I have created many hosts using the FQDN of the host as its name and using the same FQDN for the DNS name.

The problem is that Zabbix uses the agent's Hostname parameter to match with the host's Name, flooding the logs with this error: "Send list of active checks to [xx] failed: host [xx.domain.com] not found.

To get rid of this errors and make active checks work, I had to manually use Hostname=xx.domain.com.

So, two things:

• Enhance somehow the agent to fill Hostname with its FQDN
• Make the server try to match the DNS name in case the name does not mach, or at least make it configurable.