Hello,

I want to have like 4 machines, each one of them with Nagios and nrpe (plugin+daemon) installed so that every one of the machines could be able to monitor all of the others.. Is there any problem doing this? Or having nrpe+nagios in the same machine is ok? Thanks.

You can have NRPE and Nagios on same server. I imagine most people do have NRPE on their Nagios master in order to monitor that server's processes the same way they do others.

I don't see why you couldn't do what you suggest but it seems overkill to me. You'd have to have the nrpe.cfg on each of the hosts allow all four servers' IPs to connect. However, since check_nrpe from a Nagios master to an nrpe client makes it run a command at the time of the check it means you'd have 4 times as many processes run on each system that was being checked by each of the Nagios masters. That is to say NRPE doesn't continuously save state information - it only gets it when the master asks for it. The daemon (or xinetd) is running all the time but that is only so it can LISTEN for connections from the master.

Another downside to such a setup is you'd have to update each of the 4 masters any time you wanted to make a monitoring change. (Imagine just acknowledging alerts or putting systems in downtime.) Also if you configured each to do notifications (especially paging) you'd get four notifications for every issue. I don't know about you but I once worked in a place that used Patrol for monitoring and the folks who administered it had set it to page every 15 minutes until a problem was resolved. This was quite annoying when working on a failed system at 3 AM. (At least with Nagios you can give users permissions to acknowledge alerts for which they have responsibility but getting those first 4 notifications all at once might be a bit of an annoyance to say the least.)

MensaWatter,

First of all thanks for your reply. I understand what you mean, but my idea is like: imagine I have like N machines and in all of them I have an interface where I can configure things related to monitoring, specially Nagios.
My idea (and i think it is the best approach to this problem) is that each one of the machines could work as a client or as a server. That means that both nagios and nrpe daemon must be installed in all of them.
Imagine in the interface one page 'Settings':

Enable monitoring (Yes/No)
Operation Mode (Client/Server)
Monitoring Server (...)

The first option default value is 'No'. In case of 'Yes', I can configure that machine to work as a client or as a server. If I choose the 'client' option, I put the monitoring server IP address in a textbox.

That way I can guarantee that the machines can monitor and be monitored. I don't know if this is possible (i think it is) or if it is the best solution to this problem.. You haver any other idea? Thanks.