Reverse DNS

[thisisit3]

As far as i know, none of the domains (accounts) have their reverse DNS created by default. So far i've been opening tickets and asking support to manually create them.

Does anyone know if there is a way to automatically create Reverse DNS entries? or is this something that only Jag can do (or at least automate)?

[JPC-Masood]

Domains (accounts) do not have reverse DNS. Reverse DNS is for IPs.

And yes, you need to open a support ticket to have reverse DNS setup for your IPs.

[thisisit3]

yes thats what i mean, domains (accounts) have an associated IP address, as a consequence they can have a reverse DNS, its obvious that i'm talking about the IP that resolves back to the domain.

is there a way to automate this instead of opening support tickets all the time?

[JPC-Masood]

It was not clear if you were referring to IPs. Many clients keep asking for reverse dns for their domain when in fact they are on shared IP, hence my clarification that domains do not have rerverse dns. The only accounts (domain) which may need reverse dns is the one setup on unique IP.

No, there is no feature yet to automate this, nor any plans at this time. If you lease a full class C, we can arrange something.

[Ron]

Is it legal for multiple rDNS records be set up for a single IP address?

In other words, I have a dedicated (unique) IP for a domain on a shared server. Should I have a PTR pointer for that IP address pointing to either my domain or to the nocdirect domain where the mailserver is, or both (or neither)?

What about the domains I have that use the shared IP for their domain?

(and how do MX records fit into this ?)

[thisisit3]

Thanks Masood, i guess i'll have to keep on opening tickets :P

[JPC-Masood]

Is it legal for multiple rDNS records be set up for a single IP address?

It is legal but not recommended and will definitely cause problems for email (during reverse dns lookup) because according to RFC 1912 "Make sure your PTR and A records match".

In other words, I have a dedicated (unique) IP for a domain on a shared server. Should I have a PTR pointer for that IP address pointing to either my domain or to the nocdirect domain where the mailserver is, or both (or neither)?

To your domain.

What about the domains I have that use the shared IP for their domain?

(and how do MX records fit into this ?)

What about them?

[JPC-Masood]

In other words, I have a dedicated (unique) IP for a domain on a shared server. Should I have a PTR pointer for that IP address pointing to either my domain or to the nocdirect domain where the mailserver is, or both (or neither)?

Just another note, there is no requirement to have reverse dns for the above situation. At least I do not know any RFC requirement.

[Ron]

What about a reverse DNS for the mailserver?

I get very confused about this since my mailserver comes from a different IP...

[JPC-Masood]

Which mail server? Your bulk reseller hosting mail server? If yes, it already has reverse dns.

[Ron]

But, but, but....how does, say, GMAIL know that mydomain.org is allowed to send email through whatever.nocdirect.com, or that whatever.nocdirect.com is allowed to send email for mydomain.org? The IPs are different.

I think a couple of years ago I had issues with "no reverse MX record" or something like that with Yahoo or another big provider, but I haven't had that issue in a long time. I think they gave up trying to enforce the rules.

We're not even talking about SPF yet....

[JPC-Masood]

You can ask gmail or yahoo about it. I have never seen any problem myself. I don't know of any RFC requirements either where the domain must send email from an IP where its MX or A record is pointed.

[Ron]

Well, here's one I found:

Answer:
No PTR records exist for 69.73.(MY IP). [Neg TTL=480 seconds]

Details:
ns.nocdirect.com. (an authoritative nameserver for 73.69.in-addr.arpa., which is in charge of the reverse DNS for 69.73.(MY IP))
says that there are no PTR records for 69.73.(MY IP).

To get reverse DNS set up for 69.73.(MY IP), you need to speak to your Internet provider. You could also check with root@ns.nocdirect.com., who is in charge of the 73.69.in-addr.arpa. zone.

Note that all Internet accessible hosts are expected to have a reverse DNS entry (per RFC1912 2.1), and many mailservers (such as AOL) will likely block E-mail from mailservers with no reverse DNS entry.

Plus DNSStuff reports a reverse MX error:

The problem MX records are: 76.189.(MY IP) .in-addr.arpa [No reverse DNS entry (rcode: 3 ancount: 0) (check it)]

[JPC-Masood]

So what is your point?

[Ron]

RFC1912 2.1 says, in part:

Every Internet-reachable host should have a name. The consequences
of this are becoming more and more obvious. Many services available
on the Internet will not talk to you if you aren't correctly
registered in the DNS.

Make sure your PTR and A records match. For every IP address, there
should be a matching PTR record in the in-addr.arpa domain. If a
host is multi-homed, (more than one IP address) make sure that all IP
addresses have a corresponding PTR record (not just the first one).
Failure to have matching PTR and A records can cause loss of Internet
services similar to not being registered in the DNS at all. Also,
PTR records must point back to a valid A record, not a alias defined
by a CNAME. It is highly recommended that you use some software
which automates this checking, or generate your DNS data from a
database which automatically creates consistent data.

Emphasis mine.