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

[Jan Henkins]

Hello all,

On Sun, 2005-12-04 at 18:13 -0500, sip wrote:

> If the gateway has no issues with hairpinning, then yes, it's quite possible.
>  I use a Linksys gateway at home and a slightly older, pre-sip-proxy version
> of Astaro linux firewall at work, and we have multiple UAs behind each in the
> NAT space of our firewall. They can call each other. They can all outside. All
> based off registrations with a SER server on the outside of the network. 

Could you perhaps tell me the model number of your Linksys gateway?

> Netgear specifically has some serious issues both with hairpinning and with
> just plain ol' SIP. Netgear makes some mighty unfriendly gateways. :)

O dear... Well, nothing to be done about that right away though. Do you
have some more information I can use in this regard? If possible I would
like to present the chaps at Netgear with some kind of proof that their
products are SIP unfriendly, and campaign them to change this. I know
that this sounds a bit naive, but I have a bit of experience being a
"thorn-in-the-flesh-consumer" with reticent vendors, and getting what I
want! :-) They take competition with Linksys seriously, which is a good
thing.

> If you can't do it, though, it makes sense to set up some sort of proxy on the
> inside of the NAT that all the UAs register with, and have it pass things back
> and forth... forwarding the necessary data from outside to the server on the
> inside using port-fowarding rules.  For some of our customers, we've
> recommended Asterisk setups inside their NAT, just to make the passing of RTP
> packets more rational. You don't have to worry about individual client UA RTP
> settings, you can just worry about forwarding the RTP ports to Asterisk, and
> then inside the NAT do anything you wish. Since SER doesn't manage RTP, using
> just SER becomes problematic if your UAs are not homogeneous. 

OK, this makes a lot of sense. I was in the process setting up an
Asterisk box anyway for PBX duty at home.

-- 
Regards,
Jan Henkins
Cell: +27-84-951-4334