We have fritz.com as IP telephony provider. We have two DECT phones with extensions **610 and **611 (assigned by the system), and two Cisco SPA509G with extensions **620 and **621 (also assigned by the system).
The Cisco phones work properly with external calls (incoming and outcoming), and receiving internal calls: the DECT phones allows dialing **620 and **621.
The problem is the SPA509G doesn't allow dial "**". On the second asterisk it appears "invalid number", and dialing only the three numbers extensions doesn't work. The state "calling" and "SessionProgress" for a few seconds, but the DECT phones doesn't receive any call.
Well, I'm not sure I understand your description in full.
It may be problem with SPA509G's dial plan. If I remember correctly, the default dial plan doesn't allow numbers starting **. Or it may be issue related to SIP dialog between SPA509G and Fritz's switch.
Catch SIP messages between SPA509G and Fritz's switch. If no SIP INVITE had been sent by SPA509G then call has been rejected locally. Check dial plan configuration then. Have you something like **xxxS1 here ?
If phone will send INVITE to Fritz, then check calling number, called number and catch the Fritz's SIP response. It will help with further analysis.
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