BT WSIPT - SIP Trunking
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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.
Reference website: BT Wholesale
Before configuring the SIP trunk it is required to go through the following checklist and make changes where necessary:
- NAT (when used) created to 3CX
- Firewall Checker passed
- Firewall SIP ALG checked and if present disabled
Further setup information can be found in our Academy: 3CX Academy Basic Course
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
Below is a short overview of the provider's capabilities and services and whether they’re supported or not:
- CLNS (Clip No Screening): Yes
- Catch All Routing: Yes
- Fax in T38: Yes
- CLIR (Number Suppression): Yes
- DTMF via RFC 2833: Yes
- Outbound Codec Order: G711A, G711U, G722, G729, GSM
- NAT Support: Yes
- Other: Requires Public Static IP
Collecting 3CX Configuration Settings
In order to configure a BT WSIPT SIP Trunk with 3CX, you should first make sure you have the following information available which must be provided to you by your BT representative:
- The DID/DDI numbers that have been allocated to your Trunk
- The Primary BT Signalling IP
- The Backup BT Signalling IP(s) (some trunks may not be allocated a backup IP)
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.
Adding the Trunk
Specifically, to add a BT WSIPT SIP Trunk to your 3CX system, open the Management Console and navigate to “SIP Trunks”. Press the “Add SIP Trunk” button and select “UK” as the country and then “BT WSIPT” from the following drop-down.
In the “Main Trunk No” field, enter one of your DID numbers in the National UK number format (e.g. 02033272020), then press OK.
Once you have done this, in the “General” tab fill in the Primary BT Signalling IP that has been given to you by BT in the “Registrar” field:
After this, go to the “Options” tab and verify that the “Put Public IP in SIP VIA Header” option is checked and that the correct Public IP is configured in the field below. If the settings are not correct, adjust them accordingly before proceeding.
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 BT WSIPT account with 3CX, go to the Management Console → SIP Trunks, double-click on your BT WSIPT 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 UK National number format (e.g. 02033272020) 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.
Outbound Caller ID
BT WSIPT trunks support Clip No Screening which means you can present any UK 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 UK National number format (e.g. 02033272020).
There are no special instructions regarding Outbound Rules that are required; numbers can be dialed in any valid UK number format.
More information about how to create Outbound Rules and how they work can be found here.
As mentioned earlier in this guide, BT for WSIPT Trunks may also provide one or more Backup Signalling server IPs. This is for cases where the BT Primary Signalling IP may fail. The intended use is that all incoming and outgoing calls will first use the Primary Signalling IP and only upon failing should the Backup Signalling IPs be used.
Before setting up the Redundancy Trunk
The first step would be to setup your BT WSIPT Trunk as described in guide above this section using the Primary Signalling IP. 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 BT Trunk and tested that it works, all you need to do is repeat steps outlined in sections “Adding the Trunk”, “Adding Additional DIDs” and “Creating Inbound Rules” with one difference, instead of using the Primary BT Signalling IP, use the Backup BT Signalling IP that you have been given by your BT representative. You could also name your Backup Trunk slightly different so that you distinguish it, e.g. “BT WSIPT - Backup”:
Note: If you have been provided with more than one Backup Signalling IP, then you must repeat this once for each Backup Signalling IP you have.
Using the Redundancy Trunk(s)
When creating Inbound Rules, you now need to create multiple rules for each DID/number, once for every BT WSIPT Trunk you have created (Primary and all Backup ones):
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”:
Using BT WSIPT over MPLS
As an additional service, BT can enable the use of WSIPT SIP Trunking over a dedicated MPLS circuit. If you will be using this setup, a few minor changes will be required to what has already been described throughout this guide.
After configuring BT WSIPT in 3CX as described in this guide, the changes you will need to make are the following in order for the service to work over an MPLS circuit:
- In the 3CX Management Console, go to “SIP Trunks” and Edit your Primary BT WSIPT SIP Trunk entry.
- Go to the “Options” tab and here enter the MPLS IP address of the PBX in the following 2 fields:
- “Put Public IP in SIP VIA Header”, which must also be checked
- “Select which IP to use in 'Contact' (SIP) and 'Connection'(SDP) fields” and make sure the drop-down value is “Use this IP Address”
- Scroll to the top of the page and press OK.
- Repeat steps 1-3 again for each WSIPT Redundancy Trunk (if any) you have configured.
Note: 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.