Dial But can't listen to talker

Unanswered Question
Jul 15th, 2009

I have call manager 6.0 and varity of series ip phones . i face a problem with some ip phones, when i called to another ip phone i listen to the ring but when the handset is up i didn't listen to any thing . it is repeat with many ip phones . Please advise me

I have this problem too.
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CHRIS CHARLEBOIS Wed, 07/15/2009 - 06:14

Sounds like a one-way audio issue. Because the phones use one protocol for call control (TCP) and a different protocol for the actual voice traffic (RTP/UDP), it is possible (and unfortunately quite common) for a firewall, NAT, or VPN to block or interfere with one (usually the RTP) and allow the other. So you can make and receive calls, but cannot be heard by the far end.

So the question is, where are these phones located and what networking equipment is between them? Make special note of any Network Address Translation and/or any private address space in use.


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