I may be confused regarding sub delegated zone

Barry Margolin barmar at alum.mit.edu
Thu Jan 23 19:17:22 UTC 2014


In article <mailman.2135.1390499953.20661.bind-users at lists.isc.org>,
 Blason R <blason16 at gmail.com> wrote:

> Perfect this is what I m thinking. So in some case I observed that
> subdomain.example.com has ns record specified but no A record associated
> with it. But if i do query set type=ns to parent ns record it shows
> something else.
> 
> Like
> 
> Set typ=ns
> Sybdom.example.com
> 
> Ns5.example.com
> 
> Set type=a
> Ns5.example.com
> No A record
> 
> Server ns1.example.com
> 
> Set type=ns
> Subdom.example.com
> Ns2.example.com
> 
> Is this setup correct?

Resolvers don't usually query for NS records explicitly. They query for 
the record that the client has requested (e.g. the A record for 
subdom.example.com). If the server they query doesn't have that record, 
it sends the NS records for a more specific subdomain in a referral. 
Then the resolver repeats the process using ne of those servers, and so 
on. When the resolver gets NS records in a referral, it may need to 
query for their A records in order to query them (sometimes these A 
records will be included as "glue" along with the referral).

You can see this in action by using the +trace option to "dig".

> On 23 Jan 2014 23:04, "Ben Croswell" <ben.croswell at gmail.com> wrote:
> 
> > A freshly started server with no cache will be directed to nd1 first which
> > will give a referral to ns2 for the subdomain. After that it will go to ns2
> > directly until the ns records time out in cache.
> > On Jan 23, 2014 12:30 PM, "Blason R" <blason16 at gmail.com> wrote:
> >
> >> Hello friends,
> >>
> >> I may sound like novice but have basic question regarding Sub-zone which
> >> is an delegated zone. lets say I have zone example.com whose NS are
> >> ns1.example.com and then I have delegated sub-zone subdom.example.comwhose 
> >> ns record would be say
> >> ns2.example.com.
> >>
> >> So people who will be querying to A record for subdom.example.com [which
> >> @] will first be forwarded to ns1.example.com and then from there ns
> >> record of subdom.example.com will be given?
> >>
> >> Or will it directly be forwarded to n2.example.com?
> >>
> >> _______________________________________________
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> >

-- 
Barry Margolin
Arlington, MA


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