[Question] Question about recursive queries in BIND9

[Mark Andrews]

> In article <do8kd6$4pj$1 at sf1.isc.org>,
>  Hideshi Enokihara <Hideshi.Enokihara at jp.yokogawa.com> wrote:
> 
> > Hi all,
> > 
> > I have a question regarding recursion behavior of BIND9.
> > 
> > For example, I assume the following network. 
> > 
> > ----------------
> > 
> >                            org domain             example.org domain
> >         AP Server1         DNS Server2            DNS Server3
> >           |A.example.org      |NS2.example.org     |NS3.example.org
> >           |192.168.1.10       |                    |
> > Net-y   --+--------+----------+--------------------+--
> >                    |                                                       
>    
> >                               
> >                    |
> >                    |
> >                  Router
> >                    |
> >                    |
> >                    |
> > Net-z   --+--------+----------+--- 
> >           |                   |         
> >           |                   |
> >         DNS Server1 (BIND9)  DNS Client1
> > 
> > ------------------
> > 
> > In this network, I ran follwing steps.
> > 
> > Pre-sequence
> > A. DNS Client1 send the query(QNAME=A.example.org, QTYPE=A) to DNS 
> > Server2(Authoritative server for org domain).
> > B. DNS Server2 send the query to DNS Server3(Authoritative server for 
> > example.org domain).
> 
> Are you sure about this?  None of the authoritative servers for the ORG 
> domain that I was able to query (some of them didn't respond when I was 
> testing) have recursion enabled.
> 
> > C. DNS Server3 send the response(ANSWER NAME=A.example.org, ANSWER 
> > ADDRESS=192.168.1.10) to DNS Server2.
> > D. DNS Server2 send the response(ANSWER NAME=A.example.org, ANSWER 
> > ADDRESS=192.168.1.10) to DNS Client1.
> > 
> > Note:At these steps, DNS Server2 caches the answer for QNAME=A.example.org,
>  
> > QTYPE=A.  
> > 
> > Sequense
> > 1. DNS Client1 send the query(QNAME=A.example.org, QTYPE=A) to DNS 
> > Server1(BIND9). 
> > 2. DNS Server1(BIND9) send the query to DNS Server2(Authoritative server fo
> r 
> > org domain).
> > 3. DNS Server2 send the response(ANSWER NAME=A.example.org, ANSWER 
> > ADDRESS=192.168.1.10) from the cache to DNS Server1(BIND9).
> > 
> > I expected that BIND9 behave like 4A, but actually, BIND9 behave like 4B.
> > 
> > 4A. DNS Server1(BIND9) send the response(ANSWER NAME=A.example.org, ANSWER 
> > ADDRESS=192.168.1.10) to Client1.
> > 4B. DNS send the query to DNS Server3(Authoritative server for example.org 
> > domain).
> 
> ....
> 
> > I have a questin about step4A,4B.
> > Why does not DNS Server1(BIND9) send the response(4A) to DNS Client1?
> > What is the reason that DNS Server1(BIND9) does not use/trust DNS Server2's
>  
> > cache information?
> 
> Did it log a "Lame server" message?  When it's asking a server that's 
> supposed to be authoritative, it expects an authoritative answer or a 
> referral, not a non-authoritative answer.
> 
> > Is this behavior follow the RFC?
> > #If BIND9 does not use/trust the other DNS server's cache information, as a
>  
> > result, a lot of traffic will be caused in network.
> > 
> > Please tell me your opinions.
> 
> When caching servers query authoritative servers, they don't normally 
> send recursive queries.  And top-level authoritative servers don't 
> usually have recursion enabled.
> 
> -- 
> Barry Margolin, barmar at alum.mit.edu
> Arlington, MA
> *** PLEASE post questions in newsgroups, not directly to me ***
> *** PLEASE don't copy me on replies, I'll read them in the group ***


	BIND 9 has code to deal with BIND 8 incorrectly returning
	glue in the answer section w/ AA=0.

	Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org