Understanding distributed monitoring

There are many situations in which you may want to have more than one Nagios instance monitoring your IT infrastructure. One reason can be a firewall blocking all but a few machines in your company. Another reason could be the need to load balance all checks so that they don't require an enterprise-class server. Others may need to monitor machines in different physical locations from separate machines to check what is wrong within a branch, even if the links to the central servers are temporarily down.

Regardless of the reason, you may want or need to have the execution of checks split across multiple computers. This type of setup might sound complicated and hard to configure, but it is not as hard as it seems. All that's necessary is to set up multiple Nagios instances along with the NSCA agents or daemons.

There are subtle differences in how various instances need to be configured. Usually, there are one or more Nagios instances that report information...