Solved intermittent outbound audio failures

[jholbrookFTLtechnology]

I have a system that i have been battling rare random outbound audio issues with. i have taken packet captures and have heard the audio on the call. the one that i have a capture on they talk for about a minute and then all of a sudden the external participant cannot hear the internal participant any longer. the phone system is getting incoming audio and the internal person can her them but they cannot hear the internal. i have replaced the firewall appliance, tripple checked the settings (sonicwall, same setup that i have in multiple other places, all working fine). i am at a loss at this point. not all calls fail, just today they had multiple calls that lasted 30 minutes or longer with no issue then boom call audio stops going out and they have to hang up can call back.

my gut is telling me ISP issue, i had them come and replace the cable modem already and it lasted about a day.

 

[AWS2P]

Please start here to help us for a better understanding
https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

 

[JohnS_3CX]

Hi,

1. If this affects only external calls, and your capture contains legible outgoing audio, then you can remove the PBX from the equation entirely.

2. Next step is to also capture from your firewall and verify the same as above.

3. Once this checks out, it's time to contact your trunk provider and ask them whether they receive the audio from you.


If the audio left the firewall WAN interface with the correct destination IPs in both the packet and the contact address, but the trunk providers don't receive it, then finally it's time to contact the ISP and make sure they don't have anything messing with SIP like ALG or something on their core network messing up the SIP messages and RTP.

 

[jholbrookFTLtechnology]

sorry for the late reply, i wound up doing a packet capture with a network tap between the router and the cable modem and was able to prove definitively that the issue lies with the ISP or beyond.

 

[JohnS_3CX]

Good work, hopefully the provider will be able to shed some more light.

I will mark this as solved then since there is no issue on the PBX side.