3CX loop SIP trunk: DNCR filter and custom outbound routing

Create a SIP trunk to the loop IP address 127.0.0.1:5060.
Create an outbound rule, for example, for outgoing calls with the 00 prefix.
Create a 3CX CFD (Call Flow Designer) voice application that will receive an incoming call and process it instantly.
Set the CFD call script number as the default route for the SIP loop trunk.
Call 00{NUM}.

NB. Please note that when making an outgoing call, the employee will usually receive a SIP 200 OK response instead of 183 Session Progress (early media).

NB. You will need a large license for 3CX.

Cases that can be solved using this life hack

DNCR-based filtering of outgoing calls (do not call registry)
Complex routing of outgoing calls based on data from an external CRM system
Dialing a subscriber by going through several numbers
Blacklist of phone numbers for outgoing calls

Screenshots

1. Loop trunk: registrar 127.0.0.1, port 5060, IP-based authentication, default route to the Call Processing Script

2. Outbound rule: prefix 00, route to the Loop trunk, strip the first 2 digits

3. Active calls: one looped call shows as two calls (extension to Loop, Loop to the CFD app)

4. CFD app: DNCR check, then transfer to the dialed number (session.did)

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