Basically, there's no need to run check_nrpe from a Nagios client because there's no reason for it to be installed on a Nagios client machine in the first place.
The check_nrpe plugin should always be running from the Nagios server.
In addition to Khaled's answer, I would also check if NRPE is configured as a stand-alone daemon or configured to be started by Xinetd.
If it's configured to run through xinetd (you can check if there's a file called nrpe under
/etc/xientd.d), it will look like so:
flags = REUSE
type = UNLISTED
port = 5666
socket_type = stream
wait = no
user = nagios
group = nagios
server = /usr/sbin/nrpe
server_args = -c /etc/nagios/nrpe.cfg --inetd
log_on_failure += USERID
disable = no
only_from = 127.0.0.1 nagios01.company.com 10.X.X.30
Make sure to include your Nagios server IP or hostname in the "only_from" line and make sure the values are separated by spaces rather than commas as in the
Another thing I would check is that the Nagios server is able to telnet the Nagios client on the NRPE port.
The default port is 5666, so you should run from your Nagios server the following command:
telnet nagios_server 5666
The output should look like so:
[root@nagios01 ~]# telnet do01.company.com 5666
Connected to do01.company.com.
Escape character is '^]'.
If you're unable to telnet from the Nagios server to the Nagios client I would start looking there.
There's an official document which I always use when trouble-shooting NRPE related issue, check it out:
Nagios Official Documentation