Configuring a BT Wholesale SIP trunk

BT Wholesale SIP Trunk Provider

Step 1: Obtain your SIP Trunk details

You need to have the following information provided to you by BT:

  1. The DID/DDI numbers that have been allocated to your Trunk
  2. The Primary BT Signaling IP
  3. The Backup BT Signaling IP(s) (some trunks may not be allocated a backup IP)

Step 2: Configuring your SIP Trunk with 3CX

  1. With the above go to the 3CX Web client and follow the guide on how to configure a SIP trunk.
  2. Enter the main trunk number in national format (e.g. 07975777666).
  3. In the “General” tab fill in the Primary BT Signaling IP that has been given to you by BT in the “Registrar” field:
  4. After this, go to the “Options” tab and verify that the “Put Public IP in SIP VIA Header” option contains the correct Public IP.
  5. Scroll to the top of the page and press Save.

Step 3: Only required if you use MPLS

If your circuit uses MPLS, you will need to make the following additional changes:

  1.  In the 3CX Management Console, go to “Voice &Chat” and Edit your BT WSIPT SIP Trunk.
  2. Go to the “Options” tab and enter the MPLS IP address of the PBX in the following 2 fields:
  • “Put Public IP in SIP VIA Header”.
  • “Select which IP to use in 'Contact' (SIP) and 'Connection'(SDP) fields” and make sure the drop-down value is “Use this IP Address”
  1. Scroll to the top of the page and press Save.
  2. Depending on your network topology/configuration, static routes may be required on the 3CX Server to route the traffic correctly. For further information, please refer to this article.
  3. MPLS trunks can not be used with 3CX Hosted.

About BT Wholesale

BT Wholesale are experts in communications. Their SIP trunking service offers businesses of any size a flexible, secure and cost-effective solution to move to next-generation voice.

Last Updated

This document was last updated on 14 March 2025

https://www.3cx.com/docs/sip-trunk/bt-wsipt-uk/