CIDR is killing my nerves

David Tonhofer david.tonhofer at
Mon Mar 5 15:46:00 UTC 2001

AFAIK, it *all* depends on how your provider has
set up things. There is no specified syntax on how to do it.
Instead the provider will set up a CNAME for the address, and delegate to you. You will
have to take up the CNAME and map to the PTR value.

For example, I have been assigned

If I want to reverse-resolve, the following
happens (I'm quoting here from a note I made up for myself to
actually know what I was doing)

SOA for seems to be down, we use
dig SOA 84983  IN   SOA 432000 IN   NS

SOA for
...we ask
dig SOA 86400 IN  CNAME 86400 IN  SOA has as CNAME: has as SOA
(dnsadmin at
(this means the P&T nameserver is set up so that the host addresses have
CNAMEs which
are subdomains of the subnetwork base addresses -- in our case

PTR for
...we ask
dig PTR 28800 IN PTR

Hope this helps,

		-- David

-----Original Message-----
From: bind-users-bounce at [mailto:bind-users-bounce at]On
Behalf Of Philipp Snizek
Sent: Monday, March 05, 2001 4:05 PM
To: bind-users at
Subject: CIDR is killing my nerves

Dear list users,

There is something I don't understand. If I put into named.conf

zone "" IN {

all is fine but one thing:
It does do reverse lookup for /24 net instead /28 net I in fact own. So far
I understand that it doesn't work. To solve the probelm, I tried this:

zone "" IN {

zone "" IN {

zone "176/" IN {

But this doesn't work. What is the syntax for my 28Bit subnet beginning on

The ISP does not have installed a delegation. But I think this should work
without my ISP delegating the CIDR block because I must be able to
reverse-resolve other hosts in network on my dns servers.
With my today's config, it doesn't do it.

Thank you

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