By default, the Oracle Enterprise Communications Broker (ECB) rejects a REGISTER request from a domain for which it is not the registrar. You can enable the ECB 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 ECB to proxy the registration towards the intended registrar. When you deselect Proxy Registration, the ECB responds with a 403: Unauthorized message.