3CX V18

SIP Trunk - 3CX Version 18+
⦁ Navigate to the “SIP Trunks” menu on the left menu column and click "Add SIP Trunk." Select “US” as the Country and “SIP Trunk” as the Provider. Enter your Trunk number in the “Main Trunk Number” field. Click OK.

⦁ On the “General” tab of the Trunk configuration, your “Registrar/Server/Gateway” host should already be populated with “” with the “Auto Discovery” box checked. Below in the “Authentication” section, enter your Trunk Number as the “Authentication ID” and your “Trunk Password” (found in the SIP Trunk Customer Portal under SIP Trunking --> SIP Trunks) as the “Authentication Password.” 

⦁  Select the “Options” tab in the Trunk configuration. Scroll down to “Advanced” and confirm the template has “Alternative Proxy” configured with “” in the field. This will enable failover to our redundant gateway if the zombie apocalypse begins in Atlanta and is taken down. 

⦁ Select the “Inbound Parameters” tab in the Trunk configuration. Change the “CalledNum” parameter from “To: User Part” to “Request-Line URI: User Part.” Click OK to save the Trunk configuration.

⦁ Congratulations, your Trunk should now show as green to indicate it’s registered with SIP Trunk! We now need to tell 3CX how to route outbound calls. Select “Outbound Rules” in the left menu and click “Add.” We will be adding 3 separate rules as described below:

For general dialing of 11-digit North American numbers, this route will take the number and route it directly to SIP.US.


For general dialing of 10-digit North American telephone numbers, this route will route dialed numbers with a length of 10 digits and add a "1" to the front of the number. Then it will route to SIP Trunk. Pay special attention to the "Prepend" column. 

For Emergency Calling, this route will take all calls that begin with a "9" and are 3-digits in length. These calls will then be routed to SIP Trunk.

For International Calling, this route will take all calls that begin with "011" which is the International Exit code, and then send the calls to SIP Trunk after stripping the first digits (011) from the number. Specifically, notice the "3" under the "Strip Digits" column.

⦁ For inbound call routing, you will first need to obtain DID (Direct Inward Dial) numbers from SIP Trunk. This can be done in your Customer Portal under SIP Trunking --> Order Telephone Numbers.

Once you have at least one DID, navigate to “SIP Trunks” in your 3CX. Edit your existing SIP Trunk trunk and select the “DIDs” tab. Click “Add Single DID” and enter your DID in an 11-Digit format (i.e. 14045964200) and press ENTER. Click OK to save changes. 

⦁ Navigate to the “Inbound Rules” menu. Click the “Add DID Rule” button. Name the rule whatever you'd like, and verify that the correct DID is selected in the “DID/DDI” drop down. You may then use the “Route calls to” section to route inbound calls accordingly. 

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