Reverse DNS lookups

Joe Kattner joe.kattner at
Mon Feb 25 18:54:41 UTC 2002

I'm assuming the original post contained the correct information, the ISP
has allocated 4 addresses out of a /25. ( is 128 addresses,
not 4) If that is the case the zone file for the ISP would have to delegate
them individually within that subnet, as it's broken up with these smaller
groups of 4 or whatever, and couldn't delegate the subnet as a whole (RFC
2317 style).

If the original poster uses the example you give below then he becomes
authoritative for the whole Class C address space and blind
himself to the rest of that zone, which is what he is trying to avoid, as he
only has 4 of the addresses.

The ISP would need create the NS records for delegation of each IP in their zone, and he would have 4 zones, etc.. Getting a whole subnet is much easier as
they could delegate the whole thing to him as a single zone with an
arbitrary name.


-----Original Message-----
From: John R. Shearer [mailto:john at]
Sent: Friday, February 22, 2002 10:40 PM
To: bind-users at
Subject: FW: Reverse DNS lookups

I'll make it easy for you, but Read the Fine Manual anyway; I might have
made a mistake.

; ------ Begin db.217.8.136 ------
$TTL 604800
@ IN SOA yourdomain.tld. hostmaster.yourdomain.tld. (
        200202060       ; Serial number
        28800   ; Refresh after (seconds)
        7200    ; Retry after (seconds)
        604800  ; Expire after (seconds)
        86400   ; Negative Cache TTL (seconds)
; Nameserver entries
 IN     NS      ns1.yourdomain.tld.
; Host Entries
1       IN PTR  host1.yourdomain.tld.
2       IN PTR  host2.yourdomain.tld.
3       IN PTR  host3.yourdomain.tld.
4       IN PTR  host4.yourdomain.tld.
; ...where host1's IP address is, and so on
; ------ End db.217.8.136 ------

In named.conf...

zone "" {
        type master;
        file "db.217.8.136";

  - John R. S. 

From: "Christian Opsahl" <copsahl at>
Newsgroups: comp.protocols.dns.bind
Date: Sat, 23 Feb 2002 01:23:13 GMT
To: comp-protocols-dns-bind at
Subject: Reverse DNS lookups

I want to administrate my own reverse, but im a bit out of my league here.

I have 4 ip adresses which my ISP is administrating the reverse for, but i
wanna do this my self. My ISP can forward this to me but, I dont know how to
set up reverse for ip adresses that is`nt a part of a class C net.

Here is an example on how it looks like:


How should the input in my named.conf file be? And how would my zone file
for these ip adresses look like.


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