RTP ports 3CX - Voxbone: Audio for outgoing calls

[Greentube-ASM]

Hi,
I´m a bit confused. We are using 3CX 16.0.655 with Voxbone as telephony and SIP trunk provider.
Basically it is working fine but recently we´ve issues with outgoing calls. The calls are initiated but audio is not working.
Restarting services helps but it happens again.
I checked ports and firewall settings. I wounder because 3CX is using RTP 9000-10999 and Voxbone is using RTP ports 10000 – 24000. May I´m completely wrong but could this be an issue?
If not is there anything I can do to figure out why audio is not working once it happens again?

Thanks!

 

[ChrisC_3CX]

Hey @Greentube-ASM,

3CX does indeed use UDP Ports 9000 - 10999 for the external RTP traffic, however, these are the 3CX's source ports. If your Firewall has been configured to forward incoming traffic destined for these ports to 3CX, then you do not need to worry about what ports the provider uses, since, the ports you mention are the provider's source ports. They do not have to be the same. Just make sure that you are not restricting traffic on your firewall in a way that would affect traffic towards or from those ports(10000-24000).

First thing I would recommend is having a look at our port requirements and making sure that the necessary firewall configuration is in place: https://www.3cx.com/docs/ports/
Do make sure that you can pass the firewall checker but do not assume all ports are configured based on the fact that it passes because it does not test all ports.

Then you should consider upgrading 3CX to the latest stable version which currently is 16.0.7.1078. If the issue remains, try recreating the SIP Trunk using the provider's template without making any additional changes to the SIP Trunk configuration other that the account details if any.

If you there are still no improvements, provide all information mentioned in this post to help us get a better understanding of the setup: https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

 

[Greentube-ASM]

Hi,
The information given was super helpful!
One more thing. The firewall check tool - is it performing the tests from the stun servers?
I couldn´t do the test so far as the fw rules are limited to our VOIP provider subnets.
If I would know from which IPs the tests are performed I can ask to add them.
Thanks!

 

[ChrisC_3CX]

@Greentube-ASM,

Glad I could help! That is correct, the Firewall checker performs the test using 3CX's STUN servers which are specified under Settings >> Network. It also uses the following address to check if a SIP ALG exists: sip-alg-detector.3cx.com.

Just check to what IPs these FQDNs resolve to.

 

[Greentube-ASM]

Thanks you for your fast reply!