asterisk users - Jun 2008 - externip not setting extern ip/ loop detected issues

Hello ppl,
This is an Asterisk behind a NAT issue.
I know, this issue has been beaten around to death on the lists, but somehow I
haven't been able to find a solution, yet.

My set up :
Asterisk behind a NAT. The Asterisk has a dedicated public IP allocated on the
NAT. Rest all peers (esp 3rd party SIP gateways) are on public.

So, I tried to set externip to the allocated external(public) IP. 
But unfortunately * doesn't really send this IP in its SIP/SDP messages.
Only when I add localnet, does it send the extern IP in the SIP/ SDP messages.
But, the responses being received from my SIP gateway are somehow not recognized
(i.e. as a response I think) and retransmissions of the initial INVITE occur.
Through this I do get 180 adn 200 responses from my SIP gateway for the initial
INVITE. After sometime I start getting '482 Loop Detected' from the SIP
gateway.

Am attaching the SIP message flow for this.
externip=aaa.bbb.ccc.ddd
localnet=10.0.0.177/255.255.252.0

SIP gateway : mmm.nnn.ooo.ppp

A thing I noticed, the call Id in the invites is :
Call-ID: 1de93b843bc7a10275c36c145669e9d7 at aaa.bbb.ccc.ddd

whereas in the responses, it shows up as :
Call-ID: 1de93b843bc7a10275c36c145669e9d7 at 10.0.0.177

Is it because of this that * isn't able to recognize the response as the one
to the original request?

I am using Asterisk 1.4.13 on Fedora 7.

Anybody faced similar issues? Any workarounds? or am I missing something?

Regards
- Benjamin Jacob.









      
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: externIP_loopDetected.txt
Url:
http://lists.digium.com/pipermail/asterisk-users/attachments/20080603/5d0b184f/attachment.txt