How FreeBSD Handles a DNS that is Down

[Martin McCormick]

	This is an extremely novice question on my part, but
after what I recently witnessed, I am not so sure I understand
all I know.

	The normal procedure on internet-connected systems is to
set the resolv.conf file to include at least 2 domain name
servers. Example:

nameserver	139.78.100.1
nameserver	139.78.200.1

	Last night, I had to take down our primary DNS for
maintenance and lots of systems began having trouble of various
kinds.

	While I expected the FreeBSD system I was on to hang for
a couple of seconds and then start using the second DNS, it
basically froze while some Linux boxes also began exhibiting
similar behavior.

	I finally manually changed the resolv.conf on the system
I was using to force the slave DNS to be first in the list and
that helped, but loosing the primary DNS was not the slight
slowdown one might expect. It was a full-blown outage.

	Are we missing some other configuration directive for Unix systems
that would make the systems use the redundancy a little
more gracefully than what happened? Otherwise, why have it if
somebody has to manually intervene? The only thing we should
have lost was dynamic updates. The systems that I know that were
basically hosed were FreeBSD and Linux. As soon as the mother
ship came back on line, everything was sweetness and light.

	Thanks for any thoughts on this issue. I have only been
running DNS for around 18 years and we fortunately do not get to
see this condition often and when we do, it's hopefully for very
short periods, but the disruption is total.

Martin McCormick WB5AGZ  Stillwater, OK 
Systems Engineer
OSU Information Technology Department Telecommunications Services Group