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It's common to host your own forward DNS if you own your domains. Setup bind9, compose zone files for your domains, and change the name servers from your registrar's to your own. This seems to be straightforward. However, if I own a block of IP addresses, and if I want to setup my own DNS server to manage my own reverse DNS, how can I change the reverse name server from my ISP to my own reverse DNS server? Is it a normal practice? Or ISP will not allow this to happen?

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  • I didn't fully understand it until I managed an IPv6 block. It's actually no difference than a ip6.arpa. domain, where .arpa is yet another tld just like .com, .net and .org.
    – Qian Chen
    Oct 2, 2015 at 2:36

2 Answers 2

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Your provider needs to delegate the reverse DNS for the netblock to you. That's something that should be simple, and in some rare cases it is simple, but usually it's more complicated - your provider sets up a CNAME for each IP address that points at your nameserver.

As an example, if you're running 10.105.179.128/25 then your provider will add 128 CNAMEs, looking like this:

153.179.105.10.in-addr.arpa CNAME 153.128-25.179.105.10.in-addr.arpa

and some NS records:

128-25.179.105.10.in-addr.arpa. 86400 IN NS ns1.yournameserver.com.
128-25.179.105.10.in-addr.arpa. 86400 IN NS ns2.yournameserver.com.

And you'll create the zone 128-25.179.105.10.in-addr.arpa. on your nameserver and populate it with PTR records. Everything works perfectly.

There are several different ways of doing it. Hurricane Electric have a decent doc describing them here.

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  • This is the correct answer and usually works. However, I already had trouble running an email server with such delegated reverse DNS. Some third-party servers were refusing smtp connections because they didn't consider the reverse record valid.
    – JFL
    Aug 4, 2015 at 18:30
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Your ISP must delegate your netblock to you. This will not work if you don't own a complete subnet, however small but just a few adresses in a larger block. In the latter case, your provider should offer some way to edit the reverse entries.

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  • If I own a whole block of /25, can I talk to my ISP to let me manage the reverse DNS with my own reverse DNS server?
    – Qian Chen
    Aug 3, 2015 at 17:32
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    @ElgsQianChen Quite possibly, you can certainly check with them. For a smaller than /24 network some special handling will be required.
    – Håkan Lindqvist
    Aug 3, 2015 at 17:40
  • Thanks @HåkanLindqvist. I don't really want to touch that hot potato, yet. I'm just wondering how the whole process works. Thanks for the link. It's informative reading. I'm wondering whether it is also a change (reverse) name server process, just like to change the name servers from registrar for forward zones?
    – Qian Chen
    Aug 3, 2015 at 17:44
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    @ElgsQianChen On a technical level it's the same (a reverse zone is a zone like any other, there's nothing different about how delegation works) but the process is usually less formalised, particularly if you're not getting the delegation done directly by the RIR but some smaller portion delegated by your ISP/the LIR.
    – Håkan Lindqvist
    Aug 3, 2015 at 18:06
  • I've never worked with a provider who had an interface for me to edit rDNS. Instead, I've always had to submit a ticket to their network engineers.
    – Todd Wilcox
    Aug 3, 2015 at 20:14

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