As a developer, you may be familiar with NRPE (Nagios Remote Plugin Executor). NRPE allows you to execute Nagios plugins on remote Linux/Unix machines. It is also possible to set up NRPE to talk to Windows servers.
The NRPE protocol uses SSL encryption to exchange data between two computers. But when the SSL handshake fails, NRPE sends an error message.
If you receive an SSL handshake error in your driver system log, you may be experiencing difficulty in establishing the connection from the server side.
Why is the NRPE SSL Handshake Error Occurring?
The NRPE protocol uses SSL to encrypt data exchange between two computers. On your server, the NRPE daemon acts as the server and will listen for incoming NRPE requests.
When the connection from the client side is made, the NRPE daemon will respond with an error message if the SSL handshake fails. This is usually caused by any of the following:
- Incorrect/missing/invalid NRPE SSL parameters on the client side
- Server's firewall rules blocking the incoming connection
- TLS/SSL protocol version not supported on the client side
- Missing NRPE SSL certificates on the server side
How to Fix the SSL Handshake Error?
The most important part of resolving the SSL handshake error is to identify the exact cause. This can be done by running tests on the server and the client using troubleshooting tools.
The following steps will help you to effectively fix the NRPE SSL handshake error quickly and easily:
- Check the NRPE SSL Certificate on the Server Side
Verify that the NRPE SSL certificate is present in the appropriate directory and is valid. Check the file permissions, date, and the expiration date of the certificate.
- Update IPTables Firewall
If there is a firewall configured on the server side, check if it’s blocking the incoming NRPE requests. Allow the related ports on the server side IPTables firewall.
- Check the Client Server Configuration
Verify that the client server is configured with the correct and valid NRPE SSL parameters. This includes the certificates, TLS/SSL versions, and encryption ciphers.
FAQ
How do I know if my NRPE SSL handshake failed?
If you receive an “SSL handshake failed” error message in your system log, your NRPE SSL handshake has failed.
What are the main causes of the NRPE SSL handshake error?
The main causes of the NRPE SSL handshake error are incorrect server configuration, firewall rules blocking the incoming connection, TLS/SSL protocol version not supported on the client side, or missing NRPE SSL certificates on the server side.
How can I determine what is causing my NRPE SSL handshake error?
The best way to determine what is causing your NRPE SSL handshake error is to run diagnostic tests on the server and the client. This will help you to identify the exact cause of the problem.
What impact will the NRPE SSL handshake error have on my system?
If you experience an NRPE SSL handshake error, your system will not be able to complete the connection between the server side and the client side. This will prevent the NRPE protocol from functioning correctly and could cause system disruption.
What is the best way to fix the NRPE SSL handshake error?
The best way to fix the NRPE SSL handshake error is to identify the exact cause and then make the appropriate changes to the server and client configurations. This could include updating the firewall rules or ensuring the correct NRPE SSL parameters are present.