SIP trunk callout - can not hear voice from SIP trunk

[ufgeorge]

I try to add Generic SIP trunk.
When I callout from internal phone, I can not hear the voice from other side. But other side can hear my voice.

But if I add trunk info to my CISCO phone and callout, no problem at all.

The firewall checker has no error except
detecting SIP ALG... failed

Dont know how to solve it...

George

 

[YiannisH_3CX]

Hello @ufgeorge

The first thing you need to do is pass the firewall checker in order to ensure that the issue is not with the firewall.
The next thing i would recommend is choosing a supported provider so we are sure that the trunk is setup correctly in the PBX to avoid compatibility issues.

 

[lneblett]

Depending on how connected to the Internet, there is usually a setting in the ISP modem and/or your router that is called SIP ALG or SIP Helper or similar. These normally need to be turned off.

The ALG is one of the prime suspects in one-way audio as it re-writes headers in an effort to set-up the messaging correctly using the assumption that it knows best, when usually it does not.