If you have configured multihoming on an Apple Remote Desktop (ARD) client, the management feature is restricted to the primary IP address, which is determined by the port order in System Preferences. The Observe, Control, and Curtain features will work on all IP addresses regardless of priority.
If you try to manage the client via a secondary IP address, Remote Desktop will display the message "This task will fail."
This issue affects Remote Desktop 2.0 and later.
To avoid the issue, use the IP address with higher priority on multihomed ARD clients for management functions.