[AusNOG] PTR Records

[Scott Howard]

On Mon, Nov 17, 2014 at 6:16 PM, Aaron Wigley <aaron.wigley at rea-group.com>
wrote:

> RFC 1912, under "2.1 Inconsistent, Missing, or Bad Data: 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."
>
>
> So, if there is an A RR for mail.mycompany.com, there should be a PTR RR
> pointing back to it.  This is commonly used for email spam detection
> (
> https://en.wikipedia.org/wiki/Anti-spam_techniques#PTR.2Freverse_DNS_check
> s)
>

No!  That is NOT what it says!!

It says that for every IP address there should be a PTR. It does not say
that for every A record there should be a PTR.

You should be able to go  IP ---> Hostname (via PTR record) -> same IP.
(via A record)

Having multiple PTR records for a single IP address is completely legal,
but has caused many problems over the years, especially with
email/anti-spam.

  Scott
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