North American Network Operators Group

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Re: How to handle AAAA query for v4 only host

  • From: Mark Andrews
  • Date: Wed Apr 12 19:38:23 2006

>Apologies if anyone thinks this does not require coordination or is somehow
>not operational.
>However, I have a situation where some nameservers for which I am=20
>are receiving AAAA queries for hosts for which we are authoritative.  We
>return the SOA only as it seems we are supposed to, but, we are seeing a
>significant delay before we get an A query back from the resolver, which,
>we believe represents a significant delay for the end user in getting to
>the web page in question.

	Both NAME ERROR and NOERROR NODATA responses can include the SOA
	record in the authority section (RFC 1034, RFC 2308).  You don't
	give enough information to determine which of the abore responses
	you are talking about.

>Is there a better way to answer an AAAA query for a v4 only host?  Is it
>permitted and/or desirable to return a 6to4 or IPv4-Mapped address?
>Is there some other preferable thing to return?

	NOERROR NODATA is the correct response.

	As for why there is a delay between the AAAA and A queries there
	are lots of possible reason.

	Non RFC1535 aware resolvers.
	Not looking for AAAA/A in parallel when walking the search list.
	Firewalls block EDNS queries so you only see plain DNS queries.