reverse lookup entry in BIND configuration

[Mark Andrews]

> Hi All,
> I am just learning how to configure a DNS name server using BIND.
> 
> I am confused regarding the reverse lookup entry in /etc/named.conf
> 
> For reverse lookup the entry is something like
> 
> zone "16.16.172.in-addr.arpa" IN {
> type master;
> file "example.in.local";
> allow-update { none; };
> };
> 
> My confusion is regarding the 16.16.172.in-addr.arpa . Is it
> necessary that for 16.16.172.in-addr.arpa , it should always
> contain the first three octets in an ip address irrespective of
> the class of ip address . Or it depends on ip address class. That
> is for a B class address, the entry will be somewhat like
> 
> zone "16.172.in-addr.arpa" IN {
> type master;
> file "example.in.local";
> allow-update { none; };
> };
> 
> Also , it will be helpful to me if somebody can tell regarding the
> significance of using half part of the ip address instead of using
> the complete ip address.
> Thanks in Advance

	Firstly, the Internet went classless years ago.

	To answer your question:
	If you have a /16 you can put the PTR records in B.A.IN-ADDR.ARPA
	or you can have a B.A.IN-ADDR.ARPA which delegated to
	multiple C.B.A.IN-ADDR.ARPA zones which have the PTR records
	in them or you can do both.  Basically you do whatever is
	easier for you and how you have sub allocated the space.

	Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org