Subject: Re: IPv6 AAAA weirdness

Re: IPv6 AAAA weirdness

From: Paul Marks via c-ares <>
Date: Tue, 13 Dec 2016 13:36:58 -0800

On Tue, Dec 13, 2016 at 5:41 AM, Joe Kemp <> wrote:
> I'm using c-ares via the python gevent module on AWS. When resolving an AWS
> Elastic Load Balancer (ELB) hostname a valid A record is returned but the
> AAAA response contains an Authority RR with a SOA record. When gevent is
> configured to use the native resolver it gets the valid A record and
> continues on ignoring the AAAA response. When gevent is configured to use
> ares it treats the AAAA SOA record as invalid and does additional AAAA
> queries using the search list. In my particular configuration this is
> causing an issue because the search list has 4 domains which is causing
> every lookup to result in a bunch of unneeded queries and load on the DNS
> servers.
> I wasn't sure where to start to figure out what is causing this behavior.
> It looks like the underlying c-ares library is misinterpreting the AAAA SOA
> response but I'm not super familiar with c-ares or IPv6. I think it should
> either stop with the valid A response or query the provided NS for with the
> initial AAAA query.

I tried starting a thread about this last year:
Received on 2016-12-13