Though following questions came to me: Do you need to setup Nagios again on all servers that we want to monitor? How do you add another MySQL server to this monitoring?
This post is an answer to those questions.
To add remote server to nagios monitoring, We need NRPE (Nagios Remote Plugin Executor) along with Xinetd (Extended Internet Daemon) and Nagios Plugins to be setup.
(This assumes you have already setup the nagios server and adding new host. Refer links in first line of the article)