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Date:      Mon, 23 Jul 2007 11:04:16 +0700 (ICT)
From:      Olivier Nicole <>
Subject:   Re: is is able to setting up DNS server reverse lookup with	DynamicIP?
Message-ID:  <>
In-Reply-To: <> (message from Chuck Swiger on Mon, 16 Jul 2007 09:55:06 -0700)
References:  <> <> <> <> <>

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Hi Chuck,

With some delay, several answers together.

> > For the example I gave, I am of course authoritative.
> Are you?  Depending on which servers I query, I either get an  
> NXDOMAIN, an answer with no authoritative nameservers listed, or the  
> results you've shown.  That implies that there is something wrong  
> with the DNS delegation, and/or the various nameservers aren't  
> returning reliable results.

I think that the no authoritative means it is an answer from a
chache. Am I wrong?

> Perhaps part of the problem seems to be that:
> % dig -t ns
> ; <<>> DiG 9.3.4 <<>> -t ns
> ;; global options:  printcmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19501
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
> ;         IN      NS
>  43049   IN      NS
> ;; Query time: 1 msec
> ;; SERVER:
> ;; WHEN: Mon Jul 16 12:48:42 2007
> ;; MSG SIZE  rcvd: 57
> ...doesn't return any A records to go with the NS record for  
>  It's also the case that every domain should have  
> at least two nameservers listed, and by strong preference at least  
> one nameserver should be on another subnet to improve reliability.

It should, because has had a very stable IP for many
years and this one is served by 3 name servers.

When I set-up the dynamic DNS, I did not replicate it because I was
not sure it woul dnot generate huge traffic, nor that redundancy was
as needed as for the static DNS.

But I am in the process of upgrading the hardware, so I will duplicate
the name servers also for the dynamic part.

> It's not anticipated that a reverse lookup would return a CNAME  
> rather than a PTR.

CNAME in rDNS is to my knowledge the only way to delegate a subnet of
a class C:

I have a /24 IP range, /25 is static and /25 is dynamic. For
separation, stability, etc, I want to rDNS on /25 and that is not
possible without a trick:

in the zone declaration for the rDNS of the /24 I have a line that says:

$GENERATE 128-254 $     IN      CNAME   $

hence the CNAME and the PTR are generated dynamically in the zone

Best regards,


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