Voice is no heard when call is answered

Unanswered Question
Apr 16th, 2007


Please it is urgent. I have a call manager express natted to a real IP. This real IP is used by users from other remote sites (in Dubai), in order to register to the CCME and call our extensions in Beirut. The IP phones (IP communicator) are registering, and are able to call each other(the phones are ringing), but we can't hear each other when we answer the calls, no voice is heard.

Please advice urgently (maybe it is ports problem or ... ???!!)


I have this problem too.
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Tommer Catlin Mon, 04/16/2007 - 12:19

You have a NAT problem for sure. Remember, once CCM sets up the call between IP and IP phone, CCM drops out of the equation. Now it is just IP phone and IP phone talking.

So if your subnets between the two IP phones are not properly configured, you will get no audio.

You probably have the the subnet from IP to CCM external IP working, which would explain why the phone is registered. But to get Audio working, you will need to work on NAT the audio through.

tarek issa Tue, 04/17/2007 - 03:22

i have red the following,if i want to use mtp to try to solve the issue:

"If a firewall is present, it can be easily configured to pass the RTP packets because the router uses a specified UDP port for media packets. In this way, RTP packets from remote IP phones can be delivered to IP phones

on the same system though they must pass through a firewall".

So which port should the firewall open if i m using mtp? Should UDP be always opened for all ports ?

Please advice

omendieta77 Thu, 04/19/2007 - 12:27


In the ACL of the firewall yoou can set up h323 ports, but the problem is that there is a huge range of UDP ports for RTP packets, if I'm not wrong from 16384 to 32000 something. AS the RTP packets are no enabled you can't hear the voice. Other point is that then the destination address is the remote phone, so you can try to do PAT or No NAT in the Firewall.



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