If you want to hide your Nagios Web interface behind a reverse proxy you can use this config (for Apache 2):
- ProxyRequests Off
- ProxyPass /nagios3 http://nagiosip/nagios3 ProxyPassReverse /nagios3 http://nagiosip/nagios3 ProxyPass /cgi-bin/nagios3 http://nagiosip/cgi-bin/nagios3 ProxyPassReverse /cgi-bin/nagios3 http://nagiosip/cgi-bin/nagios3
It is important to include the /cgi-bin/nagios3 directory, otherwise only the static part of Nagios will work.