Hostname used in RURI

Fellow Members,

I have a session-agent IP, 1.1.1.1, which is configured with hostname1 & hostname2 for further call processing. When the call is leaving the SBC, sip-interface --> SA, the R-URI is turned into something like this, INVITE sip:+123@hostname:5060;user=phone SIP/2.0 which our partner does not like.

To overcome this, I have a sip-manipulation, where the host part is replaced by the L3 addresses in the RURI, From, and To headers. Unfortunately, our partner would be sending their proxy IPs in the contact header of the response messages to the initial INVITE. When sending the ACK to the SA, the IPs are again re-written causing the signaling to break.