If you have this error “CHECK_NRPE: Error – Could not complete SSL handshake” while configuring Nagios or Centreon, make sure that your (Nagios|Centreon) poller IP address is allowed in the remote monitored nrpe server configuration file. Just add the IP address :

Debian : cat  /etc/nagios/nrpe.cfg

allowed_hosts=your_ip_here

then, reload the nrpe server configuration file :

root@localhost:~#/etc/init.d/nagios-nrpe-server reload

RedHat : cat  /etc/nagios/nrpe.cfg

allowed_hosts=your_ip_here

Then, restart the nrpe server configuration file (no option for reloading) :

root@localhost:~#service nrpe restart