime Valencia Mon, 04/07/2008 - 07:58
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do you have the proper routing so the RTP from the GW is sent to the IP Phone IP???

any FWs?? ACLS?? anything that could block the RTP stream?


adowfille Mon, 04/07/2008 - 21:17
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Routing works fine. I can ping the Phones from the gateway and vice-versa. There is no FIREWALL or ACL implemented. Im just using two subnets : Subnet 1 for Gateway and CM and another for phones. I will try to collapse all into one subnet and see if this will help

adowfille Tue, 04/08/2008 - 00:34
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Have collapsed al devices into one L3 switch but still nothing. Have also tried with a different phone with same result. The following is a MGCP debug output.Any help appreciated.

adowfille Tue, 04/08/2008 - 23:01
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Thanks a lot for your kind assistance. The problem is actually not DSP but with clocking. I added 'network-clock-participate slot 1'and it is now working fine.

Kind Regards


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