On Solaris hosts I see the following error message pretty frequently:
Apparently this error is generated when the interface in question does not have a MAC address associated with it. It can be suppressed by adding it to /var/cfengine/inputs/ignore_interfaces.rx but I don't think that failing to identify a mac address on an interface really warrents an error level log. Perhaps it would be useful in INFORM or DEBUG.
This adds a lot of relatively useless information to emails and log files.
Additionally I think the error message could be made more human readable by saying Could not get interface dmxgrp0 MAC address (ioctl(SIOCGARP)) instead of assuming the reader will understand what ioctl(SIOCGARP is.