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[DNSOP] Re: ordering of RRSets in the answer section of a DNS response

Paul Wouters <paul@nohats.ca> Thu, 15 January 2026 01:32 UTC

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Date: Wed, 14 Jan 2026 20:32:29 -0500
From: Paul Wouters <paul@nohats.ca>
To: Robert Edmonds <edmonds@mycre.ws>
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Subject: [DNSOP] Re: ordering of RRSets in the answer section of a DNS response
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On Wed, 14 Jan 2026, Robert Edmonds wrote:

> Petr Špaček wrote:
>> Is it 'protocol-legal' to have multiple identical RRs in the message?
>>
>> I would think it is not, but also I don't see test prohibiting it.
>
> "...servers should suppress such duplicates if encountered."
>
> (RFC 2181, Section 5)
>
> "A Resource Record Set should only be included once in any DNS reply.
> It may occur in any of the Answer, Authority, or Additional Information
> sections, as required.  However it should not be repeated in the
> same, or any other, section, except where explicitly required by a
> specification."
>
> (RFC 2181, Section 5.5)

This advise of suppressing it seems outdated, as it would invalidate the
RRSIG over the RRset.

Paul

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