Common Issues with Inbound Call Transfer to PSTN
Question
A user reports that when receiving an inbound call on their IP Phone from the PSTN they are unable to transfer this call to another PSTN number.
What is the reason for this failures?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.D.
The most likely reason for the user's inability to transfer an inbound call on their IP phone to another PSTN number is answer B: "The incoming calling search space of the SIP trunk does not include the partition of the line in the IP phone."
When a call comes in from the PSTN, it typically goes through a gateway before reaching the IP phone. The gateway connects the traditional phone network (PSTN) to the IP phone network, and it is usually configured with a SIP trunk that allows it to communicate with the call control manager (CCM).
When the user tries to transfer the inbound call to another PSTN number, the call goes through the gateway and out to the PSTN. To do this, the gateway needs to have access to the correct route pattern, which specifies how to route the call to the correct destination. The route pattern is determined by the partition assigned to the line on the IP phone.
In this case, the incoming calling search space of the SIP trunk does not include the partition of the line in the IP phone. This means that the gateway does not have access to the correct route pattern to transfer the call to the PSTN number. Therefore, the transfer fails.
Answer A: "The IP phone is configured with the wrong region" is unlikely to be the cause of the problem because the region settings do not affect call transfer functionality.
Answer C: "The service parameter related to Offnet to Offnet Call Transfer is set to TRU" is also unlikely to be the cause of the problem because this service parameter enables or disables the ability to transfer calls between two offnet (external) destinations, not between onnet (internal) and offnet destinations.
Answer D: "The gateway is configured with the wrong device pool" is also unlikely to be the cause of the problem because device pools are used to specify settings such as the date/time group, region, and network settings for devices, and they do not affect call transfer functionality.
