MySQL Server "No such host is known"

Question

I am seeing a weird MySQL warning in Windows server event viewer. The error says : IP Address 'xx.xx.xx.xx' could not be resolved: no such host is known.

Any idea what this means and how critical it is ?

Solution

Is MySQL attempting to do reverse resolution of the hostname of connecting clients' IP addresses? (And do those entries not exist?)

Try adding skip-name-resolve to your MySQL configuration. If you don't need name resolution (no hostnames in the host specification of user accounts) then you may as well have it off.