DNS question from a network guy

Kevin Darcy kcd at daimlerchrysler.com
Tue Jan 21 20:26:38 UTC 2003

dzember wrote:

> I am not a DNS guru.  I did search the archives first...
> If you have two or more records for a host, DNS will use round robin in its
> replies... What is the behavior if you delegate a domain, for instance
> www.mydomain.com to two name servers?
> in the mydomain.com name server...
> www   in    ns    ns3.mydomain.com
>            in    ns    ns4.mydomain.com
> ns3        in    a
> ns4        in    a

Queries for that name will be referred to those two nameservers, which are
expected to have the same data for the zone. If the name owns multiple A
records, then those nameservers *may* round-robin their responses, depending
on what nameserver software they are running and how they are configured.

The decision of which nameserver to query is usually made on the basis of
which nameserver  has answered recent queries faster. Chances are, many if not
most of the queries will be sent from nameservers which don't have a good
"scoresheet" of response times from your nameservers, so this tends to inject
a large random element into the nameserver-selection algorithm.

- Kevin

More information about the bind-users mailing list