This chapter caused me a bit of mental agony. Having worked with Zabbix since 2001, there were a lot of potential problem cases to describe. I'd wake up in the middle of the night with an idea of a brilliant problem (and solution) to include, only to have forgotten it by the time morning came. But this could have been a never-ending chapter. A compromise was needed, and reluctantly accepted. This chapter does not aim to help you with every single problem you will ever encounter in your life, or with Zabbix. It tries to help with more common issues, and give you some hints and starting points for further debugging.