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UC 540 | One way audio through SIP and PSTN

Hi I am having a problem with a UC 540 where there is only one way audio. Initially I was having it with outgoing SIP calls which I am still troubleshooting but as a temporary solution I had made all outgoing calls via PSTN. This had the same result, I can hear the person I am calling from the VoIP phone but the caller cannot hear me.

I have done the Impedance test and all but still no luck.

Also, In regards to the SIP problem, from the SIP server side the RTP packets are being sent but not getting a reply from the UC. The UC has been configured using CCA and also the router connected to it does not have any firewall or access list blocking it.

I have attached my entire configurations below, with a few debug files.


Your thoughts and suggestions are welcome. Thank you.

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I have attached SIP trace for

I have done multiple tests and still no go.


Did notice that the on hold music works and can be heard on the other end.

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