Question on resolving domain with multiple NS records

Barry Margolin barmar at alum.mit.edu
Wed Dec 21 20:56:51 UTC 2005


In article <doc7eg$1jbg$1 at sf1.isc.org>,
 "robertwessel2 at yahoo.com" <robertwessel2 at yahoo.com> wrote:

> Joe Shen wrote:
> > Hi,
> >
> >
> > If a domain name has multiple NS records, which NS
> > record will be used when a cache server is trying to
> > resolve a name in domain?
> >
> >
> > e.g.
> >
> > I'm trying to resolve domain name www.zjedu.gov.cn,
> > and I found there is two NS records for that domain
> >
> >    zjedu.gov.cn     21600     IN NS   dns.zjedu.org
> >    zjedu.gov.cn     21600     IN NS   dns1.zjedu.org
> >
> > Which NS will be used in further recursive lookup
> > procedure?
> 
> 
> Most resolvers will just use the first one returned, and switch to the
> second one only if they get no response from the first.

Not true, I believe.

Caching servers normally keep a record of server response times, and use 
the server that has the best track record.  If they have similar 
response times, I think it will choose among them randomly, to attempt 
to balance the load.

-- 
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 ***



More information about the bind-users mailing list