DNS concept about recursive query

[Barry Margolin]

In article <ctui7a$2dod$1 at sf1.isc.org>, "Jay zh" <jayzh at hotmail.com> 
wrote:

> Dear:
> 
>     I have a question about DNS recursive query. For example, xyz-domain.com 
> has two dns servers which are www.xyz-domain.com and dns.xyz-domain.com. In 
> the root server, these two servers also have glue records.
> 
>     www.xyz-domain.com. IN A 1.1.1.1
>     dns.xyz-domain.com. IN A 2.2.2.2
> 
>     Now both 1.1.1.1 and 2.2.2.2 are not available. If someone use my dns 
> server to do recursive query and want to get the A record of 
> www.xyz-domain.com and this result is not in the cache, can it get the A 
> record? Someone said that it can get the answer because root server has the 
> A record and the resolver got this then stopped doing query. I found some 
> dns server's behavior is like this, but I test it in my dns ( bind 8 and 9) 
> and  I can't get this behavior. Which option should I set?

Older versions of BIND will return glue records in response to queries.  
Newer versions only use glue records when necessary to make use of the 
NS records -- if they're asked to perform a recursive query, they won't 
give an answer unless they can actually get it from one of the 
authoritative servers.  Parent zone servers are not considered 
authoritative for the glue records.

If you want to get the glue records from your server, send it a 
non-recursive query: dig www.xyz-domain.com a +norecurse

>     If I am not wrong, I know that resolver should stop doing recursive 
> query after asking authoritative dns server and get a response from it if 
> this answer is not in the local cache. In this case, both of the 
> authoritative dns servers are unreachable and the dns server will response 
> timeout, is it true?

Right.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***