I have also just tried this simple Extensions.conf entry.
exten => _*.,1,Dial(SIP/sipbroker.com/${EXTEN:0}) ;; * Sipbroker prefix Dialing.
When I try and dial back out with the monkey test. (*266300) I get a little bit of audio and then nothing.
So there must be an issue elsewhere.
I have been able to do this OK with IAX2
exten => 2583,1,Dial(IAX2/cnetguest@projectmf.homelinux.com/17622600) ;; ext for ProjectMF (BlueBoxing)
When I try and use IAX2 with SipBroker I just get a congestion error in the console.
.-.-.