Newbie: in-addr.arpa file for a C Class

[Barry Margolin]

In article <ca4u3m$1eha$1 at sf1.isc.org>, bela at webnet-x.com (belacyrf) 
wrote:

> Most likely I'm confusing what the customer is looking for to be
> honest.
> Heres my confusion.  In our DNS server for block 216.X.X we have this
> file:
> 
> X.X.216.in-addr.arpa.  86400   SOA    ns1.myserver.net
> support.myserver.net (
>                         2003012918      ; serial
>                         3600    ;refresh
>                         600     ;retry
>                         604800  ;expire
>                         86400 ) ;minim
> ;
> ; Nameservers
> ;
>                 NS      ns1.myserver.net.
>                 NS      ns2.myserver.net.
> ;
> ; Other records for this domain (as domain.com).
> ;
> ;   example
> ;               IN A    cus.tom.er.ip
> ;               MX 0    mailserver.domain.com
> ;
> ; Host Records (xxx.domain.com)
> ;
> localhost       IN A    127.0.0.1
> ;
> ; Momentum Securities Reverse Entries
> ;
> 10              IN PTR  mail.domain1.com.
> 11              IN PTR  mail.domain2.com.
> 12              IN PTR  mail.domain3.com.
> 112             IN PTR  machine1.domain4.com.
> 135             IN PTR  bigblue.domain5.org.
> 
> So obviously if I lookup .10 in this block, I get the associated
> domain.  The odd thing is, when I look up an IP that does not have a
> PTR record I get:
> 
> 
> Name:    wsip-216-X-X-9.sub.mydomain.net
> Address:  216.231.10.9
> 
> How is that done?? 
> Thanks again for the help and education.

Since you obviously haven't posted the real zone file, it's impossible 
for us to tell.

Also, if you use dig, its output may provide some more clues in the 
Authority section.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***