[Asterisk-Users] asterisk as sip client behind nat

[Guillermo]

Hi, I am pretty new to all of this but was able to
set up an asterisk server and have been able to 
succesfully connect to asterisk with x-lite as sip client.
I have also connected asterisk to FWD (using iax2) and
to voipjet (also using iax2).
Now I am trying to connect asterisk to Stanaphone.
It has to register as a SIP client but I am not being
succesful at all.
My asterisk server sits behind a Linksys WRT54GS router
(latest linksys firmware) acting as DHCP and NAT for
my home equipment. I have tried forwarding the SIP and
RTP ports to the asterisk machine, and I have also tried
putting the asterisk machine on the routers DMZ. No luck.
I have tried every configuration recommended for stanaphone
that I found on the web, including a couple I found on
the asterisk wiki and a few I found on the stanaphone forums.
I tried, explicitly defining the private and public ips,
qualifying, using the same number as assigned in stanaphone
for my local extension (a recommendation I found), etc.
Then I found a message in a forum about a person with the
same problem that claims it got fixed when asterisk was
put with a public IP address. So my question is....
is it at all possible to connect asterisk as a SIP client
when it sits behind a NAT? If yes, can somebody tell me
what I should do please.
thank you,
-guillermo
PS1.- When I connected the x-lite to asterisk both where
on the same side of the NAT
PS2.- The error I continuosuly get is "SIP/2.0 401 Unauthorized".
PS3.- I connected x-lite directly to stanaphone with no problems
even behind the nat...and I didn't have to set any port forwarding
or anything...so I am thinking that whatever x-lite is doing
asterisk should do...how do I emulate what its doing?