[AusNOG] PTR Records

[Mark ZZZ Smith]

>________________________________
> From: Colin Stubbs <colin.stubbs at equatetechnologies.com.au>
>To: Mark Andrews <marka at isc.org> 
>Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net> 
>Sent: Tuesday, 18 November 2014, 12:46
>Subject: Re: [AusNOG] PTR Records
> 
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>What Mark said.
>
>I'd also note, that while the value returned by the PTR request is *intended* to be another valid RR (A, AAAA etc)... it can actually be any ASCII string.

>

If you want to have a bit of fun, change PTRs for router interfaces to "censored" or similar. When I did something similar (I wanted to obscure something just to that it wouldn't be used temporarily), traceroute just displayed it. IOW, traceroute wasn't validating in any way the PTR string returned, it was purely displaying it.
>
>Windows server DNS will convert everything to lowercase and encode some of the characters however, e.g.
>
>
>[user at box ~]$ dig @10.4.32.32 PTR 255.32.4.10.in-addr.arpa. +short
>my\032isp\032is\032staffed\032by\032muppets.
>[user at box ~]$
>
>
>By the look of it RFC 1035 describes what's expected for DNS resource records generally, and what PTR is expected to be.
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>
>-Colin
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>On 18 November 2014 11:34, Mark Andrews <marka at isc.org> wrote:
>
>
>>In message <CAM9f+Zw4fbWXbr2gne0iLWppywN-oU32Uf4P3H17M1cK3D+JLw at mail.gmail.com>, David Beveridge writes:
>>>
>>> Can anyone point me to any RFC which says that there are restrictions on
>>> the name a PTR can point to.
>>>
>>> I have been told by a certain ISP that I cannot have a PTR pointing to
>>> mycompany.com.au as it is NON-standard and which cannot and should not be
>>> done.  They insist on setting the PTR to mail.mycompany.com.au and refuse
>>> to do as I ask.
>>>
>>> I have never heard of any such thing.
>>>
>>> dave.
>>
>>There isn't such a restriction.
>>
>>That said if you are sending email from mail.mycompany.com.au and
>>it announces itself as mail.mycompany.com.au in the HELO / EHLO
>>then it would be wise for the PTR record to be mail.mycompany.com.au
>>and for there to be A/AAAA records for mail.mycompany.com.au.
>>
>>If your mail server announces itself as mycompany.com.au then the
>>PTR record should be set to mycompany.com.au.
>>
>>Mark
>>--
>>Mark Andrews, ISC
>>1 Seymour St., Dundas Valley, NSW 2117, Australia
>>PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org
>>
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