You can enable the VoIP profile open-via-pinhole options to accept a SIP Register response message from a SIP server even if the source port of the Register response message is different from the destination port.

Most SIP servers use 5060 as the source port in the SIP register response. Some SIP servers, however, may use a different source port. If your SIP server uses a different source port, you can enable open-via-pinhole and the SIP ALG will create a temporary pinhole when the Register request from a SIP client includes a different source port. The FortiGate unit will accept a SIP Register response with any source port number from the SIP server.

Enter the following command to enable accepting any source port from a SIP server: