IN STRICTEST CONFIDENCE
BT Wholesale
Issue 1: 2012© British Telecommunications plc
Page 33 of 33
IN STRICTEST CONFIDENCE
9.4
Inbound Calls Fail
Check that the Device is registered as above.
Check that the SIP/RTP ports are not being blocked by a firewall on the network. Details of the
ports can be found in the Security Guide under Support Centre
»
Downloads
»
General Help &
Information.
Check whether any calls can be made between extensions on the PBX; if not they the issue is
likely to be local to the PBX.
Check that the device is receiving SIP messaging for calls by taking a SIP Protocol Trace and
looking for inbound INVITES within this.
Check that the expected outbound CLI of either the Trunk Group or the Trunk User is being
presented in the TO header of the inbound SIP INVITE.
If the Trunk Group or Trunk User DDI’s are being received make sure that they match the
format of the numbers in your DDI / DID Table i.e. 441234567890.
If the DDI / DID Table is correct for the inbound INVITE make sure that the destination for the
call is available to other extensions on the PBX.
If none of the above points highlight the cause please take a SIP trace of a call failing where
possible and raise a ticket with Support.