I am maintaining a DNS and mail server in win 2003, and the ISP made me authoritative for the domain. They say:

----- Start of the email received from the ISP--------


The reverse ip zone is currently being delegated to the following nameservers:



You will need to verify with your current DNS provider whether they will accept IP delegation and have them set up the reverse zone and add pointer records as needed.

It is a common misconception that the owner of the IP block has to create the PTR records or only the owners of the IP address can add the PTR record, but that is not the case.

Please refer to: RFC 2317 http://www.faqs.org/rfcs/rfc2317.html for more information on IP delegations.

------------- End of the email from ISP -------------------

My question:

How do I define these cnames and ptr records in my DNS, I am confused.

Thanks in advance.


I am sorry for the confusion I caused.

Yes, the ISP delegated me this IP range (a subnet, rather than a full class C). I manage those 2 DNSs (dns1.DNSdomain.net, dns2.DNSdomain.net)

My problem was (I now found the answer by trial and error) how to define a PTR for a subnet.

The solution is:

Create a primary and a secondary zone with the name: 96_28.204.xxx.yyy.in-addr.arpa.dns

The lookup will be made to: 96/28.204.xxx.yyy.in-addr.arpa.dns

Thanks for your answer and my apologies for taking your time.


  • No apologies necessary for me. Glad to hear you got it working! – Evan Anderson Sep 10 '09 at 4:31

The authoritative DNS servers for that reverse zone are, as stated, dns1.DNSdomain.net and dns1.DNSdomain.net. Are those ones the servers you manage, or are they your ISP's servers?

In the first case, you need to define a reverse lookup zone in your DNS servers and put the right PTR entries into that; in the second case, it's your ISP which should do it on its servers.

  • Have at, man. I've tried to write an answer 3 times now, and I'm getting frustrated at the lack of information. FWIW, it sounds to me like the poster's ISP delegated the reverse lookup zone for IP addresses that the poster's using on his own servers to the DNS servers listed as authoritative for the poster's Internet domain name. Whether or not that's the on-site W2K3 DNS server that the post is talking about or not you'll have to find out. Good luck. – Evan Anderson Sep 9 '09 at 22:48
  • Yes, I've noticed there are lots of bad questions around. A lot more than bad answers. Makes one wonder... – Massimo Sep 9 '09 at 22:57
  • Everyone is either more or less competent and experienced than everyone else. Sure, there's a lack of detail in the question but look at the spirit of the query and not the quality. I certainly don't know everything and I might be inclined to ask a non-intuitive or informative question about a subject that I'm iffy about. – joeqwerty Sep 9 '09 at 23:00

This really isn't that bad of a question (as long as I'm reading it right =)...

The OP was just asking how to setup the zone for PTR lookups. The delegation he's referring to is really quite common from my experience (I've dealt with most major bandwidth providers at one point or another). It goes something like:

  1. ISP delegates PTRs with either a wildcard, subnet, or per record NS entry pointing to your server
  2. you setup the actual PTR record in your DNS servers

    [greeblesnort@dhdx421 greeblesnort]$ dig +trace D.C.B.A.in-addr.arpa

    B.A.in-addr.arpa. 86400 IN NS tuldns1.wcg.net.
    B.A.in-addr.arpa. 86400 IN NS stldns1.wcg.net.
    ;; Received 94 bytes from in 10 ms
    C.B.A.in-addr.arpa. 3600 IN NS ns2.mydomain.com.
    C.B.A.in-addr.arpa. 3600 IN NS ns3.mydomain.com.
    ;; Received 121 bytes from in 15 ms
    C.B.A.in-addr.arpa. 38400 IN SOA ns3.mydomain.com. techcontact.mydomain.com. 2005083101 10800 3600 604800 38400

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