underscore in A or PTR records

Mark Andrews marka at isc.org
Wed Feb 17 17:20:55 UTC 2021


No. The PTR records that map from IP address to hostname enforce the hostname rules. 

-- 
Mark Andrews

> On 18 Feb 2021, at 02:20, Sten Carlsen <stenc at s-carlsen.dk> wrote:
> 
> 
> 
>> On 17 Feb 2021, at 12.34, ONRUBIA AVILES Carlos (CCS/MST) <carlos.onrubia.aviles at proximus.com> wrote:
>> 
>> Hello,
>> 
>> Indeed my question was on A record but the issue is on PTR record.
>> I can configure the following line:
>> 
>> _ptr.dekil.nl.      3600    IN      PTR     _81.99-129-109.adsl-dyn.isp.dekil.nl
>> 
>> It works....we can use "_"  in both sides.
>> 
>> 
>> But what is strange is that the following configuration do not work:
>> 
>> 9.10.238.195.in-addr.arpa.       3600    IN      PTR     por_tal-bis.skynet.be.
>> 
>> "_" is not allowed
>> 
>> Is it due to extra check by bind when it sees it is an arpa zone so no  "_" is allowed?
> 
> As previously mentioned, the RFCs expressly forbids the "_" in names.
> 
> I assume that a leading "_" slips past Bind's control because it "could" be part of a valid but at compile time unknown _tcp -like label.
> 
>> 
>> 
>> Regards,
>> 
>> Carlos,
>> 
>> 
>> Sensitivity: Internal Use Only
>> 
>> -----Original Message-----
>> From: Ondřej Surý <ondrej at isc.org>
>> Sent: 17 February 2021 10:52
>> To: ONRUBIA AVILES Carlos (CCS/MST) <carlos.onrubia.aviles at proximus.com>
>> Cc: Mark Andrews <marka at isc.org>; bind-users at lists.isc.org
>> Subject: Re: underscore in A or PTR records
>> 
>>> 
>>>> On 17. 2. 2021, at 9:50, ONRUBIA AVILES Carlos (CCS/MST) <carlos.onrubia.aviles at proximus.com> wrote:
>>> 
>>> The issue we face is that a telecom provider ask us to implement a PTR record with a name like “example_try.net"
>> 
>> You are mixing the two things here. If the provider has asked you to create a PTR record, why do you keep trying to create a forward record? There’s some information missing somewhere.
>> 
>> Ondrej
>> --
>> Ondřej Surý (He/Him)
>> ondrej at isc.org
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