Configuring a BT SIP Trunk with 3CX

BT SIP Trunk Provider logo

Step 1: Configure your BT SIP Trunk

  1. Go to the 3CX Web client and follow the guide on how to configure a SIP trunk.
  2. Enter the main trunk number in international format (e.g. 447975777666).
  3. BT HSIPT trunk template to be chosen.
  4. The Authentication Username provided by BT must be entered under “3 Way Authentication Password”.

Step 2: Outbound Caller ID configuration

By default, BT SIP-T Trunks can only have their exact DID number used as outbound caller IDs.

Clip No Screening (which allows different outbound caller IDs) can be activated through the BT customer portal. BT refers to this functionality as Class 5 CLI. Enabling this functionality will allow you to use any number as your Outbound Caller ID but some extra configuration is required on the 3CX side.

When Type 5 CLI is enabled all caller IDs must be sent in the E164 number format (e.g. +448135791691) so the caller ID is presented correctly.

To have this functionality working you will need to replace the main trunk number (pilot number) with a DID assigned to your trunk. To do so:

  1. Open your 3CX BT HSIPT trunk settings and navigate to the “DIDs'' tab.
  2. Find the DID you want to use as your new main trunk number and delete from the list.
  3. Press OK to save your settings.
  4. Now go back into your trunk settings and replace the main trunk number with the DID you deleted from the DID list.
  5. Optionally you can go and add the pilot number back to the list of DIDs.
  6. Optionally, navigate to the trunk's “Outbound Parameters” and change the “From:UserPart” SIP field from “OutboundCallerID” to “OriginatorCallerID”. This will enable forwarded calls to contain the originator caller ID.
  7. Press OK to save your changes.

About BT

BT SIP Trunk is a cost effective SIP Trunking solution for businesses across the UK. With no compromise on quality of service and increased flexibility, compared to traditional phone lines, BT offers a reliable, affordable and secure SIP Trunking service.

Last Updated

This document was last updated on 7 July 2023

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