The title says it all, but I will try and expand although my knowledge of Voip is beginner at best.
PBX is an Avaya IP500 with v9 software. The Internet Telephony Provider is also the Internet Provider and the internet itself is a fibre leased line. The connection to SIP is direct through the ethernet demarcation device which handles QoS. There is no firewall or NATing. I am porting a 200 DDI block of numbers from ISDN to SIP. I have some sample numbers from the ISP to get the system up and running and tested before the porting date. A few hiccups and learning curves later, I have calls working inbound and outbound with audio both ways at very high quality. The last piece I need to get working is the Ringback Tone. This is the tone the outside caller should hear before the phone is answered. Currently there is silence. Help.
Is this a PBX or ISP configuration problem? If it is ISP what should I instruct them to do to in order to get the tone?
If I have missed out some information, please ask me. Thank you in advance for your answers.