We are trying to get Kamailio working as an SBC using rtpproxy();

The config seems to work except with some carriers, kamailio does not recognize the ACK because it does not match the contact header of the OK

I've been trying to figure out how to get kamailio to send the OK back using the public IP address but I cannot figure out how.

I've tried using various deployments of the nathelper module such as

fix_nated_contact()

set_contact_alias()

No matter what though, Kamailio will not change the contact header it receives from FS before sending it back to the carriers.

This has become frustrating as I read tutorials that showed this is possible, yet I am unable.

Thank you.

/V