Issue 3249 in mobicents: Not able to send ACK to INVITE ANSWER when client is behind NAT

[mobicents]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 3249 by lakshmi....@gmail.com: Not able to send ACK to INVITE  
ANSWER when client is behind NAT
http://code.google.com/p/mobicents/issues/detail?id=3249

What steps will reproduce the problem?
1. Send invite from client 1 to client 2 behind NAT
2. Client 1 sends  answer to SIP server
3. SIP Server failed to send ACK to INVITE ANSWER  to client 1 because  
internal IPs are used in INVITE ANSWER. When ack is created on INVITE  
ANSWER response, the ack contains again internal IPs.

What is the expected output? What do you see instead?
SIP Server should be able to send ACK to controller

What version of the product are you using? On what operating system?
Mobicents SIP Server lets on ubuntu 10.x using tomcat

Please provide any additional information below.
I sent ACK to INVITE ANSWER as below. Here response is the INVITE ANSWER  
object with SDP details.

SipServletResponse response;
SipServletRequest ack= response.createAck();
ack.send();