asterisk users - Feb 2004 - Make outbound calls only from certain hosts

Hi,

I'm testing outbound calls for the fist time, using isdn4linux and a cheap 
20$ ISDN CARD: it works !

I have more problems restricting pstn calls .... can I allow inbound sip 
access to ALL asterisk features ONLY from the requests sent by my Ser 
proxy/registrar  ?

In Ser I use this to rewrite authorized requests

if (uri=~"0*@domainname") {

rewritehostport("ipaddress:5090");
t_relay_to_udp("ipaddress", "5090");
break;
};

requests are then managed by asterisk running on the same machine and port 5090

What I want to do is to avoid access to someone calling directly 
0whatever@domainame:5090 prior of authenticating with ser.


Tnx for any help !

Alessio Focardi