Point a domain to a subdomain

[fesqel]

Hi there,
I have 2 domains hosted on 1 server and the A records are the same:

fist.com A bbbbbbb
second.com A bbbbbbb

Also I have a few subdomains on first.com like:

sub1.first.com A bbbbbbb

And now, I just want to point second.com to sub1.first.com. For now I did a 302 redirection that is not appropriate. I want a mask-like thing. The question is how. I didn't sure if it's related to Apache so I posted it here.
I really appreciate if anyone helps.

Thanks

 

[scsi]

cname it to the other subdomain and use apache redirect with htaccess

 

[zEitEr]

And now, I just want to point second.com to sub1.first.com. For now I did a 302 redirection that is not appropriate. I want a mask-like thing. The question is how. I didn't sure if it's related to Apache so I posted it here.
I really appreciate if anyone helps.

Thanks

Google it with "Point a domain to a subdomain site:directadmin.com", it was discussed here many times