Putting a DNS server on a network allows for the replacement of IP addresses of individual machines by a name.
As a result, it's even possible to associate multiple names to the same machine to update the different available services.
Note: There are some issues with this Howto, too numerable to fix quickly, and it requires bringing up to standard. in all other places, the document uses the machine name example ns.
I'm mentioning this to help anyone to avoid the unnecessary time trying to resolve their DNS, owing the the inconsistencies in this document, particularly if you're new to DNS configuration. Here it changes to box (I believe the author was simply trying to show that additional computers would be listed, but failed to use a different address for box.
This led to an interesting issue with updating the zone files…