is is able to setting up DNS server reverse lookup
on at cs.ait.ac.th
Mon Jul 23 04:04:27 UTC 2007
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 desktops.cs.ait.ac.th
> ; <<>> DiG 9.3.4 <<>> -t ns desktops.cs.ait.ac.th
> ;; global options: printcmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19501
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
> ;; QUESTION SECTION:
> ;desktops.cs.ait.ac.th. IN NS
> ;; ANSWER SECTION:
> desktops.cs.ait.ac.th. 43049 IN NS dns.cs.ait.ac.th.
> ;; Query time: 1 msec
> ;; SERVER: 127.0.0.1#53(127.0.0.1)
> ;; 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
> dns.cs.ait.ac.th. 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 dns.cs.ait.ac.th 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
170.41.192.in-addr.arpa. I have a line that says:
$GENERATE 128-254 $ IN CNAME $.170.41.192.rev-dns.cs.ait.ac.th.
hence the CNAME and the PTR are generated dynamically in the zone
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