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3CX rinstance configuration

3CX phone system now expects all providers to include the “rinstance” parameter in SIP messages. This directly impacts how we handle inbound calls and SIP registrations between Flowroute and 3CX. In order to comply with new 3CX requirements we are implementing important changes to how interconnection for 3CX is handled.

After March 28, 2023, only one SIP registration from 3CX will be allowed per account if you use SIP registration as your inbound routing strategy. Otherwise, inbound calls will fail.

What's new? When 3CX sends a REGISTER message, it also sends a “rinstance” parameter with a unique value in the “Contact” header. 3CX initially attempts to find a match against a SIP Trunk. If a match exists, 3CX will then check if this “rinstance” value was used to register one of the configured SIP Trunks. If found, 3CX matches it with that specific Trunk. This hard-coded function cannot be disabled.

Who is impacted? If your Flowroute account has more than 1 active SIP registration from 3CX and at least 1 DID number that is using SIP Registration as its primary inbound routing strategy (doesn't apply to failover route) then you have to take an action to address this change.

There are a couple of options to choose from: 

  1. reconfigure default inbound routes to use host-based routes instead (requires static IP or hostname)
  2. distribute affected DID numbers between different (sub)accounts - please get in touch with our Support team to get assistance during this process.



(3CX) Inbound Calls

(3CX) Registration / Authentication

(3CX) Requirements for VoIP Providers