[Asterisk-Users] NATted phones transferring calls - BUG0003710

[Douglas Garstang]

I made a call from 3254102 to 2944093. I then tried to do a transfer to 3254107. 
IP addresses have been changed to protect the innocent.

It appears this related to bug 3710. It's unclear from the bug if the problem has been fixed or not. If it hasn't, then this seems pretty serious and would I guess affect any NAT-ted phones ability to transfer calls.

Here's the REFER that the phone at 2944093 sends directly to Asterisk:

U 216.186.128.68:5060 -> 216.186.142.203:5060
REFER sip:3254102 at 216.186.142.203 SIP/2.0.
Via: SIP/2.0/UDP 216.186.128.68;branch=z9hG4bKba3b074892377BD1.
From: <sip:2944093 at 216.186.128.68>;tag=C06397B-C3C1D97A.
To: "Test User" <sip:3254102 at 216.186.142.203>;tag=as33e7dd7c.
CSeq: 2 REFER.
Call-ID: 4053b9972e7851f455d9d16e7706d3f4 at 216.186.142.203.
Contact: <sip:2944093 at 216.186.128.68>.
User-Agent: PolycomSoundPointIP-SPIP_601-UA/1.6.3.0067.
Refer-To: 
<sip:3254107 at ipt.oneeighty.com;user=phone?Replaces=a13c692-349c9c70-7bd27d33%40172.31.99.4%3Bto-tag%3Das2a8d818b%3Bfrom-tag%3D3DE1A6BE-7262B959>.
Referred-By: <sip:2944093 at 216.186.128.68>.
Max-Forwards: 70.
Content-Length: 0.

Asterisk then goes and complains:

Mar 27 16:25:57 NOTICE[20511]: chan_sip.c:6734 get_refer_info: Supervised transfer requested, but unable to find callid 'a13c692-349c9c70-7bd27d33 at 172.31.99.4'.  Both legs must reside on Asterisk box to transfer at this time.

The phone's real IP address is 172.31.99.4. 
I'm not really sure what the problem is except that it works fine when there's no NAT involved. I can see the real IP address in the dialog. I wonder if that's what is confusing Asterisk?

Doug.