[asterisk-users] SIP: difference between Grandstream and Cisco when behind NAT

[Tony Mountifield]

In article <Pine.LNX.4.64.0810161740260.29686 at unicorn.drogon.net>,
Gordon Henderson <gordon+asterisk at drogon.net> wrote:
> On Thu, 16 Oct 2008, Tony Mountifield wrote:
> 
> > I have used Grandstream phones for years, and have just started testing
> > a Cisco 7940 (with SIP firmware 7.4). I have found something puzzling
> > and don't know whether it's just a limitation or something I haven't
> > done correctly.
> >
> > The Asterisk server is directly on the Internet with a public IP.
> > The phones are on a private LAN with a NAT router to the Internet.
> > The sip.conf entries for both phones say nat=yes. For the Grandstream,
> > this is always sufficient to make it work properly with Asterisk,
> > even though in the Grandstream config I have "NAT traversal: no" and
> > leave "Use NAT IP" blank. All the clever stuff is done automatically
> > by Asterisk.
> 
> Is it? I've always needed a STUN server in Grandstreams behind a NAT 
> router - maybe the NAT router has a (shock horror!) working SIP ALG in it? 
> (What make is it?)

I don't think the router does anything special. It's a Vigor 2800G.
I've also used a Speedtouch 608WL successfully.

> > However, with the Cisco, that doesn't seem to be the case. I have found
> > it necessary in the SIPDefault.cnf file to set "nat_enable: 1" and
> > then specify as nat_address the public address of my router.
> >
> > Is this normal? What is different between the Grandstream and the Cisco?
> > Is there any way to avoid having to program the external address into
> > the Cisco when it is behind NAT?
> 
> Does the Cisco support STUN?

There's no mention of STUN in the config file template, nor in the Network
Setup menu.

Cheers
Tony
-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org