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3CX PBX does not ACK 200

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pheitkemper

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Aug 31, 2011
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We have implemented a service which registers as an extension to 3CX. I have sucessfully called to this service from various softphones and a Cisco 504G. It works great.

The problem comes when I try to use a Grandstream 4104 on our house PBX to call this service. When I call from the analog side, the invite occurs. My service sends a 100Trying, 180 Ringing, and 200 OK messages. However, does not ACK my 200, and 3CX continues to send me invite requests. These occur with the time-doubling you would expect if the PBX has not received the 200 msg. Using Wireshark, I can see that the machine always receives these packets.

The other interesting aspect comes when I replace my service with a soft phone (3CXPhone, Phonerlite) configured for the same extension. The call works perfectly. This also occurs when I change the forwarding rules to forward to another extension, be it softphone or the Cisco 504G mentioned before.

Why would my service work perfectly with 3CX and a softphone, but not with 3CX and a Grandstream? That would suggest a configuration error on the Grandstream. But I can make calls to anything else besides my service.

This is repeatable behavior. I have also had the same results using a Patton 4114 Smartnode. Also, I have used this service before with this PBX and Grandstream device (and our house analog PBX for that matter).

Please help me understand what's happening. How do I go about debugging this?

Thanks,
Paul
 
Hi,

Please see http: //www.3cx.com/voip-gateways/Grandstream-GXW-41044108 - NO LONGER AVAILABLE
 
danhriscanu said:
Hi,

Please see http: //www.3cx.com/voip-gateways/Grandstream-GXW-41044108 - NO LONGER AVAILABLE

I used this to set up the gateway in the first place. What am I missing?
 
Did you also try to activate "PBX Delivers Audio" in Advance tab of Grandstream device?
 
It looks like that the response 200 OK, which is replied by your service, is malformed in this call scenario...
 
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