Overview

3CX is gold standard in the commercial PBX world. Not only does 3CX have killer features, it also is easy to get up and running, and a pleasure to configure. You can learn more about 3CX here: https://www.3cx.com/

Additionally - here is 3CX's pricing: https://www.3cx.com/ordering/pricing/ 

Lastly - this is 3CX's excellent Administrator Documentation: https://www.3cx.com/docs/manual/

Configuring SIP Trunks

As of this writing, Skyetel is not currently a part of 3CX's built in templates. (We are however working toward being added to their PBX). Because of this, we have to use a "Generic" SIP Trunk Setting. 

Inbound SIP Trunk

Step 1 - Navigate to the SIP Trunks Menu

The SIP Trunk Menu can be found on the left side of the 3CX administrator interface:

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Step 2 - Click Add SIP Trunk

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Step 3 - Select Generic SIP Trunk

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Your "Main Trunk No" should be the first number you plan on using on this SIP Trunk. We recommend using a wildcard (*) in place of a 1. 

Step 4 - Add Skyetel's IPs to the Registrar/Server/Gateway Hostname or IP Field

This option can be found in the "General" Tab

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Here they are so you can Copy Paste : 

52.41.52.34, 52.8.201.128, 52.60.138.31, 50.17.48.216, 35.156.192.164

Step 5 - Update Options

Uncheck "Allow Outbound Calls"

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Verify that "Supports Re-Invite" and "Supports Replaces" are both unchecked and "PBX Delivers Audio" is checked:

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Step 6 - Configure Inbound Parameters

This option can be found in the "Inbound Parameters" Tab

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Make sure you set the following parameters:

"CalledNum" number that has been dialed (default: To->user) --→ To: User Part
"CallerName" caller's name (default: From->display name) --→ From: Display Name
"CallerNum" caller's number (default: From->user) --→ From: User Part

Also - uncheck "Call Source Identification"

Step 7 - Click Ok

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You should now see your Skyetel Inbound Trunk in the list:

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A Note About DIDs

By default, Skyetel routes all calls to the PBX using 11 digits. We do this in the SIP URI (the first line in the SIP INVITE packet). For example, when you call our number, this is what the SIP URI looks like:

INVITE sip:13609865200@52.41.52.34:5060 SIP/2.0

However, in order to organize our traffic, we send all Caller ID information in E.164 format. Therefore, the TO in a Skyetel INVITE looks like this:

To: <sip:+13609865200@52.41.52.34>  

This discrepancy can confuse 3CX - it would prefer that the To and the URI are identical. In order to accommodate this, we recommend you use a wildcard for your Skyetel numbers. Per 3CX documentation: 

3CX will match the number inserted in this field with the “to” header, starting from the last part of the received string, thus avoiding any differences in the format of the number. For example, if you are based in the UK and your DID number is 0845-2304024, then you can enter the number *2304024. This will match any DID number inserted in the “to” field ending with these numbers, including +448452304024, 08452304024, 00448452304024, and, of course, *2304024.
https://www.3cx.com/docs/manual/inbound-rules/#h.kp49xtr98uu1

This means that we would recommend that you configure your DIDs in this format: *3609865200 

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Outbound SIP Trunk

Step 1 - Repeat Steps 1-3 from Inbound SIP Trunk

Step 2 - Add Skyetel's First IP to the Registrar/Server/Gateway Hostname or IP Field

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Step 2.5 (optional) - Set your Caller ID

This step is optional - but its a good idea to have a default Caller ID for your deployment

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Step 3 - Set Trunk Options 

Uncheck "Allow inbound calls" 

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Verify that "Supports Re-Invite" and "Supports Replaces" are both unchecked and "PBX Delivers Audio" is checked:

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Step 4 - Set Outbound Parameters

You can find these options in the "Outbound Parameters" tab

This menu has a lot of options, fortunatly you only need to set two

Step 5 - Click Ok

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You should now see your Skyetel Outbound Priority 1 in the list:

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Step 6 - Repeat steps 1-5 until all of our Outbound IPs have been added

Once you are done, your SIP Trunk Menu should look like this:

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Create your Outbound Gateway

This part is pretty cool - here you specify 3CX to use Priority 1 and then go through 1-4 in the case that one of our systems does not respond

Step 1 - Navigate to the Outbound Rules Menu

It can be found on the left hand side of the Administrator Menu

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Step 2 - Create the Outbound Priority List

Choose a name for your List

We like Skyetel Outbound 

Set where these rules should apply

You'll need to specify this for your own uses, but we usually use the "Calls from extension group(s)" option and add the "DEFAULT" extensions

Set "Make Outbound Calls On"

This is where you can set our Trunks for your gateways:

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Save your settings by clicking OK

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Conclusion

Thats it! Your done! You should now be able to place and receive calls on our network using 3CX. We will update this guide when 3CX adds us to their Supported Providers.