I have a setup where there are occasional problems with attended transfers. I have already checked the devices as well as the relevant DTMF modes (SIP INFO and rfc2833). I could not find any problems here.
The setup is a follows:
The front desk (F) accepts calls from customers (C). In some cases F needs to transfer C to a specific department (D). If D cannot handle the problem, D tries to transfer to a specialist S. The problem sometimes occurs when D tries an attended transfer for C to S. The description I
have so far is that Asterisk sometimes does not seem to accept DTMF signals.
Is it conceivable that that this is a re-INVITE/directmedia problem?
Since I have only limited access to the system, I’d like to rule out some causes. I am also not sure if the transfer from F to D is handled via Asterisk using DTMF signalling, or whether F
uses the SIP phone‘s capabilities for the transfer, so that Asterisk might already not know anything about D. Except for C, everybody is inside the same subnet.