If you’re getting the error below, there are 2 simple things to check:
CHECK_NRPE: Error – Could not complete SSL handshake.

1 – make sure you compiled nrpe on both monitoring server and the monitored host, with ssl :
./configure –enable-ssl

2 – in nrpe.cfg file from the monitored host, make sure you edit the parameter below.

allowed_hosts=monitoring.server

[root@storage01 nrpe-2.12]# /usr/local/nagios/libexec/check_nrpe -H 1.2.3.4
NRPE v2.12