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

[Gordon Henderson]

On Thu, 16 Oct 2008, Tony Mountifield wrote:

> 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.

Hm. Drayteks are on my list of modems to turn any SIP ALG off on! You must 
have a goodun :)

Or maybe you're not using asterisk 1.2 ...

>>> 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.

I guess STUN and NAT aren't in the "enterprise" then.... Or Cisco makes
their kit work when talking to another Cisco box..

No chance of putting the asterisk box on the inside of the NAT router 
then?

Gordon