one way no audio internal to external calling

[de.101]

Hi,

 I'm trying to get an idea on how to approach troubleshooting one way no audio issue as below. 

-Cisco IP phone to PSTN, calls connect but external party cannot hear audio, Cisco Phone can hear external party.

-Internal to Internal calling, no audio issues

-Calls from PSTN to Cisco IP phones, no audio issues.

This was escalated to Telephone Service provider and senior team, but out of interest and keen junior Cisco technician I would like to see proper way to approach and troubleshoot the above issue. From Firewall to Voice Gateway.

Thanks in advance!

[balaji.bandi]

Most of the time one way voice Due to NAT issue, also  considering looking at  Codec Translation.

[luis_cordova]

Hi @dan.10,

Check this link:

https://community.cisco.com/t5/collaboration-voice-and-video/how-to-troubleshoot-one-way-no-audio-issues/ta-p/3164442

Maybe can help you.

Regards

[HARIS_HUSSAIN · Accepted solution]

As a starter you can try below

1) Approach :1 :- Find out Packets sent and received on Phone

         ===> Here we will make a live test call see the Packet received and sent counters on IP Phone To isolate issue is between Which Subnet to Which Subnet

                  ====> Once Call is active you can view Call Statistics in Phone by settings > Admin Settings >Status>Call Statistices on 7800 Model or Press ? button twice on 7900 Models

2) Check if required Ports are open in the path were you are facing issue i,e RTP Ports  16384 - 32767 UDP. Check the ACLs, Routing , Firewall Rules

3) Check if SIP/SCCP Inspection is disabled in firewall. Also check if path involved any NAT.

Thanks,

Haris

** Please rate and mark solution accepted if applicable.

[de.101]

We have done Wireshark capturing from Cisco IP Phone, no issues were picked up, all looked good.

We have then disabled SIP/SCCP Inspection. Once disabled the one way audio issue was resolved.

Now, is it best practice to leave SIP/SCCP Inspection disabled permanently? are there any issues with leaving it disabled in this case?

Much appreciated with help received!

[George Sotiropoulos]

Hello,

You better check on your firewall if SIP inspection is enabled and if it is test by disabling it.

George