CHECK_NRPE: Response packet had invalid CRC32

[kohlbach]

Greetings,

We have 2 servers running Nagios, version 3.5.0 and version 4.4.2. There are currently hundreds of servers monitored, with Linux, Unix and Windows.

We installed in Windows 2019 the version of NSClient 0.5.2.35, however, it returns the error "CHECK_NRPE: Response packet had invalid CRC32" in both versions of Nagios.

Does anyone know how to handle this error?

ps: follows attachments

Thank you,
Kohlbach

[tgriep]

The NRPE settings in the nsclient.ini file need to be changed for the NRPE server.

Edit the nsclient.ini file and under this section

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[/settings/NRPE/server]

Remove this line

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allowed ciphers = ALL:!MD5:@STRENGTH

and add all of following lines.

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ssl options = 
verify mode = none
insecure = true
allow arguments = true
allow nasty characters = true
use ssl = 1
port = 5666
extended response = 1

Save the change and restart NSClient++ and see if that fixes the issue.

[kohlbach]

Greetings tgriep,

Thanks a lot for the help.

Unfortunately the problem has not yet been solved, both servers continue to receive the same error.

Attachments follow the log file, nsclient.ini, and the error message.

Best regards,
Kohlbach

[tgriep]

Is the nagios server's IP address 10.11.44.137 the one with the errors?

If so, add it to the allowed hosts option in the nsclient.ini file like below and restart NSClient++.

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allowed hosts = 172.19.1.113,172.19.4.113,172.19.4.114,172.19.4.151,10.11.76.103,10.41.76.103,10.11.44.137

You also did not add this option

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ssl options = 

under here in the ini file.

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[/settings/NRPE/server]

Put it in and restart the agent.
Then test it again.

[kohlbach]

Hi tgriep,

Many thanks for the feedback.

I have made changes, but the error continues.

follow attach the files.

Best regards,
Kohlbach.

[tgriep]

The nagios.log file was empty so that did not help at all.

Add this to the nsclient.ini file to enable trace level logging.

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[/settings/log]

; LOG LEVEL - Log level to use. Available levels are error,warning,info,debug,trace
level = trace

; FILENAME - The file to write log data to. Set this to none to disable log to file.
file name = nsclient.log

; DATEMASK - The size of the buffer to use when getting messages this affects the speed and maximum size of messages you can recieve.
date format = %Y-%m-%d %H:%M:%S


[/settings/log/file]

; MAXIMUM FILE SIZE - When file size reaches this it will be truncated to 50% if set to 0 (default) truncation will be disabled
max size = 2048000

Restart the agent, let the checks run and post the nsclient.log file.

[kohlbach]

Hi,

Follows the attached file.

Thank you for your help.

[tgriep]

Run this on the nagios server so we can see what version of the check_nrpe plugin you are using. It may be that you are using an older plugin that is causing the issue with the newer NSClient++.

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/usr/local/nagios/libexec/check_nrpe

Then to test the connectivity to the Windows server, run the next commands and post the output. Change the xxx.xxx.xxx.xxx to the IP address of the Windows Host.

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/usr/local/nagios/libexec/check_nrpe -H xxx.xxx.xxx.xxx
/usr/local/nagios/libexec/check_nrpe -H xxx.xxx.xxx.xxx -n

If you like, try upgrading the check_nrpe plugin and the following link are the instructions for doing that. Search it for this string "Install check_nrpe Plugin Only" for the instructions.

https://support.nagios.com/kb/article.php?id=515

[kohlbach]

Greetings tgriep,

Attached are the results of the requested commands.

Updating the nrpe is complicated, because currently we are with hundreds of servers (around 650) running 3 OS with different versions, only this is where the problem happens.

Thank you for your help!

Best regards,
Kohlbach

[tgriep]

When you ran the check_nrpe test with only the IP address, it connected to the NSClient agent and returned the version number so it is working.

What we have to do now is to look at how the command and the service checks are defined in the Nagios config files.
There may be an option that is causing the issue so can you post the check_nrpe command and the service checks?

Another quick test you can try is to run the following command to run a memory test against that host to see if it responds.

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/usr/local/nagios/libexec/check_nrpe -H 10.11.20.177 -c CheckMEM