[asterisk-users] Restrict SIP registration to one ip address only?

[Remco Barendse]

Maybe a bit silly question, but why doesn't Asterisk accept if you set 
both a username&password as well as an ip address for a phone?

My fixed phones in my home all have a fixed ip address, but i also have 2 
Nokia GSM phones that can talk sip wich i would like to use from public 
wifi.

It's obvious that the more phones you have the more successful a brute 
force attack on the server will be, so i would only like to allow access 
to he 2 Nokia phones from "any" ip.

Why doesn't Asterisk allow both username&pass as well as setting an ip 
adress on a sip.extension?