I have this structure
domain.com
sub1.domain.com
sub2.domain.com
sub3.domain.com
What i`d like to do is allow entrance the the 3 subdomains only for visitors coming from domain.com. If visitors type sub.domain.com in the address bar they should be redirected to
www.domain.com.
I have no idea if it is possible and if there is an efficient way of doing this ....