May 12 12:10:11 my_dns named[3998]: Zone "123.192.in-addr.arpa" (file db.rev): no NS RRs found at zone top May 12 12:10:11 my_dns named[3998]: primary zone "123.192.in-addr.arpa" rejected due to errors (serial 3) May 12 12:10:11 my_dns named[3998]: Ready to answer queries. what does the 'no NS RRs found at zone top' mean and how can i repair this? insights...rf