It looks like some server is querying your DNS server recursively for
the zone that its not authorative for.
So either you can locate that machine and shut it down or put an access list on your
router to drop the traffic coming form that host to your dns.
You can setup the debug as follows to find out exactly where the request is coming from.
Go to nrcmd
Login with username and passwd. Then type the following for the debug.
nrcmd>dns setdebug DP=6
Please do this when your cpu is high and you see those lame server error messages in the
logs.
After capturing the log , unset the debug as follows:
nrcmd>dns unsetdebug
