Does BIND always query the other authorative nameserver if the first authorative nameserver is down or unreachable

tsar.peter at gmail.com tsar.peter at gmail.com
Thu Mar 30 21:23:28 UTC 2006


Assuming a domain has 2 auth nameservers, call them A and B.
The parent domain should delegate ( with NS records) to A and B.
bind will randomly choose one and send a query. At the same time a
timer
is started. If the timer triggers before an answer is received a
timeout is detected,
and the other server will be tried.

If one server replies with NXDOMAIN the attempts ends here.

Note that the  zonefile itself should list both A and B, and both A and
B should
answer authoratitive ( AA bit set)

When all avaliable NS is tried ( a number of times, mark, figures
please ?) an
error is returned to the client.

The client itself might in some obscure ways try other sources (
hostfile NIS etc)
but that is usually not what you want. See your vendors documentation.



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