Wow, it seems like this is a common issue but no real definitive solution that I have found so far. So, here is my issue:
Nagios server IP is 192.168.1.5 and the remote server I want to monitor is 192.168.5.15.
Installed NRPE on the remote server using ./configure first, then ./configure --with-ssl=/usr//lib/ too, no luck, same result.
In the the /etc/xinetd.d/nrpe I changed the line to only_from = 192.168.1.5 (this is the IP address of the Nagios server, not the client)
In the file /usr/local/nagios/etc/Nrpe.cfg file I uncommented the line and put server_address=192.168.1.5 (The IP of the Nagios Server)
In the file /usr/local/nagios/etc/Nrpe.cfg file I put allowed_hosts=192.168.1.5 (the IP of the Nagios server)
I added the port, 5666 to the firewall.
I do: netstat -at | grep nrpe
tcp 0 0 :nrpe *: LISTEN
I have restarted xinetd several times, same result when I run sudo /usr/local/nagios/libexec/check_nrpe -H 192.168.1.15 (the IP of the remote server) when I run it FROM the remote server.
Please give me some help. I am new to Linux and need to get Nagios up and running for several servers. It's been very slow so far...
I appreciate it!