FILE db.124.168.192: This file does the opposite of db.kulai: give it an ip address and it returns the computer name. I use ***** to seperate the file listing from the rest of this article, so do not copy them into your file. Bold items are explaned below - bold is not part of the regular file.  Here is what mine looks like:
@    IN    SOA (
                  86400 );

         IN NS
10       IN PTR
10       IN PTR
10       IN PTR
10       IN PTR
11       IN PTR
1        IN PTR
20       IN PTR

NOTE: The biggest problem in creating these files is missing a period where one is required. The period says: this is the end of the name. Without the period, the domain name will be tacked on, so will become:  In other words, the period is the difference between absolute and relative names.

This file is basically the same concept as the db.kulai file:
This is shorthand for the base domain name. Note: the @ must appear on the top line and with NO spaces before it.  This is the server's name.  This is actually an email address with the @ replaced by a period. If there is a problem, this person will be notified via email.
All those numbers: These are the default times. If you want to change them, read the books - the defaults work just fine for home use.
IN NS this line tells named that is the name server. Note: the first part of the line is blank, so named will add there (no period).
The numbers on the left (10,11,1,20) are the last digits of the ip address, e.g. name will expand 10 to:

Notice that we use IN PRT instead of IN A in this file.