With the release of V15.5 Update 2 (BETA), we have made many stability improvements in regards to the operation of supported SIP Trunk Providers. These changes now include the support for SIP over TCP for the providers that support it.
This is already built into the templates included in Update 2, however for users of Ironton and Telnyx SIP Trunks that are upgrading from a previous version of 3CX, you must do the following for your SIP Trunk to work correctly.
- Log into your Management Console, go to “SIP Trunks” and edit your SIP Trunk provider (Ironton or Telnyx).
- In the “General” tab, modify the “Registrar” field by appending “transport-tcp.” (without the quotes).
- So if your Registrar value is: sip.contoso.com You need to change it to: transport-tcp.sip.contoso.com
- Once you have made this change, press OK.