The Hong Kong sip trunk operator HKT not only provides local line connection to the 3CX server’s network port for inbound and outbound calls but also offers Internet registration sip trunk. If you are using a Internet registration sip trunk, you can refer to the following method to configure it on the 3CX server:

Assume the following account information is provided by HKT provider:

Setup Steps:

1.The Modification of outbound parameters:

This setup was tested using the SIP trunk template for V20 update 5. After verification, we found it necessary to modify the outbound parameters PAI and the Contact field to meet HKT’s requirements. The modified content is as follows:

For the modification method, refer to this document. If extensions can make outbound calls from the main number but not from other numbers, check these outbound parameter settings.

2.In addition to modifying the outbound parameters, the other settings are as follows:

Create a registration-based SIP trunk

Enter the account information

Click the “Add” button to add the required DIDs, which will allow inbound calls to be directed to different destinations:

If SRTP mode is set to “Enabled” (not “Enforced”), 3CX will send both RTP and SRTP to HKT in the INVITE request. Since HKT only supports SRTP, this may cause outbound call failures.

Finally, click “Save” and configure the outbound rules as needed. Under normal circumstances, once saved successfully, the trunk will show a green registered status.

3.Now you can test inbound and outbound calls:

For inbound calls, you can direct the call to different destinations based on the DID number:

For outbound calls, if the extension hopes to call out through the other number(not main number), you can set the other number as the extension’s outbound caller ID.