One-way audio after latest update

[YP@R2K]

We are on version 20 for sometime now and have 3 sip-trunks configured in 3CX. After the update to Version 20.0 Update 9, one of the sip-trunks started having only one-way audio (audio from 3CX is transmitted to PSTN, audio from PSTN is not transmitted to 3CX extensions). There were no changes to sip-trunks. And no changes to firewall (everything works fine on 2 other sip-trunks). While testing this sip-trunk on another PBX (Granstream) and on another sip-client (MicroSip) there were no issues with this sip-trunk. Also there are no issues with other 2 sip-trunks with other 2 providers.

So it looks like something has changed in 3CX after the update.

How to troubleshoot?

 

[YP@R2K]

Telefony provider informed that according to their logs, they are sending the audio stream. So for some reason 3CX is not accepting it.



27.03.2026 09:28:04.734 +02:00: 20.103.254.41:43939 -> lifecell:5061
SIP/2.0 200 OK Via: SIP/2.0/TLS 212.58.160.214:5061;branch=z9hG4bKf4ae.558bd6370db2302902eb993c635d848d.0 Contact: <sip:38093205221[email protected]:5061;transport=TLS> To: <sip:[email protected];user=phone>;tag=43e86d60 From: <sip:[email protected]>;tag=08002674401704 Call-ID: [email protected] CSeq: 697738818 INVITE Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REGISTER, SUBSCRIBE, NOTIFY, REFER, INFO, MESSAGE, UPDATE Content-Type: application/sdp Supported: replaces, timer User-Agent: 3CXPhoneSystem 20.0.9.670 (670) Content-Length: 315 v=0 o=3cxPS 24081943805034496 31206515801063426 IN IP4 20.103.254.41 s=3cxPS Audio call c=IN IP4 20.103.254.41 t=0 0 m=audio 9030 RTP/SAVP 8 96 a=rtpmap:8 PCMA/8000 a=rtpmap:96 telephone-event/8000 a=crypto:1 AEAD_AES_256_GCM inline:xXf8PFB+WzM9r/9nwYJ8ZudHKYRwihw7MbMFK1GxdYLJZSLGve4KbxCWHvU= a=sendrecv

tshark -i any -f "dst host 20.103.254.41"

Running as user "root" and group "root". This could be dangerous.

Capturing on 'any'

1 0.000000000 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

2 0.000001745 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

3 0.000002391 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

4 0.019992056 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

5 0.019993103 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

6 0.019993653 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

7 0.039985113 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

8 0.039986302 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

9 0.039986907 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

10 0.059985575 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

11 0.059986662 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

12 0.059987238 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

13 0.079986748 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

14 0.079989234 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

15 0.079989827 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

16 0.099988753 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

17 0.099989893 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

18 0.099990361 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

19 0.119985454 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

20 0.119986562 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

21 0.119987039 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

22 0.139987141 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

23 0.139988270 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

24 0.139988876 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

25 0.159997197 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

26 0.159998440 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

27 0.159999335 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

28 0.179988972 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

29 0.179990078 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

30 0.179990674 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

31 0.199984082 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

32 0.199985172 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

33 0.199985884 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

34 0.219988346 lifecell → 20.103.254.41 UDP 232 44670 → 9030 Len=188

35 0.219989406 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

36 0.219990090 lifecell → 20.103.254.41 UDP 236 44670 → 9030 Len=188

 

[edossantos_sipcaller]

Check the Secure RTP settings. It seems 3CX is requesting SRTP, maybe the provider doesn't support it? In that case try disabling it.

 

[YP@R2K]

Sip-provider supports SRTP and it worked with SRTP for serveral years already.

It seams like v20.9 broke something. I have deployed a new VM (it installs with version 20.8), configured same sip-trunk and everything was working. Once I updated to v20.9 - only one-way audio. I then restored the backup of this test VM back to previous version 20.8 and everything started working again.

 

[edossantos_sipcaller]

Update 9 is still in alpha stage, you should stick to Update 8 for now. The issue will probably be fixed when the final version is released.

 

[YP@R2K]

Is there any way I can downgrade to v.20.8 without reinstalling the whole instance?

 

[edossantos_sipcaller]

No, you will need to reinstall and restore a backup taken in Update 8.

 

[Christos Chatzaras]

I have the same issue after upgrading to the latest Alpha release. If I disable SRTP mode, the problem disappears, but my provider does support SRTP. Does anyone know whether the 3CX team is aware of this issue?

 

[ivank]

Hello, please put activity log setting to Verbose, reproduce, generate support info and provide the link to .zip in a DM to me.

 

[ivank]

Please also specify the SIP provider you use.

 

[YP@R2K]

No, you will need to reinstall and restore a backup taken in Update 8.

Reinstalling the 3CX instance and restore from previous backup has resolved the issue.

The strange thing was that the backup file during installation was not accepted (some error with absent admin email address despite not being correct). But I was able to restore from backup after the installation was complete.

 

[ivank]

@YP@R2K could you share any logs from the case with me?

 

[RDKTechSupport]

Also experiencing a one-way audio issue for outbound calls with TLS/SRTP enabled. This is on 3CX free cloud [Version 20.0 Update 9 (Build 873 - AI 1.2.5)] with Voxtelesys. Don't appear to have any way to resolve this other than to temporarily disable TLS/SRTP and wait for an update.

 

[ivank]

Could you collect verbose logs and share with me?

 

[ivank]

temporarily disable TLS/SRTP and wait for an update.

The problem is, since nobody yet shared the logs, there will be no update. It's been thoroughly tested on all supported trunks and we just don't know what to "fix".

 

[YiannisH_3CX]

Did you ask Voxtelesys to enable SRTP on your account? SRTP has to be enabled on Voxtelesys end in order to work, it does not happen automatically when you switch to TLS.

Go in your trunks settings and set the SRTP Mode option to "Enabled" and try again.