We have our own DNS server for our domain installed on a BM 3.7 server (this
DNS server sends updates to our ISP)

Now we have users on our school who have a laptop and would like to access
inside and outside the school our domain names.

All our webservers are inside the school with private ipaddresses
(172.31.x.x - 255-255.0.0) Now on this moment we use on the internal
computers a HOSTS file with "172.31.x x host.domain.nl"

How can I set this up in the DNS server so that the users can access all the
time and where they are our websites inside and outside?