I think these three config fields should be set to 'ignore' by default if undef and a warning should be emitted that this was set automatically.
I'm not convinced that setting default values should produce a warning. Why not just trust the defaults? Or if these settings are very important, then why not remove the defaults altogether and make it an error (i.e. the daemon won't start) if they are missing?
If the failure if unset is mitigated somehow, I'm fine with whatever.