how to associate an ip with a name?

view full story

http://serverfault.com – I have installed an asterisk on my private network(so it s behind a router ). Is there anu way to set the asterisk on a public ip though it's installed in a server with private ip? As Ive read it ispossible using externip and externhost. My second question is: Can I set a specific name over the domain? I mean can I associate ip:xxx.xxx.xxx.xx with my_domain? How to set this on asterisk? I am new to this stuff. need some help! appreciate (HowTos)