It’s possible that the trunk is registered but that there is an issue with calls.


Step 1: Check Both Inbound Calls, Outbound Calls and Extension Calls


  1. Always check the status of extension calls first: can a handset contact the PBX itself, for example to call the voicemail server? If so, can extension to extension calls be made?
  2. Can inbound calls be made?
  3. Can outbound calls be made?


Step 2: Check The Internet Service Configuration


  1. Has your internet service provider set the router’s ‘Disable SIP-ALG’ setting to true? In nearly all networks, SIP-ALG should be disabled to allow SIP traffic to route correctly.
  2. Are firewall rules blocking the connection? Is the ST+ main domain / IP address set as a route / policy in the client’s firewall? Is port 5060 (or any specific port you set up for the trunk) open for UDP, TCP?


Step 3: Check How The PBX Is Presenting Numbers


  1. Different PBX’s present numbers in different ways: the ST+ portal can cater for either ‘National’ or ‘International’ number formats as set on the trunk details page: ensure the format used by the PBX matches that of the trunk.
  2. What number is being presented? For authenticated trunks, the ‘From’ number must be the main trunk ID / number, not the CLI that is to be presented. The ‘RPID’ (remote party ID) number can also be the same as the main trunk number if spoofing or different CLI presentation is not required, or can alternatively be set to be spoofed or CLI number - but importantly the 'From' number must always be the main trunk number.  For further details on RPID settings please refer to I Can’t Get Spoofing / Number (CLI) Presentation to Work.
  3. Are you attempting to ‘spoof’ or present a number that is not first set up on the SIP Trunk Plus portal 'Numbers' tab?


Step 4: Check The ST+ Portal


  1. The ST+ system allows you to check if a trunk is registered: when logged on, select your client account and go to the ‘Registrations’ page. If the trunk is showing as registered (that is, there is an entry shown on the ‘Registrations’ page corresponding to the trunk in question), do the ‘Port’ and ‘NAT’ settings match those expected / configured in your client’s firewall?
  2. What limit profile is being applied to the trunk? Is the attempted call being barred because a profile limit is being exceeded?
  3. The ‘CDR’ tab is very useful and displays more detailed information at the top reseller level than at individual client level: attempt to locate the call by typing in the ‘Destination Number’ (often referred to as the ‘B Number’ for an outbound call) and check the ‘Start Time’ and ‘Hangup Code’.

Please also refer to Why Am I Getting 'Forbidden' When I Make A Call?