[Freeswitch-users] Strange Reg

Dave lists+freeswitch at bigfatdave.com
Mon May 21 00:20:53 PDT 2007

Hi guys,

I've got a rather interesting situation, here.  I've got an ATA
registering to a FreeSWITCH(TM) (FS2), both behind NAT.  So far, so good.
Now, the FreeSWITCH(TM) registers to another FreeSWITCH(TM) outside the
NAT (FS2), and that's where the problems start.  Here's the configuration:


ATA: (behind NAT)
FS2: (behind NAT)
FS1: freeswitch1.asnetinc.net (

Now, here's where it gets very interesting.  This is what FS1 gets when
FS2 registers:
> From:    [R352928 at freeswitch1.asnetinc.net]
> Contact: ["user" <sip:R352928 at>]
> Expires: [3600]
> nta_agent: tport: Bad message

Now, where on Earth did come from???  (I've actually hardcoded
both external_rtp_ip and server_name to the public IP of the NAT in the
FS2 config, but for some strange reason, FS2 apparently claims to be at, which isn't even its local IP.)

As if that's not interesting enough, I get this from FS1, too, when it
tries to connect to another SIP server on the public Internet:
> outbound(0xb4e1e1a0): detected NAT: freeswitch1.asnetinc.net !=

Now, since a forward DNS resolution claims that the inequality is false, I
assume it attempted a reverse DNS lookup, which would fail (since my ISP
takes forever to update PTR records).

As usual, any hints, tips, tricks, ideas, suggestions, flames, questions,
or (ideally) answers are greatly appreciated :-)

Thank you,
 - Dave

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