Network Monitoring - Communication between Nagios & NRPE
 

Hello,

The communication between nagios and nrpe agent in the monitored host, can be without SSL? The problem is that I have 2 different versions of debian running on the machines and there are problems related to the libssl-dev package! Thanks

Yes, it can.
What exactly is your problem?

I already forgot the idea to use SSL. Now i have installed both nagios and nrpe plugin with the --disable-ssl option. I am following the NRPE official documentation but in this step:

ii. Test communication with the NRPE daemon
Make sure the check_nrpe plugin can talk to the NRPE daemon on the remote host. Replace "192.168.0.1" in the
command below with the IP address of the remote host that has NRPE installed.
/usr/local/nagios/libexec/check_nrpe -H 192.168.0.1
You should get a string back that tells you what version of NRPE is installed on the remote host, like this:
NRPE v2.8

I get an error: CHECK_NRPE: Received 0 bytes from daemon. Check the remote server logs for error messages.

Any idea?

Hello,

What error do you get in the remote server logs? That should tell you something. Also, do you have firewall enabled (IPTABLES)?

Kind regards,

Eric

Remote server logs is /var/log/messages ? There's nothing there about npre..
Yap, firewall was configured:

# iptables -I INPUT -p tcp -m tcp --dport 5666 -j DROP
# iptables -I INPUT -s <IP_SERVIDOR_NAGIOS> -p tcp -m tcp --dport 5666 -j ACCEPT

Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- 192.168.100.110 anywhere tcp dpt:nrpe
DROP tcp -- anywhere anywhere tcp dpt:nrpe
ACCEPT tcp -- 192.168.100.110 anywhere tcp dpt:nrpe
DROP tcp -- anywhere anywhere tcp dpt:nrpe

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

I think the problem is in the connection between the server and the remote machine.. But i don't know how to solve this!
If i try 'telnet 192.168.100.1 5666' in the Monitoring machine:

Trying 192.168.100.1...
Connected to 192.168.100.1.
Escape character is '^]'.
Connection closed by foreign host.

Which mode did you run NRPE: standalone or under xinetd (inetd)?

the problem was solved.. i had to add the IP of the server to /etc/hosts.allow otherweise there was no connection!thank u all :)

Surprising! I have never been forced to add the monitoring host's IP to /etc/hosts.allow on remote host. What Nagios and NRPE version did you run?

Hi,

Neither did I have to modify those settings. Do you have by any chance SELinux activated?

Kind regards,

Eric

nagios 3.2.3 & nrpe 2.12 :)