By default, the Oracle Enterprise Communications Broker (Communications Broker) rejects a REGISTER request from a domain for which it is not the registrar. You can enable the Communications Broker to proxy such registration requests by way of the Proxy Registration control in the SIP Config configuration.

In the SIP Config configuration, select Proxy Registration to tell the Communications Broker to proxy the registration towards the intended registrar. When you deselect Proxy Registration, the Communications Broker responds with a 403: Unauthorized message.