Following SIP Refer messages

[sam.phillips]

We have a requirement to integrate with a third-party IVR system.

To do so we have two SIP trunks:
- Primary trunk - proper "outside facing" trunk from an ISP that has the DDI's that customers actually ring in on
- Secondary trunk - direct SIP peer between 3CX and the IVR system.

The call flow is like:
- Incoming call on primary trunk, to a DDI
- Inbound DDI route is set to "Forward to outside number" Value: 7100
- Outbound route is set match numbers that start with 7, 4 digits in length
- Outbound route sends call over secondary trunk
- Secondary trunk answers, does IVR functions, etc
- Secondary trunk then sends a SIP REFER with the "Refer-to" value of "<sip:[email protected].3cx>"

However, at that point, 3cx throws a 403 and the call fails.

7101 is the DN of a 3CX queue. Internally on 3CX, I can dial 7101 and get put in the queue as expected.

How do I get 3CX to follow the SIP refer, and drop the call back in to the queue?

I've tried added "7101" as a DDI to the secondary trunk, and setting an inbound route to the queue from there.

Edit: Just FYI, I have a proper ticket in with support too. Just thought it might be good to get community feedback.

 

[eddv123]

I have a proper ticket in with support too

I would be keen to hear if you had any constructive response from them since you are trying to integrate with a third party IVR system.

The only thing that springs to mind for integrating in this way (and it is only a thought currently) is putting an SBC between the 2 entities (proper SBC not a 3CX one) so that you can control both legs of the call.

 

[sam.phillips]

Yea I don't expect much help with the IVR itself. But the issue seems more to do with how 3CX deals with that Refer-to.
Instead of throwing a 403, I need to follow the given URI. I assume it's the way it deals with URI calls?

 

[eddv123]

I assume you are building a trunk between the two ? this is why I recommended a proper SBC as part of their job is SIP manipulation: https://www.audiocodes.com/media/13319/sip-message-manipulation-reference-guide-ver-70.pdf