Resolver not always resolving hostnames

Hey,

I think something odd is going on in the resolver.  It seems like it
doesn't resolve hostnames some of the time.  It's not really easily
reproducible, but I have seen it happen several times with cvsup where
it can't resolve the cvsup server.  If I re-run cvsup it works fine.

I see it on recent -CURRNET's (server running cvsup below is October
12, system running host(1) is October 15).

The cvsup log:

CVSup update begins at 2006-10-18 17:29:00
Updating from cvsup3.dk.freebsd.org
Name lookup failure for "cvsup3.dk.freebsd.org": Host name lookup failed
Updating local ncvs
CVSup update ends at 2006-10-18 17:29:01

I also seen odd things happen with host(1).  These two commands were
run right after each other.  I don't know if it's related, but I
suspect it is.

$ host cvsup3.dk.freebsd.org
cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
$ host cvsup3.dk.freebsd.org
cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
mirror03.inet.tele.dk has address 195.41.53.219
cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.

I only have one name-server in resolv.conf, so the problem isn't due
to hitting different caching name-servers.

Initially I thought it was a local problem for me, but joel_at_ has seen
the same on RELENG_6 (from July 8), and xride_at_ has seen the
same/similar with csup where his workaround was to ping the cvsup
server before running csup.

So, has anyone seen anything similar?  Since I can't reproduce the
issue at will I don't really know where to look for what's going on,
and of course it could be DNS issue...

-- 
Simon L. Nielsen