3CX Version 16+


We have recently been blessed with a new version of 3CX, version 16. With this version we are given the capability to setup redundant gateways without the need for a secondary trunk and the duplication of DIDs and inbound routes that was necessary with version 15. 


1. Navigate to the SIP Trunks menu on the left menu column and click "Add SIP Trunk". Select 'US' as the country and '' as the Provider. Enter your trunk number in the 'Main Trunk Number' field. Click OK.




2. On the General tab of the trunk configuration, your 'Registrar/Server/Gateway' host should already be populated with '' with the 'Auto Discovery' box checked. Under the Authentication section, enter your Trunk Number as the the Authentication ID and your Trunk Password (found in the SIPTRUNK portal under SIP Trunking --> SIP Trunks) as the Authentication Password. 




3. Select the 'Options' tab in the trunk configuration. Under 'Advanced', the template should have 'Alternative Proxy' configured with ''. This will enable failover to our redundant gateway if the zombie apocalypse begins in Atlanta and is taken down. 




4. 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.




5. Congratulations, your trunk should now be registered with SIPTRUNK! We now need to tell 3CX how to route outbound calls. Navigate to the 'Outbound Rules' 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 SIPTRUNK.



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 SIPTRUNK. 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 SIPTRUNK. 



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



6. For inbound call routing, you will first need to obtain DID (Direct Inward Dial) numbers from SIPTRUNK. This can be done in your SIPTRUNK 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 SIPTRUNK 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. 




7. Navigate to the 'Inbound Rules' menu. Click 'Add DID Rule'. 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. 



Was this article helpful?
6 out of 6 found this helpful
Have more questions? Submit a request


  • Avatar
    Felicia King

    For clarification, on a retrofit of an existing 3CX PBX config, after the alternate gateway has been configured, then the secondary trunk for should be removed from the PBX, correct? This will make the inbound rules a lot cleaner and easier to manage.
    Also the old recommendation for the DIDs included a *10-digit format, but you now have specified the 11-digit format. We cannot do an edit on DIDs on a trunk in order to preserve the inbound rules as is. Is the *10-digit format still acceptable?

  • Avatar
    Terry Suellentrop

    I have the same questions

  • Avatar
    Felix Perez Jr

    I have found that if you installed 3cx in the past and performed in-place upgrades you will need to use *10-digit format. However, if you un-install and re-install a clean installation of 3CX you can use the 11-digit format. Using the *10-digit format will still work. We have over a dozen installs that are operating with the *10-digit format. If you have issues with inbound rules not working with DID's, check if they are 11-digit or *10-digit format. Hope this will help someone out.

Powered by Zendesk