3CX Softphone intermittent 1 way audio

[Warren@liquidsky]

Hi Guys,

I am struggling with an issue with one of our clients, they have 1 physical Yealink desk phone and 20 SoftPhone extensions,

From a networking point of view we have 25mbps dedicated fiber and have set up 2mbps for voice and 23mbps for data. the PBX is hosted offsite at a reputable data-center.

when making or receiving calls from the physical desk phone we have absolutely no issues, audio quality is good, no delays etc.

when making calls from a softphone we seem to be experiencing intermittent 1 way audio, where the person they are calling cant hear them (outbound audio) inbound audio is fine, when this happens you need to make an additional 2 calls before finally getting 2way audio

we have run wireshark captures and compared calls that work and calls that dont work and have found nothing, we have also confirmed that SIP-ALG isnt enabled on any devices.

can anyone weigh in, or should we just scrap using the 3CX app and get this company to go hardware phones.

thanks for your time

 

[Saqqara]

When you say you have allocated 2mbps for voice, have you included port 5090 tcp and udp as the softphone will use 3CX tunnel.

 

[Warren@liquidsky]

we have done it on a static IP route, through a mikrotik firewall, so the internal LAN only knows about the hosted PBX through that 2mbps channel

 

[JohnS_3CX]

Wireshark should at the very least confirm that the audio stream is missing, so not sure what you saw there. I don't know how busy the 2MB link is during the times of the issue, but usually bandwidth starvation will manifest in choppy or stuttery audio, and if using G711 you should have enough b/w.

One way audio might be pointing more towards a network or port issue depending in your setup.

Are you over SBC or VPN?
What version of the 3CX Softphone are you using?

 

[Warren@liquidsky]

interestingly enough we are using the 3CX app through the tunnel, we have 0 issues on the 1 physical phone there running on STUN and on the 3rd attempt when a phone starts working on 2 way audio everything is fine, its just the first 2 calls that we have 1 way audio and its always the client not hearing them and not the other way around.

so to clarify, its audio out that's the issue, they can hear their client but their client cant hear them untill the 3rd call

 

[JohnS_3CX]

You have not clarified which softphone version/platform you are using, and whether you use the tunnel or not, its difficult we don't have much information to help you with and the stun phone uses different ports to do its job so it is unrelated/unaffected

 

[Warren@liquidsky]

we are running version 16 on the PBX and the lastest 3CX version on the phones which at the time of this test was i think version 15.5

the 3CX app is using the 3CX tunnel to connect to the PBX

 

[JohnS_3CX]

Some tests you can do to isolate the source of the problem. Check them in this order to save time:

1. Firstly run the firewall test on your PBX first and ensure that all checks will pass. Resolve any issues here if it doesn't pass, before you even spend precious time looking elsewhere
2. Check if internal calls between users on 3CX clients also face the issue. If not, it could indicate an issue with the provider. If yes, then see next step for verification
3. Call *777 which is the echo test between your client and the PBX. If you hear your own voice echoed back always, then your 3CX clients and their internet access/tunnel are most likely ok and the issue is after the PBX or with the provider
4. As a last test, take a capture on the PBX for some of the problematic calls (select all interfaces since we are using tunnel). You will find out whether outbound audio from the client reaches the PBX. You will also find out if outbound audio is sent to the provider successfully.

Let me know how it goes for each step you tried