How to setup Belgian SIP Trunk Provider, Intertel, with 3CX
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Intertel – SIP Trunking

Intertel - SIP Trunking

On this topic

Intertel - SIP Trunking

About Intertel

System Preparation

3CX Version

Provider Capabilities

Collecting 3CX Configuration Settings

Configuring the Trunk with 3CX

Finding the IP of the Primary SIP Server

Adding the Trunk

Adding Additional DIDs

Creating Inbound Rules

Number Format

Outbound Caller ID

Outbound Rules

Redundancy Trunk(s)

Before setting up the Redundancy Trunk

How to set up the Redundancy Trunk

Using the Redundancy Trunk(s)

About Intertel

Intertel offers a reliable SIP Trunk service for Belgian businesses. You can either signup for a VOIP Account which is a single account that allows you to register one phone number or a SIP (VoIP) trunk from which you can register multiple numbers or number blocks.

Reference website: Intertel

System Preparation

Before configuring the SIP trunk it is required to go through the following checklist and make changes where necessary:

Further setup information can be found in our Academy: 3CX Academy Basic Course

3CX Version

Some providers gained support and compatibility with 3CX on a specific product version. It is advisable to always run the latest version of 3CX to ensure ongoing compatibility.

Minimum 3CX Version: 3CX Phone System 15.5 SP2

Provider Capabilities

Below is a short overview of the provider's capabilities and services and whether they’re supported or not:

  1. CLNS (Clip No Screening): Yes
  2. Catch All Routing: Yes
  3. Fax in T38: No (audio only)
  4. CLIR (Number Suppression): Yes
  5. DTMF via RFC 2833:        Yes
  6. Outbound Codec Order: G711U, G711A, G729, G722, GSM
  7. NAT Support: Yes
  8. Other: Requires Public Static IP

Collecting 3CX Configuration Settings

In order to configure a Intertel SIP Trunk with 3CX, you should first make sure you have the following information available which must be provided to you by your Intertel representative:

  • The DID/DDI numbers that have been allocated to your Trunk
  • The Primary Intertel SIP Server
  • The Backup Intertel SIP Server (some trunks may not be allocated a backup IP)

You will receive this information in a format similar to in the following image:

With the above information you can proceed to the next section which explains how you use this information to configure the Trunk in 3CX.

Configuring the Trunk with 3CX

The general instructions outlining how to add a new SIP Trunk to your 3CX installation can be found here.

Finding the IP of the Primary SIP Server

Before beginning to add the Trunk in 3CX, you must first find the IP of the Primary SIP Server that you have been allocated by Intertel. To do this, from any PC open a command line and type:

nslookup <Primary SIP Server Address> 8.8.8.8

This will look like in the following image:

The IP Address will be used in the next section of this guide.

Note: You must use the IP address of the server you have been given by Intertel. Not using the specific one will result in incoming calls failing!

Adding the Trunk

To add a Intertel SIP Trunk to your 3CX system, open the Management Console and navigate to “SIP Trunks”. Press the “Add SIP Trunk” button and select “BE” as the country and then “Intertel” from the following drop-down.

In the “Main Trunk No” field, enter one of your DID numbers in the International number format (e.g. 325114740240), then press OK.

Once you have done this, in the “General” tab, in the:

  • In the “Registrar” field enter the Primary SIP Server address:
  • In the “Outbound Proxy” field enter the IP of the Primary SIP Server, as you resolved in section “Finding the IP of the Primary SIP Server”.

Once you have done the above, scroll to the top of the page and press OK and your Trunk will now be configured.

Adding Additional DIDs

To associate all other DIDs/Numbers you have in your Intertel account with 3CX, go to the Management Console → SIP Trunks, double-click on your Intertel Trunk and go to the “DIDs” tab.

Here you should already see 1 entry that is the Main Trunk number you have set. Add all other DIDs/Number you have to the list in the International number format (e.g. 325114740240) and press OK once you have finished.

Creating Inbound Rules

Now that you have associated all your DIDs/Number with your SIP Trunk in 3CX, you can create Inbound Rules to set where calls will be routed when those numbers are called. Instructions on how to create Inbound Rules can be found here.

Number Format

Outbound Caller ID

Intertel trunks support Clip No Screening which means you can present any number you want when calling outbound. For this to work correctly however, in all 3CX fields where the Outbound Caller ID can be set, the number must be entered in the International number format (e.g. 325114740240).

Outbound Rules

There are no special instructions regarding Outbound Rules that are required; numbers can be dialed in any valid number format.

More information about how to create Outbound Rules and how they work can be found here.

Redundancy Trunk

Intertel may also provide a Backup SIP Server address. This is for cases where the Intertel Primary SIP Server fails. The intended use is that all incoming and outgoing calls will first use the Primary SIP Server and only upon failing should the Backup SIP Server be used.

Before setting up the Redundancy Trunk

The first step would be to setup your Primary Intertel Trunk as described in guide above this section using the Primary SIP Server. This also includes adding all the DIDs associated with your Trunk as described in section “Adding Additional DIDs” and then creating Inbound Rules for all your DIDs as described in section “Creating Inbound Rules”. It is best this section is not skipped to avoid confusion.

How to set up the Redundancy Trunk

Once you have setup your Primary Intertel Trunk and tested that it works, all you need to do is repeat steps outlined in sections “Finding the IP of the Primary SIP Server”, “Adding the Trunk”, “Adding Additional DIDs” and “Creating Inbound Rules” with one difference, instead of using the Primary Intertel SIP Server, use the Backup SIP Server that you have been given by Intertel. You could also name your Backup Trunk slightly different so that you distinguish it, e.g. “Intertel - Backup”:

Note: You must use the IP address of the server you have been given by Intertel. Not using the specific one will result in incoming calls failing!

Using the Redundancy Trunk(s)

When creating Inbound Rules, you now need to create multiple rules for each DID/number, once for every Intertel Trunk you have created (Primary and Backup):

For your Outbound Rules, in order to make use of the backup trunk(s), all you need to do is make sure that you have set them as the subsequent “Route” options. Note that the Primary Trunk should always be set to “Route 1”:

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