Answer call and hear ringing

I’m having a very odd issue. Several times a day we have a call come in, the caller id shows up correctly and we answer the line. We do not hear the person but instead hear an odd ringing (like we placed a call). I then hang up and a couple seconds later the phone rings with “Unknow” in the caller id, I answer and it is the same person (I’ve verified this by the first caller id. The person says that the phone has been ringing for some time). Below is a list of hardware/etc (which I have completly replaced once and reprogramed the pbx from scratch). Any help would be greatly appricaited because I’m going nuts.

Note: This happens on multiple phones/extenstions.

OS: CentOS release 5.3 (Final)
Asterisk 1.4.22-4
Trixbox v2.6.2.3
Grandstream 4108 FXO Gateway
Grandstream 2020 and 1200 IP Phones

System Specs:
Intel® Xeon™ CPU 2.40GHz
1GB Memory
20GB Hard Drive
10/100/1000 NIC

Other Info:
Load Averages: 0.14 0.15 0.15
Analog Lines: 6
Extensions: 17


When that happens, open Wireshark and see if you can capture RTP coming from the Grandstream SIP gateways - play it back and see if you can hear the caller. If you can, then something is causing Asterisk not to answer properly (some problem in Asterisk, some problem in the Grandstreams). If you can’t, then something is definitely wrong with the Grandstreams.


Thank you for the info, I will try and capture the stream and see what I get.

I did replace the Grandstream Gateway once already but it did not help. Any ideas on a configuration that might cause this? I’ve never run into it before and have been fighting with it for 3 months :frowning:

Could it be a switch or network issues?

Thank you!


Could it be a switch or network issues?

Thank you![/quote]

Anything’s possible, but if it is, you’d see other problems, most likely - other data traffic not flowing.


That is what I figured and there is not really any other issues on the network.

I did capture some data and it looks like when the issue happends there is no audio on the gateway side but only on the extension side. So I’m guesssing that it is a bad Gateway? It was replaced already but guess I was lucky and got two bad ones in a row. I’ll replace the Grandstream and see what happends. I’ll post back and update once I replace it.

Thanks Again!

Best of luck. :smile:

Ok after my last post I continued to filter through calls and found another call that had the issue. The difference here is that it was not just silent but have was silent then its like the two channels merged (I could hear the PBX feed over Gateway feed) and then a distorted ring. Still guessing the gateway but thought I would try and get feed back. I could send you the packet snipet if you would like.

So you’re pulling RTP from the wire and it sounds like there’s a problem with audio mixing that’s occurring at the Asterisk side, or at the gateway side?

The audio mixing is on the Gateway side. The Asterisk side sounds clear each every call.

Okay, well that bodes well for Asterisk then. Still a bummer about the troubles.

Well I finally got the replacement from Grandstream and still have the same issue but it seems to be a little different than before.

The phone rings and the Caller ID is correct.
The user picks up the phone and no one is there (slient), so they hang up.
Once they hang up the phone rings again but this time the Caller ID says “Unknow” or “0”.
The user picks up and the caller is there.
The caller says they did not call back but did hear a brief pause during the ringing.

Any help I could get on this would be great because I’m at a loss.