On the client you need to specify that the server is allowed to connect (in this case the server is 192.168.8.2)
server_port=5666 # SERVER ADDRESS # Address that nrpe should bind to in case there are more than one interface # and you do not want nrpe to bind on all interfaces. # NOTE: This option is ignored if NRPE is running under either inetd or xinetd server_address=192.168.8.1 allowed_hosts=127.0.0.1,192.168.8.2 # Hosts allowed to talk to nrpe nrpe_user=nagios nrpe_group=nagios dont_blame_nrpe=0 # If this is 1 (true), allow passing of # arguments to commands command_timeout=60 # kill command after this many seconds include=/etc/nagios/nrpe_local.cfg # So we make our changes in nrpe_local.cfg not nrpe.cfg