Dear All,

I wonder if anyone can help with the following strange network problem
I'm having on my SL7.3 machine, please:

Every day, just after midday, I suddenly lose access to DNS name
resolution, and therefore become unable to interact with any remote
hosts, even though my network interface is still up.  Manually taking
the network interface down then up again restores name resolution
(although bringing the interface back up is surprisingly slow), but
only for a few minutes before it fails again.  These cycles go on
until about 1pm, after which all is fine once more.

If I try to ping the nameserver (by IP address) during one of the
periods of name resolution failure, I'm met with ICMP "destination
unreachable" packets originating from my own IP address on the
relevant interface.  (Whereas pinging the nameserver at any other time
produces successful responses.)

The regular nature of the failures led me to take a look in
/var/log/cron.  There seems to be a bit of a pattern that, a few
minutes before a failure, /var/log/cron contains entries pertaining to
the following executables:

/usr/lib64/sa/sa1
/usr/libexec/pcp/bin/pmlogger_check
/usr/libexec/pcp/bin/pmie_check

Does anyone have any idea what's going on, please?

Kind regards,

Dan