When using Nagios check_http, an SSL error may be encountered. Read the article to learn more about troubleshooting it. Bobcares, as a part of our Server Management Service offers solutions to every query that comes our way.

SSL Error with Nagios CHECK_HTTP

When we see an SSL error when monitoring a website using Nagios’ check_http plugin, it typically means that there is an issue with either the SSL certificate or the SSL/TLS negotiation. The following actions can be taken to troubleshoot the problem:

1. Verify that the SSL certificate that the website is displaying is legitimate and set up correctly.

2. Verify if the SSL certificate is still valid. Should it have, we must renew it.

3. Intermediary certificates are occasionally issued with SSL certificates. Verify that the web server is set up to contain all required intermediate certificates in the SSL configuration.

4. Verify whether the hostname specified in the Nagios check corresponds to either the SSL certificate’s Subject Alternative Names (SANs) or Common Name (CN). We’ll need to adjust the Nagios configuration if they don’t match.

5. Verify whether the check_http plugin’s default settings support any TLS versions or cypher suites that the website requires. The -S option allows us to define the TLS version and cypher suite. For e.g.,

6. Make sure the proxy server is set up correctly to support SSL/TLS connections if we’re using one.

7. Verify that the Nagios server is able to establish an SSL/TLS connection to the website without any interference from firewall rules or network problems.

8. Make sure the Nagios plugins are up to current on the system. Since, the most recent SSL/TLS standards might not be supported by outdated plugins.

9. Examine the server’s HTTP response. The -r option allows us to search for particular strings in the answer. This could assist us in determining problems that pertain to the functionality of the website rather than SSL. For e.g.,

10. Also, we can use the -d option to execute the check_http command in debug mode if none of the aforementioned fixes the problem. This will produce results that are more detailed and may assist us in determining the underlying reason.

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Conclusion

To sum up, our Tech team went over the troubleshooting details of the Nagios check_http SSL error.