[97547] in RedHat Linux List
Re: Reverse lookup?
daemon@ATHENA.MIT.EDU (Ramon Gandia)
Tue Nov 3 16:09:09 1998
Date: Tue, 03 Nov 1998 12:00:44 -0900
From: Ramon Gandia <rfg@nook.net>
To: redhat-list@redhat.com
Resent-From: redhat-list@redhat.com
Reply-To: redhat-list@redhat.com
Greg Thomas wrote:
>
> Hello all,
>
> I'm changing IPs on our network due to an ISP change. After I change
> the IP address on a workstation when I try to telnet to or check
> mail on our mail server running RH 4.1 I'm getting connection refused.
> The only thing that has changed is the workstation's IP address so I
> figure it's a problem with reverse IP lookup???
A DNS has two files associated with the IP address.
Typically one called /var/named/db.nook (for example)
and another called /var/named/db.216.47.28 (for example)
The db.nook file is the forward file, it would have an
entry for your computer like this:
green IN A 216.47.28.11
and the other file, db.216.47.28 would have
11 IN PTR green.nook.net.
notice the period after net!
OK, if you change an entry, you need to change both files.
But if you change networks, but still int he same domain,
then you need to put your IP in the appropiate reverse file,
even if you have to create it.
Example. Lets say the domain name is nook.net, and that the
network is 208.161.169.0. Along comes the need to add another
network, like 216.47.28.0. In that case, there would be three
files involved:
db.nook
db.208.161.169
db.216.47.28
Each machine in the domain is listed in db.nook, but only in
the appropiate reverse file, depending on the net they are in
on.
Please note that you can call these files just about anything,
and jsut about put them wherever you want in the filesystem.
It is common practice to name them as I did above, and put them
in /var/named. There are directives for this. If you use
bind 4, then the file that sets all this out is
/etc/named.boot
for bind 8 its /etc/named.conf
They are similar, but bind 4 is much easier to understand. There
is a directive called directory:
directory /var/named
which puts it there. It could be in /usr/timbuctoo if you want
to be non-standard.
There is also a line there that creates the relationship of
the zones and the files. In other words, if you add a network
like in the example above, you add the 216.47.28 net where one
did not exist before, then you need a line calling for the
in-addr.arpa.28.47.216. Just use your existing lines as an
example. The nameserver then will look for the proper file in
the right directory. I suggest you stay with the naming
convention of your existing files.
--
Ramon Gandia ==== Sysadmin ==== Nook Net ==== http://www.nook.net
285 West First Avenue rfg@nook.net
P.O. Box 970 tel. 907-443-7575
Nome, Alaska 99762-0970 ======================= fax. 907-443-2487
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