Unblock with 'mysqladmin flush-hosts'

Hello Experts,
Recently I found following error on application end. Unblock with ‘mysqladmin flush-hosts’ To resolve this as per mention in mysqldocs use FLUSH HOST command or mysqladmin -uroot -p[password] flush-hosts.
I also increase the value of max_connection_error = 1000.

But here question is why such error occur so frequently. How to resolve this error permanently?

Hi, MySQL manual page explains this really well. Please check for details here http://dev.mysql.com/doc/refman/5.5/en/blocked-host.html