question about how a particular dig works ...

[Chris Buxton]

My guess is that MS DNS is failing to treat the authoritative CNAME result from the www.careerone.com.au servers (which shouldn't even be authoritative) as more trustworthy than the NS records it received in the referral from the parent zone. This then causes that CNAME record to be rejected, which then kills the whole process.

The BIND name server sees the CNAME record and, apparently, at least works with it long enough to build an answer to the query it received. It doesn't seem to want to cache it, and so ends up looking it up again more often than should be necessary. But at least it's able to answer queries.

Chris Buxton
BlueCat Networks

On Sep 18, 2012, at 9:59 AM, M. Meadows wrote:

> 
> Thanks Kevin. I understand how the chained alias works. Sorry, I didn't explain my question very well.
> 
> I can see that the 8.8.8.8 google public dns server gets an answer.
> 
> I know that this domain has a cname coexisting with an SOA record and NS records ... both of which I have read are a bad thing. And I've seen the other reply that indicates that this combination of records in a zone file wouldn't even load in BIND ... so it's done with some other more forgiving DNS app. 
> 
> What I also see (but failed to explain) is that we have a local nameserver that can't find an answer to the digwww.careerone.com.au query. Gets no record back. Our local nameserver is an AD server that just throws up its imaginary hands in despair. So is this what we should expect from this problematic DNS setup in the www.careerone.com.au zone file? Erratic or somewhat erratic results? Just curious why google and some other public facing dns servers get an answer when our own local nameserver can't figure it out.
> 
> 
> 
> Date: Tue, 18 Sep 2012 11:18:58 -0400
> From: kcd at chrysler.com
> To: bind-users at lists.isc.org
> Subject: Re: question about how a particular dig works ...
> 
> On 9/18/2012 9:45 AM, M. Meadows wrote:
> 
> dig www.careerone.com.au +short @8.8.8.8
> www.careerone.com.au.edgesuite.net.
> a903.g.akamai.net.
> 208.44.23.99
> 208.44.23.121
> 
> Why does the above dig work when 
> 
> dig careerone.com.au +nssearch @8.8.8.8
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server usw1.akam.net in 106 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server usw4.akam.net in 136 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server usc4.akam.net in 124 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server usc1.akam.net in 40 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server usw5.akam.net in 190 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server ns1-24.akam.net in 171 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server asia1.akam.net in 161 ms.
> SOA dns0.news.com.au. hostmaster.news.com.au. 2012082200 3600 1200 86400 1200 from server ns1-50.akam.net in 161 ms.
> 
> shows 8 auth nameservers for careerone.com.au
> 
> and if you use 
> 
> dig www.careerone.com.au +short @<any of the 8 auth nameservers> 
> 
> you get no answer.
> 
> How does that work? Where does the 8.8.8.8 google public dns server get its answer from?
> 
> www.careerone.com.au is an alias (through chained aliasing) ultimately to a903.g.akamai.net. To get an authoritative answer for a903g.akamai.net you'd need to ask one of the g.akamai.net nameservers. Which is presumably what Google's public resolver did to get the answers it returned to your query.
> 
>                                                                                                                                                     - Kevin
> 
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