Helo, i am trying to connect my N900 to my asterisk server, but i am having many problems related to NAT i guess.

I read a lot os post, but i did not find anything i could realy use. Sorry if i did not see what i needed!

So, lets go to the problem.

I have my asterisk server in with a public address.
My sip.conf looks like.
[100]
callerid = N900
type=friend
secret=*******
;net=yes ( i already use both, with or without nat )
qualify=5000
port=5060
host=dynamic
dtmfmode=rfc2833
allow=gsm,alaw,ulaw,iLBC
context=sip-prod
callgroup = 1
pickupgroup = 1

On my N900 i have configured like this, in advanced i have marked
Discover public address
Auto detect STUN

I already have tried many confs, but none of them worked when i am behind a nat.

My question is:
I have a laptop and connect to the same network as my N900, and with ekiga i can register to my asterisk and make the call with sound. In my n900 i have no sound when i am in my home network. When i conect over 3G i the sip phone work as expect. Only when i am on a nat network that does not work.

Does any one have any help??
Thanks