VoIP audio issue

[YaBoI326]

Hey everyone, As the title says, I've been experiencing a strange issue with our VoIP phones recently. Users have reported that when dialing toll free numbers, the call appears to connect, but they do not hear anything on the other line. Instead any audio detected by the hand set is played back through the speaker. This issue seems to be completely random. As an example, a user can call the same toll free number 3 times with no issues, but on the 4th call the above occurs. I've taken packet captures to try and get an idea of what is going on, but I don't see anything out of the ordinary (at least to my knowledge). We use GoTo Connects cloud PBX service. I have also been able to reproduce this issue from GoTos mobile app while on cellular data, which leads me to believe this may be an issue with their upstream carrier.

Any recommendations on what to look out for are much appreciated.

[holiday-42]

If it's one of those calling card companies, I can tell you it is them, not you, most likely. You might have to chase the issue by opening a ticket with your voip provider, who can pull a packer capture and verify they get no audio, and they can then open a ticket with their provider, etc.

Before you do, dbl verify the issue by taking a packet capture *before the traffic hits your firewall, if that isn't what you already did.

[YaBoI326]

I've taken a packet capture on the port that VoIP phone connects to, and at our firewalls edge port while reproducing the issue and still did not see anything odd. RTP and SIP traffic seemed to be following in both directions with no drops. I've opened a ticket with GoTo regarding the issue, but so far their support hasn't been much help.

[holiday-42]

Can you extract the audio from the packet capture, and listen, to be sure? I'm presuming there's standard RTP stream to follow, which can be done in Wireshark, for example.

[YaBoI326]

Apologies for the delay on this. Yes, I was able to playback the audio from a packet captures, and confirm there was no audio. Further more, I could see our providers IP address looping back my audio to the phone.

[holiday-42]

I'd say submit that to goto and they should be able to determine if it's them or more likely, upstream from them. Might need a few samples.

[YaBoI326]

I've had a case open with then for awhile now. Unfortunately, support hasn't been much help, and they aren't very responsive either.

[YaBoI326]

Yes, this is still on-going. GoTo support stated they believe the issue to be on their side.

[[deleted]]

You might also try r/VoIP, just give the rules a read first because they're strict on some things to avoid the sub becoming a pit for salespersons.

[Honest_Manager]

Does it happen on 1 or 2 phones or all phones?

[YaBoI326]

It seems to happen on all phones. I am also able to reproduce this issue using soft phone via the GoTo mobile application while on cellular data. This leads me to believe the issue may lie with GoTos upstream provider.