[dns-operations] Ultra DNS responding with NXDOMAIN for "www.uber.com"

Paul Vixie paul at redbarn.org
Sun Aug 8 17:49:03 UTC 2021

On Sun, Aug 08, 2021 at 03:20:24PM +0530, Shreyas Zare wrote:
> ... The resolver I have does restart for the last CNAME regardless
> of the RCODE but, the negative cache implementation based on RFC2308 and
> RFC8020 caused the NXDOMAIN response to get cached causing the issue.

that's exactly what should happen. i regularly correspond with operators
of dns-based load balancers that return NXDOMAIN for some qtypes, which
prevents a standards-conforming recursive dns server from asking about
that name for other qtypes. we have to strengthen the failure case here,
so that such authoritative responders fail earlier and more often.

Paul Vixie

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