[Spce-user] UA NAT identification

John Murray john.murray at skyracktelecom.com
Wed Jul 24 13:32:54 EDT 2013

Andreas hi,

As usual you have been a great help. That has fixed it.

The settings for nathelper are:

> Tries to guess if client's request originated behind a nat. The parameter
determines what heuristics is used.
> Meaning of the flags is as follows:
> 1 - Contact header field is searched for occurrence of RFC1918 addresses.
> 2 - the "received" test is used: address in Via is compared against source
IP address of signaling
> 4 - Top Most VIA is searched for occurrence of RFC1918 addresses
> 8 - SDP is searched for occurrence of RFC1918 addresses
> 16 - test if the source port is different from the port in Via
> 32 - test if the source IP address of signaling is a RFC1918 address
> All flags can be bitwise combined, the test returns true if any of the
tests identified a NAT.

The settings currently are '17' so option 1 and 16.
I added in option 2 making the setting '19' which I think represents NAT
well. 'The Via address is different from the signalling address'.

Rfc1918 addressing is used on consumer devices and many corporate but a
large number of corporates have more complicated addressing as in this case.

Can I be the first to vote for a default setting of '19' in SPCE.

Many thanks


-----Original Message-----
From: Andreas Granig [mailto:agranig at sipwise.com] 
Sent: 24 July 2013 15:27
To: John Murray
Cc: spce-user at lists.sipwise.com
Subject: Re: [Spce-user] UA NAT identification

Hi John,

On 07/24/2013 04:22 PM, John Murray wrote:
> It doesn't look like it. It doesn't refer to the public address 
> anywhere in the header, just the private address.
> So I guess without changing the address of the PBX to rfc1918 I'm stuck.

Well, yeah, you'd probably need to do some customizations to
/etc/ngcp-config/templates/etc/kamailio/lb/kamailio.cfg.tt2. See
for some flags controlling the NAT detection.


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