Sunday, March 22, 2009

Sorry I have been absent for the last month from my postings. I have been absolutely swamped with installs and support. Which, in this economy, is a good thing.

Over the last month I have done work for several 3CX customers who are using 3CX as a softswitch to provide VoIP services to business and residential customers. Let's assume the customer is feeding 3CX with a SIP Trunk. In this scenario, the customer typically wants each extension to outpulse a different CallerID to the world. The issue is, by default, 3CX will send the authentication ID you have configured on the Trunk (typically the main number assigned to the trunk by the SIP provider). So, how do we do this?

The first thing I will caution, is that you must check with your SIP Trunk carrier to verify they will accept caller ID from your 3CX system. Some providers override anything you send. Now, assuming they will accept this data form you on each call, you need to find out which SIP header fields they need this data to be in. The most common are for it to be in the From: and the Contact: fields of the outgoing INVITE from 3CX to the SIP carrier. So, we need to do some advanced customization of our SIP headers on our main outbound SIP Trunk.

  1. On your VoIP Provider account go to 'Outbound Paramaters'
  2. Set the 'From: Display Name', 'From: User Part', "Contact: User Part' fields to "CallerNum".
  3. Set the Outbound Caller ID field on each extension in Extension->Other->Outbound Caller ID to be the value you want to outpulse for each extension.

You will now be sending your customized Caller ID in your SIP INVITE.

Happy 3CXing!!!!