How do you connect to the nethserver?
Via openvpn roadwarrior?
if yes, add these two commands at the end of the openvpn configuration file on each computer (not on the server)
register-dns
block-outside-dns
this should allow you to redirect all client dns requests to the nethserver dns server.
at that point just add the host names (complete with domain) and their IP in the nethserver dns server
of course computers that are in the local network and have dns pointing to nethserver should work without problems and without having to set up vpn