Question : Domain names and Domain Alias's

I may already have answer to this but I am unsure.
When you join a computer to a domain you dont use the fully qualified name xxxx.xxx.net you use like a shortened name or something that has nothing to do with the full name do you put an entry in the dns for this alias or where??

Answer : Domain names and Domain Alias's

Fire is the netbios name of the domain.  When AD was installed and the domain "fire" was created, the FQDN fire2.gov was created.  There is no such thing as an alias for a domain.  There is the FQDN and the netbios name.  That's it.  If you want a different "alias" then you need to create a new domain (complete with it's own domain controller(s) and trust relationships) for that different name.