Configuring SIP IP address conservation for the SIP ALG
You can use the following command to enable or disable SIP IP address conservation in a VoIP profile for the SIP ALG. SIP IP address conservation is enabled by default in a VoIP profile.
config voip profile edit VoIP_Pro_1 config sip set nat-trace disable
If the SIP message does not include an i= line and if the original source IP address of the traffic (before NAT) was 10.31.101.20 then the FortiGate would add the following i= line.
i=(o=IN IP4 10.31.101.20)
You can also use the preserve-override option to configure the SIP ALG to either add the original o= line to the end of the i= line or replace the i= line in the original message with a new i= line in the same form as above for adding a new i= line.
By default, preserver-override is disabled and the SIP ALG adds the original o= line to the end of the original i= line. Use the following command to configure the SIP ALG to replace the original i= line:
config voip profile edit VoIP_Pro_1 config sip set preserve-override enable
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