Controlling NAT for addresses in SDP lines
You can use the no-sdp-fixup option to control whether the FortiGate performs NAT on addresses in SDP lines in the SIP message body.
The no-sdp-fixup option is disabled by default and the FortiGate performs NAT on addresses in SDP lines. Enable this option if you don’t want the FortiGate to perform NAT on the addresses in SDP lines.
config voip profile
edit VoIP_Pro_1
config sip
set no-sdp-fixup enable
end
end