SV9100 One way sound / Silent on call

[LeeEng]

Hi

I'm having problems with my SV9100 and incoming call. It is not all the time but 2 or 3 phone calls a day we get coming in are silent and I cant work out how to solve this. I have all the ports that my Sip provider has recommended open on my router (locked to their IP's for security) but we still get the silent calls. Our customer has to ring back and the call is fine.
I tried activating the ALC on my router but the somehow stop the communication with our sip provider. I get the Sip Out Of Range displayed on the phones.
Is there anything else I can try to stop getting silent/One way calls.
What ports do you recommend opening up that the NEC systems uses for the Audio Streams?
Any help on the would be great.

 

[OzzieGeorge]

What make of router do you have? the only reason I ask is that I have a vague memory that Cisco use a different port range to everybody else as I was once sent to change the range to match on a system. This was ages ago so sorry I can't remember the details and it wasn't explained to me, I was just told by one of NEC's VoIP experts to do this!

 

[LeeEng]

@OzzieGeorge We are using a Draytek Vigor 3910. Do you know what ports The NEC uses?

 

[OzzieGeorge]

Off hand, no, I was simply told what to do. I will see if I can track the info down tomorrow.

 

[LeeEng]

Found out what the problem was.
In my NAT routing I was porting the UDP port 10020 to the incorrect internal IP. This was the port that was causing the loss of audio in some of the calls. I have now routed it to the correct IP and all seems to be fine.