[Serusers] nathelper/rtpproxy when both SIP UA are behind same NAT

[Jan Henkins]

Interesting! In my particular case, it's a Netgear ADSL router running a
version of uCLinux or something similar. The Netgear firmware is
apparently available for download (minus some proprietry WWW frontend
and related stuff) in order to comply to the GPLv2, but I haven't taken
the time to do this in order to check which Netfilter modules are being
used by the particluar 2.4.x kernel. In any case, I'm not particularly
good at C, so it wouldn't do me any good anyway. However, in my
experience the "statefulness" of a Linux Netfilter-based gateway should
be sufficient to be able to handle a situation like this transparently,
unless there is still something fundamental that I'm missing. 

Be that as it may, the simple question still remains: is it possible to
handle more than one UA behind a single NAT gateway with a single SER
setup on the outside of the NAT gateway (RFC 1918 address space inside,
normal routable IP outside)? Alternatively, would it be best to have an
inside SER that simply forwards all SIP traffic to the outside SER?

On Sun, 2005-12-04 at 11:05 +0100, Harry Behrens wrote:
> could be an issue of the local gateway. most NAT devices explicitly 
> block "hairpinning", which is happening in your case.
> 
> 
>     -h
> 
> Jan Henkins wrote:
> 
> >Hello Rafael,
> >
> >This is an issue I'm having at the moment as well, where two UA's are
> >behind the same nat. SIP obviously works fine, I can ring one UA from
> >the other (one UA a Grandstream Budgetone 100 and the other the X-Lite
> >softphone from Counterpath). Audio doesn't work. Did you get this
> >working with forcing rtpproxy?
> >
> >On Fri, 2005-12-02 at 09:44 -0500, Rafael R. GV wrote:
> >  
> >
> >>Hi
> >>I need to let the UAs speak directly to each other without force
> >>rtpproxy, Is there any solution for this issue?
> >>
> >>rafael
> >>
> >>
> >>---------- Forwarded message ----------
> >>From: Rafael J. Risco G.V. <rafael.risco at gmail.com>
> >>Date: Apr 22, 2005 2:17 PM
> >>Subject: UA´s behind same NAT using na thelper/rtpproxy, No Audio...
> >>To: serusers at lists.iptel.org
> >>
> >>I am using avpops to enable SER to see if the UAs are located behind
> >>the same address and now I need to let the UAs speak directly to each
> >>other (without force rtpproxy), please someone see my configuration 
> >>below and send some advice.
> >>
> >>rafael
> >>
> >>----.
> >>               if (!lookup("location")) {
> >>                       log(1,"unable to locate user \n");
> >>                       # handle user which was not found 
> >>                       route(4);
> >>                       break;
> >>               };
> >>
> >>               ### Test if UAS are in the same NAT:
> >>               # get the host part of the final uri (IP part)
> >>               # and store it in AVP ID 13 
> >>
> >>               avp_write("$ruri/domain", "i:13");
> >>               if (avp_check("i:13","eq/$src_ip/i")) {
> >>                       log(1, "source IP is the same as destination IP
> >>\n"); 
> >>                       route(3);
> >>                       break;
> >>               };
> >>               avp_delete("i:13/g");
> >>.
> >>.
> >># -------------- Same NAT Call Routing (no force rtpproxy) ----
> >>
> >>route[3]{
> >>       log(1," route[3]: UAs are in the same nat, NO force_rtp_proxy
> >>");
> >>
> >>### Do something!!!!
> >>
> >>       if(!t_relay()){
> >>               sl_reply_error();
> >>       };
> >>}
> >>_______________________________________________
> >>Serusers mailing list
> >>serusers at lists.iptel.org
> >>http://lists.iptel.org/mailman/listinfo/serusers
> >>    
> >>

-- 
Regards,
Jan Henkins