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Re: [FC3] Sites 'disappearing' from DNS



Brian Fahrlander wrote:
On Sun, 2005-04-03 at 14:43 -0700, Craig White wrote:


the fact that it doesn't find it the first time but does on subsequent
tries suggest that you have some problem with the setup and latency so
your client times out before the dns lookup completes.

Probably the best way to fix that is to fix your caching dns server.


    Well, if I had to get it twice to actually make it, sure...the funny
thing is, if I go there first with 'host' and find it, then use Firefox,
it still doesn't. (Denying all reason that *I* know)  Firefox just won't
find it. That's what makes me think Firefox is involved.   These are
sites I've visited every day or so for years...and I've not changed the
local /etc/resolv.conf or anything on my end for about as long.

How can this be?


I would start by looking at nscd. It's responsible for caching all sorts of info on the client and quite often gets itself very confused.


The 'host' command queries DNS directly without referring to nscd, whereas the resolver library will use nscd if its running. If your DNS server fails to resolve an entry this failure is cached by nscd (by default for 300s). So, a 'host' command might return a valid response whereas any attempt to contact it via the resolver/nscd would fail.

Next time this happens, try flushing the nscd hosts cache:

# nscd -i hosts

and try again.

--
Nigel Wade, System Administrator, Space Plasma Physics Group,
            University of Leicester, Leicester, LE1 7RH, UK
E-mail :    nmw ion le ac uk
Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555


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